ClickHouse/src/Storages/MergeTree/ReplicatedMergeTreeRestartingThread.cpp
2022-08-24 18:32:03 +00:00

411 lines
13 KiB
C++

#include <IO/Operators.h>
#include <Storages/StorageReplicatedMergeTree.h>
#include <Storages/MergeTree/ReplicatedMergeTreeRestartingThread.h>
#include <Storages/MergeTree/ReplicatedMergeTreeQuorumEntry.h>
#include <Storages/MergeTree/ReplicatedMergeTreeAddress.h>
#include <Interpreters/Context.h>
#include <Common/ZooKeeper/KeeperException.h>
#include <Common/randomSeed.h>
#include <boost/algorithm/string/replace.hpp>
namespace ProfileEvents
{
extern const Event ReplicaPartialShutdown;
}
namespace CurrentMetrics
{
extern const Metric ReadonlyReplica;
}
namespace DB
{
namespace ErrorCodes
{
extern const int REPLICA_IS_ALREADY_ACTIVE;
extern const int REPLICA_STATUS_CHANGED;
}
namespace
{
constexpr auto retry_period_ms = 10 * 1000;
}
/// Used to check whether it's us who set node `is_active`, or not.
static String generateActiveNodeIdentifier()
{
return "pid: " + toString(getpid()) + ", random: " + toString(randomSeed());
}
ReplicatedMergeTreeRestartingThread::ReplicatedMergeTreeRestartingThread(StorageReplicatedMergeTree & storage_)
: storage(storage_)
, log_name(storage.getStorageID().getFullTableName() + " (ReplicatedMergeTreeRestartingThread)")
, log(&Poco::Logger::get(log_name))
, active_node_identifier(generateActiveNodeIdentifier())
{
const auto storage_settings = storage.getSettings();
check_period_ms = storage_settings->zookeeper_session_expiration_check_period.totalSeconds() * 1000;
task = storage.getContext()->getSchedulePool().createTask(log_name, [this]{ run(); });
}
void ReplicatedMergeTreeRestartingThread::run()
{
if (need_stop)
return;
size_t reschedule_period_ms = check_period_ms;
try
{
bool replica_is_active = runImpl();
if (!replica_is_active)
reschedule_period_ms = retry_period_ms;
}
catch (const Exception & e)
{
/// We couldn't activate table let's set it into readonly mode
partialShutdown();
tryLogCurrentException(log, __PRETTY_FUNCTION__);
if (e.code() == ErrorCodes::REPLICA_STATUS_CHANGED)
reschedule_period_ms = 0;
}
catch (...)
{
partialShutdown();
tryLogCurrentException(log, __PRETTY_FUNCTION__);
}
if (first_time)
{
if (storage.is_readonly)
{
/// We failed to start replication, table is still readonly, so we should increment the metric. See also setNotReadonly().
CurrentMetrics::add(CurrentMetrics::ReadonlyReplica);
}
/// It does not matter if replication is actually started or not, just notify after the first attempt.
storage.startup_event.set();
first_time = false;
}
if (need_stop)
return;
if (reschedule_period_ms)
task->scheduleAfter(reschedule_period_ms);
else
task->schedule();
}
bool ReplicatedMergeTreeRestartingThread::runImpl()
{
if (!storage.is_readonly && !storage.getZooKeeper()->expired())
return true;
if (first_time)
{
LOG_DEBUG(log, "Activating replica.");
assert(storage.is_readonly);
}
else if (storage.is_readonly)
{
LOG_WARNING(log, "Table was in readonly mode. Will try to activate it.");
}
else if (storage.getZooKeeper()->expired())
{
LOG_WARNING(log, "ZooKeeper session has expired. Switching to a new session.");
partialShutdown();
}
else
{
__builtin_unreachable();
}
try
{
storage.setZooKeeper();
}
catch (const Coordination::Exception &)
{
/// The exception when you try to zookeeper_init usually happens if DNS does not work. We will try to do it again.
