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Querying in ClickHouse CloudThe data in this system table is held locally on each node in ClickHouse Cloud. Obtaining a complete view of all data, therefore, requires the clusterAllReplicas function. See here for further details.

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Description

This table does not exist if ZooKeeper is not configured. The ‘system.zookeeper_connection’ table shows current connections to ZooKeeper (including auxiliary ZooKeepers). Each row shows information about one connection.

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Columns

  • name (String) — ZooKeeper cluster’s name.
  • host (String) — The hostname/IP of the ZooKeeper node that ClickHouse connected to.
  • port (UIn16) — The port of the ZooKeeper node that ClickHouse connected to.
  • index (Nullable(UInt8)) — The index of the ZooKeeper node that ClickHouse connected to. The index is from ZooKeeper config. If not connected, this column is NULL.
  • connected_time (DateTime) — When the connection was established
  • session_uptime_elapsed_seconds (UInt64) — Seconds elapsed since the connection was established.
  • is_expired (UInt8) — Is the current connection expired.
  • keeper_api_version (UInt8) — Keeper API version.
  • client_id (Int64) — Session id of the connection.
  • xid (Int64) — XID of the current session.
  • enabled_feature_flags (Array(Enum16)) — Feature flags which are enabled. Only applicable to ClickHouse Keeper. Possible values are FILTERED_LIST, MULTI_READ, CHECK_NOT_EXISTS, CREATE_IF_NOT_EXISTS, REMOVE_RECURSIVE.
  • availability_zone (String) — Availability zone.
  • session_timeout_ms (UInt64) — Session timeout (in milliseconds).
  • last_zxid_seen (Int64) — Last zxid seen by the current session.
Example: 
SELECT * FROM system.zookeeper_connection;

┌─name────┬─host──────┬─port─┬─index─┬──────connected_time─┬─session_uptime_elapsed_seconds─┬─is_expired─┬─keeper_api_version─┬─client_id─┬─xid─┬─enabled_feature_flags────────────────────────────────────────────────────┬─availability_zone─┐
│ default │ 127.0.0.1 │ 2181 │     0 │ 2025-04-10 14:30:00 │                            943 │          0 │                  0 │       420 │  69 │ ['FILTERED_LIST','MULTI_READ','CHECK_NOT_EXISTS','CREATE_IF_NOT_EXISTS'] │ eu-west-1b        │
└─────────┴───────────┴──────┴───────┴─────────────────────┴────────────────────────────────┴────────────┴────────────────────┴───────────┴─────┴──────────────────────────────────────────────────────────────────────────┴───────────────────┘