ClickHouse/src/Storages/MergeTree/ReplicatedMergeTreeSink.cpp

#include <Storages/StorageReplicatedMergeTree.h>
#include <Storages/MergeTree/ReplicatedMergeTreeQuorumEntry.h>
#include <Storages/MergeTree/ReplicatedMergeTreeSink.h>
#include <DataTypes/ObjectUtils.h>
#include <Interpreters/PartLog.h>
#include <Common/SipHash.h>
#include <Common/ZooKeeper/KeeperException.h>
#include <Core/Block.h>
#include <IO/Operators.h>


namespace ProfileEvents
{
    extern const Event DuplicatedInsertedBlocks;
}

namespace DB
{

namespace ErrorCodes
{
    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;
    extern const int PART_IS_TEMPORARILY_LOCKED;
    extern const int LOGICAL_ERROR;
}

struct ReplicatedMergeTreeSink::DelayedChunk
{
    struct Partition
    {
        MergeTreeDataWriter::TemporaryPart temp_part;
        UInt64 elapsed_ns;
        String block_id;
    };

    DelayedChunk() = default;
    explicit DelayedChunk(size_t replicas_num_) : replicas_num(replicas_num_) {}

    size_t replicas_num = 0;

    std::vector<Partition> partitions;
};

ReplicatedMergeTreeSink::ReplicatedMergeTreeSink(
    StorageReplicatedMergeTree & storage_,
    const StorageMetadataPtr & metadata_snapshot_,
    size_t quorum_size,
    size_t quorum_timeout_ms_,
    size_t max_parts_per_block_,
    bool quorum_parallel_,
    bool deduplicate_,
    bool majority_quorum,
    ContextPtr context_,
    bool is_attach_)
    : SinkToStorage(metadata_snapshot_->getSampleBlock())
    , storage(storage_)
    , metadata_snapshot(metadata_snapshot_)
    , required_quorum_size(majority_quorum ? std::nullopt : std::make_optional<size_t>(quorum_size))
    , quorum_timeout_ms(quorum_timeout_ms_)
    , max_parts_per_block(max_parts_per_block_)
    , is_attach(is_attach_)
    , quorum_parallel(quorum_parallel_)
    , deduplicate(deduplicate_)
    , log(&Poco::Logger::get(storage.getLogName() + " (Replicated OutputStream)"))
    , context(context_)
    , storage_snapshot(storage.getStorageSnapshot(metadata_snapshot, context))
{
    /// The quorum value `1` has the same meaning as if it is disabled.
    if (required_quorum_size == 1)
        required_quorum_size = 0;
}

ReplicatedMergeTreeSink::~ReplicatedMergeTreeSink() = default;

/// Allow to verify that the session in ZooKeeper is still alive.
static void assertSessionIsNotExpired(zkutil::ZooKeeperPtr & zookeeper)
{
    if (!zookeeper)
        throw Exception("No ZooKeeper session.", ErrorCodes::NO_ZOOKEEPER);

    if (zookeeper->expired())
        throw Exception("ZooKeeper session has been expired.", ErrorCodes::NO_ZOOKEEPER);
}

size_t ReplicatedMergeTreeSink::checkQuorumPrecondition(zkutil::ZooKeeperPtr & zookeeper)
{
    if (!isQuorumEnabled())
        return 0;

    quorum_info.status_path = storage.zookeeper_path + "/quorum/status";

    Strings replicas = zookeeper->getChildren(fs::path(storage.zookeeper_path) / "replicas");
    std::vector<std::future<Coordination::ExistsResponse>> replicas_status_futures;
    replicas_status_futures.reserve(replicas.size());
    for (const auto & replica : replicas)
        if (replica != storage.replica_name)
            replicas_status_futures.emplace_back(zookeeper->asyncExists(fs::path(storage.zookeeper_path) / "replicas" / replica / "is_active"));

    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");

    size_t active_replicas = 1;     /// Assume current replica is active (will check below)
    for (auto & status : replicas_status_futures)
        if (status.get().error == Coordination::Error::ZOK)
            ++active_replicas;

    size_t replicas_number = replicas.size();
    size_t quorum_size = getQuorumSize(replicas_number);

    if (active_replicas < quorum_size)
        throw Exception(ErrorCodes::TOO_FEW_LIVE_REPLICAS, "Number of alive replicas ({}) is less than requested quorum ({}/{}).",
                        active_replicas, quorum_size, replicas_number);

