ClickHouse/src/Storages/Freeze.cpp

#include <Storages/Freeze.h>

#include <Disks/ObjectStorages/IMetadataStorage.h>
#include <Storages/PartitionCommands.h>
#include <Common/escapeForFileName.h>
#include <Common/logger_useful.h>

/**
 * When ClickHouse has frozen data on remote storage it required 'smart' data removing during UNFREEZE.
 * For remote storage actually frozen not remote data but local metadata with referrers on remote data.
 * So remote data can be referred from working and frozen data sets (or two frozen) at same time.
 * In this case during UNFREEZE ClickHouse should remove only local metadata and keep remote data.
 * But when data was already removed from working data set ClickHouse should remove remote data too.
 * To detect is current data used or not in some other place ClickHouse uses
 *   - ref_count from metadata to check if data used in some other metadata on the same replica;
 *   - Keeper record to check if data used on other replica.
 * StorageReplicatedMergeTree::removeSharedDetachedPart makes required checks, so here this method
 * called for each frozen part.
 */

namespace DB
{

namespace ErrorCodes
{
    extern const int SUPPORT_IS_DISABLED;
}

void FreezeMetaData::fill(const StorageReplicatedMergeTree & storage)
{
    replica_name = storage.getReplicaName();
    zookeeper_name = storage.getZooKeeperName();
    table_shared_id = storage.getTableSharedID();
}

void FreezeMetaData::save(DiskPtr data_disk, const String & path) const
{
    auto metadata_storage = data_disk->getMetadataStorage();

    auto file_path = getFileName(path);
    auto tx = metadata_storage->createTransaction();
    WriteBufferFromOwnString buffer;

    writeIntText(version, buffer);
    buffer.write("\n", 1);
    if (version == 1)
    {
        /// is_replicated and is_remote are not used
        bool is_replicated = true;
        writeBoolText(is_replicated, buffer);
        buffer.write("\n", 1);
        bool is_remote = true;
        writeBoolText(is_remote, buffer);
        buffer.write("\n", 1);
    }
    writeString(escapeForFileName(replica_name), buffer);
    buffer.write("\n", 1);
    writeString(zookeeper_name, buffer);
    buffer.write("\n", 1);
    writeString(table_shared_id, buffer);
    buffer.write("\n", 1);

    tx->writeStringToFile(file_path, buffer.str());
    tx->commit();
}

bool FreezeMetaData::load(DiskPtr data_disk, const String & path)
{
    auto metadata_storage = data_disk->getMetadataStorage();
    auto file_path = getFileName(path);

    if (!metadata_storage->exists(file_path))
        return false;
    auto metadata_str = metadata_storage->readFileToString(file_path);
    ReadBufferFromString buffer(metadata_str);
    readIntText(version, buffer);
    if (version < 1 or version > 2)
    {
        LOG_ERROR(&Poco::Logger::get("FreezeMetaData"), "Unknown frozen metadata version: {}", version);
        return false;
    }
    DB::assertChar('\n', buffer);
    if (version == 1)
    {
        /// is_replicated and is_remote are not used
        bool is_replicated;
        readBoolText(is_replicated, buffer);
        DB::assertChar('\n', buffer);
        bool is_remote;
        readBoolText(is_remote, buffer);
        DB::assertChar('\n', buffer);
    }
    auto unescaped_replica_name = unescapeForFileName(replica_name);
    readString(unescaped_replica_name, buffer);
    DB::assertChar('\n', buffer);
    readString(zookeeper_name, buffer);
    DB::assertChar('\n', buffer);
    readString(table_shared_id, buffer);
    DB::assertChar('\n', buffer);
    return true;
}

void FreezeMetaData::clean(DiskPtr data_disk, const String & path)
{
    auto metadata_storage = data_disk->getMetadataStorage();
    auto fname = getFileName(path);
    if (metadata_storage->exists(fname))
    {
        auto tx = metadata_storage->createTransaction();
        tx->unlinkFile(fname);
        tx->commit();
    }
}

String FreezeMetaData::getFileName(const String & path)
{
    return fs::path(path) / "frozen_metadata.txt";
}

