Rework notifications used in access management.

programs/server/Server.cpp

@@ -1314,7 +1314,7 @@ int Server::main(const std::vector<std::string> & /*args*/)
     global_context->setConfigReloadCallback([&]()
     {
         main_config_reloader->reload();
-        access_control.reloadUsersConfigs();
+        access_control.reload();
     });
 
     /// Limit on total number of concurrently executed queries.
@@ -1406,6 +1406,7 @@ int Server::main(const std::vector<std::string> & /*args*/)
         /// Stop reloading of the main config. This must be done before `global_context->shutdown()` because
         /// otherwise the reloading may pass a changed config to some destroyed parts of ContextSharedPart.
         main_config_reloader.reset();
+        access_control.stopPeriodicReloading();
 
         async_metrics.stop();
 
@@ -1629,7 +1630,7 @@ int Server::main(const std::vector<std::string> & /*args*/)
         buildLoggers(config(), logger());
 
         main_config_reloader->start();
-        access_control.startPeriodicReloadingUsersConfigs();
+        access_control.startPeriodicReloading();
         if (dns_cache_updater)
             dns_cache_updater->start();
 

src/Access/AccessChangesNotifier.cpp

@@ -0,0 +1,122 @@
+#include <Access/AccessChangesNotifier.h>
+#include <boost/range/algorithm/copy.hpp>
+
+
+namespace DB
+{
+
+AccessChangesNotifier::AccessChangesNotifier() : handlers(std::make_shared<Handlers>())
+{
+}
+
+AccessChangesNotifier::~AccessChangesNotifier() = default;
+
+void AccessChangesNotifier::onEntityAdded(const UUID & id, const AccessEntityPtr & new_entity)
+{
+    std::lock_guard lock{queue_mutex};
+    Event event;
+    event.id = id;
+    event.entity = new_entity;
+    event.type = new_entity->getType();
+    queue.push(std::move(event));
+}
+
+void AccessChangesNotifier::onEntityUpdated(const UUID & id, const AccessEntityPtr & changed_entity)
+{
+    std::lock_guard lock{queue_mutex};
+    Event event;
+    event.id = id;
+    event.entity = changed_entity;
+    event.type = changed_entity->getType();
+    queue.push(std::move(event));
+}
+
+void AccessChangesNotifier::onEntityRemoved(const UUID & id, AccessEntityType type)
+{
+    std::lock_guard lock{queue_mutex};
+    Event event;
+    event.id = id;
+    event.type = type;
+    queue.push(std::move(event));
+}
+
+scope_guard AccessChangesNotifier::subscribeForChanges(AccessEntityType type, const OnChangedHandler & handler)
+{
+    std::lock_guard lock{handlers->mutex};
+    auto & list = handlers->by_type[static_cast<size_t>(type)];
+    list.push_back(handler);
+    auto handler_it = std::prev(list.end());
+
+    return [handlers=handlers, type, handler_it]
+    {
+        std::lock_guard lock2{handlers->mutex};
+        auto & list2 = handlers->by_type[static_cast<size_t>(type)];
+        list2.erase(handler_it);
+    };
+}
+
+scope_guard AccessChangesNotifier::subscribeForChanges(const UUID & id, const OnChangedHandler & handler)
+{
+    std::lock_guard lock{handlers->mutex};
+    auto it = handlers->by_id.emplace(id, std::list<OnChangedHandler>{}).first;
+    auto & list = it->second;
+    list.push_back(handler);
+    auto handler_it = std::prev(list.end());
+
+    return [handlers=handlers, it, handler_it]
+    {
+        std::lock_guard lock2{handlers->mutex};
+        auto & list2 = it->second;
+        list2.erase(handler_it);
+        if (list2.empty())
+            handlers->by_id.erase(it);
+    };
+}
+
+
+scope_guard AccessChangesNotifier::subscribeForChanges(const std::vector<UUID> & ids, const OnChangedHandler & handler)
+{
+    scope_guard subscriptions;
+    for (const auto & id : ids)
+        subscriptions.join(subscribeForChanges(id, handler));
+    return subscriptions;
+}
+
+void AccessChangesNotifier::sendNotifications()
+{
+    /// Only one thread can send notification at any time.
+    std::lock_guard sending_notifications_lock{sending_notifications};
+
+    std::unique_lock queue_lock{queue_mutex};
+    while (!queue.empty())
+    {
+        auto event = std::move(queue.front());
+        queue.pop();
+        queue_lock.unlock();
+
+        std::vector<OnChangedHandler> current_handlers;
+        {
+            std::lock_guard handlers_lock{handlers->mutex};
+            boost::range::copy(handlers->by_type[static_cast<size_t>(event.type)], std::back_inserter(current_handlers));
+            auto it = handlers->by_id.find(event.id);
+            if (it != handlers->by_id.end())
+                boost::range::copy(it->second, std::back_inserter(current_handlers));
+        }
+
+        for (const auto & handler : current_handlers)
+        {
+            try
+            {
+                handler(event.id, event.entity);
+            }
+            catch (...)
+            {
+                tryLogCurrentException(__PRETTY_FUNCTION__);
+            }
+        }
+
+        queue_lock.lock();
+    }
+}
+
+}

src/Access/AccessChangesNotifier.h

@@ -0,0 +1,73 @@
+#pragma once
+
+#include <Access/IAccessEntity.h>
+#include <base/scope_guard.h>
+#include <list>
+#include <queue>
+#include <unordered_map>
+
+
+namespace DB
+{
+
+/// Helper class implementing subscriptions and notifications in access management.
+class AccessChangesNotifier
+{
+public:
+    AccessChangesNotifier();
+    ~AccessChangesNotifier();
+
+    using OnChangedHandler
+        = std::function<void(const UUID & /* id */, const AccessEntityPtr & /* new or changed entity, null if removed */)>;
+
+    /// Subscribes for all changes.
+    /// Can return nullptr if cannot subscribe (identifier not found) or if it doesn't make sense (the storage is read-only).
+    scope_guard subscribeForChanges(AccessEntityType type, const OnChangedHandler & handler);
+
+    template <typename EntityClassT>
+    scope_guard subscribeForChanges(OnChangedHandler handler)
+    {
+        return subscribeForChanges(EntityClassT::TYPE, handler);
+    }
+
+    /// Subscribes for changes of a specific entry.
+    /// Can return nullptr if cannot subscribe (identifier not found) or if it doesn't make sense (the storage is read-only).
+    scope_guard subscribeForChanges(const UUID & id, const OnChangedHandler & handler);
+    scope_guard subscribeForChanges(const std::vector<UUID> & ids, const OnChangedHandler & handler);
+
+    /// Called by access storages after a new access entity has been added.
+    void onEntityAdded(const UUID & id, const AccessEntityPtr & new_entity);
+
+    /// Called by access storages after an access entity has been changed.
+    void onEntityUpdated(const UUID & id, const AccessEntityPtr & changed_entity);
+
+    /// Called by access storages after an access entity has been removed.
+    void onEntityRemoved(const UUID & id, AccessEntityType type);
+
+    /// Sends notifications to subscribers about changes in access entities
+    /// (added with previous calls onEntityAdded(), onEntityUpdated(), onEntityRemoved()).
+    void sendNotifications();
+
+private:
+    struct Handlers
+    {
+        std::unordered_map<UUID, std::list<OnChangedHandler>> by_id;
+        std::list<OnChangedHandler> by_type[static_cast<size_t>(AccessEntityType::MAX)];
+        std::mutex mutex;
+    };
+
+    /// shared_ptr is here for safety because AccessChangesNotifier can be destroyed before all subscriptions are removed.
+    std::shared_ptr<Handlers> handlers;
+
+    struct Event
+    {
+        UUID id;
+        AccessEntityPtr entity;
+        AccessEntityType type;
+    };
+    std::queue<Event> queue;
+    std::mutex queue_mutex;
+    std::mutex sending_notifications;
+};
+
+}

src/Access/AccessControl.cpp

@@ -14,6 +14,7 @@
 #include <Access/SettingsProfilesCache.h>
 #include <Access/User.h>
 #include <Access/ExternalAuthenticators.h>
+#include <Access/AccessChangesNotifier.h>
 #include <Core/Settings.h>
 #include <base/find_symbols.h>
 #include <Poco/ExpireCache.h>
@@ -142,7 +143,8 @@ AccessControl::AccessControl()
       quota_cache(std::make_unique<QuotaCache>(*this)),
       settings_profiles_cache(std::make_unique<SettingsProfilesCache>(*this)),
       external_authenticators(std::make_unique<ExternalAuthenticators>()),
-      custom_settings_prefixes(std::make_unique<CustomSettingsPrefixes>())
+      custom_settings_prefixes(std::make_unique<CustomSettingsPrefixes>()),
+      changes_notifier(std::make_unique<AccessChangesNotifier>())
 {
 }
 
@@ -231,35 +233,6 @@ void AccessControl::addUsersConfigStorage(
     LOG_DEBUG(getLogger(), "Added {} access storage '{}', path: {}", String(new_storage->getStorageType()), new_storage->getStorageName(), new_storage->getPath());
 }
 
-void AccessControl::reloadUsersConfigs()
-{
-    auto storages = getStoragesPtr();
-    for (const auto & storage : *storages)
-    {
-        if (auto users_config_storage = typeid_cast<std::shared_ptr<UsersConfigAccessStorage>>(storage))
-            users_config_storage->reload();
-    }
-}
-
-void AccessControl::startPeriodicReloadingUsersConfigs()
-{
-    auto storages = getStoragesPtr();
-    for (const auto & storage : *storages)
-    {
-        if (auto users_config_storage = typeid_cast<std::shared_ptr<UsersConfigAccessStorage>>(storage))
-            users_config_storage->startPeriodicReloading();
-    }
-}
-
-void AccessControl::stopPeriodicReloadingUsersConfigs()
-{
-    auto storages = getStoragesPtr();
-    for (const auto & storage : *storages)
-    {
-        if (auto users_config_storage = typeid_cast<std::shared_ptr<UsersConfigAccessStorage>>(storage))
-            users_config_storage->stopPeriodicReloading();
-    }
-}
 
 void AccessControl::addReplicatedStorage(
     const String & storage_name_,
@@ -272,10 +245,9 @@ void AccessControl::addReplicatedStorage(
         if (auto replicated_storage = typeid_cast<std::shared_ptr<ReplicatedAccessStorage>>(storage))
             return;
     }
-    auto new_storage = std::make_shared<ReplicatedAccessStorage>(storage_name_, zookeeper_path_, get_zookeeper_function_);
+    auto new_storage = std::make_shared<ReplicatedAccessStorage>(storage_name_, zookeeper_path_, get_zookeeper_function_, *changes_notifier);
     addStorage(new_storage);
     LOG_DEBUG(getLogger(), "Added {} access storage '{}'", String(new_storage->getStorageType()), new_storage->getStorageName());
-    new_storage->startup();
 }
 
 void AccessControl::addDiskStorage(const String & directory_, bool readonly_)
@@ -298,7 +270,7 @@ void AccessControl::addDiskStorage(const String & storage_name_, const String &
             }
         }
     }
-    auto new_storage = std::make_shared<DiskAccessStorage>(storage_name_, directory_, readonly_);
+    auto new_storage = std::make_shared<DiskAccessStorage>(storage_name_, directory_, readonly_, *changes_notifier);
     addStorage(new_storage);
     LOG_DEBUG(getLogger(), "Added {} access storage '{}', path: {}", String(new_storage->getStorageType()), new_storage->getStorageName(), new_storage->getPath());
 }
@@ -312,7 +284,7 @@ void AccessControl::addMemoryStorage(const String & storage_name_)
         if (auto memory_storage = typeid_cast<std::shared_ptr<MemoryAccessStorage>>(storage))
             return;
     }
-    auto new_storage = std::make_shared<MemoryAccessStorage>(storage_name_);
+    auto new_storage = std::make_shared<MemoryAccessStorage>(storage_name_, *changes_notifier);
     addStorage(new_storage);
     LOG_DEBUG(getLogger(), "Added {} access storage '{}'", String(new_storage->getStorageType()), new_storage->getStorageName());
 }
@@ -320,7 +292,7 @@ void AccessControl::addMemoryStorage(const String & storage_name_)
 
 void AccessControl::addLDAPStorage(const String & storage_name_, const Poco::Util::AbstractConfiguration & config_, const String & prefix_)
 {
-    auto new_storage = std::make_shared<LDAPAccessStorage>(storage_name_, this, config_, prefix_);
+    auto new_storage = std::make_shared<LDAPAccessStorage>(storage_name_, *this, config_, prefix_);
     addStorage(new_storage);
     LOG_DEBUG(getLogger(), "Added {} access storage '{}', LDAP server name: {}", String(new_storage->getStorageType()), new_storage->getStorageName(), new_storage->getLDAPServerName());
 }
@@ -423,6 +395,57 @@ void AccessControl::addStoragesFromMainConfig(
 }
 
