system.zookeeper

The table does not exist if ZooKeeper is not configured. Allows reading data from the ZooKeeper cluster defined in the config.
The query must have a ‘path’ equality condition in the WHERE clause. This is the path in ZooKeeper for the children that you want to get data for.

The query SELECT * FROM system.zookeeper WHERE path = '/clickhouse' outputs data for all children on the /clickhouse node.
To output data for all root nodes, write path = ‘/’.
If the path specified in ‘path’ doesn’t exist, an exception will be thrown.

Columns:

  • name (String) — The name of the node.
  • path (String) — The path to the node.
  • value (String) — Node value.
  • dataLength (Int32) — Size of the value.
  • numChildren (Int32) — Number of descendants.
  • czxid (Int64) — ID of the transaction that created the node.
  • mzxid (Int64) — ID of the transaction that last changed the node.
  • pzxid (Int64) — ID of the transaction that last deleted or added descendants.
  • ctime (DateTime) — Time of node creation.
  • mtime (DateTime) — Time of the last modification of the node.
  • version (Int32) — Node version: the number of times the node was changed.
  • cversion (Int32) — Number of added or removed descendants.
  • aversion (Int32) — Number of changes to the ACL.
  • ephemeralOwner (Int64) — For ephemeral nodes, the ID of the session that owns this node.

Example:

  1. SELECT *
  2. FROM system.zookeeper
  3. WHERE path = '/clickhouse/tables/01-08/visits/replicas'
  4. FORMAT Vertical
  1. Row 1:
  2. ──────
  3. name:           example01-08-1.yandex.ru
  4. value:
  5. czxid:          932998691229
  6. mzxid:          932998691229
  7. ctime:          2015-03-27 16:49:51
  8. mtime:          2015-03-27 16:49:51
  9. version:        0
  10. cversion:       47
  11. aversion:       0
  12. ephemeralOwner: 0
  13. dataLength:     0
  14. numChildren:    7
  15. pzxid:          987021031383
  16. path:           /clickhouse/tables/01-08/visits/replicas
  18. Row 2:
  19. ──────
  20. name:           example01-08-2.yandex.ru
  21. value:
  22. czxid:          933002738135
  23. mzxid:          933002738135
  24. ctime:          2015-03-27 16:57:01
  25. mtime:          2015-03-27 16:57:01
  26. version:        0
  27. cversion:       37
  28. aversion:       0
  29. ephemeralOwner: 0
  30. dataLength:     0
  31. numChildren:    7
  32. pzxid:          987021252247
  33. path:           /clickhouse/tables/01-08/visits/replicas

Original article