tryLogCurrentException(log, __PRETTY_FUNCTION__);
assert(storage.is_readonly);
return false;
}
if (need_stop)
return false;
if (!tryStartup())
{
assert(storage.is_readonly);
return false;
}
setNotReadonly();
/// Start queue processing
storage.background_operations_assignee.start();
storage.queue_updating_task->activateAndSchedule();
storage.mutations_updating_task->activateAndSchedule();
storage.mutations_finalizing_task->activateAndSchedule();
storage.merge_selecting_task->activateAndSchedule();
storage.cleanup_thread.start();
storage.part_check_thread.start();
return true;
}
bool ReplicatedMergeTreeRestartingThread::tryStartup()
{
try
{
removeFailedQuorumParts();
activateReplica();
const auto & zookeeper = storage.getZooKeeper();
const auto storage_settings = storage.getSettings();
storage.cloneReplicaIfNeeded(zookeeper);
try
{
storage.queue.initialize(zookeeper);
storage.queue.load(zookeeper);
storage.queue.createLogEntriesToFetchBrokenParts();
/// pullLogsToQueue() after we mark replica 'is_active' (and after we repair if it was lost);
/// because cleanup_thread doesn't delete log_pointer of active replicas.
storage.queue.pullLogsToQueue(zookeeper, {}, ReplicatedMergeTreeQueue::LOAD);
}
catch (...)
{
std::lock_guard lock(storage.last_queue_update_exception_lock);
storage.last_queue_update_exception = getCurrentExceptionMessage(false);
throw;
}
storage.queue.removeCurrentPartsFromMutations();
storage.last_queue_update_finish_time.store(time(nullptr));
updateQuorumIfWeHavePart();
/// Anything above can throw a KeeperException if something is wrong with ZK.
/// Anything below should not throw exceptions.
storage.partial_shutdown_called = false;
storage.partial_shutdown_event.reset();
return true;
}
catch (...)
{
storage.replica_is_active_node = nullptr;
try
{
throw;
}
catch (const Coordination::Exception & e)
{
LOG_ERROR(log, "Couldn't start replication (table will be in readonly mode): {}. {}", e.what(), DB::getCurrentExceptionMessage(true));
return false;
}
catch (const Exception & e)
{
if (e.code() != ErrorCodes::REPLICA_IS_ALREADY_ACTIVE)
throw;
LOG_ERROR(log, "Couldn't start replication (table will be in readonly mode): {}. {}", e.what(), DB::getCurrentExceptionMessage(true));
return false;
}
}
}
void ReplicatedMergeTreeRestartingThread::removeFailedQuorumParts()
{
auto zookeeper = storage.getZooKeeper();
Strings failed_parts;
if (zookeeper->tryGetChildren(storage.zookeeper_path + "/quorum/failed_parts", failed_parts) != Coordination::Error::ZOK)
return;
/// Firstly, remove parts from ZooKeeper
storage.removePartsFromZooKeeperWithRetries(failed_parts);
for (const auto & part_name : failed_parts)
{
auto part = storage.getPartIfExists(
part_name, {MergeTreeDataPartState::PreActive, MergeTreeDataPartState::Active, MergeTreeDataPartState::Outdated});
if (part)
{
LOG_DEBUG(log, "Found part {} with failed quorum. Moving to detached. This shouldn't happen often.", part_name);
storage.forgetPartAndMoveToDetached(part, "noquorum");
storage.queue.removeFailedQuorumPart(part->info);
}
}
}
void ReplicatedMergeTreeRestartingThread::updateQuorumIfWeHavePart()
{
auto zookeeper = storage.getZooKeeper();
String quorum_str;
if (zookeeper->tryGet(fs::path(storage.zookeeper_path) / "quorum" / "status", quorum_str))
{
ReplicatedMergeTreeQuorumEntry quorum_entry(quorum_str);
if (!quorum_entry.replicas.contains(storage.replica_name)
&& storage.getActiveContainingPart(quorum_entry.part_name))
{
LOG_WARNING(log, "We have part {} but we is not in quorum. Updating quorum. This shouldn't happen often.", quorum_entry.part_name);
storage.updateQuorum(quorum_entry.part_name, false);
}
}
Strings part_names;
String parallel_quorum_parts_path = fs::path(storage.zookeeper_path) / "quorum" / "parallel";
if (zookeeper->tryGetChildren(parallel_quorum_parts_path, part_names) == Coordination::Error::ZOK)
{
for (auto & part_name : part_names)
{
if (zookeeper->tryGet(fs::path(parallel_quorum_parts_path) / part_name, quorum_str))
{
ReplicatedMergeTreeQuorumEntry quorum_entry(quorum_str);
if (!quorum_entry.replicas.contains(storage.replica_name)
&& storage.getActiveContainingPart(part_name))
{
LOG_WARNING(log, "We have part {} but we is not in quorum. Updating quorum. This shouldn't happen often.", part_name);
storage.updateQuorum(part_name, true);
}
}
}
}
}
void ReplicatedMergeTreeRestartingThread::activateReplica()
{
auto zookeeper = storage.getZooKeeper();
/// How other replicas can access this one.
