ClickHouse/src/Storages/MergeTree/ReplicatedMergeTreeBlockOutputStream.cpp

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#include <Storages/StorageReplicatedMergeTree.h>
#include <Storages/MergeTree/ReplicatedMergeTreeQuorumEntry.h>
#include <Storages/MergeTree/ReplicatedMergeTreeBlockOutputStream.h>
#include <Interpreters/PartLog.h>
#include <DataStreams/IBlockOutputStream.h>
#include <Common/SipHash.h>
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#include <Common/ZooKeeper/KeeperException.h>
#include <IO/Operators.h>
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namespace ProfileEvents
{
extern const Event DuplicatedInsertedBlocks;
}
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namespace DB
{
namespace ErrorCodes
{
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extern const int TOO_FEW_LIVE_REPLICAS;
extern const int UNSATISFIED_QUORUM_FOR_PREVIOUS_WRITE;
extern const int UNEXPECTED_ZOOKEEPER_ERROR;
extern const int NO_ZOOKEEPER;
extern const int READONLY;
extern const int UNKNOWN_STATUS_OF_INSERT;
extern const int INSERT_WAS_DEDUPLICATED;
extern const int TIMEOUT_EXCEEDED;
extern const int NO_ACTIVE_REPLICAS;
extern const int DUPLICATE_DATA_PART;
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extern const int PART_IS_TEMPORARILY_LOCKED;
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extern const int LOGICAL_ERROR;
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}
ReplicatedMergeTreeBlockOutputStream::ReplicatedMergeTreeBlockOutputStream(
StorageReplicatedMergeTree & storage_,
const StorageMetadataPtr & metadata_snapshot_,
size_t quorum_,
size_t quorum_timeout_ms_,
size_t max_parts_per_block_,
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bool quorum_parallel_,
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bool deduplicate_,
bool optimize_on_insert_,
bool is_attach_)
: storage(storage_)
, metadata_snapshot(metadata_snapshot_)
, quorum(quorum_)
, quorum_timeout_ms(quorum_timeout_ms_)
, max_parts_per_block(max_parts_per_block_)
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, quorum_parallel(quorum_parallel_)
, deduplicate(deduplicate_)
, log(&Poco::Logger::get(storage.getLogName() + " (Replicated OutputStream)"))
, optimize_on_insert(optimize_on_insert_)
, is_attach(is_attach_)
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{
/// The quorum value `1` has the same meaning as if it is disabled.
if (quorum == 1)
quorum = 0;
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}
Block ReplicatedMergeTreeBlockOutputStream::getHeader() const
{
return metadata_snapshot->getSampleBlock();
}
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/// Allow to verify that the session in ZooKeeper is still alive.
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static void assertSessionIsNotExpired(zkutil::ZooKeeperPtr & zookeeper)
{
if (!zookeeper)
throw Exception("No ZooKeeper session.", ErrorCodes::NO_ZOOKEEPER);
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if (zookeeper->expired())
throw Exception("ZooKeeper session has been expired.", ErrorCodes::NO_ZOOKEEPER);
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}
void ReplicatedMergeTreeBlockOutputStream::checkQuorumPrecondition(zkutil::ZooKeeperPtr & zookeeper)
{
quorum_info.status_path = storage.zookeeper_path + "/quorum/status";
std::future<Coordination::GetResponse> is_active_future = zookeeper->asyncTryGet(storage.replica_path + "/is_active");
std::future<Coordination::GetResponse> host_future = zookeeper->asyncTryGet(storage.replica_path + "/host");
/// List of live replicas. All of them register an ephemeral node for leader_election.
Coordination::Stat leader_election_stat;
zookeeper->get(storage.zookeeper_path + "/leader_election", &leader_election_stat);
if (leader_election_stat.numChildren < static_cast<int32_t>(quorum))
throw Exception("Number of alive replicas ("
+ toString(leader_election_stat.numChildren) + ") is less than requested quorum (" + toString(quorum) + ").",
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ErrorCodes::TOO_FEW_LIVE_REPLICAS);
/** Is there a quorum for the last part for which a quorum is needed?
* Write of all the parts with the included quorum is linearly ordered.
* This means that at any time there can be only one part,
* for which you need, but not yet reach the quorum.
