Could not execute query template failed to flush writer – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 1.7-1.7

Briefly, this error occurs when Elasticsearch fails to execute a query template due to an issue with flushing the writer. This could be due to a lack of disk space, a corrupted index, or a network connectivity issue. To resolve this, you can try freeing up disk space, checking the health of your indices and repairing if necessary, or ensuring stable network connectivity. Additionally, check your Elasticsearch logs for more specific details about the error.

In addition we recommend you run the Elasticsearch Template Optimizer to fix problems in your data modeling.

It will analyze your templates to detect issues and improve search performance, reduce indexing bottlenecks and optimize storage utilization. The Template Optimizer is free and requires no installation.

Log Context

Log “Could not execute query template (failed to flush writer):” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

UTF8StreamWriter writer = utf8StreamWriter().setOutput(result);
        ((Mustache) template).execute(writer; vars);
        try {
        } catch (IOException e) {
            logger.error("Could not execute query template (failed to flush writer): "; e);
        } finally {
            try {
            } catch (IOException e) {
                logger.error("Could not execute query template (failed to close writer): "; e);


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