    /** 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,
                        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;

    return replicas_number;
}

void ReplicatedMergeTreeSink::consume(Chunk chunk)
{
    auto block = getHeader().cloneWithColumns(chunk.detachColumns());

    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.
      */
    size_t replicas_num = checkQuorumPrecondition(zookeeper);

    deduceTypesOfObjectColumns(storage_snapshot, block);
    auto part_blocks = storage.writer.splitBlockIntoParts(block, max_parts_per_block, metadata_snapshot, context);

    using DelayedPartitions = std::vector<ReplicatedMergeTreeSink::DelayedChunk::Partition>;
    DelayedPartitions partitions;

    size_t streams = 0;
    bool support_parallel_write = false;
    const Settings & settings = context->getSettingsRef();

    for (auto & current_block : part_blocks)
    {
        Stopwatch watch;

        /// Write part to the filesystem under temporary name. Calculate a checksum.

        auto temp_part = storage.writer.writeTempPart(current_block, metadata_snapshot, context);

        /// If optimize_on_insert setting is true, current_block could become empty after merge
        /// and we didn't create part.
        if (!temp_part.part)
            continue;

        String block_id;

        if (deduplicate)
        {
            String block_dedup_token;

            /// 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.

            const String & dedup_token = settings.insert_deduplication_token;
            if (!dedup_token.empty())
            {
                /// multiple blocks can be inserted within the same insert query
                /// an ordinal number is added to dedup token to generate a distinctive block id for each block
                block_dedup_token = fmt::format("{}_{}", dedup_token, chunk_dedup_seqnum);
                ++chunk_dedup_seqnum;
            }

            block_id = temp_part.part->getZeroLevelPartBlockID(block_dedup_token);
            LOG_DEBUG(log, "Wrote block with ID '{}', {} rows{}", block_id, current_block.block.rows(), quorumLogMessage(replicas_num));
        }
        else
        {
            LOG_DEBUG(log, "Wrote block with {} rows{}", current_block.block.rows(), quorumLogMessage(replicas_num));
        }

        UInt64 elapsed_ns = watch.elapsed();

        size_t max_insert_delayed_streams_for_parallel_write = DEFAULT_DELAYED_STREAMS_FOR_PARALLEL_WRITE;
        if (!support_parallel_write || settings.max_insert_delayed_streams_for_parallel_write.changed)
            max_insert_delayed_streams_for_parallel_write = settings.max_insert_delayed_streams_for_parallel_write;

        /// In case of too much columns/parts in block, flush explicitly.
        streams += temp_part.streams.size();
        if (streams > max_insert_delayed_streams_for_parallel_write)
        {
            finishDelayedChunk(zookeeper);
            delayed_chunk = std::make_unique<ReplicatedMergeTreeSink::DelayedChunk>(replicas_num);
            delayed_chunk->partitions = std::move(partitions);
            finishDelayedChunk(zookeeper);

            streams = 0;
            support_parallel_write = false;
            partitions = DelayedPartitions{};
        }

        partitions.emplace_back(ReplicatedMergeTreeSink::DelayedChunk::Partition{
            .temp_part = std::move(temp_part),
            .elapsed_ns = elapsed_ns,
            .block_id = std::move(block_id)
        });
    }

    finishDelayedChunk(zookeeper);
    delayed_chunk = std::make_unique<ReplicatedMergeTreeSink::DelayedChunk>();
    delayed_chunk->partitions = std::move(partitions);

    /// If deduplicated data should not be inserted into MV, we need to set proper
    /// value for `last_block_is_duplicate`, which is possible only after the part is committed.
    /// Othervide we can delay commit.
    /// TODO: we can also delay commit if there is no MVs.
    if (!settings.deduplicate_blocks_in_dependent_materialized_views)
        finishDelayedChunk(zookeeper);
}

void ReplicatedMergeTreeSink::finishDelayedChunk(zkutil::ZooKeeperPtr & zookeeper)
{
    if (!delayed_chunk)
        return;

    last_block_is_duplicate = false;

    for (auto & partition : delayed_chunk->partitions)
    {
        partition.temp_part.finalize();

        auto & part = partition.temp_part.part;

        try
        {
            commitPart(zookeeper, part, partition.block_id, partition.temp_part.builder, delayed_chunk->replicas_num);

            last_block_is_duplicate = last_block_is_duplicate || part->is_duplicate;