ReplicatedMergeTreeAddress address = storage.getReplicatedMergeTreeAddress();
String is_active_path = fs::path(storage.replica_path) / "is_active";
zookeeper->waitForEphemeralToDisappearIfAny(is_active_path);
/// Simultaneously declare that this replica is active, and update the host.
Coordination::Requests ops;
ops.emplace_back(zkutil::makeCreateRequest(is_active_path, active_node_identifier, zkutil::CreateMode::Ephemeral));
ops.emplace_back(zkutil::makeSetRequest(fs::path(storage.replica_path) / "host", address.toString(), -1));
try
{
zookeeper->multi(ops);
}
catch (const Coordination::Exception & e)
{
String existing_replica_host;
zookeeper->tryGet(fs::path(storage.replica_path) / "host", existing_replica_host);
if (existing_replica_host.empty())
existing_replica_host = "without host node";
else
boost::replace_all(existing_replica_host, "\n", ", ");
if (e.code == Coordination::Error::ZNODEEXISTS)
throw Exception(ErrorCodes::REPLICA_IS_ALREADY_ACTIVE,
"Replica {} appears to be already active ({}). If you're sure it's not, "
"try again in a minute or remove znode {}/is_active manually",
storage.replica_path, existing_replica_host, storage.replica_path);
throw;
}
/// `current_zookeeper` lives for the lifetime of `replica_is_active_node`,
/// since before changing `current_zookeeper`, `replica_is_active_node` object is destroyed in `partialShutdown` method.
storage.replica_is_active_node = zkutil::EphemeralNodeHolder::existing(is_active_path, *storage.current_zookeeper);
}
void ReplicatedMergeTreeRestartingThread::partialShutdown(bool part_of_full_shutdown)
{
setReadonly(part_of_full_shutdown);
ProfileEvents::increment(ProfileEvents::ReplicaPartialShutdown);
storage.partial_shutdown_called = true;
storage.partial_shutdown_event.set();
storage.replica_is_active_node = nullptr;
LOG_TRACE(log, "Waiting for threads to finish");
storage.merge_selecting_task->deactivate();
storage.queue_updating_task->deactivate();
storage.mutations_updating_task->deactivate();
storage.mutations_finalizing_task->deactivate();
storage.cleanup_thread.stop();
storage.part_check_thread.stop();
/// Stop queue processing
{
auto fetch_lock = storage.fetcher.blocker.cancel();
auto merge_lock = storage.merger_mutator.merges_blocker.cancel();
auto move_lock = storage.parts_mover.moves_blocker.cancel();
storage.background_operations_assignee.finish();
}
LOG_TRACE(log, "Threads finished");
}
void ReplicatedMergeTreeRestartingThread::shutdown()
{
/// Stop restarting_thread before stopping other tasks - so that it won't restart them again.
need_stop = true;
task->deactivate();
LOG_TRACE(log, "Restarting thread finished");
/// Stop other tasks.
partialShutdown(/* part_of_full_shutdown */ true);
}
void ReplicatedMergeTreeRestartingThread::setReadonly(bool on_shutdown)
{
bool old_val = false;
bool became_readonly = storage.is_readonly.compare_exchange_strong(old_val, true);
/// Do not increment the metric if replica became readonly due to shutdown.
if (became_readonly && on_shutdown)
return;
if (became_readonly)
CurrentMetrics::add(CurrentMetrics::ReadonlyReplica);
/// Replica was already readonly, but we should decrement the metric, because we are detaching/dropping table.
if (on_shutdown)
CurrentMetrics::sub(CurrentMetrics::ReadonlyReplica);
}
void ReplicatedMergeTreeRestartingThread::setNotReadonly()
{
bool old_val = true;
/// is_readonly is true on startup, but ReadonlyReplica metric is not incremented,
/// because we don't want to change this metric if replication is started successfully.
/// So we should not decrement it when replica stopped being readonly on startup.
if (storage.is_readonly.compare_exchange_strong(old_val, false) && !first_time)
CurrentMetrics::sub(CurrentMetrics::ReadonlyReplica);
}
}