Unfreezer::Unfreezer(ContextPtr context) : local_context(context), zookeeper()
{
    const auto & config = local_context->getConfigRef();
    static constexpr auto config_key = "enable_system_unfreeze";
    if (!config.getBool(config_key, false))
    {
        throw Exception(ErrorCodes::SUPPORT_IS_DISABLED, "Support for SYSTEM UNFREEZE query is disabled. You can enable it via '{}' server setting", config_key);
    }
    if (local_context->hasZooKeeper())
        zookeeper = local_context->getZooKeeper();
}

BlockIO Unfreezer::unfreeze(const String & backup_name)
{
    LOG_DEBUG(log, "Unfreezing backup {}", escapeForFileName(backup_name));
    auto disks_map = local_context->getDisksMap();
    Disks disks;
    for (auto & [name, disk]: disks_map)
    {
        disks.push_back(disk);
    }
    auto backup_path = fs::path(backup_directory_prefix) / escapeForFileName(backup_name);
    auto store_paths = {backup_path / "store", backup_path / "data"};

    PartitionCommandsResultInfo result_info;

    for (const auto & disk: disks)
    {
        for (auto store_path: store_paths)
        {
            if (!disk->exists(store_path))
                continue;
            for (auto prefix_it = disk->iterateDirectory(store_path); prefix_it->isValid(); prefix_it->next())
            {
                auto prefix_directory = store_path / prefix_it->name();
                for (auto table_it = disk->iterateDirectory(prefix_directory); table_it->isValid(); table_it->next())
                {
                    auto table_directory = prefix_directory / table_it->name();
                    auto current_result_info = unfreezePartitionsFromTableDirectory(
                        [](const String &) { return true; }, backup_name, {disk}, table_directory);
                    for (auto & command_result : current_result_info)
                    {
                        command_result.command_type = "SYSTEM UNFREEZE";
                    }
                    result_info.insert(
                        result_info.end(),
                        std::make_move_iterator(current_result_info.begin()),
                        std::make_move_iterator(current_result_info.end()));
                }
            }
        }
        if (disk->exists(backup_path))
        {
            /// After unfreezing we need to clear revision.txt file and empty directories
            disk->removeRecursive(backup_path);
        }
    }

    BlockIO result;
    if (!result_info.empty())
    {
        result.pipeline = QueryPipeline(convertCommandsResultToSource(result_info));
    }
    return result;
}

bool Unfreezer::removeFreezedPart(DiskPtr disk, const String & path, const String & part_name, ContextPtr local_context, zkutil::ZooKeeperPtr zookeeper)
{
    if (disk->supportZeroCopyReplication())
    {
        FreezeMetaData meta;
        if (meta.load(disk, path))
        {
            FreezeMetaData::clean(disk, path);
            return StorageReplicatedMergeTree::removeSharedDetachedPart(disk, path, part_name, meta.table_shared_id, meta.zookeeper_name, meta.replica_name, "", local_context, zookeeper);
        }
    }

    disk->removeRecursive(path);

    return false;
}

PartitionCommandsResultInfo Unfreezer::unfreezePartitionsFromTableDirectory(MergeTreeData::MatcherFn matcher, const String & backup_name, const Disks & disks, const fs::path & table_directory)
{
    PartitionCommandsResultInfo result;

    for (const auto & disk : disks)
    {
        if (!disk->exists(table_directory))
            continue;

        for (auto it = disk->iterateDirectory(table_directory); it->isValid(); it->next())
        {
            const auto & partition_directory = it->name();

            /// Partition ID is prefix of part directory name: <partition id>_<rest of part directory name>
            auto found = partition_directory.find('_');
            if (found == std::string::npos)
                continue;
            auto partition_id = partition_directory.substr(0, found);

            if (!matcher(partition_id))
                continue;

            const auto & path = it->path();

            bool keep_shared = removeFreezedPart(disk, path, partition_directory, local_context, zookeeper);

            result.push_back(PartitionCommandResultInfo{
                .partition_id = partition_id,
                .part_name = partition_directory,
                .backup_path = disk->getPath() + table_directory.generic_string(),
                .part_backup_path = disk->getPath() + path,
                .backup_name = backup_name,
            });

            LOG_DEBUG(log, "Unfreezed part by path {}, keep shared data: {}", disk->getPath() + path, keep_shared);
        }
    }

    LOG_DEBUG(log, "Unfreezed {} parts", result.size());

    return result;
}
}