ClickHouse/docs/en/system_tables/system.zookeeper.md

system.zookeeper

Allows reading data from the ZooKeeper cluster defined in the config. The query must have a 'path' equality condition in the WHERE clause. This is the path in ZooKeeper for the children that you want to get data for.

The query SELECT * FROM system.zookeeper WHERE path = '/clickhouse' outputs data for all children on the /clickhouse node. To output data for all root nodes, write path = '/'. If the path specified in 'path' doesn't exist, an exception will be thrown.

Columns:

name String          - Name of the node.
path String          - Path to the node.
value String         - Value of the node.
dataLength Int32     - Size of the value.
numChildren Int32    - Number of children.
czxid Int64          - ID of the transaction that created the node.
mzxid Int64          - ID of the transaction that last changed the node.
pzxid Int64          - ID of the transaction that last added or removed children.
ctime DateTime       - Time of node creation.
mtime DateTime       - Time of the last node modification.
version Int32        - Node version - the number of times the node was changed.
cversion Int32       - Number of added or removed children.
aversion Int32       - Number of changes to ACL.
ephemeralOwner Int64 - For ephemeral nodes, the ID of the session that owns this node.

Example:

SELECT *
FROM system.zookeeper
WHERE path = '/clickhouse/tables/01-08/visits/replicas'
FORMAT Vertical

Row 1:
──────
name:           example01-08-1.yandex.ru
value:
czxid:          932998691229
mzxid:          932998691229
ctime:          2015-03-27 16:49:51
mtime:          2015-03-27 16:49:51
version:        0
cversion:       47
aversion:       0
ephemeralOwner: 0
dataLength:     0
numChildren:    7
pzxid:          987021031383
path:           /clickhouse/tables/01-08/visits/replicas

Row 2:
──────
name:           example01-08-2.yandex.ru
value:
czxid:          933002738135
mzxid:          933002738135
ctime:          2015-03-27 16:57:01
mtime:          2015-03-27 16:57:01
version:        0
cversion:       37
aversion:       0
ephemeralOwner: 0
dataLength:     0
numChildren:    7
pzxid:          987021252247
path:           /clickhouse/tables/01-08/visits/replicas