clickhouse cluster : data not replicated

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I have a cluster with 2 nodes for a test. 1 Shard and 2 replica. 3 nodes in the zookeeper cluster

<remote_servers>
  <ch_cluster>
    <shard>
      <internal_replication>true</internal_replication>
      <replica>
        <host>ch1</host>
        <port>9000</port>
      </replica>
      <replica>
        <host>ch2</host>
        <port>9000</port>
      </replica>
    </shard>
  </ch_cluster>
</remote_servers>

macros in ch1 :

  <macros>
        <shard>shard_01</shard>
        <replica>replica-01</replica>
    </macros>

macro in ch2 :

   <macros>
        <shard>shard_01</shard>
        <replica>replica-02</replica>
    </macros>

zookeeper configuration :

   <zookeeper>
        <node>
            <host>zoo1</host>
            <port>2181</port>
        </node>
        <node>
            <host>zoo2</host>
            <port>2181</port>
        </node>
        <node>
            <host>zoo3</host>
            <port>2181</port>
        </node>
    </zookeeper>

I create the first table

CREATE TABLE IF NOT EXISTS test.hits_local ON CLUSTER ch_cluster
(
  `date` Datetime,
  `user_id` String,
  `pageviews` Int32
)
ENGINE = ReplicatedMergeTree('/clickhouse/ch_cluster/tables/{shard}/hits_local', '{replica}')
PARTITION BY toStartOfHour(date)
ORDER BY (date)

then i create a distributed table :

CREATE TABLE IF NOT EXISTS test.hits ON CLUSTER 'ch_cluster'
AS test.hits_local 
 (
      `date` Datetime,
      `user_id` String,
      `pageviews` Int32
    )
ENGINE = Distributed('ch_cluster', 'test', 'hits_local')

then i insert data in test.hits_local table in ch1 when select data from test.hits_local in ch2 there is no data

then i tried to select from test.hits Distributed table in ch2 the data appear after 5-6 min but no data in test.hits_local in ch2

my question when the data replicated to ch2? who is responsible to replicate data to another node ? is it a zookeeper or should i insert the data into tables in ch1 and ch2? should i change <internal_replication>true</internal_replication> to false ?

is it necessary for the data to be replicated to test.hits_local in ch2?

thank you.

clickhouse database-replication replication
1 Answers

should i change <internal_replication>true</internal_replication> to false ?

No, you should not. If you use ReplicatedMergeTree internal_replication MUST BE true.

Replication is done by ReplicatedMergeTree table engine internally.

Replicas communicate using their hostnames and port=9009. Check system.replication_queue table for errors.

Most probably the node "ch1" announced own hostname in Zookeeper i.e. "localhost". So the second node "ch2" unable to access localhost:9009 or something. Such issues you can find in clickhouse-server.log or system.replication_queue (it has a column with errors).

Usually replication lag is less than 2 seconds even in very high-loaded setups.

user_116443080
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