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Fix ExternalLoader without additional mutex.

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This commit is contained in:
Vitaly Baranov 2021-10-13 09:56:34 +03:00
parent 9bc7ca6dd5
commit a140f4127e
2 changed files with 33 additions and 41 deletions
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66
src/Interpreters/ExternalLoader.cpp
View File

@ -133,7 +133,13 @@ public:
settings = settings_;
}
using ObjectConfigsPtr = std::shared_ptr<const std::unordered_map<String /* object's name */, std::shared_ptr<const ObjectConfig>>>;
struct ObjectConfigs
{
std::unordered_map<String /* object's name */, std::shared_ptr<const ObjectConfig>> configs_by_name;
size_t counter = 0;
};
using ObjectConfigsPtr = std::shared_ptr<const ObjectConfigs>;
/// Reads all repositories.
ObjectConfigsPtr read()
@ -336,7 +342,7 @@ private:
need_collect_object_configs = false;
// Generate new result.
auto new_configs = std::make_shared<std::unordered_map<String /* object's name */, std::shared_ptr<const ObjectConfig>>>();
auto new_configs = std::make_shared<ObjectConfigs>();
for (const auto & [repository, repository_info] : repositories)
{
@ -344,8 +350,8 @@ private:
{
for (const auto & [object_name, key_in_config] : file_info.objects)
{
auto already_added_it = new_configs->find(object_name);
if (already_added_it == new_configs->end())
auto already_added_it = new_configs->configs_by_name.find(object_name);
if (already_added_it == new_configs->configs_by_name.end())
{
auto new_config = std::make_shared<ObjectConfig>();
new_config->config = file_info.file_contents;
@ -353,7 +359,7 @@ private:
new_config->repository_name = repository->getName();
new_config->from_temp_repository = repository->isTemporary();
new_config->path = path;
new_configs->emplace(object_name, std::move(new_config));
new_configs->configs_by_name.emplace(object_name, std::move(new_config));
}
else
{
@ -372,6 +378,7 @@ private:
}
}
new_configs->counter = counter++;
object_configs = new_configs;
}
@ -383,6 +390,7 @@ private:
std::unordered_map<Repository *, RepositoryInfo> repositories;
ObjectConfigsPtr object_configs;
bool need_collect_object_configs = false;
size_t counter = 0;
};
@ -433,13 +441,22 @@ public:
if (configs == new_configs)
return;
/// The following check prevents a race when two threads are trying to update configuration
/// at almost the same time:
/// 1) first thread reads a configuration (for example as a part of periodic updates)
/// 2) second thread sets a new configuration (for example after executing CREATE DICTIONARY)
/// 3) first thread sets the configuration it read in 1) and thus discards the changes made in 2).
/// So we use `counter` here to ensure we exchange the current configuration only for a newer one.
if (configs && (configs->counter >= new_configs->counter))
return;
configs = new_configs;
std::vector<String> removed_names;
for (auto & [name, info] : infos)
{
auto new_config_it = new_configs->find(name);
if (new_config_it == new_configs->end())
auto new_config_it = new_configs->configs_by_name.find(name);
if (new_config_it == new_configs->configs_by_name.end())
{
removed_names.emplace_back(name);
}
@ -462,7 +479,7 @@ public:
}
/// Insert to the map those objects which added to the new configuration.
for (const auto & [name, config] : *new_configs)
for (const auto & [name, config] : new_configs->configs_by_name)
{
if (infos.find(name) == infos.end())
{
@ -1198,8 +1215,8 @@ class ExternalLoader::PeriodicUpdater : private boost::noncopyable
public:
static constexpr UInt64 check_period_sec = 5;
PeriodicUpdater(LoadablesConfigReader & config_files_reader_, LoadingDispatcher & loading_dispatcher_, std::recursive_mutex & config_mutex_)
: config_files_reader(config_files_reader_), loading_dispatcher(loading_dispatcher_), config_mutex(config_mutex_)
PeriodicUpdater(LoadablesConfigReader & config_files_reader_, LoadingDispatcher & loading_dispatcher_)
: config_files_reader(config_files_reader_), loading_dispatcher(loading_dispatcher_)
{
}