 
+void AccessControl::reload()
+{
+    MultipleAccessStorage::reload();
+    changes_notifier->sendNotifications();
+}
+
+scope_guard AccessControl::subscribeForChanges(AccessEntityType type, const OnChangedHandler & handler) const
+{
+    return changes_notifier->subscribeForChanges(type, handler);
+}
+
+scope_guard AccessControl::subscribeForChanges(const UUID & id, const OnChangedHandler & handler) const
+{
+    return changes_notifier->subscribeForChanges(id, handler);
+}
+
+scope_guard AccessControl::subscribeForChanges(const std::vector<UUID> & ids, const OnChangedHandler & handler) const
+{
+    return changes_notifier->subscribeForChanges(ids, handler);
+}
+
+std::optional<UUID> AccessControl::insertImpl(const AccessEntityPtr & entity, bool replace_if_exists, bool throw_if_exists)
+{
+    auto id = MultipleAccessStorage::insertImpl(entity, replace_if_exists, throw_if_exists);
+    if (id)
+        changes_notifier->sendNotifications();
+    return id;
+}
+
+bool AccessControl::removeImpl(const UUID & id, bool throw_if_not_exists)
+{
+    bool removed = MultipleAccessStorage::removeImpl(id, throw_if_not_exists);
+    if (removed)
+        changes_notifier->sendNotifications();
+    return removed;
+}
+
+bool AccessControl::updateImpl(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists)
+{
+    bool updated = MultipleAccessStorage::updateImpl(id, update_func, throw_if_not_exists);
+    if (updated)
+        changes_notifier->sendNotifications();
+    return updated;
+}
+
+AccessChangesNotifier & AccessControl::getChangesNotifier()
+{
+    return *changes_notifier;
+}
+
+
 UUID AccessControl::authenticate(const Credentials & credentials, const Poco::Net::IPAddress & address) const
 {
     try

src/Access/AccessControl.h

@@ -3,8 +3,8 @@
 #include <Access/MultipleAccessStorage.h>
 #include <Common/SettingsChanges.h>
 #include <Common/ZooKeeper/Common.h>
+#include <base/scope_guard.h>
 #include <boost/container/flat_set.hpp>
-#include <Access/UsersConfigAccessStorage.h>
 
 #include <memory>
 
@@ -40,6 +40,7 @@ class SettingsProfilesCache;
 class SettingsProfileElements;
 class ClientInfo;
 class ExternalAuthenticators;
+class AccessChangesNotifier;
 struct Settings;
 
 
@@ -50,6 +51,7 @@ public:
     AccessControl();
     ~AccessControl() override;
 
+    /// Initializes access storage (user directories).
     void setUpFromMainConfig(const Poco::Util::AbstractConfiguration & config_, const String & config_path_,
                              const zkutil::GetZooKeeper & get_zookeeper_function_);
 
@@ -74,9 +76,6 @@ public:
                                const String & preprocessed_dir_,
                                const zkutil::GetZooKeeper & get_zookeeper_function_ = {});
 
-    void reloadUsersConfigs();
-    void startPeriodicReloadingUsersConfigs();
-    void stopPeriodicReloadingUsersConfigs();
     /// Loads access entities from the directory on the local disk.
     /// Use that directory to keep created users/roles/etc.
     void addDiskStorage(const String & directory_, bool readonly_ = false);
@@ -106,6 +105,26 @@ public:
                                    const String & config_path,
                                    const zkutil::GetZooKeeper & get_zookeeper_function);
 
+    /// Reloads and updates entities in this storage. This function is used to implement SYSTEM RELOAD CONFIG.
+    void reload() override;
+
+    using OnChangedHandler = std::function<void(const UUID & /* id */, const AccessEntityPtr & /* new or changed entity, null if removed */)>;
+
+    /// Subscribes for all changes.
+    /// Can return nullptr if cannot subscribe (identifier not found) or if it doesn't make sense (the storage is read-only).
+    scope_guard subscribeForChanges(AccessEntityType type, const OnChangedHandler & handler) const;
+
+    template <typename EntityClassT>
+    scope_guard subscribeForChanges(OnChangedHandler handler) const { return subscribeForChanges(EntityClassT::TYPE, handler); }
+
+    /// Subscribes for changes of a specific entry.
+    /// Can return nullptr if cannot subscribe (identifier not found) or if it doesn't make sense (the storage is read-only).
+    scope_guard subscribeForChanges(const UUID & id, const OnChangedHandler & handler) const;
+    scope_guard subscribeForChanges(const std::vector<UUID> & ids, const OnChangedHandler & handler) const;
+
+    UUID authenticate(const Credentials & credentials, const Poco::Net::IPAddress & address) const;
+    void setExternalAuthenticatorsConfig(const Poco::Util::AbstractConfiguration & config);
+
     /// Sets the default profile's name.
     /// The default profile's settings are always applied before any other profile's.
     void setDefaultProfileName(const String & default_profile_name);
@@ -135,9 +154,6 @@ public:
     void setOnClusterQueriesRequireClusterGrant(bool enable) { on_cluster_queries_require_cluster_grant = enable; }
     bool doesOnClusterQueriesRequireClusterGrant() const { return on_cluster_queries_require_cluster_grant; }
 
-    UUID authenticate(const Credentials & credentials, const Poco::Net::IPAddress & address) const;
-    void setExternalAuthenticatorsConfig(const Poco::Util::AbstractConfiguration & config);
-
     std::shared_ptr<const ContextAccess> getContextAccess(
         const UUID & user_id,
         const std::vector<UUID> & current_roles,
@@ -178,10 +194,17 @@ public:
 
     const ExternalAuthenticators & getExternalAuthenticators() const;
 
+    /// Gets manager of notifications.
+    AccessChangesNotifier & getChangesNotifier();
+
 private:
     class ContextAccessCache;
     class CustomSettingsPrefixes;
 
+    std::optional<UUID> insertImpl(const AccessEntityPtr & entity, bool replace_if_exists, bool throw_if_exists) override;
+    bool removeImpl(const UUID & id, bool throw_if_not_exists) override;
+    bool updateImpl(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists) override;
+
     std::unique_ptr<ContextAccessCache> context_access_cache;
     std::unique_ptr<RoleCache> role_cache;
     std::unique_ptr<RowPolicyCache> row_policy_cache;
@@ -189,6 +212,7 @@ private:
     std::unique_ptr<SettingsProfilesCache> settings_profiles_cache;
     std::unique_ptr<ExternalAuthenticators> external_authenticators;
     std::unique_ptr<CustomSettingsPrefixes> custom_settings_prefixes;
+    std::unique_ptr<AccessChangesNotifier> changes_notifier;
     std::atomic_bool allow_plaintext_password = true;
     std::atomic_bool allow_no_password = true;
     std::atomic_bool users_without_row_policies_can_read_rows = false;

src/Access/ContextAccess.cpp

@@ -149,6 +149,21 @@ ContextAccess::ContextAccess(const AccessControl & access_control_, const Params
 }
 
 
+ContextAccess::~ContextAccess()
+{
+    enabled_settings.reset();
+    enabled_quota.reset();
+    enabled_row_policies.reset();
+    access_with_implicit.reset();
+    access.reset();
+    roles_info.reset();
+    subscription_for_roles_changes.reset();
+    enabled_roles.reset();
+    subscription_for_user_change.reset();
+    user.reset();
+}
+
+
 void ContextAccess::initialize()
 {
      std::lock_guard lock{mutex};

src/Access/ContextAccess.h

@@ -155,6 +155,8 @@ public:
     /// without any limitations. This is used for the global context.
     static std::shared_ptr<const ContextAccess> getFullAccess();
 
+    ~ContextAccess();
+
 private:
     friend class AccessControl;
     ContextAccess() {} /// NOLINT

src/Access/DiskAccessStorage.cpp

@@ -1,5 +1,6 @@
 #include <Access/DiskAccessStorage.h>
 #include <Access/AccessEntityIO.h>
+#include <Access/AccessChangesNotifier.h>
 #include <IO/WriteHelpers.h>
 #include <IO/ReadHelpers.h>
 #include <IO/ReadBufferFromFile.h>
@@ -164,13 +165,8 @@ namespace
 }
 
 
-DiskAccessStorage::DiskAccessStorage(const String & directory_path_, bool readonly_)
-    : DiskAccessStorage(STORAGE_TYPE, directory_path_, readonly_)
-{
-}
-
-DiskAccessStorage::DiskAccessStorage(const String & storage_name_, const String & directory_path_, bool readonly_)
-    : IAccessStorage(storage_name_)
+DiskAccessStorage::DiskAccessStorage(const String & storage_name_, const String & directory_path_, bool readonly_, AccessChangesNotifier & changes_notifier_)
+    : IAccessStorage(storage_name_), changes_notifier(changes_notifier_)
 {
     directory_path = makeDirectoryPathCanonical(directory_path_);
     readonly = readonly_;
@@ -199,7 +195,15 @@ DiskAccessStorage::DiskAccessStorage(const String & storage_name_, const String
 DiskAccessStorage::~DiskAccessStorage()
 {
     stopListsWritingThread();
-    writeLists();
+
+    try
+    {
+        writeLists();
+    }
+    catch (...)
+    {
+        tryLogCurrentException(__PRETTY_FUNCTION__);
+    }
 }
 
 
@@ -470,19 +474,16 @@ std::optional<String> DiskAccessStorage::readNameImpl(const UUID & id, bool thro
 
 std::optional<UUID> DiskAccessStorage::insertImpl(const AccessEntityPtr & new_entity, bool replace_if_exists, bool throw_if_exists)
 {
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
-
     UUID id = generateRandomID();
     std::lock_guard lock{mutex};
-    if (insertNoLock(id, new_entity, replace_if_exists, throw_if_exists, notifications))
+    if (insertNoLock(id, new_entity, replace_if_exists, throw_if_exists))
         return id;
 
     return std::nullopt;
 }
 
 
-bool DiskAccessStorage::insertNoLock(const UUID & id, const AccessEntityPtr & new_entity, bool replace_if_exists, bool throw_if_exists, Notifications & notifications)
+bool DiskAccessStorage::insertNoLock(const UUID & id, const AccessEntityPtr & new_entity, bool replace_if_exists, bool throw_if_exists)
 {
     const String & name = new_entity->getName();
     AccessEntityType type = new_entity->getType();
@@ -514,7 +515,7 @@ bool DiskAccessStorage::insertNoLock(const UUID & id, const AccessEntityPtr & ne
     writeAccessEntityToDisk(id, *new_entity);
 
     if (name_collision && replace_if_exists)
-        removeNoLock(it_by_name->second->id, /* throw_if_not_exists = */ false, notifications);
+        removeNoLock(it_by_name->second->id, /* throw_if_not_exists = */ false);
 
     /// Do insertion.
     auto & entry = entries_by_id[id];
@@ -523,22 +524,20 @@ bool DiskAccessStorage::insertNoLock(const UUID & id, const AccessEntityPtr & ne
     entry.name = name;
     entry.entity = new_entity;
     entries_by_name[entry.name] = &entry;
-    prepareNotifications(id, entry, false, notifications);
+
+    changes_notifier.onEntityAdded(id, new_entity);
     return true;
 }
 
 
 bool DiskAccessStorage::removeImpl(const UUID & id, bool throw_if_not_exists)
 {
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
-
     std::lock_guard lock{mutex};
-    return removeNoLock(id, throw_if_not_exists, notifications);
+    return removeNoLock(id, throw_if_not_exists);
 }
 