* Information about this part will be located in `/quorum/status` node.
* If the quorum is reached, then the node is deleted.
*/
String quorum_status;
if (!quorum_parallel && zookeeper->tryGet(quorum_info.status_path, quorum_status))
throw Exception("Quorum for previous write has not been satisfied yet. Status: " + quorum_status,
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ErrorCodes::UNSATISFIED_QUORUM_FOR_PREVIOUS_WRITE);
/// Both checks are implicitly made also later (otherwise there would be a race condition).
auto is_active = is_active_future.get();
auto host = host_future.get();
if (is_active.error == Coordination::Error::ZNONODE || host.error == Coordination::Error::ZNONODE)
throw Exception("Replica is not active right now", ErrorCodes::READONLY);
quorum_info.is_active_node_value = is_active.data;
quorum_info.is_active_node_version = is_active.stat.version;
quorum_info.host_node_version = host.stat.version;
}
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void ReplicatedMergeTreeBlockOutputStream::write(const Block & block)
{
last_block_is_duplicate = false;
auto zookeeper = storage.getZooKeeper();
assertSessionIsNotExpired(zookeeper);
/** If write is with quorum, then we check that the required number of replicas is now live,
* and also that for all previous parts for which quorum is required, this quorum is reached.
* And also check that during the insertion, the replica was not reinitialized or disabled (by the value of `is_active` node).
* TODO Too complex logic, you can do better.
*/
if (quorum)
checkQuorumPrecondition(zookeeper);
auto part_blocks = storage.writer.splitBlockIntoParts(block, max_parts_per_block, metadata_snapshot);
for (auto & current_block : part_blocks)
{
Stopwatch watch;
/// Write part to the filesystem under temporary name. Calculate a checksum.
MergeTreeData::MutableDataPartPtr part = storage.writer.writeTempPart(current_block, metadata_snapshot, optimize_on_insert);
String block_id;
if (deduplicate)
{
SipHash hash;
part->checksums.computeTotalChecksumDataOnly(hash);
union
{
char bytes[16];
UInt64 words[2];
} hash_value;
hash.get128(hash_value.bytes);
/// We add the hash from the data and partition identifier to deduplication ID.
/// That is, do not insert the same data to the same partition twice.
block_id = part->info.partition_id + "_" + toString(hash_value.words[0]) + "_" + toString(hash_value.words[1]);
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LOG_DEBUG(log, "Wrote block with ID '{}', {} rows", block_id, current_block.block.rows());
}
else
{
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LOG_DEBUG(log, "Wrote block with {} rows", current_block.block.rows());
}
try
{
commitPart(zookeeper, part, block_id);
/// Set a special error code if the block is duplicate
int error = (deduplicate && last_block_is_duplicate) ? ErrorCodes::INSERT_WAS_DEDUPLICATED : 0;
PartLog::addNewPart(storage.global_context, part, watch.elapsed(), ExecutionStatus(error));
}
catch (...)
{
PartLog::addNewPart(storage.global_context, part, watch.elapsed(), ExecutionStatus::fromCurrentException(__PRETTY_FUNCTION__));
throw;
}
}
}
void ReplicatedMergeTreeBlockOutputStream::writeExistingPart(MergeTreeData::MutableDataPartPtr & part)
{
last_block_is_duplicate = false;
/// NOTE: No delay in this case. That's Ok.
auto zookeeper = storage.getZooKeeper();
assertSessionIsNotExpired(zookeeper);
if (quorum)
checkQuorumPrecondition(zookeeper);
Stopwatch watch;
try
{
commitPart(zookeeper, part, "");
PartLog::addNewPart(storage.global_context, part, watch.elapsed());
}
catch (...)
{
PartLog::addNewPart(storage.global_context, part, watch.elapsed(), ExecutionStatus::fromCurrentException(__PRETTY_FUNCTION__));
throw;
}
}
void ReplicatedMergeTreeBlockOutputStream::commitPart(
zkutil::ZooKeeperPtr & zookeeper, MergeTreeData::MutableDataPartPtr & part, const String & block_id)
{
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metadata_snapshot->check(part->getColumns());
assertSessionIsNotExpired(zookeeper);
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String temporary_part_relative_path = part->relative_path;
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/// There is one case when we need to retry transaction in a loop.
