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

system.zookeeper_connection_log

The 'system.zookeeper_connection_log' table shows the history of ZooKeeper connections (including auxiliary ZooKeepers). Each row shows information about one event regarding connections.

:::note The table doesn't contain events for disconnections caused by server shutdown. :::

Columns:

hostname (LowCardinality(String)) — Hostname of the server which is connected to or disconnected from ZooKeeper.
type (Enum8) - The type of the event. Possible values: Connected, Disconnected.
event_date (Date) - Date of the entry.
event_time (DateTime) - Time of the entry.
event_time_microseconds (Date) - Time of the entry with microseconds precision.
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 (UInt8) — The index of the ZooKeeper node that ClickHouse connected to or disconnected from. The index is from ZooKeeper config.
client_id (Int64) — Session id of the connection.
keeper_api_version (UInt8) — Keeper API version.
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.
reason (String) — Reason for the connection or disconnection.

Example:

sql

SELECT * FROM system.zookeeper_connection_log;

text

    ┌─hostname─┬─type─────────┬─event_date─┬──────────event_time─┬────event_time_microseconds─┬─name───────────────┬─host─┬─port─┬─index─┬─client_id─┬─keeper_api_version─┬─enabled_feature_flags───────────────────────────────────────────────────────────────────────┬─availability_zone─┬─reason──────────────┐
 1. │ node     │ Connected    │ 2025-05-12 │ 2025-05-12 19:49:35 │ 2025-05-12 19:49:35.713067 │ zk_conn_log_test_4 │ zoo2 │ 2181 │     0 │        10 │                  0 │ ['FILTERED_LIST','MULTI_READ','CHECK_NOT_EXISTS','CREATE_IF_NOT_EXISTS','REMOVE_RECURSIVE'] │                   │ Initialization      │
 2. │ node     │ Connected    │ 2025-05-12 │ 2025-05-12 19:49:23 │ 2025-05-12 19:49:23.981570 │ default            │ zoo1 │ 2181 │     0 │         4 │                  0 │ ['FILTERED_LIST','MULTI_READ','CHECK_NOT_EXISTS','CREATE_IF_NOT_EXISTS','REMOVE_RECURSIVE'] │                   │ Initialization      │
 3. │ node     │ Connected    │ 2025-05-12 │ 2025-05-12 19:49:28 │ 2025-05-12 19:49:28.104021 │ default            │ zoo1 │ 2181 │     0 │         5 │                  0 │ ['FILTERED_LIST','MULTI_READ','CHECK_NOT_EXISTS','CREATE_IF_NOT_EXISTS','REMOVE_RECURSIVE'] │                   │ Initialization      │
 4. │ node     │ Connected    │ 2025-05-12 │ 2025-05-12 19:49:29 │ 2025-05-12 19:49:29.459251 │ zk_conn_log_test_2 │ zoo2 │ 2181 │     0 │         6 │                  0 │ ['FILTERED_LIST','MULTI_READ','CHECK_NOT_EXISTS','CREATE_IF_NOT_EXISTS','REMOVE_RECURSIVE'] │                   │ Initialization      │
 5. │ node     │ Connected    │ 2025-05-12 │ 2025-05-12 19:49:29 │ 2025-05-12 19:49:29.574312 │ zk_conn_log_test_3 │ zoo3 │ 2181 │     0 │         7 │                  0 │ ['FILTERED_LIST','MULTI_READ','CHECK_NOT_EXISTS','CREATE_IF_NOT_EXISTS','REMOVE_RECURSIVE'] │                   │ Initialization      │
 6. │ node     │ Disconnected │ 2025-05-12 │ 2025-05-12 19:49:29 │ 2025-05-12 19:49:29.909890 │ default            │ zoo1 │ 2181 │     0 │         5 │                  0 │ ['FILTERED_LIST','MULTI_READ','CHECK_NOT_EXISTS','CREATE_IF_NOT_EXISTS','REMOVE_RECURSIVE'] │                   │ Config changed      │
 7. │ node     │ Connected    │ 2025-05-12 │ 2025-05-12 19:49:29 │ 2025-05-12 19:49:29.909895 │ default            │ zoo2 │ 2181 │     0 │         8 │                  0 │ ['FILTERED_LIST','MULTI_READ','CHECK_NOT_EXISTS','CREATE_IF_NOT_EXISTS','REMOVE_RECURSIVE'] │                   │ Config changed      │
 8. │ node     │ Disconnected │ 2025-05-12 │ 2025-05-12 19:49:29 │ 2025-05-12 19:49:29.912010 │ zk_conn_log_test_2 │ zoo2 │ 2181 │     0 │         6 │                  0 │ ['FILTERED_LIST','MULTI_READ','CHECK_NOT_EXISTS','CREATE_IF_NOT_EXISTS','REMOVE_RECURSIVE'] │                   │ Config changed      │
 9. │ node     │ Connected    │ 2025-05-12 │ 2025-05-12 19:49:29 │ 2025-05-12 19:49:29.912014 │ zk_conn_log_test_2 │ zoo3 │ 2181 │     0 │         9 │                  0 │ ['FILTERED_LIST','MULTI_READ','CHECK_NOT_EXISTS','CREATE_IF_NOT_EXISTS','REMOVE_RECURSIVE'] │                   │ Config changed      │
10. │ node     │ Disconnected │ 2025-05-12 │ 2025-05-12 19:49:29 │ 2025-05-12 19:49:29.912061 │ zk_conn_log_test_3 │ zoo3 │ 2181 │     0 │         7 │                  0 │ ['FILTERED_LIST','MULTI_READ','CHECK_NOT_EXISTS','CREATE_IF_NOT_EXISTS','REMOVE_RECURSIVE'] │                   │ Removed from config │
    └──────────┴──────────────┴────────────┴─────────────────────┴────────────────────────────┴────────────────────┴──────┴──────┴───────┴───────────┴────────────────────┴─────────────────────────────────────────────────────────────────────────────────────────────┴───────────────────┴─────────────────────┘