            /// Set a special error code if the block is duplicate
            int error = (deduplicate && part->is_duplicate) ? ErrorCodes::INSERT_WAS_DEDUPLICATED : 0;
            PartLog::addNewPart(storage.getContext(), part, partition.elapsed_ns, ExecutionStatus(error));
            storage.incrementInsertedPartsProfileEvent(part->getType());
        }
        catch (...)
        {
            PartLog::addNewPart(storage.getContext(), part, partition.elapsed_ns, ExecutionStatus::fromCurrentException(__PRETTY_FUNCTION__));
            throw;
        }
    }

    delayed_chunk.reset();
}

void ReplicatedMergeTreeSink::writeExistingPart(MergeTreeData::MutableDataPartPtr & part)
{
    /// NOTE: No delay in this case. That's Ok.

    auto zookeeper = storage.getZooKeeper();
    assertSessionIsNotExpired(zookeeper);

    size_t replicas_num = checkQuorumPrecondition(zookeeper);

    Stopwatch watch;

    try
    {
        part->version.setCreationTID(Tx::PrehistoricTID, nullptr);
        commitPart(zookeeper, part, "", part->data_part_storage->getBuilder(), replicas_num);
        PartLog::addNewPart(storage.getContext(), part, watch.elapsed());
    }
    catch (...)
    {
        PartLog::addNewPart(storage.getContext(), part, watch.elapsed(), ExecutionStatus::fromCurrentException(__PRETTY_FUNCTION__));
        throw;
    }
}

void ReplicatedMergeTreeSink::commitPart(
    zkutil::ZooKeeperPtr & zookeeper,
    MergeTreeData::MutableDataPartPtr & part,
    const String & block_id,
    DataPartStorageBuilderPtr builder,
    size_t replicas_num)
{
    metadata_snapshot->check(part->getColumns());
    assertSessionIsNotExpired(zookeeper);

    String temporary_part_relative_path = part->data_part_storage->getPartDirectory();

    /// 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;

    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);

        /// 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;

        Int64 block_number = 0;
        String existing_part_name;
        if (block_number_lock)
        {
            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);

            StorageReplicatedMergeTree::LogEntry log_entry;

            if (is_attach)
            {
                log_entry.type = StorageReplicatedMergeTree::LogEntry::ATTACH_PART;

                /// We don't need to involve ZooKeeper to obtain checksums as by the time we get
                /// 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;

            log_entry.create_time = time(nullptr);
            log_entry.source_replica = storage.replica_name;
            log_entry.new_part_name = part->name;
            /// TODO maybe add UUID here as well?
            log_entry.quorum = getQuorumSize(replicas_num);
            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);

            /** 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 (isQuorumEnabled())
            {
                ReplicatedMergeTreeQuorumEntry quorum_entry;
                quorum_entry.part_name = part->name;
                quorum_entry.required_number_of_replicas = getQuorumSize(replicas_num);
                quorum_entry.replicas.insert(storage.replica_name);

                /** 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));

                /// 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));

                /// Unfortunately, just checking the above is not enough, because `is_active`
                /// node can be deleted and reappear with the same version.
                /// 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
        {
            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))
            {
                part->is_duplicate = true;
                ProfileEvents::increment(ProfileEvents::DuplicatedInsertedBlocks);
                if (isQuorumEnabled())
                {
                    LOG_INFO(log, "Block with ID {} already exists locally as part {}; ignoring it, but checking quorum.", block_id, existing_part_name);

                    std::string quorum_path;
                    if (quorum_parallel)
                        quorum_path = storage.zookeeper_path + "/quorum/parallel/" + existing_part_name;
                    else
                        quorum_path = storage.zookeeper_path + "/quorum/status";

                    waitForQuorum(zookeeper, existing_part_name, quorum_path, quorum_info.is_active_node_value, replicas_num);
                }
                else
                {
                    LOG_INFO(log, "Block with ID {} already exists locally as part {}; ignoring it.", block_id, existing_part_name);
                }

                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 PreActive 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);
            /// Used only for exception messages.
            block_number = part->info.min_block;

            /// Do not check for duplicate on commit to ZK.
            block_id_path.clear();
        }

        /// Information about the part.
        storage.getCommitPartOps(ops, part, block_id_path);

