import SystemTableCloud from '@site/docs/_snippets/_system_table_cloud.md';

system.zookeeper_connection

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 (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        │
└─────────┴───────────┴──────┴───────┴─────────────────────┴────────────────────────────────┴────────────┴────────────────────┴───────────┴─────┴──────────────────────────────────────────────────────────────────────────┴───────────────────┘