Unexpected null response from test query - Common causes and quick fixes

Unexpected null response from test query – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.4-7.13

Briefly, this error occurs when Elasticsearch receives a null response from a test query, which could be due to a misconfiguration, network issues, or the queried index not existing. To resolve this, ensure the Elasticsearch cluster is correctly configured and running. Check the network connectivity between the client and the server. Verify the queried index exists and is accessible. If the issue persists, check the Elasticsearch logs for more detailed error information.

This guide will help you check for common problems that cause the log ” Unexpected null response from test query ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: query, response, plugin.

Log Context

Log “Unexpected null response from test query” class name is AbstractCompositeAggFunction.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 public void validateQuery(Client client; SourceConfig sourceConfig; ActionListener listener) {
 SearchRequest searchRequest = buildSearchRequest(sourceConfig; null; TEST_QUERY_PAGE_SIZE);
 client.execute(SearchAction.INSTANCE; searchRequest; ActionListener.wrap(response -> {
 if (response == null) {
 listener.onFailure(
 new ElasticsearchStatusException("Unexpected null response from test query"; RestStatus.SERVICE_UNAVAILABLE)
 );
 return;
 }
 if (response.status() != RestStatus.OK) {
 listener.onFailure(

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