Open index request failed to be acknowledged – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.7-8.9

Briefly, this error occurs when Elasticsearch does not receive an acknowledgement for an open index request within a specified timeout period. This could be due to network issues, heavy load on the cluster, or the index being in a state that prevents it from being opened. To resolve this issue, you can increase the timeout period, ensure the index is in a state that allows it to be opened, or optimize the cluster to handle requests more efficiently. Additionally, check your network connectivity to ensure requests are being sent and received correctly.

This guide will help you check for common problems that cause the log ” open index request failed to be acknowledged ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin, index, request.

Log Context

Log “open index request failed to be acknowledged” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 ) {
 if (indexMetadata.getState() == IndexMetadata.State.CLOSE) {
 OpenIndexRequest request = new OpenIndexRequest(indexMetadata.getIndex().getName()).masterNodeTimeout(TimeValue.MAX_VALUE);
 getClient().admin().indices().open(request; ActionListener.wrap(openIndexResponse -> {
 if (openIndexResponse.isAcknowledged() == false) {
 throw new ElasticsearchException("open index request failed to be acknowledged");
 }; listener::onFailure));  } else {


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