system.clusters
Contains information about clusters available in the config file and the servers in them.
Columns:
cluster(String) — The cluster name.shard_num(UInt32) — The shard number in the cluster, starting from 1.shard_weight(UInt32) — The relative weight of the shard when writing data.replica_num(UInt32) — The replica number in the shard, starting from 1.host_name(String) — The host name, as specified in the config.host_address(String) — The host IP address obtained from DNS.port(UInt16) — The port to use for connecting to the server.is_local(UInt8) — Flag that indicates whether the host is local.user(String) — The name of the user for connecting to the server.default_database(String) — The default database name.errors_count(UInt32) — The number of times this host failed to reach replica.slowdowns_count(UInt32) — The number of slowdowns that led to changing replica when establishing a connection with hedged requests.estimated_recovery_time(UInt32) — Seconds remaining until the replica error count is zeroed and it is considered to be back to normal.
Example
Query:
SELECT * FROM system.clusters LIMIT 2 FORMAT Vertical;
Result:
Row 1:
──────
cluster: test_cluster_two_shards
shard_num: 1
shard_weight: 1
replica_num: 1
host_name: 127.0.0.1
host_address: 127.0.0.1
port: 9000
is_local: 1
user: default
default_database:
errors_count: 0
slowdowns_count: 0
estimated_recovery_time: 0
Row 2:
──────
cluster: test_cluster_two_shards
shard_num: 2
shard_weight: 1
replica_num: 1
host_name: 127.0.0.2
host_address: 127.0.0.2
port: 9000
is_local: 0
user: default
default_database:
errors_count: 0
slowdowns_count: 0
estimated_recovery_time: 0
See Also