 
-bool DiskAccessStorage::removeNoLock(const UUID & id, bool throw_if_not_exists, Notifications & notifications)
+bool DiskAccessStorage::removeNoLock(const UUID & id, bool throw_if_not_exists)
 {
     auto it = entries_by_id.find(id);
     if (it == entries_by_id.end())
@@ -559,25 +558,24 @@ bool DiskAccessStorage::removeNoLock(const UUID & id, bool throw_if_not_exists,
     deleteAccessEntityOnDisk(id);
 
     /// Do removing.
-    prepareNotifications(id, entry, true, notifications);
+    UUID removed_id = id;
     auto & entries_by_name = entries_by_name_and_type[static_cast<size_t>(type)];
     entries_by_name.erase(entry.name);
     entries_by_id.erase(it);
+
+    changes_notifier.onEntityRemoved(removed_id, type);
     return true;
 }
 
 
 bool DiskAccessStorage::updateImpl(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists)
 {
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
-
     std::lock_guard lock{mutex};
-    return updateNoLock(id, update_func, throw_if_not_exists, notifications);
+    return updateNoLock(id, update_func, throw_if_not_exists);
 }
 
 
-bool DiskAccessStorage::updateNoLock(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists, Notifications & notifications)
+bool DiskAccessStorage::updateNoLock(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists)
 {
     auto it = entries_by_id.find(id);
     if (it == entries_by_id.end())
@@ -626,7 +624,8 @@ bool DiskAccessStorage::updateNoLock(const UUID & id, const UpdateFunc & update_
         entries_by_name[entry.name] = &entry;
     }
 
-    prepareNotifications(id, entry, false, notifications);
+    changes_notifier.onEntityUpdated(id, new_entity);
+
     return true;
 }
 
@@ -650,74 +649,4 @@ void DiskAccessStorage::deleteAccessEntityOnDisk(const UUID & id) const
         throw Exception("Couldn't delete " + file_path, ErrorCodes::FILE_DOESNT_EXIST);
 }
 
-
-void DiskAccessStorage::prepareNotifications(const UUID & id, const Entry & entry, bool remove, Notifications & notifications) const
-{
-    if (!remove && !entry.entity)
-        return;
-
-    const AccessEntityPtr entity = remove ? nullptr : entry.entity;
-    for (const auto & handler : entry.handlers_by_id)
-        notifications.push_back({handler, id, entity});
-
-    for (const auto & handler : handlers_by_type[static_cast<size_t>(entry.type)])
-        notifications.push_back({handler, id, entity});
-}
-
-
-scope_guard DiskAccessStorage::subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const
-{
-    std::lock_guard lock{mutex};
-    auto it = entries_by_id.find(id);
-    if (it == entries_by_id.end())
-        return {};
-    const Entry & entry = it->second;
-    auto handler_it = entry.handlers_by_id.insert(entry.handlers_by_id.end(), handler);
-
-    return [this, id, handler_it]
-    {
-        std::lock_guard lock2{mutex};
-        auto it2 = entries_by_id.find(id);
-        if (it2 != entries_by_id.end())
-        {
-            const Entry & entry2 = it2->second;
-            entry2.handlers_by_id.erase(handler_it);
-        }
-    };
-}
-
-scope_guard DiskAccessStorage::subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const
-{
-    std::lock_guard lock{mutex};
-    auto & handlers = handlers_by_type[static_cast<size_t>(type)];
-    handlers.push_back(handler);
-    auto handler_it = std::prev(handlers.end());
-
-    return [this, type, handler_it]
-    {
-        std::lock_guard lock2{mutex};
-        auto & handlers2 = handlers_by_type[static_cast<size_t>(type)];
-        handlers2.erase(handler_it);
-    };
-}
-
-bool DiskAccessStorage::hasSubscription(const UUID & id) const
-{
-    std::lock_guard lock{mutex};
-    auto it = entries_by_id.find(id);
-    if (it != entries_by_id.end())
-    {
-        const Entry & entry = it->second;
-        return !entry.handlers_by_id.empty();
-    }
-    return false;
-}
-
-bool DiskAccessStorage::hasSubscription(AccessEntityType type) const
-{
-    std::lock_guard lock{mutex};
-    const auto & handlers = handlers_by_type[static_cast<size_t>(type)];
-    return !handlers.empty();
-}
-
 }

src/Access/DiskAccessStorage.h

@@ -7,14 +7,15 @@
 
 namespace DB
 {
+class AccessChangesNotifier;
+
 /// Loads and saves access entities on a local disk to a specified directory.
 class DiskAccessStorage : public IAccessStorage
 {
 public:
     static constexpr char STORAGE_TYPE[] = "local directory";
 
-    DiskAccessStorage(const String & storage_name_, const String & directory_path_, bool readonly_ = false);
-    DiskAccessStorage(const String & directory_path_, bool readonly_ = false);
+    DiskAccessStorage(const String & storage_name_, const String & directory_path_, bool readonly_, AccessChangesNotifier & changes_notifier_);
     ~DiskAccessStorage() override;
 
     const char * getStorageType() const override { return STORAGE_TYPE; }
@@ -27,8 +28,6 @@ public:
     bool isReadOnly() const override { return readonly; }
 
     bool exists(const UUID & id) const override;
-    bool hasSubscription(const UUID & id) const override;
-    bool hasSubscription(AccessEntityType type) const override;
 
 private:
     std::optional<UUID> findImpl(AccessEntityType type, const String & name) const override;
@@ -38,8 +37,6 @@ private:
     std::optional<UUID> insertImpl(const AccessEntityPtr & entity, bool replace_if_exists, bool throw_if_exists) override;
     bool removeImpl(const UUID & id, bool throw_if_not_exists) override;
     bool updateImpl(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists) override;
-    scope_guard subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const override;
-    scope_guard subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const override;
 
     void clear();
     bool readLists();
@@ -50,9 +47,9 @@ private:
     void listsWritingThreadFunc();
     void stopListsWritingThread();
 
-    bool insertNoLock(const UUID & id, const AccessEntityPtr & new_entity, bool replace_if_exists, bool throw_if_exists, Notifications & notifications);
-    bool removeNoLock(const UUID & id, bool throw_if_not_exists, Notifications & notifications);
-    bool updateNoLock(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists, Notifications & notifications);
+    bool insertNoLock(const UUID & id, const AccessEntityPtr & new_entity, bool replace_if_exists, bool throw_if_exists);
+    bool removeNoLock(const UUID & id, bool throw_if_not_exists);
+    bool updateNoLock(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists);
 
     AccessEntityPtr readAccessEntityFromDisk(const UUID & id) const;
     void writeAccessEntityToDisk(const UUID & id, const IAccessEntity & entity) const;
@@ -65,11 +62,8 @@ private:
         String name;
         AccessEntityType type;
         mutable AccessEntityPtr entity; /// may be nullptr, if the entity hasn't been loaded yet.
-        mutable std::list<OnChangedHandler> handlers_by_id;
     };
 
-    void prepareNotifications(const UUID & id, const Entry & entry, bool remove, Notifications & notifications) const;
-
     String directory_path;
     std::atomic<bool> readonly;
     std::unordered_map<UUID, Entry> entries_by_id;
@@ -79,7 +73,7 @@ private:
     ThreadFromGlobalPool lists_writing_thread;                   /// List files are written in a separate thread.
     std::condition_variable lists_writing_thread_should_exit;    /// Signals `lists_writing_thread` to exit.
     bool lists_writing_thread_is_waiting = false;
-    mutable std::list<OnChangedHandler> handlers_by_type[static_cast<size_t>(AccessEntityType::MAX)];
+    AccessChangesNotifier & changes_notifier;
     mutable std::mutex mutex;
 };
 }

src/Access/EnabledRoles.cpp

@@ -6,7 +6,7 @@
 
 namespace DB
 {
-EnabledRoles::EnabledRoles(const Params & params_) : params(params_)
+EnabledRoles::EnabledRoles(const Params & params_) : params(params_), handlers(std::make_shared<Handlers>())
 {
 }
 
@@ -15,42 +15,50 @@ EnabledRoles::~EnabledRoles() = default;
 
 std::shared_ptr<const EnabledRolesInfo> EnabledRoles::getRolesInfo() const
 {
-    std::lock_guard lock{mutex};
+    std::lock_guard lock{info_mutex};
     return info;
 }
 
 
 scope_guard EnabledRoles::subscribeForChanges(const OnChangeHandler & handler) const
 {
-    std::lock_guard lock{mutex};
-    handlers.push_back(handler);
-    auto it = std::prev(handlers.end());
+    std::lock_guard lock{handlers->mutex};
+    handlers->list.push_back(handler);
+    auto it = std::prev(handlers->list.end());
 
-    return [this, it]
+    return [handlers=handlers, it]
     {
-        std::lock_guard lock2{mutex};
-        handlers.erase(it);
+        std::lock_guard lock2{handlers->mutex};
+        handlers->list.erase(it);
     };
 }
 
 
-void EnabledRoles::setRolesInfo(const std::shared_ptr<const EnabledRolesInfo> & info_, scope_guard & notifications)
+void EnabledRoles::setRolesInfo(const std::shared_ptr<const EnabledRolesInfo> & info_, scope_guard * notifications)
 {
-    std::lock_guard lock{mutex};
-
-    if (info && info_ && *info == *info_)
-        return;
-
-    info = info_;
-
-    std::vector<OnChangeHandler> handlers_to_notify;
-    boost::range::copy(handlers, std::back_inserter(handlers_to_notify));
-
-    notifications.join(scope_guard([info = info, handlers_to_notify = std::move(handlers_to_notify)]
     {
-        for (const auto & handler : handlers_to_notify)
-            handler(info);
-    }));
+        std::lock_guard lock{info_mutex};
+        if (info && info_ && *info == *info_)
+            return;
+
+        info = info_;
+    }
+
+    if (notifications)
+    {
+        std::vector<OnChangeHandler> handlers_to_notify;
+        {
+            std::lock_guard lock{handlers->mutex};
+            boost::range::copy(handlers->list, std::back_inserter(handlers_to_notify));
+        }
+
+        notifications->join(scope_guard(
+            [info = info, handlers_to_notify = std::move(handlers_to_notify)]
+            {
+                for (const auto & handler : handlers_to_notify)
+                    handler(info);
+            }));
+    }
 }
 
 }

src/Access/EnabledRoles.h

@@ -4,6 +4,7 @@
 #include <base/scope_guard.h>
 #include <boost/container/flat_set.hpp>
 #include <list>
+#include <memory>
 #include <mutex>
 #include <vector>
 
@@ -43,12 +44,21 @@ private:
     friend class RoleCache;
     explicit EnabledRoles(const Params & params_);
 
-    void setRolesInfo(const std::shared_ptr<const EnabledRolesInfo> & info_, scope_guard & notifications);
+    void setRolesInfo(const std::shared_ptr<const EnabledRolesInfo> & info_, scope_guard * notifications);
 
     const Params params;
-    mutable std::shared_ptr<const EnabledRolesInfo> info;
-    mutable std::list<OnChangeHandler> handlers;
-    mutable std::mutex mutex;
+
+    std::shared_ptr<const EnabledRolesInfo> info;
+    mutable std::mutex info_mutex;
+
+    struct Handlers
+    {
+        std::list<OnChangeHandler> list;
+        std::mutex mutex;
+    };
+
+    /// shared_ptr is here for safety because EnabledRoles can be destroyed before all subscriptions are removed.
+    std::shared_ptr<Handlers> handlers;
 };
 
 }

src/Access/IAccessStorage.cpp

@@ -410,34 +410,6 @@ bool IAccessStorage::updateImpl(const UUID & id, const UpdateFunc &, bool throw_
 }
 
