How To Solve Issues Related to Log – Failed to send response for search

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Updated: Feb-20

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Troubleshooting background

To troubleshoot Elasticsearch log “Failed to send response for search” it’s important to understand common problems related to Elasticsearch concepts: response, search. See detailed explanations below complete with common problems, examples and useful tips.

Search in Elasticsearch

What it is

Search refers to the searching of documents in an index or multiple indices. The simple search is just a GET request to _search endpoint. The search query can either be provided in query string or through  a request body.

Examples

When looking for any documents in this index, if search parameters are not provided, every document is a hit and by default 10 hits will be returned.

GET my_documents/_search

A JSON object is returned in response to a search query. A 200 response code will mean the request completed successfully.

{
"took" : 1,
"timed_out" : false,
"_shards" : {
"total" : 2,
"successful" : 2,
"failed" : 0
},
"hits" : {
"total" : 2,
"max_score" : 1.0,
"hits" : [
...
]
}
}
Notes
  • Distributed search is challenging and every shard of the index needs to be searched for hits, and then those hits are combined into a single sorted list as a final result.
  • There are two phases of search: the query phase and the fetch phase.
  • In the query phase, the query is executed on each shard locally and top hits are returned to the coordinating node. The coordinating node merges the results and creates a global sorted list. 
  • In the fetch phase, the coordinating node brings the actual documents for those hit IDs and returns them to the requesting client.
  • A coordinating node needs enough memory and CPU in order to handle the fetch phase.


To help troubleshoot related issues we have gathered selected Q&A from the community and issues from Github , please review the following for further information :

1 Failed To Send Ping To  

2Watcher Failed To Send Sample Slack  


Log Context

Log ”Failed to send response for search” classname is TransportSearchAction.java
We have extracted the following from Elasticsearch source code to get an in-depth context :

                 
Override
                public void onFailure(Throwable e) {
                    try {
                        channel.sendResponse(e);
                    } catch (Exception e1) {
                        logger.warn("Failed to send response for search"; e1);
                    }
                }
            });
        }






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