ClickHouse/docs/en/operations/system-tables/clusters.md

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---
slug: /en/operations/system-tables/clusters
---
# clusters
Contains information about clusters available in the config file and the servers in them.
Columns:
- `cluster` ([String](../../sql-reference/data-types/string.md)) — The cluster name.
- `shard_num` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The shard number in the cluster, starting from 1.
- `shard_weight` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The relative weight of the shard when writing data.
- `replica_num` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The replica number in the shard, starting from 1.
- `host_name` ([String](../../sql-reference/data-types/string.md)) — The host name, as specified in the config.
- `host_address` ([String](../../sql-reference/data-types/string.md)) — The host IP address obtained from DNS.
- `port` ([UInt16](../../sql-reference/data-types/int-uint.md)) — The port to use for connecting to the server.
- `is_local` ([UInt8](../../sql-reference/data-types/int-uint.md)) — Flag that indicates whether the host is local.
- `user` ([String](../../sql-reference/data-types/string.md)) — The name of the user for connecting to the server.
- `default_database` ([String](../../sql-reference/data-types/string.md)) — The default database name.
- `errors_count` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The number of times this host failed to reach replica.
- `slowdowns_count` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The number of slowdowns that led to changing replica when establishing a connection with hedged requests.
- `estimated_recovery_time` ([UInt32](../../sql-reference/data-types/int-uint.md)) — Seconds remaining until the replica error count is zeroed and it is considered to be back to normal.
**Example**
Query:
```sql
SELECT * FROM system.clusters LIMIT 2 FORMAT Vertical;
```
Result:
```text
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**
- [Table engine Distributed](../../engines/table-engines/special/distributed.md)
- [distributed_replica_error_cap setting](../../operations/settings/settings.md#settings-distributed_replica_error_cap)
- [distributed_replica_error_half_life setting](../../operations/settings/settings.md#settings-distributed_replica_error_half_life)