 
-scope_guard IAccessStorage::subscribeForChanges(AccessEntityType type, const OnChangedHandler & handler) const
-{
-    return subscribeForChangesImpl(type, handler);
-}
-
-
-scope_guard IAccessStorage::subscribeForChanges(const UUID & id, const OnChangedHandler & handler) const
-{
-    return subscribeForChangesImpl(id, handler);
-}
-
-
-scope_guard IAccessStorage::subscribeForChanges(const std::vector<UUID> & ids, const OnChangedHandler & handler) const
-{
-    scope_guard subscriptions;
-    for (const auto & id : ids)
-        subscriptions.join(subscribeForChangesImpl(id, handler));
-    return subscriptions;
-}
-
-
-void IAccessStorage::notify(const Notifications & notifications)
-{
-    for (const auto & [fn, id, new_entity] : notifications)
-        fn(id, new_entity);
-}
-
-
 UUID IAccessStorage::authenticate(
     const Credentials & credentials,
     const Poco::Net::IPAddress & address,

src/Access/IAccessStorage.h

@@ -3,7 +3,6 @@
 #include <Access/IAccessEntity.h>
 #include <Core/Types.h>
 #include <Core/UUID.h>
-#include <base/scope_guard.h>
 #include <functional>
 #include <optional>
 #include <vector>
@@ -22,7 +21,7 @@ enum class AuthenticationType;
 
 /// Contains entities, i.e. instances of classes derived from IAccessEntity.
 /// The implementations of this class MUST be thread-safe.
-class IAccessStorage
+class IAccessStorage : public boost::noncopyable
 {
 public:
     explicit IAccessStorage(const String & storage_name_) : storage_name(storage_name_) {}
@@ -41,6 +40,15 @@ public:
     /// Returns true if this entity is readonly.
     virtual bool isReadOnly(const UUID &) const { return isReadOnly(); }
 
+    /// Reloads and updates entities in this storage. This function is used to implement SYSTEM RELOAD CONFIG.
+    virtual void reload() {}
+
+    /// Starts periodic reloading and update of entities in this storage.
+    virtual void startPeriodicReloading() {}
+
+    /// Stops periodic reloading and update of entities in this storage.
+    virtual void stopPeriodicReloading() {}
+
     /// Returns the identifiers of all the entities of a specified type contained in the storage.
     std::vector<UUID> findAll(AccessEntityType type) const;
 
@@ -130,23 +138,6 @@ public:
     /// Updates multiple entities in the storage. Returns the list of successfully updated.
     std::vector<UUID> tryUpdate(const std::vector<UUID> & ids, const UpdateFunc & update_func);
 
-    using OnChangedHandler = std::function<void(const UUID & /* id */, const AccessEntityPtr & /* new or changed entity, null if removed */)>;
-
-    /// Subscribes for all changes.
-    /// Can return nullptr if cannot subscribe (identifier not found) or if it doesn't make sense (the storage is read-only).
-    scope_guard subscribeForChanges(AccessEntityType type, const OnChangedHandler & handler) const;
-
-    template <typename EntityClassT>
-    scope_guard subscribeForChanges(OnChangedHandler handler) const { return subscribeForChanges(EntityClassT::TYPE, handler); }
-
-    /// Subscribes for changes of a specific entry.
-    /// Can return nullptr if cannot subscribe (identifier not found) or if it doesn't make sense (the storage is read-only).
-    scope_guard subscribeForChanges(const UUID & id, const OnChangedHandler & handler) const;
-    scope_guard subscribeForChanges(const std::vector<UUID> & ids, const OnChangedHandler & handler) const;
-
-    virtual bool hasSubscription(AccessEntityType type) const = 0;
-    virtual bool hasSubscription(const UUID & id) const = 0;
-
     /// Finds a user, check the provided credentials and returns the ID of the user if they are valid.
     /// Throws an exception if no such user or credentials are invalid.
     UUID authenticate(const Credentials & credentials, const Poco::Net::IPAddress & address, const ExternalAuthenticators & external_authenticators, bool allow_no_password, bool allow_plaintext_password) const;
@@ -160,8 +151,6 @@ protected:
     virtual std::optional<UUID> insertImpl(const AccessEntityPtr & entity, bool replace_if_exists, bool throw_if_exists);
     virtual bool removeImpl(const UUID & id, bool throw_if_not_exists);
     virtual bool updateImpl(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists);
-    virtual scope_guard subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const = 0;
-    virtual scope_guard subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const = 0;
     virtual std::optional<UUID> authenticateImpl(const Credentials & credentials, const Poco::Net::IPAddress & address, const ExternalAuthenticators & external_authenticators, bool throw_if_user_not_exists, bool allow_no_password, bool allow_plaintext_password) const;
     virtual bool areCredentialsValid(const User & user, const Credentials & credentials, const ExternalAuthenticators & external_authenticators) const;
     virtual bool isAddressAllowed(const User & user, const Poco::Net::IPAddress & address) const;
@@ -181,9 +170,6 @@ protected:
     [[noreturn]] static void throwAddressNotAllowed(const Poco::Net::IPAddress & address);
     [[noreturn]] static void throwInvalidCredentials();
     [[noreturn]] static void throwAuthenticationTypeNotAllowed(AuthenticationType auth_type);
-    using Notification = std::tuple<OnChangedHandler, UUID, AccessEntityPtr>;
-    using Notifications = std::vector<Notification>;
-    static void notify(const Notifications & notifications);
 
 private:
     const String storage_name;

src/Access/LDAPAccessStorage.cpp

@@ -27,10 +27,10 @@ namespace ErrorCodes
 }
 
 
-LDAPAccessStorage::LDAPAccessStorage(const String & storage_name_, AccessControl * access_control_, const Poco::Util::AbstractConfiguration & config, const String & prefix)
-    : IAccessStorage(storage_name_)
+LDAPAccessStorage::LDAPAccessStorage(const String & storage_name_, AccessControl & access_control_, const Poco::Util::AbstractConfiguration & config, const String & prefix)
+    : IAccessStorage(storage_name_), access_control(access_control_), memory_storage(storage_name_, access_control.getChangesNotifier())
 {
-    setConfiguration(access_control_, config, prefix);
+    setConfiguration(config, prefix);
 }
 
 
@@ -40,7 +40,7 @@ String LDAPAccessStorage::getLDAPServerName() const
 }
 
 
-void LDAPAccessStorage::setConfiguration(AccessControl * access_control_, const Poco::Util::AbstractConfiguration & config, const String & prefix)
+void LDAPAccessStorage::setConfiguration(const Poco::Util::AbstractConfiguration & config, const String & prefix)
 {
     std::scoped_lock lock(mutex);
 
@@ -80,7 +80,6 @@ void LDAPAccessStorage::setConfiguration(AccessControl * access_control_, const
         }
     }
 
-    access_control = access_control_;
     ldap_server_name = ldap_server_name_cfg;
     role_search_params.swap(role_search_params_cfg);
     common_role_names.swap(common_roles_cfg);
@@ -91,7 +90,7 @@ void LDAPAccessStorage::setConfiguration(AccessControl * access_control_, const
     granted_role_names.clear();
     granted_role_ids.clear();
 
-    role_change_subscription = access_control->subscribeForChanges<Role>(
+    role_change_subscription = access_control.subscribeForChanges<Role>(
         [this] (const UUID & id, const AccessEntityPtr & entity)
         {
             return this->processRoleChange(id, entity);
@@ -215,7 +214,7 @@ void LDAPAccessStorage::assignRolesNoLock(User & user, const LDAPClient::SearchR
         auto it = granted_role_ids.find(role_name);
         if (it == granted_role_ids.end())
         {
-            if (const auto role_id = access_control->find<Role>(role_name))
+            if (const auto role_id = access_control.find<Role>(role_name))
             {
                 granted_role_names.insert_or_assign(*role_id, role_name);
                 it = granted_role_ids.insert_or_assign(role_name, *role_id).first;
@@ -450,33 +449,6 @@ std::optional<String> LDAPAccessStorage::readNameImpl(const UUID & id, bool thro
 }
 
 
-scope_guard LDAPAccessStorage::subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const
-{
-    std::scoped_lock lock(mutex);
-    return memory_storage.subscribeForChanges(id, handler);
-}
-
-
-scope_guard LDAPAccessStorage::subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const
-{
-    std::scoped_lock lock(mutex);
-    return memory_storage.subscribeForChanges(type, handler);
-}
-
-
-bool LDAPAccessStorage::hasSubscription(const UUID & id) const
-{
-    std::scoped_lock lock(mutex);
-    return memory_storage.hasSubscription(id);
-}
-
-
-bool LDAPAccessStorage::hasSubscription(AccessEntityType type) const
-{
-    std::scoped_lock lock(mutex);
-    return memory_storage.hasSubscription(type);
-}
-
 std::optional<UUID> LDAPAccessStorage::authenticateImpl(
     const Credentials & credentials,
     const Poco::Net::IPAddress & address,

src/Access/LDAPAccessStorage.h

@@ -32,7 +32,7 @@ class LDAPAccessStorage : public IAccessStorage
 public:
     static constexpr char STORAGE_TYPE[] = "ldap";
 
-    explicit LDAPAccessStorage(const String & storage_name_, AccessControl * access_control_, const Poco::Util::AbstractConfiguration & config, const String & prefix);
+    explicit LDAPAccessStorage(const String & storage_name_, AccessControl & access_control_, const Poco::Util::AbstractConfiguration & config, const String & prefix);
     virtual ~LDAPAccessStorage() override = default;
 
     String getLDAPServerName() const;
@@ -42,19 +42,15 @@ public:
     virtual String getStorageParamsJSON() const override;
     virtual bool isReadOnly() const override { return true; }
     virtual bool exists(const UUID & id) const override;
-    virtual bool hasSubscription(const UUID & id) const override;
-    virtual bool hasSubscription(AccessEntityType type) const override;
 
 private: // IAccessStorage implementations.
     virtual std::optional<UUID> findImpl(AccessEntityType type, const String & name) const override;
     virtual std::vector<UUID> findAllImpl(AccessEntityType type) const override;
     virtual AccessEntityPtr readImpl(const UUID & id, bool throw_if_not_exists) const override;
     virtual std::optional<String> readNameImpl(const UUID & id, bool throw_if_not_exists) const override;
-    virtual scope_guard subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const override;
-    virtual scope_guard subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const override;
     virtual std::optional<UUID> authenticateImpl(const Credentials & credentials, const Poco::Net::IPAddress & address, const ExternalAuthenticators & external_authenticators, bool throw_if_user_not_exists, bool allow_no_password, bool allow_plaintext_password) const override;
 
-    void setConfiguration(AccessControl * access_control_, const Poco::Util::AbstractConfiguration & config, const String & prefix);
+    void setConfiguration(const Poco::Util::AbstractConfiguration & config, const String & prefix);
     void processRoleChange(const UUID & id, const AccessEntityPtr & entity);
 
     void applyRoleChangeNoLock(bool grant, const UUID & role_id, const String & role_name);
@@ -66,7 +62,7 @@ private: // IAccessStorage implementations.
         const ExternalAuthenticators & external_authenticators, LDAPClient::SearchResultsList & role_search_results) const;
 
     mutable std::recursive_mutex mutex;
-    AccessControl * access_control = nullptr;
+    AccessControl & access_control;
     String ldap_server_name;
     LDAPClient::RoleSearchParamsList role_search_params;
     std::set<String> common_role_names;                         // role name that should be granted to all users at all times

src/Access/MemoryAccessStorage.cpp

@@ -1,4 +1,5 @@
 #include <Access/MemoryAccessStorage.h>
+#include <Access/AccessChangesNotifier.h>
 #include <base/scope_guard.h>
 #include <boost/container/flat_set.hpp>
 #include <boost/range/adaptor/map.hpp>
@@ -7,8 +8,8 @@
 
 namespace DB
 {
-MemoryAccessStorage::MemoryAccessStorage(const String & storage_name_)
-    : IAccessStorage(storage_name_)
+MemoryAccessStorage::MemoryAccessStorage(const String & storage_name_, AccessChangesNotifier & changes_notifier_)
+    : IAccessStorage(storage_name_), changes_notifier(changes_notifier_)
 {
 }
 
