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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](/docs/operations/system-tables/overview#system-tables-in-clickhouse-cloud) for further details.

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](/docs/sql-reference/data-types/string)) — ZooKeeper cluster's name.
- `host` ([String](/docs/sql-reference/data-types/string)) — The hostname/IP of the ZooKeeper node that ClickHouse connected to.
- `port` ([UIn16](/docs/sql-reference/data-types/int-uint)) — The port of the ZooKeeper node that ClickHouse connected to.
- `index` ([Nullable(UInt8)](/docs/sql-reference/data-types/int-uint)) — 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](/docs/sql-reference/data-types/datetime)) — When the connection was established
- `session_uptime_elapsed_seconds` ([UInt64](/docs/sql-reference/data-types/int-uint)) — Seconds elapsed since the connection was established.
- `is_expired` ([UInt8](/docs/sql-reference/data-types/int-uint)) — Is the current connection expired.
- `keeper_api_version` ([UInt8](/docs/sql-reference/data-types/int-uint)) — Keeper API version.
- `client_id` ([Int64](/docs/sql-reference/data-types/int-uint)) — Session id of the connection.
- `xid` ([Int64](/docs/sql-reference/data-types/int-uint)) — XID of the current session.
- `enabled_feature_flags` ([Array(Enum16)](/docs/sql-reference/data-types/array)) — 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](/docs/sql-reference/data-types/string)) — Availability zone.
- `session_timeout_ms` ([UInt64](/docs/sql-reference/data-types/int-uint)) — Session timeout (in milliseconds).
- `last_zxid_seen` ([Int64](/docs/sql-reference/data-types/int-uint)) — 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        │
└─────────┴───────────┴──────┴───────┴─────────────────────┴────────────────────────────────┴────────────┴────────────────────┴───────────┴─────┴──────────────────────────────────────────────────────────────────────────┴───────────────────┘
```

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