        /// It's important to create it outside of lock scope because
        /// otherwise it can lock parts in destructor and deadlock is possible.
        MergeTreeData::Transaction transaction(storage, NO_TRANSACTION_RAW); /// If you can not add a part to ZK, we'll remove it back from the working set.
        bool renamed = false;

        try
        {
            auto lock = storage.lockParts();
            renamed = storage.renameTempPartAndAdd(part, transaction, builder, lock);
        }
        catch (const Exception & e)
        {
            if (e.code() != ErrorCodes::DUPLICATE_DATA_PART
                && e.code() != ErrorCodes::PART_IS_TEMPORARILY_LOCKED)
                throw;
        }

        if (!renamed)
        {
            if (is_already_existing_part)
            {
                LOG_INFO(log, "Part {} is duplicate and it is already written by concurrent request or fetched; ignoring it.", part->name);
                return;
            }
            else
                throw Exception(ErrorCodes::LOGICAL_ERROR, "Part with name {} is already written by concurrent request."
                    " It should not happen for non-duplicate data parts because unique names are assigned for them. It's a bug",
                    part->name);
        }

        storage.lockSharedData(*part, false, {});

        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.",
                    block_id, part->name, temporary_part_relative_path);

                /// 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;
                part->renameTo(temporary_part_relative_path, false, builder);
                builder->commit();

                /// 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.
                ++loop_counter;
                if (loop_counter == max_iterations)
                {
                    part->is_duplicate = true; /// Part is duplicate, just remove it from local FS
                    throw Exception("Too many transaction retries - it may indicate an error", ErrorCodes::DUPLICATE_DATA_PART);
                }
                continue;
            }
            else if (multi_code == Coordination::Error::ZNODEEXISTS && failed_op_path == quorum_info.status_path)
            {
                storage.unlockSharedData(*part);
                transaction.rollback();
                throw Exception("Another quorum insert has been already started", ErrorCodes::UNSATISFIED_QUORUM_FOR_PREVIOUS_WRITE);
            }
            else
            {
                storage.unlockSharedData(*part);
                /// 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))
        {
            storage.unlockSharedData(*part);
            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
        {
            storage.unlockSharedData(*part);
            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 (isQuorumEnabled())
    {
        if (is_already_existing_part)
        {
            /// 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);
        }

        waitForQuorum(zookeeper, part->name, quorum_info.status_path, quorum_info.is_active_node_value, replicas_num);
    }
}

void ReplicatedMergeTreeSink::onStart()
{
    /// 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, context);
}

void ReplicatedMergeTreeSink::onFinish()
{
    auto zookeeper = storage.getZooKeeper();
    assertSessionIsNotExpired(zookeeper);
    finishDelayedChunk(zookeeper);
}

void ReplicatedMergeTreeSink::waitForQuorum(
    zkutil::ZooKeeperPtr & zookeeper,
    const std::string & part_name,
    const std::string & quorum_path,
    const std::string & is_active_node_value,
    size_t replicas_num) const
{
    /// We are waiting for quorum to be satisfied.
    LOG_TRACE(log, "Waiting for quorum '{}' for part {}{}", quorum_path, part_name, quorumLogMessage(replicas_num));

    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_path, value, nullptr, event))
                break;

            LOG_TRACE(log, "Quorum node {} still exists, will wait for updates", quorum_path);

            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);

            LOG_TRACE(log, "Quorum {} for part {} updated, will check quorum node still exists", quorum_path, part_name);
        }

        /// 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 != 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);
    }

    LOG_TRACE(log, "Quorum '{}' for part {} satisfied", quorum_path, part_name);
}

String ReplicatedMergeTreeSink::quorumLogMessage(size_t replicas_num) const
{
    if (!isQuorumEnabled())
        return "";
    return fmt::format(" (quorum {} of {} replicas)", getQuorumSize(replicas_num), replicas_num);
}

size_t ReplicatedMergeTreeSink::getQuorumSize(size_t replicas_num) const
{
    if (!isQuorumEnabled())
        return 0;

    if (required_quorum_size)
        return required_quorum_size.value();

    return replicas_num / 2 + 1;
}

bool ReplicatedMergeTreeSink::isQuorumEnabled() const
{
    return !required_quorum_size.has_value() || required_quorum_size.value() > 1;
}

}