@@ -63,19 +64,16 @@ AccessEntityPtr MemoryAccessStorage::readImpl(const UUID & id, bool throw_if_not
 
 std::optional<UUID> MemoryAccessStorage::insertImpl(const AccessEntityPtr & new_entity, bool replace_if_exists, bool throw_if_exists)
 {
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
-
     UUID id = generateRandomID();
     std::lock_guard lock{mutex};
-    if (insertNoLock(id, new_entity, replace_if_exists, throw_if_exists, notifications))
+    if (insertNoLock(id, new_entity, replace_if_exists, throw_if_exists))
         return id;
 
     return std::nullopt;
 }
 
 
-bool MemoryAccessStorage::insertNoLock(const UUID & id, const AccessEntityPtr & new_entity, bool replace_if_exists, bool throw_if_exists, Notifications & notifications)
+bool MemoryAccessStorage::insertNoLock(const UUID & id, const AccessEntityPtr & new_entity, bool replace_if_exists, bool throw_if_exists)
 {
     const String & name = new_entity->getName();
     AccessEntityType type = new_entity->getType();
@@ -103,7 +101,7 @@ bool MemoryAccessStorage::insertNoLock(const UUID & id, const AccessEntityPtr &
     if (name_collision && replace_if_exists)
     {
         const auto & existing_entry = *(it_by_name->second);
-        removeNoLock(existing_entry.id, /* throw_if_not_exists = */ false, notifications);
+        removeNoLock(existing_entry.id, /* throw_if_not_exists = */ false);
     }
 
     /// Do insertion.
@@ -111,22 +109,19 @@ bool MemoryAccessStorage::insertNoLock(const UUID & id, const AccessEntityPtr &
     entry.id = id;
     entry.entity = new_entity;
     entries_by_name[name] = &entry;
-    prepareNotifications(entry, false, notifications);
+    changes_notifier.onEntityAdded(id, new_entity);
     return true;
 }
 
 
 bool MemoryAccessStorage::removeImpl(const UUID & id, bool throw_if_not_exists)
 {
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
-
     std::lock_guard lock{mutex};
-    return removeNoLock(id, throw_if_not_exists, notifications);
+    return removeNoLock(id, throw_if_not_exists);
 }
 
 
-bool MemoryAccessStorage::removeNoLock(const UUID & id, bool throw_if_not_exists, Notifications & notifications)
+bool MemoryAccessStorage::removeNoLock(const UUID & id, bool throw_if_not_exists)
 {
     auto it = entries_by_id.find(id);
     if (it == entries_by_id.end())
@@ -141,27 +136,25 @@ bool MemoryAccessStorage::removeNoLock(const UUID & id, bool throw_if_not_exists
     const String & name = entry.entity->getName();
     AccessEntityType type = entry.entity->getType();
 
-    prepareNotifications(entry, true, notifications);
-
     /// Do removing.
+    UUID removed_id = id;
     auto & entries_by_name = entries_by_name_and_type[static_cast<size_t>(type)];
     entries_by_name.erase(name);
     entries_by_id.erase(it);
+
+    changes_notifier.onEntityRemoved(removed_id, type);
     return true;
 }
 
 
 bool MemoryAccessStorage::updateImpl(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists)
 {
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
-
     std::lock_guard lock{mutex};
-    return updateNoLock(id, update_func, throw_if_not_exists, notifications);
+    return updateNoLock(id, update_func, throw_if_not_exists);
 }
 
 
-bool MemoryAccessStorage::updateNoLock(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists, Notifications & notifications)
+bool MemoryAccessStorage::updateNoLock(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists)
 {
     auto it = entries_by_id.find(id);
     if (it == entries_by_id.end())
@@ -195,7 +188,7 @@ bool MemoryAccessStorage::updateNoLock(const UUID & id, const UpdateFunc & updat
         entries_by_name[new_entity->getName()] = &entry;
     }
 
-    prepareNotifications(entry, false, notifications);
+    changes_notifier.onEntityUpdated(id, new_entity);
     return true;
 }
 
@@ -212,16 +205,8 @@ void MemoryAccessStorage::setAll(const std::vector<AccessEntityPtr> & all_entiti
 
 void MemoryAccessStorage::setAll(const std::vector<std::pair<UUID, AccessEntityPtr>> & all_entities)
 {
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
-
     std::lock_guard lock{mutex};
-    setAllNoLock(all_entities, notifications);
-}
 
-
-void MemoryAccessStorage::setAllNoLock(const std::vector<std::pair<UUID, AccessEntityPtr>> & all_entities, Notifications & notifications)
-{
     boost::container::flat_set<UUID> not_used_ids;
     std::vector<UUID> conflicting_ids;
 
@@ -256,7 +241,7 @@ void MemoryAccessStorage::setAllNoLock(const std::vector<std::pair<UUID, AccessE
     boost::container::flat_set<UUID> ids_to_remove = std::move(not_used_ids);
     boost::range::copy(conflicting_ids, std::inserter(ids_to_remove, ids_to_remove.end()));
     for (const auto & id : ids_to_remove)
-        removeNoLock(id, /* throw_if_not_exists = */ false, notifications);
+        removeNoLock(id, /* throw_if_not_exists = */ false);
 
     /// Insert or update entities.
     for (const auto & [id, entity] : all_entities)
@@ -269,84 +254,14 @@ void MemoryAccessStorage::setAllNoLock(const std::vector<std::pair<UUID, AccessE
                 const AccessEntityPtr & changed_entity = entity;
                 updateNoLock(id,
                              [&changed_entity](const AccessEntityPtr &) { return changed_entity; },
-                             /* throw_if_not_exists = */ true,
-                             notifications);
+                             /* throw_if_not_exists = */ true);
             }
         }
         else
         {
-            insertNoLock(id, entity, /* replace_if_exists = */ false, /* throw_if_exists = */ true, notifications);
+            insertNoLock(id, entity, /* replace_if_exists = */ false, /* throw_if_exists = */ true);
         }
     }
 }
 
-
-void MemoryAccessStorage::prepareNotifications(const Entry & entry, bool remove, Notifications & notifications) const
-{
-    const AccessEntityPtr entity = remove ? nullptr : entry.entity;
-    for (const auto & handler : entry.handlers_by_id)
-        notifications.push_back({handler, entry.id, entity});
-
-    for (const auto & handler : handlers_by_type[static_cast<size_t>(entry.entity->getType())])
-        notifications.push_back({handler, entry.id, entity});
-}
-
-
-scope_guard MemoryAccessStorage::subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const
-{
-    std::lock_guard lock{mutex};
-    auto & handlers = handlers_by_type[static_cast<size_t>(type)];
-    handlers.push_back(handler);
-    auto handler_it = std::prev(handlers.end());
-
-    return [this, type, handler_it]
-    {
-        std::lock_guard lock2{mutex};
-        auto & handlers2 = handlers_by_type[static_cast<size_t>(type)];
-        handlers2.erase(handler_it);
-    };
-}
-
-
-scope_guard MemoryAccessStorage::subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const
-{
-    std::lock_guard lock{mutex};
-    auto it = entries_by_id.find(id);
-    if (it == entries_by_id.end())
-        return {};
-    const Entry & entry = it->second;
-    auto handler_it = entry.handlers_by_id.insert(entry.handlers_by_id.end(), handler);
-
-    return [this, id, handler_it]
-    {
-        std::lock_guard lock2{mutex};
-        auto it2 = entries_by_id.find(id);
-        if (it2 != entries_by_id.end())
-        {
-            const Entry & entry2 = it2->second;
-            entry2.handlers_by_id.erase(handler_it);
-        }
-    };
-}
-
-
-bool MemoryAccessStorage::hasSubscription(const UUID & id) const
-{
-    std::lock_guard lock{mutex};
-    auto it = entries_by_id.find(id);
-    if (it != entries_by_id.end())
-    {
-        const Entry & entry = it->second;
-        return !entry.handlers_by_id.empty();
-    }
-    return false;
-}
-
-
-bool MemoryAccessStorage::hasSubscription(AccessEntityType type) const
-{
-    std::lock_guard lock{mutex};
-    const auto & handlers = handlers_by_type[static_cast<size_t>(type)];
-    return !handlers.empty();
-}
 }

src/Access/MemoryAccessStorage.h

@@ -9,13 +9,15 @@
 
 namespace DB
 {
+class AccessChangesNotifier;
+
 /// Implementation of IAccessStorage which keeps all data in memory.
 class MemoryAccessStorage : public IAccessStorage
 {
 public:
     static constexpr char STORAGE_TYPE[] = "memory";
 
-    explicit MemoryAccessStorage(const String & storage_name_ = STORAGE_TYPE);
+    explicit MemoryAccessStorage(const String & storage_name_, AccessChangesNotifier & changes_notifier_);
 
     const char * getStorageType() const override { return STORAGE_TYPE; }
 
@@ -24,8 +26,6 @@ public:
     void setAll(const std::vector<std::pair<UUID, AccessEntityPtr>> & all_entities);
 
     bool exists(const UUID & id) const override;
-    bool hasSubscription(const UUID & id) const override;
-    bool hasSubscription(AccessEntityType type) const override;
 
 private:
     std::optional<UUID> findImpl(AccessEntityType type, const String & name) const override;
@@ -34,25 +34,20 @@ private:
     std::optional<UUID> insertImpl(const AccessEntityPtr & entity, bool replace_if_exists, bool throw_if_exists) override;
     bool removeImpl(const UUID & id, bool throw_if_not_exists) override;
     bool updateImpl(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists) override;
-    scope_guard subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const override;
-    scope_guard subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const override;
+
+    bool insertNoLock(const UUID & id, const AccessEntityPtr & entity, bool replace_if_exists, bool throw_if_exists);
+    bool removeNoLock(const UUID & id, bool throw_if_not_exists);
+    bool updateNoLock(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists);
 
     struct Entry
     {
         UUID id;
         AccessEntityPtr entity;
-        mutable std::list<OnChangedHandler> handlers_by_id;
     };
 
-    bool insertNoLock(const UUID & id, const AccessEntityPtr & entity, bool replace_if_exists, bool throw_if_exists, Notifications & notifications);
-    bool removeNoLock(const UUID & id, bool throw_if_not_exists, Notifications & notifications);
-    bool updateNoLock(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists, Notifications & notifications);
-    void setAllNoLock(const std::vector<std::pair<UUID, AccessEntityPtr>> & all_entities, Notifications & notifications);
-    void prepareNotifications(const Entry & entry, bool remove, Notifications & notifications) const;
-
-    mutable std::recursive_mutex mutex;
+    mutable std::mutex mutex;
     std::unordered_map<UUID, Entry> entries_by_id; /// We want to search entries both by ID and by the pair of name and type.
     std::unordered_map<String, Entry *> entries_by_name_and_type[static_cast<size_t>(AccessEntityType::MAX)];
-    mutable std::list<OnChangedHandler> handlers_by_type[static_cast<size_t>(AccessEntityType::MAX)];
+    AccessChangesNotifier & changes_notifier;
 };
 }

src/Access/MultipleAccessStorage.cpp

@@ -45,7 +45,6 @@ void MultipleAccessStorage::setStorages(const std::vector<StoragePtr> & storages
     std::unique_lock lock{mutex};
     nested_storages = std::make_shared<const Storages>(storages);
     ids_cache.reset();
-    updateSubscriptionsToNestedStorages(lock);
 }
 
 void MultipleAccessStorage::addStorage(const StoragePtr & new_storage)
@@ -56,7 +55,6 @@ void MultipleAccessStorage::addStorage(const StoragePtr & new_storage)
     auto new_storages = std::make_shared<Storages>(*nested_storages);
     new_storages->push_back(new_storage);
     nested_storages = new_storages;
-    updateSubscriptionsToNestedStorages(lock);
 }
 
 void MultipleAccessStorage::removeStorage(const StoragePtr & storage_to_remove)
@@ -70,7 +68,6 @@ void MultipleAccessStorage::removeStorage(const StoragePtr & storage_to_remove)
     new_storages->erase(new_storages->begin() + index);
     nested_storages = new_storages;
     ids_cache.reset();
-    updateSubscriptionsToNestedStorages(lock);
 }
 
 std::vector<StoragePtr> MultipleAccessStorage::getStorages()
@@ -225,6 +222,28 @@ bool MultipleAccessStorage::isReadOnly(const UUID & id) const
 }
 
 
+void MultipleAccessStorage::reload()
+{
+    auto storages = getStoragesInternal();
+    for (const auto & storage : *storages)
+        storage->reload();
+}
+
+void MultipleAccessStorage::startPeriodicReloading()
+{
+    auto storages = getStoragesInternal();
+    for (const auto & storage : *storages)
+        storage->startPeriodicReloading();
+}
+
+void MultipleAccessStorage::stopPeriodicReloading()
+{
+    auto storages = getStoragesInternal();
+    for (const auto & storage : *storages)
+        storage->stopPeriodicReloading();
+}
+
+
 std::optional<UUID> MultipleAccessStorage::insertImpl(const AccessEntityPtr & entity, bool replace_if_exists, bool throw_if_exists)
 {
     std::shared_ptr<IAccessStorage> storage_for_insertion;
@@ -310,145 +329,6 @@ bool MultipleAccessStorage::updateImpl(const UUID & id, const UpdateFunc & updat
 }
 
