Replica leadership in Clickhouse












0















I would like to have more details on the leadership of a replica (ie. system.replicas.is_leader) in a ClickHouse DB.



The documentation states the following :



is_leader:          Whether the replica is the leader.
Only one replica can be the leader at a time. The leader is responsible for selecting background merges to perform.
Note that writes can be performed to any replica that is available and has a session in ZK, regardless of whether it is a leader.


This appears vague to me.
Does someone have more details about a leader replica?




  • Is there something to care about with a leader replica?


  • Can I read/write to/from a leader replica, like a standard one?


  • How does the leader election work?


  • When do the leadership change?











share|improve this question





























    0















    I would like to have more details on the leadership of a replica (ie. system.replicas.is_leader) in a ClickHouse DB.



    The documentation states the following :



    is_leader:          Whether the replica is the leader.
    Only one replica can be the leader at a time. The leader is responsible for selecting background merges to perform.
    Note that writes can be performed to any replica that is available and has a session in ZK, regardless of whether it is a leader.


    This appears vague to me.
    Does someone have more details about a leader replica?




    • Is there something to care about with a leader replica?


    • Can I read/write to/from a leader replica, like a standard one?


    • How does the leader election work?


    • When do the leadership change?











    share|improve this question



























      0












      0








      0








      I would like to have more details on the leadership of a replica (ie. system.replicas.is_leader) in a ClickHouse DB.



      The documentation states the following :



      is_leader:          Whether the replica is the leader.
      Only one replica can be the leader at a time. The leader is responsible for selecting background merges to perform.
      Note that writes can be performed to any replica that is available and has a session in ZK, regardless of whether it is a leader.


      This appears vague to me.
      Does someone have more details about a leader replica?




      • Is there something to care about with a leader replica?


      • Can I read/write to/from a leader replica, like a standard one?


      • How does the leader election work?


      • When do the leadership change?











      share|improve this question
















      I would like to have more details on the leadership of a replica (ie. system.replicas.is_leader) in a ClickHouse DB.



      The documentation states the following :



      is_leader:          Whether the replica is the leader.
      Only one replica can be the leader at a time. The leader is responsible for selecting background merges to perform.
      Note that writes can be performed to any replica that is available and has a session in ZK, regardless of whether it is a leader.


      This appears vague to me.
      Does someone have more details about a leader replica?




      • Is there something to care about with a leader replica?


      • Can I read/write to/from a leader replica, like a standard one?


      • How does the leader election work?


      • When do the leadership change?








      clickhouse






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Nov 25 '18 at 16:31









      user6910411

      33.6k976100




      33.6k976100










      asked Nov 23 '18 at 14:28









      ntochiurntochiur

      12




      12
























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          Leader replica just coordinates some background processes, leveraging ZooKeeper cluster. So unlike master/slave setup in other DBMS, in ClickHouse you shouldn't care about replica leadership status for reads and writes.



          More details are over here: https://clickhouse.yandex/docs/en/operations/table_engines/replication/






          share|improve this answer























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            1 Answer
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            active

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            0














            Leader replica just coordinates some background processes, leveraging ZooKeeper cluster. So unlike master/slave setup in other DBMS, in ClickHouse you shouldn't care about replica leadership status for reads and writes.



            More details are over here: https://clickhouse.yandex/docs/en/operations/table_engines/replication/






            share|improve this answer




























              0














              Leader replica just coordinates some background processes, leveraging ZooKeeper cluster. So unlike master/slave setup in other DBMS, in ClickHouse you shouldn't care about replica leadership status for reads and writes.



              More details are over here: https://clickhouse.yandex/docs/en/operations/table_engines/replication/






              share|improve this answer


























                0












                0








                0







                Leader replica just coordinates some background processes, leveraging ZooKeeper cluster. So unlike master/slave setup in other DBMS, in ClickHouse you shouldn't care about replica leadership status for reads and writes.



                More details are over here: https://clickhouse.yandex/docs/en/operations/table_engines/replication/






                share|improve this answer













                Leader replica just coordinates some background processes, leveraging ZooKeeper cluster. So unlike master/slave setup in other DBMS, in ClickHouse you shouldn't care about replica leadership status for reads and writes.



                More details are over here: https://clickhouse.yandex/docs/en/operations/table_engines/replication/







                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered Dec 8 '18 at 17:01









                Ivan BlinkovIvan Blinkov

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