Método de codificación de datos: 

Copia datos de las tablas de un clúster en tablas de otro (o del mismo) clúster.

Puede ejecutar varios clickhouse-copier instancias en diferentes servidores para realizar el mismo trabajo. ZooKeeper se utiliza para sincronizar los procesos.

Después de comenzar, clickhouse-copier:

  • Se conecta a ZooKeeper y recibe:

    • Copia de trabajos.
    • El estado de los trabajos de copia.
  • Realiza los trabajos.

    Cada proceso en ejecución elige el “closest” el fragmento del clúster de origen y copia los datos en el clúster de destino, reafirmando los datos si es necesario.

clickhouse-copier realiza un seguimiento de los cambios en ZooKeeper y los aplica sobre la marcha.

Para reducir el tráfico de red, recomendamos ejecutar clickhouse-copier en el mismo servidor donde se encuentran los datos de origen.

Ejecución de Clickhouse-copiadora 

La utilidad debe ejecutarse manualmente:

$ clickhouse-copier copier --daemon --config zookeeper.xml --task-path /task/path --base-dir /path/to/dir

Parámetros:

  • daemon — Starts clickhouse-copier en modo daemon.
  • config — The path to the zookeeper.xml con los parámetros para la conexión a ZooKeeper.
  • task-path — The path to the ZooKeeper node. This node is used for syncing clickhouse-copier procesos y tareas de almacenamiento. Las tareas se almacenan en $task-path/description.
  • task-file — Optional path to file with task configuration for initial upload to ZooKeeper.
  • task-upload-force — Force upload task-file incluso si el nodo ya existe.
  • base-dir — The path to logs and auxiliary files. When it starts, clickhouse-copier crear clickhouse-copier_YYYYMMHHSS_<PID> subdirectorios en $base-dir. Si se omite este parámetro, los directorios se crean en el directorio donde clickhouse-copier se puso en marcha.

Formato de Zookeeper.XML 

<yandex>
    <logger>
        <level>trace</level>
        <size>100M</size>
        <count>3</count>
    </logger>

    <zookeeper>
        <node index="1">
            <host>127.0.0.1</host>
            <port>2181</port>
        </node>
    </zookeeper>
</yandex>

Configuración de tareas de copia 

<yandex>
    <!-- Configuration of clusters as in an ordinary server config -->
    <remote_servers>
        <source_cluster>
            <shard>
                <internal_replication>false</internal_replication>
                    <replica>
                        <host>127.0.0.1</host>
                        <port>9000</port>
                    </replica>
            </shard>
            ...
        </source_cluster>

        <destination_cluster>
        ...
        </destination_cluster>
    </remote_servers>

    <!-- How many simultaneously active workers are possible. If you run more workers superfluous workers will sleep. -->
    <max_workers>2</max_workers>

    <!-- Setting used to fetch (pull) data from source cluster tables -->
    <settings_pull>
        <readonly>1</readonly>
    </settings_pull>

    <!-- Setting used to insert (push) data to destination cluster tables -->
    <settings_push>
        <readonly>0</readonly>
    </settings_push>

    <!-- Common setting for fetch (pull) and insert (push) operations. Also, copier process context uses it.
         They are overlaid by <settings_pull/> and <settings_push/> respectively. -->
    <settings>
        <connect_timeout>3</connect_timeout>
        <!-- Sync insert is set forcibly, leave it here just in case. -->
        <insert_distributed_sync>1</insert_distributed_sync>
    </settings>

    <!-- Copying tasks description.
         You could specify several table task in the same task description (in the same ZooKeeper node), they will be performed
         sequentially.
    -->
    <tables>
        <!-- A table task, copies one table. -->
        <table_hits>
            <!-- Source cluster name (from <remote_servers/> section) and tables in it that should be copied -->
            <cluster_pull>source_cluster</cluster_pull>
            <database_pull>test</database_pull>
            <table_pull>hits</table_pull>

            <!-- Destination cluster name and tables in which the data should be inserted -->
            <cluster_push>destination_cluster</cluster_push>
            <database_push>test</database_push>
            <table_push>hits2</table_push>

            <!-- Engine of destination tables.
                 If destination tables have not be created, workers create them using columns definition from source tables and engine
                 definition from here.

                 NOTE: If the first worker starts insert data and detects that destination partition is not empty then the partition will
                 be dropped and refilled, take it into account if you already have some data in destination tables. You could directly
                 specify partitions that should be copied in <enabled_partitions/>, they should be in quoted format like partition column of
                 system.parts table.
            -->
            <engine>
            ENGINE=ReplicatedMergeTree('/clickhouse/tables/{cluster}/{shard}/hits2', '{replica}')
            PARTITION BY toMonday(date)
            ORDER BY (CounterID, EventDate)
            </engine>

            <!-- Sharding key used to insert data to destination cluster -->
            <sharding_key>jumpConsistentHash(intHash64(UserID), 2)</sharding_key>

            <!-- Optional expression that filter data while pull them from source servers -->
            <where_condition>CounterID != 0</where_condition>

            <!-- This section specifies partitions that should be copied, other partition will be ignored.
                 Partition names should have the same format as
                 partition column of system.parts table (i.e. a quoted text).
                 Since partition key of source and destination cluster could be different,
                 these partition names specify destination partitions.

                 NOTE: In spite of this section is optional (if it is not specified, all partitions will be copied),
                 it is strictly recommended to specify them explicitly.
                 If you already have some ready partitions on destination cluster they
                 will be removed at the start of the copying since they will be interpeted
                 as unfinished data from the previous copying!!!
            -->
            <enabled_partitions>
                <partition>'2018-02-26'</partition>
                <partition>'2018-03-05'</partition>
                ...
            </enabled_partitions>
        </table_hits>

        <!-- Next table to copy. It is not copied until previous table is copying. -->
        </table_visits>
        ...
        </table_visits>
        ...
    </tables>
</yandex>

clickhouse-copier seguimiento de los cambios en /task/path/description y los aplica sobre la marcha. Por ejemplo, si cambia el valor de max_workers, el número de procesos que ejecutan tareas también cambiará.

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