system.zookeeper_connection

System table which exists only if ZooKeeper is configured. Shows current connections to ZooKeeper (including auxiliary ZooKeepers).

Querying in ClickHouse Cloud

The 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.

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.

Columns

• name (String) — ZooKeeper cluster’s name.
• host (String) — The hostname/IP of the ZooKeeper node that ClickHouse connected to.
• port (UInt16) — 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(‘FILTERED_LIST’ = 0, ‘MULTI_READ’ = 1, ‘CHECK_NOT_EXISTS’ = 2, ‘CREATE_IF_NOT_EXISTS’ = 3, ‘REMOVE_RECURSIVE’ = 4, ‘MULTI_WATCHES’ = 5, ‘CHECK_STAT’ = 6, ‘PERSISTENT_WATCHES’ = 7, ‘CREATE_WITH_STATS’ = 8, ‘TRY_REMOVE’ = 9, ‘LIST_WITH_STAT_AND_DATA’ = 10, ‘GET_CHILDREN_RECURSIVE’ = 11, ‘CREATE_TTL’ = 12, ‘CREATE_CONTAINER’ = 13, ‘MAX_REQUEST_SIZE’ = 14))) — Feature flags which are enabled. Only applicable to ClickHouse Keeper.
• availability_zone (String) — Availability zone
• session_timeout_ms (UInt64) — Session timeout (in milliseconds)
• last_zxid_seen (Int64) — Last zxid seen by the current session.

Examples

SELECT
    name,
    host,
    port,
    index,
    connected_time,
    session_uptime_elapsed_seconds,
    is_expired,
    keeper_api_version,
    client_id,
    xid,
    enabled_feature_flags,
    availability_zone
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        │
└─────────┴───────────┴──────┴───────┴─────────────────────┴────────────────────────────────┴────────────┴────────────────────┴───────────┴─────┴──────────────────────────────────────────────────────────────────────────┴───────────────────┘