Search across clusters

Cross-cluster search lets you run a single search request against one or more remote clusters. For example, you can use a cross-cluster search to filter and analyze log data stored on clusters in different data centers.

The following APIs support cross-cluster search:

To perform a cross-cluster search, you must have at least one remote cluster configured.

The following cluster update settings API request adds three remote clusters:cluster_one, cluster_two, and cluster_three.

PUT _cluster/settings
{
  "persistent": {
    "cluster": {
      "remote": {
        "cluster_one": {
          "seeds": [
            "127.0.0.1:9300"
          ]
        },
        "cluster_two": {
          "seeds": [
            "127.0.0.1:9301"
          ]
        },
        "cluster_three": {
          "seeds": [
            "127.0.0.1:9302"
          ]
        }
      }
    }
  }
}

The following search API request searches the my-index-000001 index on a single remote cluster, cluster_one.

GET /cluster_one:my-index-000001/_search
{
  "query": {
    "match": {
      "user.id": "kimchy"
    }
  },
  "_source": ["user.id", "message", "http.response.status_code"]
}

The API returns the following response:

{
  "took": 150,
  "timed_out": false,
  "_shards": {
    "total": 1,
    "successful": 1,
    "failed": 0,
    "skipped": 0
  },
  "_clusters": {
    "total": 1,
    "successful": 1,
    "skipped": 0
  },
  "hits": {
    "total" : {
        "value": 1,
        "relation": "eq"
    },
    "max_score": 1,
    "hits": [
      {
        "_index": "cluster_one:my-index-000001", 
        "_type": "_doc",
        "_id": "0",
        "_score": 1,
        "_source": {
          "user": {
            "id": "kimchy"
          },
          "message": "GET /search HTTP/1.1 200 1070000",
          "http": {
            "response":
              {
                "status_code": 200
              }
          }
        }
      }
    ]
  }
}

The following search API request searches the my-index-000001 index on three clusters:

GET /my-index-000001,cluster_one:my-index-000001,cluster_two:my-index-000001/_search
{
  "query": {
    "match": {
      "user.id": "kimchy"
    }
  },
  "_source": ["user.id", "message", "http.response.status_code"]
}

The API returns the following response:

{
  "took": 150,
  "timed_out": false,
  "num_reduce_phases": 4,
  "_shards": {
    "total": 3,
    "successful": 3,
    "failed": 0,
    "skipped": 0
  },
  "_clusters": {
    "total": 3,
    "successful": 3,
    "skipped": 0
  },
  "hits": {
    "total" : {
        "value": 3,
        "relation": "eq"
    },
    "max_score": 1,
    "hits": [
      {
        "_index": "my-index-000001", 
        "_type": "_doc",
        "_id": "0",
        "_score": 2,
        "_source": {
          "user": {
            "id": "kimchy"
          },
          "message": "GET /search HTTP/1.1 200 1070000",
          "http": {
            "response":
              {
                "status_code": 200
              }
          }
        }
      },
      {
        "_index": "cluster_one:my-index-000001", 
        "_type": "_doc",
        "_id": "0",
        "_score": 1,
        "_source": {
          "user": {
            "id": "kimchy"
          },
          "message": "GET /search HTTP/1.1 200 1070000",
          "http": {
            "response":
              {
                "status_code": 200
              }
          }
        }
      },
      {
        "_index": "cluster_two:my-index-000001", 
        "_type": "_doc",
        "_id": "0",
        "_score": 1,
        "_source": {
          "user": {
            "id": "kimchy"
          },
          "message": "GET /search HTTP/1.1 200 1070000",
          "http": {
            "response":
              {
                "status_code": 200
              }
          }
        }
      }
    ]
  }
}

By default, a cross-cluster search returns an error if any cluster in the request is unavailable.

To skip an unavailable cluster during a cross-cluster search, set the skip_unavailable cluster setting to true.

The following cluster update settings API request changes cluster_two's skip_unavailable setting to true.

PUT _cluster/settings
{
  "persistent": {
    "cluster.remote.cluster_two.skip_unavailable": true
  }
}

If cluster_two is disconnected or unavailable during a cross-cluster search, Elasticsearch won’t include matching documents from that cluster in the final results.

For remote clusters using the sniff connection mode, gateway and seed nodes need to be accessible from the local cluster via your network.

By default, any non-master-eligible node can act as a gateway node. If wanted, you can define the gateway nodes for a cluster by setting cluster.remote.node.attr.gateway to true.

For cross-cluster search, we recommend you use gateway nodes that are capable of serving as coordinating nodes for search requests. If wanted, the seed nodes for a cluster can be a subset of these gateway nodes.

Proxy mode remote cluster connections support cross-cluster search. All remote connections connect to the configured proxy_address. Any desired connection routing to gateway or coordinating nodes must be implemented by the intermediate proxy at this configured address.

Because cross-cluster search involves sending requests to remote clusters, any network delays can impact search speed. To avoid slow searches, cross-cluster search offers two options for handling network delays:

Here’s how cross-cluster search works when you minimize network roundtrips.

Here’s how cross-cluster search works when you don’t minimize network roundtrips.

To run a cross-cluster search, the local and remote clusters must be compatible as outlined in the following matrix.

Cross-cluster search can also search remote clusters that are being upgraded so long as both the "upgrade from" and "upgrade to" version are compatible with the gateway node.

For example, a coordinating node running Elasticsearch 5.6 can search a remote cluster running Elasticsearch 6.8, but that cluster can not be upgraded to 7.1. In this case you should first upgrade the coordinating node to 7.1 and then upgrade remote cluster.

Only features that exist across all searched clusters are supported. Using a recent feature with a remote cluster where the feature is not supported will result in undefined behavior.