/// But don't do it too many times - just as defensive measure.
size_t loop_counter = 0;
constexpr size_t max_iterations = 10;
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bool is_already_existing_part = false;
while (true)
{
/// Obtain incremental block number and lock it. The lock holds our intention to add the block to the filesystem.
/// We remove the lock just after renaming the part. In case of exception, block number will be marked as abandoned.
/// Also, make deduplication check. If a duplicate is detected, no nodes are created.
/// Allocate new block number and check for duplicates
bool deduplicate_block = !block_id.empty();
String block_id_path = deduplicate_block ? storage.zookeeper_path + "/blocks/" + block_id : "";
auto block_number_lock = storage.allocateBlockNumber(part->info.partition_id, zookeeper, block_id_path);
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/// Prepare transaction to ZooKeeper
/// It will simultaneously add information about the part to all the necessary places in ZooKeeper and remove block_number_lock.
Coordination::Requests ops;
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Int64 block_number = 0;
String existing_part_name;
if (block_number_lock)
{
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is_already_existing_part = false;
block_number = block_number_lock->getNumber();
/// Set part attributes according to part_number. Prepare an entry for log.
part->info.min_block = block_number;
part->info.max_block = block_number;
part->info.level = 0;
part->info.mutation = 0;
part->name = part->getNewName(part->info);
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StorageReplicatedMergeTree::LogEntry log_entry;
if (is_attach)
{
log_entry.type = StorageReplicatedMergeTree::LogEntry::ATTACH_PART;
/// We don't need to involve ZooKeeper to obtain the checksums as by the time we get
/// the MutableDataPartPtr here, we already have the data thus being able to
/// calculate the checksums.
log_entry.part_checksum = part->checksums.getTotalChecksumHex();
}
else
log_entry.type = StorageReplicatedMergeTree::LogEntry::GET_PART;
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log_entry.create_time = time(nullptr);
log_entry.source_replica = storage.replica_name;
log_entry.new_part_name = part->name;
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/// TODO maybe add UUID here as well?
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log_entry.quorum = quorum;
log_entry.block_id = block_id;
log_entry.new_part_type = part->getType();
ops.emplace_back(zkutil::makeCreateRequest(
storage.zookeeper_path + "/log/log-",
log_entry.toString(),
zkutil::CreateMode::PersistentSequential));
/// Deletes the information that the block number is used for writing.
block_number_lock->getUnlockOps(ops);
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/** If we need a quorum - create a node in which the quorum is monitored.
* (If such a node already exists, then someone has managed to make another quorum record at the same time,
* but for it the quorum has not yet been reached.
* You can not do the next quorum record at this time.)
*/
if (quorum)
{
ReplicatedMergeTreeQuorumEntry quorum_entry;
quorum_entry.part_name = part->name;
quorum_entry.required_number_of_replicas = quorum;
quorum_entry.replicas.insert(storage.replica_name);
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/** At this point, this node will contain information that the current replica received a part.
* When other replicas will receive this part (in the usual way, processing the replication log),
* they will add themselves to the contents of this node.
* When it contains information about `quorum` number of replicas, this node is deleted,
* which indicates that the quorum has been reached.
*/
if (quorum_parallel)
quorum_info.status_path = storage.zookeeper_path + "/quorum/parallel/" + part->name;
ops.emplace_back(
zkutil::makeCreateRequest(
quorum_info.status_path,
quorum_entry.toString(),
zkutil::CreateMode::Persistent));
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/// Make sure that during the insertion time, the replica was not reinitialized or disabled (when the server is finished).
ops.emplace_back(
zkutil::makeCheckRequest(
storage.replica_path + "/is_active",
quorum_info.is_active_node_version));
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/// Unfortunately, just checking the above is not enough, because `is_active`
/// node can be deleted and reappear with the same version.
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/// But then the `host` value will change. We will check this.
/// It's great that these two nodes change in the same transaction (see MergeTreeRestartingThread).
ops.emplace_back(
zkutil::makeCheckRequest(
storage.replica_path + "/host",
quorum_info.host_node_version));
}
}
else
{
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is_already_existing_part = true;
/// This block was already written to some replica. Get the part name for it.