 
-scope_guard MultipleAccessStorage::subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const
-{
-    auto storage = findStorage(id);
-    if (!storage)
-        return {};
-    return storage->subscribeForChanges(id, handler);
-}
-
-
-bool MultipleAccessStorage::hasSubscription(const UUID & id) const
-{
-    auto storages = getStoragesInternal();
-    for (const auto & storage : *storages)
-    {
-        if (storage->hasSubscription(id))
-            return true;
-    }
-    return false;
-}
-
-
-scope_guard MultipleAccessStorage::subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const
-{
-    std::unique_lock lock{mutex};
-    auto & handlers = handlers_by_type[static_cast<size_t>(type)];
-    handlers.push_back(handler);
-    auto handler_it = std::prev(handlers.end());
-    if (handlers.size() == 1)
-        updateSubscriptionsToNestedStorages(lock);
-
-    return [this, type, handler_it]
-    {
-        std::unique_lock lock2{mutex};
-        auto & handlers2 = handlers_by_type[static_cast<size_t>(type)];
-        handlers2.erase(handler_it);
-        if (handlers2.empty())
-            updateSubscriptionsToNestedStorages(lock2);
-    };
-}
-
-
-bool MultipleAccessStorage::hasSubscription(AccessEntityType type) const
-{
-    std::lock_guard lock{mutex};
-    const auto & handlers = handlers_by_type[static_cast<size_t>(type)];
-    return !handlers.empty();
-}
-
-
-/// Updates subscriptions to nested storages.
-/// We need the subscriptions to the nested storages if someone has subscribed to us.
-/// If any of the nested storages is changed we call our subscribers.
-void MultipleAccessStorage::updateSubscriptionsToNestedStorages(std::unique_lock<std::mutex> & lock) const
-{
-    /// lock is already locked.
-
-    std::vector<std::pair<StoragePtr, scope_guard>> added_subscriptions[static_cast<size_t>(AccessEntityType::MAX)];
-    std::vector<scope_guard> removed_subscriptions;
-
-    for (auto type : collections::range(AccessEntityType::MAX))
-    {
-        auto & handlers = handlers_by_type[static_cast<size_t>(type)];
-        auto & subscriptions = subscriptions_to_nested_storages[static_cast<size_t>(type)];
-        if (handlers.empty())
-        {
-            /// None has subscribed to us, we need no subscriptions to the nested storages.
-            for (auto & subscription : subscriptions | boost::adaptors::map_values)
-                removed_subscriptions.push_back(std::move(subscription));
-            subscriptions.clear();
-        }
-        else
-        {
-            /// Someone has subscribed to us, now we need to have a subscription to each nested storage.
-            for (auto it = subscriptions.begin(); it != subscriptions.end();)
-            {
-                const auto & storage = it->first;
-                auto & subscription = it->second;
-                if (boost::range::find(*nested_storages, storage) == nested_storages->end())
-                {
-                    removed_subscriptions.push_back(std::move(subscription));
-                    it = subscriptions.erase(it);
-                }
-                else
-                    ++it;
-            }
-
-            for (const auto & storage : *nested_storages)
-            {
-                if (!subscriptions.contains(storage))
-                    added_subscriptions[static_cast<size_t>(type)].push_back({storage, nullptr});
-            }
-        }
-    }
-
-    /// Unlock the mutex temporarily because it's much better to subscribe to the nested storages
-    /// with the mutex unlocked.
-    lock.unlock();
-    removed_subscriptions.clear();
-
-    for (auto type : collections::range(AccessEntityType::MAX))
-    {
-        if (!added_subscriptions[static_cast<size_t>(type)].empty())
-        {
-            auto on_changed = [this, type](const UUID & id, const AccessEntityPtr & entity)
-            {
-                Notifications notifications;
-                SCOPE_EXIT({ notify(notifications); });
-                std::lock_guard lock2{mutex};
-                for (const auto & handler : handlers_by_type[static_cast<size_t>(type)])
-                    notifications.push_back({handler, id, entity});
-            };
-            for (auto & [storage, subscription] : added_subscriptions[static_cast<size_t>(type)])
-                subscription = storage->subscribeForChanges(type, on_changed);
-        }
-    }
-
-    /// Lock the mutex again to store added subscriptions to the nested storages.
-    lock.lock();
-
-    for (auto type : collections::range(AccessEntityType::MAX))
-    {
-        if (!added_subscriptions[static_cast<size_t>(type)].empty())
-        {
-            auto & subscriptions = subscriptions_to_nested_storages[static_cast<size_t>(type)];
-            for (auto & [storage, subscription] : added_subscriptions[static_cast<size_t>(type)])
-            {
-                if (!subscriptions.contains(storage) && (boost::range::find(*nested_storages, storage) != nested_storages->end())
-                    && !handlers_by_type[static_cast<size_t>(type)].empty())
-                {
-                    subscriptions.emplace(std::move(storage), std::move(subscription));
-                }
-            }
-        }
-    }
-
-    lock.unlock();
-}
-
-
 std::optional<UUID>
 MultipleAccessStorage::authenticateImpl(const Credentials & credentials, const Poco::Net::IPAddress & address,
                                         const ExternalAuthenticators & external_authenticators,

src/Access/MultipleAccessStorage.h

@@ -24,6 +24,10 @@ public:
     bool isReadOnly() const override;
     bool isReadOnly(const UUID & id) const override;
 
+    void reload() override;
+    void startPeriodicReloading() override;
+    void stopPeriodicReloading() override;
+
     void setStorages(const std::vector<StoragePtr> & storages);
     void addStorage(const StoragePtr & new_storage);
     void removeStorage(const StoragePtr & storage_to_remove);
@@ -37,8 +41,6 @@ public:
     StoragePtr getStorage(const UUID & id);
 
     bool exists(const UUID & id) const override;
-    bool hasSubscription(const UUID & id) const override;
-    bool hasSubscription(AccessEntityType type) const override;
 
 protected:
     std::optional<UUID> findImpl(AccessEntityType type, const String & name) const override;
@@ -48,19 +50,14 @@ protected:
     std::optional<UUID> insertImpl(const AccessEntityPtr & entity, bool replace_if_exists, bool throw_if_exists) override;
     bool removeImpl(const UUID & id, bool throw_if_not_exists) override;
     bool updateImpl(const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists) override;
-    scope_guard subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const override;
-    scope_guard subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const override;
     std::optional<UUID> authenticateImpl(const Credentials & credentials, const Poco::Net::IPAddress & address, const ExternalAuthenticators & external_authenticators, bool throw_if_user_not_exists, bool allow_no_password, bool allow_plaintext_password) const override;
 
 private:
     using Storages = std::vector<StoragePtr>;
     std::shared_ptr<const Storages> getStoragesInternal() const;
-    void updateSubscriptionsToNestedStorages(std::unique_lock<std::mutex> & lock) const;
 
     std::shared_ptr<const Storages> nested_storages;
     mutable LRUCache<UUID, Storage> ids_cache;
-    mutable std::list<OnChangedHandler> handlers_by_type[static_cast<size_t>(AccessEntityType::MAX)];
-    mutable std::unordered_map<StoragePtr, scope_guard> subscriptions_to_nested_storages[static_cast<size_t>(AccessEntityType::MAX)];
     mutable std::mutex mutex;
 };
 

src/Access/ReplicatedAccessStorage.cpp

@@ -1,12 +1,14 @@
 #include <Access/AccessEntityIO.h>
 #include <Access/MemoryAccessStorage.h>
 #include <Access/ReplicatedAccessStorage.h>
+#include <Access/AccessChangesNotifier.h>
 #include <IO/ReadHelpers.h>
 #include <boost/container/flat_set.hpp>
 #include <Common/ZooKeeper/KeeperException.h>
 #include <Common/ZooKeeper/Types.h>
 #include <Common/ZooKeeper/ZooKeeper.h>
 #include <Common/escapeForFileName.h>
+#include <Common/setThreadName.h>
 #include <base/range.h>
 #include <base/sleep.h>
 
@@ -30,11 +32,13 @@ static UUID parseUUID(const String & text)
 ReplicatedAccessStorage::ReplicatedAccessStorage(
     const String & storage_name_,
     const String & zookeeper_path_,
-    zkutil::GetZooKeeper get_zookeeper_)
+    zkutil::GetZooKeeper get_zookeeper_,
+    AccessChangesNotifier & changes_notifier_)
     : IAccessStorage(storage_name_)
     , zookeeper_path(zookeeper_path_)
     , get_zookeeper(get_zookeeper_)
-    , refresh_queue(std::numeric_limits<size_t>::max())
+    , watched_queue(std::make_shared<ConcurrentBoundedQueue<UUID>>(std::numeric_limits<size_t>::max()))
+    , changes_notifier(changes_notifier_)
 {
     if (zookeeper_path.empty())
         throw Exception("ZooKeeper path must be non-empty", ErrorCodes::BAD_ARGUMENTS);
@@ -45,29 +49,30 @@ ReplicatedAccessStorage::ReplicatedAccessStorage(
     /// If zookeeper chroot prefix is used, path should start with '/', because chroot concatenates without it.
     if (zookeeper_path.front() != '/')
         zookeeper_path = "/" + zookeeper_path;
+
+    initializeZookeeper();
 }
 
 ReplicatedAccessStorage::~ReplicatedAccessStorage()
 {
-    ReplicatedAccessStorage::shutdown();
+    stopWatchingThread();
 }
 
-
-void ReplicatedAccessStorage::startup()
+void ReplicatedAccessStorage::startWatchingThread()
 {
-    initializeZookeeper();
-    worker_thread = ThreadFromGlobalPool(&ReplicatedAccessStorage::runWorkerThread, this);
+    bool prev_watching_flag = watching.exchange(true);
+    if (!prev_watching_flag)
+        watching_thread = ThreadFromGlobalPool(&ReplicatedAccessStorage::runWatchingThread, this);
 }
 
-void ReplicatedAccessStorage::shutdown()
+void ReplicatedAccessStorage::stopWatchingThread()
 {
-    bool prev_stop_flag = stop_flag.exchange(true);
-    if (!prev_stop_flag)
+    bool prev_watching_flag = watching.exchange(false);
+    if (prev_watching_flag)
     {
-        refresh_queue.finish();
-
-        if (worker_thread.joinable())
-            worker_thread.join();
+        watched_queue->finish();
+        if (watching_thread.joinable())
+            watching_thread.join();
     }
 }
 
@@ -105,10 +110,8 @@ std::optional<UUID> ReplicatedAccessStorage::insertImpl(const AccessEntityPtr &
     if (!ok)
         return std::nullopt;
 
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
     std::lock_guard lock{mutex};
-    refreshEntityNoLock(zookeeper, id, notifications);
+    refreshEntityNoLock(zookeeper, id);
     return id;
 }
 
@@ -207,10 +210,8 @@ bool ReplicatedAccessStorage::removeImpl(const UUID & id, bool throw_if_not_exis
     if (!ok)
         return false;
 
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
     std::lock_guard lock{mutex};
-    removeEntityNoLock(id, notifications);
+    removeEntityNoLock(id);
     return true;
 }
 
@@ -261,10 +262,8 @@ bool ReplicatedAccessStorage::updateImpl(const UUID & id, const UpdateFunc & upd
     if (!ok)
         return false;
 
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
     std::lock_guard lock{mutex};
-    refreshEntityNoLock(zookeeper, id, notifications);
+    refreshEntityNoLock(zookeeper, id);
     return true;
 }
 
@@ -328,16 +327,18 @@ bool ReplicatedAccessStorage::updateZooKeeper(const zkutil::ZooKeeperPtr & zooke
 }
 
