opensearch-docs-cn/docs/async/index.md

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default	Asynchronous search	51	true

Asynchronous search

Searching large volumes of data can take a long time, especially if you're searching across warm nodes or multiple remote clusters.

Asynchronous search in OpenSearch lets you send search requests that run in the background. You can monitor the progress of these searches and get back partial results as they become available. After the search finishes, you can save the results to examine at a later time.

REST API

To perform an asynchronous search, send requests to _opensearch/_asynchronous_search, with your query in the request body:

POST _opensearch/_asynchronous_search

You can specify the following options.

Options	Description	Default value	Required
wait_for_completion_timeout	The amount of time that you plan to wait for the results. You can see whatever results you get within this time just like in a normal search. You can poll the remaining results based on an ID. The maximum value is 300 seconds.	1 second	No
keep_on_completion	Whether you want to save the results in the cluster after the search is complete. You can examine the stored results at a later time.	false	No
keep_alive	The amount of time that the result is saved in the cluster. For example, 2d means that the results are stored in the cluster for 48 hours. The saved search results are deleted after this period or if the search is canceled. Note that this includes the query execution time. If the query overruns this time, the process cancels this query automatically.	12 hours	No

Sample request

POST _opensearch/_asynchronous_search/?pretty&size=10&wait_for_completion_timeout=1ms&keep_on_completion=true&request_cache=false
{
  "aggs": {
    "city": {
      "terms": {
        "field": "city",
        "size": 10
      }
    }
  }
}

Sample response

{
  "*id*": "FklfVlU4eFdIUTh1Q1hyM3ZnT19fUVEUd29KLWZYUUI3TzRpdU5wMjRYOHgAAAAAAAAABg==",
  "state": "RUNNING",
  "start_time_in_millis": 1599833301297,
  "expiration_time_in_millis": 1600265301297,
  "response": {
    "took": 15,
    "timed_out": false,
    "terminated_early": false,
    "num_reduce_phases": 4,
    "_shards": {
      "total": 21,
      "successful": 4,
      "skipped": 0,
      "failed": 0
    },
    "hits": {
      "total": {
        "value": 807,
        "relation": "eq"
      },
      "max_score": null,
      "hits": []
    },
    "aggregations": {
      "city": {
        "doc_count_error_upper_bound": 16,
        "sum_other_doc_count": 403,
        "buckets": [
          {
            "key": "downsville",
            "doc_count": 1
          },
        ....
        ....
        ....
          {
            "key": "blairstown",
            "doc_count": 1
          }
        ]
      }
    }
  }
}

Response parameters

Options	Description
id	The ID of an asynchronous search. Use this ID to monitor the progress of the search, get its partial results, and/or delete the results. If the asynchronous search finishes within the timeout period, the response doesn't include the ID because the results aren't stored in the cluster.
state	Specifies whether the search is still running or if it has finished, and if the results persist in the cluster. The possible states are RUNNING, COMPLETED, and PERSISTED.
start_time_in_millis	The start time in milliseconds.
expiration_time_in_millis	The expiration time in milliseconds.
took	The total time that the search is running.
response	The actual search response.
num_reduce_phases	The number of times that the coordinating node aggregates results from batches of shard responses (5 by default). If this number increases compared to the last retrieved results, you can expect additional results to be included in the search response.
total	The total number of shards that run the search.
successful	The number of shard responses that the coordinating node received successfully.
aggregations	The partial aggregation results that have been completed by the shards so far.

Get partial results

After you submit an asynchronous search request, you can request partial responses with the ID that you see in the asynchronous search response.

GET _opensearch/_asynchronous_search/<ID>?pretty

Sample response

{
  "id": "Fk9lQk5aWHJIUUltR2xGWnpVcWtFdVEURUN1SWZYUUJBVkFVMEJCTUlZUUoAAAAAAAAAAg==",
  "state": "STORE_RESIDENT",
  "start_time_in_millis": 1599833907465,
  "expiration_time_in_millis": 1600265907465,
  "response": {
    "took": 83,
    "timed_out": false,
    "_shards": {
      "total": 20,
      "successful": 20,
      "skipped": 0,
      "failed": 0
    },
    "hits": {
      "total": {
        "value": 1000,
        "relation": "eq"
      },
      "max_score": 1,
      "hits": [
        {
          "_index": "bank",
          "_type": "_doc",
          "_id": "1",
          "_score": 1,
          "_source": {
            "email": "amberduke@abc.com",
            "city": "Brogan",
            "state": "IL"
          }
        },
       {....}
      ]
    },
    "aggregations": {
      "city": {
        "doc_count_error_upper_bound": 0,
        "sum_other_doc_count": 997,
        "buckets": [
          {
            "key": "belvoir",
            "doc_count": 2
          },
          {
            "key": "aberdeen",
            "doc_count": 1
          },
          {
            "key": "abiquiu",
            "doc_count": 1
          }
        ]
      }
    }
  }
}

After the response is successfully persisted, you get back the STORE_RESIDENT state in the response.

You can poll the ID with the wait_for_completion_timeout parameter to wait for the results received for the time that you specify.

For asynchronous searches with keep_on_completion as true and a sufficiently long keep_alive time, you can keep polling the IDs until the search finishes. If you don’t want to periodically poll each ID, you can retain the results in your cluster with the keep_alive parameter and come back to it at a later time.

Delete searches and results

You can use the DELETE API operation to delete any ongoing asynchronous search by its ID. If the search is still running, it’s canceled. If the search is complete, the saved search results are deleted.

DELETE _opensearch/_asynchronous_search/<ID>?pretty

Sample response

{
  "acknowledged": "true"
}

Monitor stats

You can use the stats API operation to monitor asynchronous searches that are running, completed, and/or persisted.

GET _opensearch/_asynchronous_search/stats

Sample response

{
  "_nodes": {
    "total": 8,
    "successful": 8,
    "failed": 0
  },
  "cluster_name": "264071961897:asynchronous-search",
  "nodes": {
    "JKEFl6pdRC-xNkKQauy7Yg": {
      "asynchronous_search_stats": {
        "submitted": 18236,
        "initialized": 112,
        "search_failed": 56,
        "search_completed": 56,
        "rejected": 18124,
        "persist_failed": 0,
        "cancelled": 1,
        "running_current": 399,
        "persisted": 100
      }
    }
  }
}

Response parameters

Options	Description
submitted	The number of asynchronous search requests that were submitted.
initialized	The number of asynchronous search requests that were initialized.
rejected	The number of asynchronous search requests that were rejected.
search_completed	The number of asynchronous search requests that completed with a successful response.
search_failed	The number of asynchronous search requests that completed with a failed response.
persisted	The number of asynchronous search requests whose final result successfully persisted in the cluster.
persist_failed	The number of asynchronous search requests whose final result failed to persist in the cluster.
running_current	The number of asynchronous search requests that are running on a given coordinator node.
cancelled	The number of asynchronous search requests that were canceled while the search was running.