<a id="ksqldb-rest-api-cluster-status-endpoint"></a>

# Get the Status of ksqlDB Servers on Confluent Platform

The `/clusterStatus` resource returns the status of all ksqlDB
servers in a cluster, useful for troubleshooting. Enable this endpoint
by setting
[ksql.heartbeat.enable](../../reference/server-configuration.md#ksqldb-reference-server-configuration-ksql-heartbeat-enable)
to `true`. Optionally, you can also set
[ksql.lag.reporting.enable](../../reference/server-configuration.md#ksqldb-reference-server-configuration-ksql-lag-reporting-enable)
to `true` to have your ksqlDB servers report state store lag, which
will then also be returned with the response from the `/clusterStatus`
endpoint.

#### NOTE
ksqlDB servers in a cluster discover each other through persistent queries.
If you have no persistent queries running, then the `/clusterStatus`
endpoint contains info for the particular server that was queried, rather
than all servers in the cluster.

You can use the `curl` command to query the `/clusterStatus`
endpoint for a particular server:

```bash
curl -sX GET "http://localhost:8088/clusterStatus" | jq '.'
```

The response object contains a `clusterStatus` field with the
following information for each ksqlDB server (represented as
`host:port`):

- **hostAlive** (boolean): whether the server is alive, as determined
  by heartbeats received by the queried server
- **lastStatusUpdateMs** (long): epoch timestamp, in milliseconds, for
  when the last status update was received for this server, by the
  queried server
- **activeStandbyPerQuery** (object): for each query ID, a collection
  of active and standby partitions and state stores on this server
- **hostStoreLags** (object): state store lag information. Empty unless
  `ksql.lag.reporting.enable` is set to `true`.
- **hostStoreLags.stateStoreLags** (object): partition-level lag
  breakdown for each state store.
- **hostStoreLags.updateTimeMs** (long): epoch timestamp, in
  milliseconds, for when the last lag update was received for this
  server, by the queried server

For a two-node cluster running a single `CREATE TABLE ... AS SELECT`
query, with lag reporting enabled, your output should resemble:

```json
{
  "clusterStatus": {
    "localhost:8088": {
      "hostAlive": true,
      "lastStatusUpdateMs": 1617609098808,
      "activeStandbyPerQuery": {
        "CTAS_MY_AGG_TABLE_3": {
          "activeStores": [
            "Aggregate-Aggregate-Materialize"
          ],
          "activePartitions": [
            {
              "topic": "my_stream",
              "partition": 1
            },
            {
              "topic": "my_stream",
              "partition": 3
            },
            {
              "topic": "_confluent-ksql-default_query_CTAS_MY_AGG_TABLE_3-Aggregate-GroupBy-repartition",
              "partition": 1
            },
            {
              "topic": "_confluent-ksql-default_query_CTAS_MY_AGG_TABLE_3-Aggregate-GroupBy-repartition",
              "partition": 3
            }
          ],
          "standByStores": [],
          "standByPartitions": []
        }
      },
      "hostStoreLags": {
        "stateStoreLags": {
          "_confluent-ksql-default_query_CTAS_MY_AGG_TABLE_3#Aggregate-Aggregate-Materialize": {
            "lagByPartition": {
              "1": {
                "currentOffsetPosition": 0,
                "endOffsetPosition": 0,
                "offsetLag": 0
              },
              "3": {
                "currentOffsetPosition": 0,
                "endOffsetPosition": 0,
                "offsetLag": 0
              }
            },
            "size": 2
          }
        },
        "updateTimeMs": 1617609168917
      }
    },
    "other.ksqldb.host:8088": {
      "hostAlive": true,
      "lastStatusUpdateMs": 1617609172614,
      "activeStandbyPerQuery": {
        "CTAS_MY_AGG_TABLE_3": {
          "activeStores": [
            "Aggregate-Aggregate-Materialize"
          ],
          "activePartitions": [
            {
              "topic": "my_stream",
              "partition": 0
            },
            {
              "topic": "my_stream",
              "partition": 2
            },
            {
              "topic": "_confluent-ksql-default_query_CTAS_MY_AGG_TABLE_3-Aggregate-GroupBy-repartition",
              "partition": 0
            },
            {
              "topic": "_confluent-ksql-default_query_CTAS_MY_AGG_TABLE_3-Aggregate-GroupBy-repartition",
              "partition": 2
            }
          ],
          "standByStores": [],
          "standByPartitions": []
        }
      },
      "hostStoreLags": {
        "stateStoreLags": {
          "_confluent-ksql-default_query_CTAS_MY_AGG_TABLE_3#Aggregate-Aggregate-Materialize": {
            "lagByPartition": {
              "0": {
                "currentOffsetPosition": 1,
                "endOffsetPosition": 1,
                "offsetLag": 0
              },
              "2": {
                "currentOffsetPosition": 0,
                "endOffsetPosition": 0,
                "offsetLag": 0
              }
            },
            "size": 2
          }
        },
        "updateTimeMs": 1617609170111
      }
    }
  }
}
```