 
-void ReplicatedAccessStorage::runWorkerThread()
+void ReplicatedAccessStorage::runWatchingThread()
 {
-    LOG_DEBUG(getLogger(), "Started worker thread");
-    while (!stop_flag)
+    LOG_DEBUG(getLogger(), "Started watching thread");
+    setThreadName("ReplACLWatch");
+    while (watching)
     {
         try
         {
             if (!initialized)
                 initializeZookeeper();
-            refresh();
+            if (refresh())
+                changes_notifier.sendNotifications();
         }
         catch (...)
         {
@@ -353,7 +354,7 @@ void ReplicatedAccessStorage::resetAfterError()
     initialized = false;
 
     UUID id;
-    while (refresh_queue.tryPop(id)) {}
+    while (watched_queue->tryPop(id)) {}
 
     std::lock_guard lock{mutex};
     for (const auto type : collections::range(AccessEntityType::MAX))
@@ -389,21 +390,20 @@ void ReplicatedAccessStorage::createRootNodes(const zkutil::ZooKeeperPtr & zooke
     }
 }
 
-void ReplicatedAccessStorage::refresh()
+bool ReplicatedAccessStorage::refresh()
 {
     UUID id;
-    if (refresh_queue.tryPop(id, /* timeout_ms: */ 10000))
-    {
-        if (stop_flag)
-            return;
+    if (!watched_queue->tryPop(id, /* timeout_ms: */ 10000))
+        return false;
 
-        auto zookeeper = get_zookeeper();
+    auto zookeeper = get_zookeeper();
 
-        if (id == UUIDHelpers::Nil)
-            refreshEntities(zookeeper);
-        else
-            refreshEntity(zookeeper, id);
-    }
+    if (id == UUIDHelpers::Nil)
+        refreshEntities(zookeeper);
+    else
+        refreshEntity(zookeeper, id);
+
+    return true;
 }
 
 
@@ -412,9 +412,9 @@ void ReplicatedAccessStorage::refreshEntities(const zkutil::ZooKeeperPtr & zooke
     LOG_DEBUG(getLogger(), "Refreshing entities list");
 
     const String zookeeper_uuids_path = zookeeper_path + "/uuid";
-    auto watch_entities_list = [this](const Coordination::WatchResponse &)
+    auto watch_entities_list = [watched_queue = watched_queue](const Coordination::WatchResponse &)
     {
-        [[maybe_unused]] bool push_result = refresh_queue.push(UUIDHelpers::Nil);
+        [[maybe_unused]] bool push_result = watched_queue->push(UUIDHelpers::Nil);
     };
     Coordination::Stat stat;
     const auto entity_uuid_strs = zookeeper->getChildrenWatch(zookeeper_uuids_path, &stat, watch_entities_list);
@@ -424,8 +424,6 @@ void ReplicatedAccessStorage::refreshEntities(const zkutil::ZooKeeperPtr & zooke
     for (const String & entity_uuid_str : entity_uuid_strs)
         entity_uuids.insert(parseUUID(entity_uuid_str));
 
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
     std::lock_guard lock{mutex};
 
     std::vector<UUID> entities_to_remove;
@@ -437,14 +435,14 @@ void ReplicatedAccessStorage::refreshEntities(const zkutil::ZooKeeperPtr & zooke
             entities_to_remove.push_back(entity_uuid);
     }
     for (const auto & entity_uuid : entities_to_remove)
-        removeEntityNoLock(entity_uuid, notifications);
+        removeEntityNoLock(entity_uuid);
 
     /// Locally add entities that were added to ZooKeeper
     for (const auto & entity_uuid : entity_uuids)
     {
         const auto it = entries_by_id.find(entity_uuid);
         if (it == entries_by_id.end())
-            refreshEntityNoLock(zookeeper, entity_uuid, notifications);
+            refreshEntityNoLock(zookeeper, entity_uuid);
     }
 
     LOG_DEBUG(getLogger(), "Refreshing entities list finished");
@@ -452,21 +450,18 @@ void ReplicatedAccessStorage::refreshEntities(const zkutil::ZooKeeperPtr & zooke
 
 void ReplicatedAccessStorage::refreshEntity(const zkutil::ZooKeeperPtr & zookeeper, const UUID & id)
 {
-    Notifications notifications;
-    SCOPE_EXIT({ notify(notifications); });
     std::lock_guard lock{mutex};
-
-    refreshEntityNoLock(zookeeper, id, notifications);
+    refreshEntityNoLock(zookeeper, id);
 }
 
-void ReplicatedAccessStorage::refreshEntityNoLock(const zkutil::ZooKeeperPtr & zookeeper, const UUID & id, Notifications & notifications)
+void ReplicatedAccessStorage::refreshEntityNoLock(const zkutil::ZooKeeperPtr & zookeeper, const UUID & id)
 {
     LOG_DEBUG(getLogger(), "Refreshing entity {}", toString(id));
 
-    const auto watch_entity = [this, id](const Coordination::WatchResponse & response)
+    const auto watch_entity = [watched_queue = watched_queue, id](const Coordination::WatchResponse & response)
     {
         if (response.type == Coordination::Event::CHANGED)
-            [[maybe_unused]] bool push_result = refresh_queue.push(id);
+            [[maybe_unused]] bool push_result = watched_queue->push(id);
     };
     Coordination::Stat entity_stat;
     const String entity_path = zookeeper_path + "/uuid/" + toString(id);
@@ -475,16 +470,16 @@ void ReplicatedAccessStorage::refreshEntityNoLock(const zkutil::ZooKeeperPtr & z
     if (exists)
     {
         const AccessEntityPtr entity = deserializeAccessEntity(entity_definition, entity_path);
-        setEntityNoLock(id, entity, notifications);
+        setEntityNoLock(id, entity);
     }
     else
     {
-        removeEntityNoLock(id, notifications);
+        removeEntityNoLock(id);
     }
 }
 
 
-void ReplicatedAccessStorage::setEntityNoLock(const UUID & id, const AccessEntityPtr & entity, Notifications & notifications)
+void ReplicatedAccessStorage::setEntityNoLock(const UUID & id, const AccessEntityPtr & entity)
 {
     LOG_DEBUG(getLogger(), "Setting id {} to entity named {}", toString(id), entity->getName());
     const AccessEntityType type = entity->getType();
@@ -494,12 +489,14 @@ void ReplicatedAccessStorage::setEntityNoLock(const UUID & id, const AccessEntit
     auto & entries_by_name = entries_by_name_and_type[static_cast<size_t>(type)];
     if (auto it = entries_by_name.find(name); it != entries_by_name.end() && it->second->id != id)
     {
-        removeEntityNoLock(it->second->id, notifications);
+        removeEntityNoLock(it->second->id);
     }
 
     /// If the entity already exists under a different type+name, remove old type+name
+    bool existed_before = false;
     if (auto it = entries_by_id.find(id); it != entries_by_id.end())
     {
+        existed_before = true;
         const AccessEntityPtr & existing_entity = it->second.entity;
         const AccessEntityType existing_type = existing_entity->getType();
         const String & existing_name = existing_entity->getName();
@@ -514,11 +511,18 @@ void ReplicatedAccessStorage::setEntityNoLock(const UUID & id, const AccessEntit
     entry.id = id;
     entry.entity = entity;
     entries_by_name[name] = &entry;
-    prepareNotifications(entry, false, notifications);
+
+    if (initialized)
+    {
+        if (existed_before)
+            changes_notifier.onEntityUpdated(id, entity);
+        else
+            changes_notifier.onEntityAdded(id, entity);
+    }
 }
 
 
-void ReplicatedAccessStorage::removeEntityNoLock(const UUID & id, Notifications & notifications)
+void ReplicatedAccessStorage::removeEntityNoLock(const UUID & id)
 {
     LOG_DEBUG(getLogger(), "Removing entity with id {}", toString(id));
     const auto it = entries_by_id.find(id);
@@ -531,7 +535,6 @@ void ReplicatedAccessStorage::removeEntityNoLock(const UUID & id, Notifications
     const Entry & entry = it->second;
     const AccessEntityType type = entry.entity->getType();
     const String & name = entry.entity->getName();
-    prepareNotifications(entry, true, notifications);
 
     auto & entries_by_name = entries_by_name_and_type[static_cast<size_t>(type)];
     const auto name_it = entries_by_name.find(name);
@@ -542,8 +545,11 @@ void ReplicatedAccessStorage::removeEntityNoLock(const UUID & id, Notifications
     else
         entries_by_name.erase(name);
 
+    UUID removed_id = id;
     entries_by_id.erase(id);
     LOG_DEBUG(getLogger(), "Removed entity with id {}", toString(id));
+
+    changes_notifier.onEntityRemoved(removed_id, type);
 }
 
 
@@ -594,73 +600,4 @@ AccessEntityPtr ReplicatedAccessStorage::readImpl(const UUID & id, bool throw_if
     return entry.entity;
 }
 
-
-void ReplicatedAccessStorage::prepareNotifications(const Entry & entry, bool remove, Notifications & notifications) const
-{
-    const AccessEntityPtr entity = remove ? nullptr : entry.entity;
-    for (const auto & handler : entry.handlers_by_id)
-        notifications.push_back({handler, entry.id, entity});
-
-    for (const auto & handler : handlers_by_type[static_cast<size_t>(entry.entity->getType())])
-        notifications.push_back({handler, entry.id, entity});
-}
-
-
-scope_guard ReplicatedAccessStorage::subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const
-{
-    std::lock_guard lock{mutex};
-    auto & handlers = handlers_by_type[static_cast<size_t>(type)];
-    handlers.push_back(handler);
-    auto handler_it = std::prev(handlers.end());
-
-    return [this, type, handler_it]
-    {
-        std::lock_guard lock2{mutex};
-        auto & handlers2 = handlers_by_type[static_cast<size_t>(type)];
-        handlers2.erase(handler_it);
-    };
-}
-
-
-scope_guard ReplicatedAccessStorage::subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const
-{
-    std::lock_guard lock{mutex};
-    const auto it = entries_by_id.find(id);
-    if (it == entries_by_id.end())
-        return {};
-    const Entry & entry = it->second;
-    auto handler_it = entry.handlers_by_id.insert(entry.handlers_by_id.end(), handler);
-
-    return [this, id, handler_it]
-    {
-        std::lock_guard lock2{mutex};
-        auto it2 = entries_by_id.find(id);
-        if (it2 != entries_by_id.end())
-        {
-            const Entry & entry2 = it2->second;
-            entry2.handlers_by_id.erase(handler_it);
-        }
-    };
-}
-
-
-bool ReplicatedAccessStorage::hasSubscription(const UUID & id) const
-{
-    std::lock_guard lock{mutex};
-    const auto & it = entries_by_id.find(id);
-    if (it != entries_by_id.end())
-    {
-        const Entry & entry = it->second;
-        return !entry.handlers_by_id.empty();
-    }
-    return false;
-}
-
-
-bool ReplicatedAccessStorage::hasSubscription(AccessEntityType type) const
-{
-    std::lock_guard lock{mutex};
-    const auto & handlers = handlers_by_type[static_cast<size_t>(type)];
-    return !handlers.empty();
-}
 }

src/Access/ReplicatedAccessStorage.h

@@ -18,32 +18,33 @@
 
 namespace DB
 {
+class AccessChangesNotifier;
+
 /// Implementation of IAccessStorage which keeps all data in zookeeper.
 class ReplicatedAccessStorage : public IAccessStorage
 {
 public:
     static constexpr char STORAGE_TYPE[] = "replicated";
 