/// Note: race condition with DROP PARTITION operation is possible. User will get "No node" exception and it is Ok.
existing_part_name = zookeeper->get(storage.zookeeper_path + "/blocks/" + block_id);
/// If it exists on our replica, ignore it.
if (storage.getActiveContainingPart(existing_part_name))
{
LOG_INFO(log, "Block with ID {} already exists locally as part {}; ignoring it.", block_id, existing_part_name);
part->is_duplicate = true;
last_block_is_duplicate = true;
ProfileEvents::increment(ProfileEvents::DuplicatedInsertedBlocks);
return;
}
LOG_INFO(log, "Block with ID {} already exists on other replicas as part {}; will write it locally with that name.",
block_id, existing_part_name);
/// If it does not exist, we will write a new part with existing name.
/// Note that it may also appear on filesystem right now in PreCommitted state due to concurrent inserts of the same data.
/// It will be checked when we will try to rename directory.
part->name = existing_part_name;
part->info = MergeTreePartInfo::fromPartName(existing_part_name, storage.format_version);
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/// Used only for exception messages.
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block_number = part->info.min_block;
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/// Do not check for duplicate on commit to ZK.
block_id_path.clear();
}
/// Information about the part.
storage.getCommitPartOps(ops, part, block_id_path);
MergeTreeData::Transaction transaction(storage); /// If you can not add a part to ZK, we'll remove it back from the working set.
bool renamed = false;
try
{
renamed = storage.renameTempPartAndAdd(part, nullptr, &transaction);
}
catch (const Exception & e)
{
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if (e.code() != ErrorCodes::DUPLICATE_DATA_PART
&& e.code() != ErrorCodes::PART_IS_TEMPORARILY_LOCKED)
throw;
}
if (!renamed)
{
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if (is_already_existing_part)
{
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LOG_INFO(log, "Part {} is duplicate and it is already written by concurrent request or fetched; ignoring it.", part->name);
return;
}
else
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throw Exception(ErrorCodes::LOGICAL_ERROR, "Part with name {} is already written by concurrent request."
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" It should not happen for non-duplicate data parts because unique names are assigned for them. It's a bug",
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part->name);
}
Coordination::Responses responses;
Coordination::Error multi_code = zookeeper->tryMultiNoThrow(ops, responses); /// 1 RTT
if (multi_code == Coordination::Error::ZOK)
{
transaction.commit();
storage.merge_selecting_task->schedule();
/// Lock nodes have been already deleted, do not delete them in destructor
if (block_number_lock)
block_number_lock->assumeUnlocked();
}
else if (multi_code == Coordination::Error::ZCONNECTIONLOSS
|| multi_code == Coordination::Error::ZOPERATIONTIMEOUT)
{
/** If the connection is lost, and we do not know if the changes were applied, we can not delete the local part
* if the changes were applied, the inserted block appeared in `/blocks/`, and it can not be inserted again.
*/
transaction.commit();
storage.enqueuePartForCheck(part->name, MAX_AGE_OF_LOCAL_PART_THAT_WASNT_ADDED_TO_ZOOKEEPER);
/// We do not know whether or not data has been inserted.
throw Exception("Unknown status, client must retry. Reason: " + String(Coordination::errorMessage(multi_code)),
ErrorCodes::UNKNOWN_STATUS_OF_INSERT);
}
else if (Coordination::isUserError(multi_code))
{
String failed_op_path = zkutil::KeeperMultiException(multi_code, ops, responses).getPathForFirstFailedOp();
if (multi_code == Coordination::Error::ZNODEEXISTS && deduplicate_block && failed_op_path == block_id_path)
{
/// Block with the same id have just appeared in table (or other replica), rollback thee insertion.
LOG_INFO(log, "Block with ID {} already exists (it was just appeared). Renaming part {} back to {}. Will retry write.",
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block_id, part->name, temporary_part_relative_path);
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/// We will try to add this part again on the new iteration as it's just a new part.
/// So remove it from storage parts set immediately and transfer state to temporary.
transaction.rollbackPartsToTemporaryState();
part->is_temp = true;
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part->renameTo(temporary_part_relative_path, false);
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/// If this part appeared on other replica than it's better to try to write it locally one more time. If it's our part
/// than it will be ignored on the next itration.
