How To Solve Issues Related to Log – Could not execute query template (failed to close writer)

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Updated: Feb-20

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Troubleshooting background

To troubleshoot Elasticsearch log “Could not execute query template (failed to close writer)” it’s important to understand common problems related to Elasticsearch concepts: delete-by-query, mustache, template. See detailed explanations below complete with common problems, examples and useful tips.

Template in Elasticsearch

What it is

A template in Elasticsearch falls into  one of the two following categories and is  indexed inside Elasticsearch using its dedicated endpoint: 

  1. Index Templates, which are a way to define a set of rules including index settings, mappings and an index pattern. The template is applied automatically whenever a new index is created with the matching pattern. Templates are also used to dynamically apply custom mapping for the fields which are not predefined inside existing mapping.
  1. Search Templates, which help in defining templates for search queries using mustache scripting language. These templates act as a placeholder for variables defined inside the search queries.
Examples

Create a dynamic index template

PUT /_template/template_1?pretty
{
  "index_patterns": [
    "logs*",
    "api*"
  ],
  "settings": {
    "number_of_shards": 2
  },
  "mappings": {
    "dynamic_templates": [
      {
        "strings": {
          "match_mapping_type": "string",
          "mapping": {
            "type": "keyword"
          }
        }
      }
    ],
    "properties": {
      "host_name": {
        "type": "keyword"
      },
      "created_at": {
        "type": "date"
      }
    }
  }
}

Create a search template

POST /_scripts/search_template_1?pretty
{
    "script": {
        "lang": "mustache",
        "source": {
            "query": {
                "match": {
                    "description": "{{query_string}}"
                }
            }
        }
    }
}

Executing a search query using search template

GET /_search/template?pretty
{
    "id": "search_template_1", 
    "params": {
        "query_string": "hello world"
    }
}

The search request will be executed by default on all the indices available in the cluster and can be limited to particular indices using an index parameter.

Notes

A dynamic index template is always useful when you do not know the field names in advance and want to control their mapping as per the business use case.


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 Spark Streaming and ElasticSearch – Could not write all entries 4.33 K 3

2Forbidden 12 Index Read Only Allow  


Log Context

Log ”Could not execute query template (failed to close writer):” classname is MustacheScriptEngineService.java
We have extracted the following from Elasticsearch source code to get an in-depth context :

             logger.error("Could not execute query template (failed to flush writer): "; e);
        } finally {
            try {
                writer.close();
            } catch (IOException e) {
                logger.error("Could not execute query template (failed to close writer): "; e);
            }
        }
        return result.bytes();
    }







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