-    ReplicatedAccessStorage(const String & storage_name, const String & zookeeper_path, zkutil::GetZooKeeper get_zookeeper);
+    ReplicatedAccessStorage(const String & storage_name, const String & zookeeper_path, zkutil::GetZooKeeper get_zookeeper, AccessChangesNotifier & changes_notifier_);
     virtual ~ReplicatedAccessStorage() override;
 
     const char * getStorageType() const override { return STORAGE_TYPE; }
 
-    virtual void startup();
-    virtual void shutdown();
+    void startPeriodicReloading() override { startWatchingThread(); }
+    void stopPeriodicReloading() override { stopWatchingThread(); }
 
     bool exists(const UUID & id) const override;
-    bool hasSubscription(const UUID & id) const override;
-    bool hasSubscription(AccessEntityType type) const override;
 
 private:
     String zookeeper_path;
     zkutil::GetZooKeeper get_zookeeper;
 
     std::atomic<bool> initialized = false;
-    std::atomic<bool> stop_flag = false;
-    ThreadFromGlobalPool worker_thread;
-    ConcurrentBoundedQueue<UUID> refresh_queue;
+
+    std::atomic<bool> watching = false;
+    ThreadFromGlobalPool watching_thread;
+    std::shared_ptr<ConcurrentBoundedQueue<UUID>> watched_queue;
 
     std::optional<UUID> insertImpl(const AccessEntityPtr & entity, bool replace_if_exists, bool throw_if_exists) override;
     bool removeImpl(const UUID & id, bool throw_if_not_exists) override;
@@ -53,37 +54,36 @@ private:
     bool removeZooKeeper(const zkutil::ZooKeeperPtr & zookeeper, const UUID & id, bool throw_if_not_exists);
     bool updateZooKeeper(const zkutil::ZooKeeperPtr & zookeeper, const UUID & id, const UpdateFunc & update_func, bool throw_if_not_exists);
 
-    void runWorkerThread();
-    void resetAfterError();
     void initializeZookeeper();
     void createRootNodes(const zkutil::ZooKeeperPtr & zookeeper);
 
-    void refresh();
+    void startWatchingThread();
+    void stopWatchingThread();
+
+    void runWatchingThread();
+    void resetAfterError();
+
+    bool refresh();
     void refreshEntities(const zkutil::ZooKeeperPtr & zookeeper);
     void refreshEntity(const zkutil::ZooKeeperPtr & zookeeper, const UUID & id);
-    void refreshEntityNoLock(const zkutil::ZooKeeperPtr & zookeeper, const UUID & id, Notifications & notifications);
+    void refreshEntityNoLock(const zkutil::ZooKeeperPtr & zookeeper, const UUID & id);
 
-    void setEntityNoLock(const UUID & id, const AccessEntityPtr & entity, Notifications & notifications);
-    void removeEntityNoLock(const UUID & id, Notifications & notifications);
+    void setEntityNoLock(const UUID & id, const AccessEntityPtr & entity);
+    void removeEntityNoLock(const UUID & id);
 
     struct Entry
     {
         UUID id;
         AccessEntityPtr entity;
-        mutable std::list<OnChangedHandler> handlers_by_id;
     };
 
     std::optional<UUID> findImpl(AccessEntityType type, const String & name) const override;
     std::vector<UUID> findAllImpl(AccessEntityType type) const override;
     AccessEntityPtr readImpl(const UUID & id, bool throw_if_not_exists) const override;
 
-    void prepareNotifications(const Entry & entry, bool remove, Notifications & notifications) const;
-    scope_guard subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const override;
-    scope_guard subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const override;
-
     mutable std::mutex mutex;
     std::unordered_map<UUID, Entry> entries_by_id;
     std::unordered_map<String, Entry *> entries_by_name_and_type[static_cast<size_t>(AccessEntityType::MAX)];
-    mutable std::list<OnChangedHandler> handlers_by_type[static_cast<size_t>(AccessEntityType::MAX)];
+    AccessChangesNotifier & changes_notifier;
 };
 }

src/Access/RoleCache.cpp

@@ -66,9 +66,6 @@ RoleCache::~RoleCache() = default;
 std::shared_ptr<const EnabledRoles>
 RoleCache::getEnabledRoles(const std::vector<UUID> & roles, const std::vector<UUID> & roles_with_admin_option)
 {
-    /// Declared before `lock` to send notifications after the mutex will be unlocked.
-    scope_guard notifications;
-
     std::lock_guard lock{mutex};
     EnabledRoles::Params params;
     params.current_roles.insert(roles.begin(), roles.end());
@@ -83,13 +80,13 @@ RoleCache::getEnabledRoles(const std::vector<UUID> & roles, const std::vector<UU
     }
 
     auto res = std::shared_ptr<EnabledRoles>(new EnabledRoles(params));
-    collectEnabledRoles(*res, notifications);
+    collectEnabledRoles(*res, nullptr);
     enabled_roles.emplace(std::move(params), res);
     return res;
 }
 
 
-void RoleCache::collectEnabledRoles(scope_guard & notifications)
+void RoleCache::collectEnabledRoles(scope_guard * notifications)
 {
     /// `mutex` is already locked.
 
@@ -107,7 +104,7 @@ void RoleCache::collectEnabledRoles(scope_guard & notifications)
 }
 
 
-void RoleCache::collectEnabledRoles(EnabledRoles & enabled, scope_guard & notifications)
+void RoleCache::collectEnabledRoles(EnabledRoles & enabled, scope_guard * notifications)
 {
     /// `mutex` is already locked.
 
@@ -170,7 +167,7 @@ void RoleCache::roleChanged(const UUID & role_id, const RolePtr & changed_role)
         return;
     role_from_cache->first = changed_role;
     cache.update(role_id, role_from_cache);
-    collectEnabledRoles(notifications);
+    collectEnabledRoles(&notifications);
 }
 
 
@@ -181,7 +178,7 @@ void RoleCache::roleRemoved(const UUID & role_id)
 
     std::lock_guard lock{mutex};
     cache.remove(role_id);
-    collectEnabledRoles(notifications);
+    collectEnabledRoles(&notifications);
 }
 
 }

src/Access/RoleCache.h

@@ -24,8 +24,8 @@ public:
         const std::vector<UUID> & current_roles_with_admin_option);
 
 private:
-    void collectEnabledRoles(scope_guard & notifications);
-    void collectEnabledRoles(EnabledRoles & enabled, scope_guard & notifications);
+    void collectEnabledRoles(scope_guard * notifications);
+    void collectEnabledRoles(EnabledRoles & enabled, scope_guard * notifications);
     RolePtr getRole(const UUID & role_id);
     void roleChanged(const UUID & role_id, const RolePtr & changed_role);
     void roleRemoved(const UUID & role_id);

src/Access/UsersConfigAccessStorage.cpp

@@ -4,6 +4,7 @@
 #include <Access/User.h>
 #include <Access/SettingsProfile.h>
 #include <Access/AccessControl.h>
+#include <Access/AccessChangesNotifier.h>
 #include <Dictionaries/IDictionary.h>
 #include <Common/Config/ConfigReloader.h>
 #include <Common/StringUtils/StringUtils.h>
@@ -14,9 +15,6 @@
 #include <Poco/JSON/JSON.h>
 #include <Poco/JSON/Object.h>
 #include <Poco/JSON/Stringifier.h>
-#include <Common/logger_useful.h>
-#include <boost/range/algorithm/copy.hpp>
-#include <boost/range/adaptor/map.hpp>
 #include <cstring>
 #include <filesystem>
 #include <base/FnTraits.h>
@@ -525,8 +523,8 @@ namespace
     }
 }
 
-UsersConfigAccessStorage::UsersConfigAccessStorage(const String & storage_name_, const AccessControl & access_control_)
-    : IAccessStorage(storage_name_), access_control(access_control_)
+UsersConfigAccessStorage::UsersConfigAccessStorage(const String & storage_name_, AccessControl & access_control_)
+    : IAccessStorage(storage_name_), access_control(access_control_), memory_storage(storage_name_, access_control.getChangesNotifier())
 {
 }
 
@@ -605,9 +603,9 @@ void UsersConfigAccessStorage::load(
         std::make_shared<Poco::Event>(),
         [&](Poco::AutoPtr<Poco::Util::AbstractConfiguration> new_config, bool /*initial_loading*/)
         {
-            parseFromConfig(*new_config);
-
             Settings::checkNoSettingNamesAtTopLevel(*new_config, users_config_path);
+            parseFromConfig(*new_config);
+            access_control.getChangesNotifier().sendNotifications();
         },
         /* already_loaded = */ false);
 }
@@ -662,27 +660,4 @@ std::optional<String> UsersConfigAccessStorage::readNameImpl(const UUID & id, bo
     return memory_storage.readName(id, throw_if_not_exists);
 }
 
-
-scope_guard UsersConfigAccessStorage::subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const
-{
-    return memory_storage.subscribeForChanges(id, handler);
-}
-
-
-scope_guard UsersConfigAccessStorage::subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const
-{
-    return memory_storage.subscribeForChanges(type, handler);
-}
-
-
-bool UsersConfigAccessStorage::hasSubscription(const UUID & id) const
-{
-    return memory_storage.hasSubscription(id);
-}
-
-
-bool UsersConfigAccessStorage::hasSubscription(AccessEntityType type) const
-{
-    return memory_storage.hasSubscription(type);
-}
 }

src/Access/UsersConfigAccessStorage.h

@@ -22,7 +22,7 @@ public:
 
     static constexpr char STORAGE_TYPE[] = "users.xml";
 
-    UsersConfigAccessStorage(const String & storage_name_, const AccessControl & access_control_);
+    UsersConfigAccessStorage(const String & storage_name_, AccessControl & access_control_);
     ~UsersConfigAccessStorage() override;
 
     const char * getStorageType() const override { return STORAGE_TYPE; }
@@ -37,13 +37,12 @@ public:
               const String & include_from_path = {},
               const String & preprocessed_dir = {},
               const zkutil::GetZooKeeper & get_zookeeper_function = {});
-    void reload();
-    void startPeriodicReloading();
-    void stopPeriodicReloading();
+
+    void reload() override;
+    void startPeriodicReloading() override;
+    void stopPeriodicReloading() override;
 
     bool exists(const UUID & id) const override;
-    bool hasSubscription(const UUID & id) const override;
-    bool hasSubscription(AccessEntityType type) const override;
 
 private:
     void parseFromConfig(const Poco::Util::AbstractConfiguration & config);
@@ -51,10 +50,8 @@ private:
     std::vector<UUID> findAllImpl(AccessEntityType type) const override;
     AccessEntityPtr readImpl(const UUID & id, bool throw_if_not_exists) const override;
     std::optional<String> readNameImpl(const UUID & id, bool throw_if_not_exists) const override;
-    scope_guard subscribeForChangesImpl(const UUID & id, const OnChangedHandler & handler) const override;
-    scope_guard subscribeForChangesImpl(AccessEntityType type, const OnChangedHandler & handler) const override;
 
-    const AccessControl & access_control;
+    AccessControl & access_control;
     MemoryAccessStorage memory_storage;
     String path;
     std::unique_ptr<ConfigReloader> config_reloader;

src/Access/tests/gtest_replicated_access_storage.cpp

@@ -1,5 +1,6 @@
 #include <gtest/gtest.h>
 #include <Access/ReplicatedAccessStorage.h>
+#include <Access/AccessChangesNotifier.h>
 
 using namespace DB;
 
@@ -12,18 +13,6 @@ namespace ErrorCodes
 }
 
 
-TEST(ReplicatedAccessStorage, ShutdownWithoutStartup)
-{
-    auto get_zk = []()
-    {
-        return std::shared_ptr<zkutil::ZooKeeper>();
-    };
-
-    auto storage = ReplicatedAccessStorage("replicated", "/clickhouse/access", get_zk);
-    storage.shutdown();
-}
-
-
 TEST(ReplicatedAccessStorage, ShutdownWithFailedStartup)
 {
     auto get_zk = []()
@@ -31,16 +20,16 @@ TEST(ReplicatedAccessStorage, ShutdownWithFailedStartup)
         return std::shared_ptr<zkutil::ZooKeeper>();
     };
 
-    auto storage = ReplicatedAccessStorage("replicated", "/clickhouse/access", get_zk);
+    AccessChangesNotifier changes_notifier;
+
     try
     {
-        storage.startup();
+        auto storage = ReplicatedAccessStorage("replicated", "/clickhouse/access", get_zk, changes_notifier);
     }
     catch (Exception & e)
     {
         if (e.code() != ErrorCodes::NO_ZOOKEEPER)
             throw;
     }
-    storage.shutdown();
 }
 

src/Interpreters/Context.cpp

@@ -342,8 +342,6 @@ struct ContextSharedPart
         /// Stop periodic reloading of the configuration files.
         /// This must be done first because otherwise the reloading may pass a changed config
         /// to some destroyed parts of ContextSharedPart.
-        if (access_control)
-            access_control->stopPeriodicReloadingUsersConfigs();
         if (external_dictionaries_loader)
             external_dictionaries_loader->enablePeriodicUpdates(false);
         if (external_user_defined_executable_functions_loader)