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++loop_counter;
if (loop_counter == max_iterations)
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{
part->is_duplicate = true; /// Part is duplicate, just remove it from local FS
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throw Exception("Too many transaction retries - it may indicate an error", ErrorCodes::DUPLICATE_DATA_PART);
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}
continue;
}
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else if (multi_code == Coordination::Error::ZNODEEXISTS && failed_op_path == quorum_info.status_path)
{
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transaction.rollback();
throw Exception("Another quorum insert has been already started", ErrorCodes::UNSATISFIED_QUORUM_FOR_PREVIOUS_WRITE);
}
else
{
/// NOTE: We could be here if the node with the quorum existed, but was quickly removed.
transaction.rollback();
throw Exception("Unexpected logical error while adding block " + toString(block_number) + " with ID '" + block_id + "': "
+ Coordination::errorMessage(multi_code) + ", path " + failed_op_path,
ErrorCodes::UNEXPECTED_ZOOKEEPER_ERROR);
}
}
else if (Coordination::isHardwareError(multi_code))
{
transaction.rollback();
throw Exception("Unrecoverable network error while adding block " + toString(block_number) + " with ID '" + block_id + "': "
+ Coordination::errorMessage(multi_code), ErrorCodes::UNEXPECTED_ZOOKEEPER_ERROR);
}
else
{
transaction.rollback();
throw Exception("Unexpected ZooKeeper error while adding block " + toString(block_number) + " with ID '" + block_id + "': "
+ Coordination::errorMessage(multi_code), ErrorCodes::UNEXPECTED_ZOOKEEPER_ERROR);
}
break;
}
if (quorum)
{
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if (is_already_existing_part)
{
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/// We get duplicate part without fetch
/// Check if this quorum insert is parallel or not
if (zookeeper->exists(storage.zookeeper_path + "/quorum/parallel/" + part->name))
storage.updateQuorum(part->name, true);
else if (zookeeper->exists(storage.zookeeper_path + "/quorum/status"))
storage.updateQuorum(part->name, false);
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}
/// We are waiting for quorum to be satisfied.
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LOG_TRACE(log, "Waiting for quorum");
try
{
while (true)
{
zkutil::EventPtr event = std::make_shared<Poco::Event>();
std::string value;
/// `get` instead of `exists` so that `watch` does not leak if the node is no longer there.
if (!zookeeper->tryGet(quorum_info.status_path, value, nullptr, event))
break;
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LOG_TRACE(log, "Quorum node {} still exists, will wait for updates", quorum_info.status_path);
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ReplicatedMergeTreeQuorumEntry quorum_entry(value);
/// If the node has time to disappear, and then appear again for the next insert.
if (quorum_entry.part_name != part->name)
break;
if (!event->tryWait(quorum_timeout_ms))
throw Exception("Timeout while waiting for quorum", ErrorCodes::TIMEOUT_EXCEEDED);
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LOG_TRACE(log, "Quorum {} updated, will check quorum node still exists", quorum_info.status_path);
}
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/// And what if it is possible that the current replica at this time has ceased to be active
/// and the quorum is marked as failed and deleted?
String value;
if (!zookeeper->tryGet(storage.replica_path + "/is_active", value, nullptr)
|| value != quorum_info.is_active_node_value)
throw Exception("Replica become inactive while waiting for quorum", ErrorCodes::NO_ACTIVE_REPLICAS);
}
catch (...)
{
/// We do not know whether or not data has been inserted
/// - whether other replicas have time to download the part and mark the quorum as done.
throw Exception("Unknown status, client must retry. Reason: " + getCurrentExceptionMessage(false),
ErrorCodes::UNKNOWN_STATUS_OF_INSERT);
}
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LOG_TRACE(log, "Quorum satisfied");
}
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}
void ReplicatedMergeTreeBlockOutputStream::writePrefix()
{
/// Only check "too many parts" before write,
/// because interrupting long-running INSERT query in the middle is not convenient for users.
storage.delayInsertOrThrowIfNeeded(&storage.partial_shutdown_event);
}
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}