@ -1242,21 +1259,14 @@ private:
while (!event.wait_for(lock, std::chrono::seconds(check_period_sec), pred))
{
lock.unlock();
{
{
std::lock_guard config_lock{config_mutex};
loading_dispatcher.setConfiguration(config_files_reader.read());
}
loading_dispatcher.reloadOutdated();
}
loading_dispatcher.setConfiguration(config_files_reader.read());
loading_dispatcher.reloadOutdated();
lock.lock();
}
}
LoadablesConfigReader & config_files_reader;
LoadingDispatcher & loading_dispatcher;
std::recursive_mutex & config_mutex;
mutable std::mutex mutex;
bool enabled = false;
ThreadFromGlobalPool thread;
@ -1270,7 +1280,7 @@ ExternalLoader::ExternalLoader(const String & type_name_, Poco::Logger * log_)
[this](auto && a, auto && b, auto && c) { return createObject(a, b, c); },
type_name_,
log_))
, periodic_updater(std::make_unique<PeriodicUpdater>(*config_files_reader, *loading_dispatcher, config_mutex))
, periodic_updater(std::make_unique<PeriodicUpdater>(*config_files_reader, *loading_dispatcher))
, type_name(type_name_)
, log(log_)
{
@ -1282,13 +1292,12 @@ scope_guard ExternalLoader::addConfigRepository(std::unique_ptr<IExternalLoaderC
{
auto * ptr = repository.get();
String name = ptr->getName();
std::lock_guard lock{config_mutex};
config_files_reader->addConfigRepository(std::move(repository));
reloadConfig(name);
return [this, ptr, name]()
{
std::lock_guard config_lock{config_mutex};
config_files_reader->removeConfigRepository(ptr);
reloadConfig(name);
};
@ -1387,10 +1396,7 @@ ReturnType ExternalLoader::load(const FilterByNameFunction & filter) const
template <typename ReturnType, typename>
ReturnType ExternalLoader::loadOrReload(const String & name) const
{
{
std::lock_guard lock{config_mutex};
loading_dispatcher->setConfiguration(config_files_reader->read());
}
loading_dispatcher->setConfiguration(config_files_reader->read());
auto result = loading_dispatcher->tryLoadOrReload<LoadResult>(name, WAIT);
checkLoaded(result, true);
return convertTo<ReturnType>(result);
@ -1399,10 +1405,7 @@ ReturnType ExternalLoader::loadOrReload(const String & name) const
template <typename ReturnType, typename>
ReturnType ExternalLoader::loadOrReload(const FilterByNameFunction & filter) const
{
{
std::lock_guard lock{config_mutex};
loading_dispatcher->setConfiguration(config_files_reader->read());
}
loading_dispatcher->setConfiguration(config_files_reader->read());
auto results = loading_dispatcher->tryLoadOrReload<LoadResults>(filter, WAIT);
checkLoaded(results, true);
return convertTo<ReturnType>(results);
@ -1490,19 +1493,16 @@ void ExternalLoader::checkLoaded(const ExternalLoader::LoadResults & results,
void ExternalLoader::reloadConfig() const
{
std::lock_guard lock{config_mutex};
loading_dispatcher->setConfiguration(config_files_reader->read());
}
void ExternalLoader::reloadConfig(const String & repository_name) const
{
std::lock_guard lock{config_mutex};
loading_dispatcher->setConfiguration(config_files_reader->read(repository_name));
}
void ExternalLoader::reloadConfig(const String & repository_name, const String & path) const
{
std::lock_guard lock{config_mutex};
loading_dispatcher->setConfiguration(config_files_reader->read(repository_name, path));
}

8
src/Interpreters/ExternalLoader.h
View File

@ -219,14 +219,6 @@ private:
LoadablePtr createObject(const String & name, const ObjectConfig & config, const LoadablePtr & previous_version) const;
/// We have to read configuration from LoadablesConfigReader and load configuration using LoadingDispatcher atomically.
/// Otherwise we can read configuration in one thread, then read and load newer configuration in another thread,
/// and then load outdated configuration from the first thread.
/// Remarkably, each class (LoadablesConfigReader, LoadingDispatcher, PeriodicUpdater) has own mutex for own purposes,
/// but it does not save from complex logical race conditions.
/// TODO Refactor dictionaries loading and get rid of this.
mutable std::recursive_mutex config_mutex;
class LoadablesConfigReader;
std::unique_ptr<LoadablesConfigReader> config_files_reader;