Unfollow request failed to be acknowledged – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.12-8.9

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Briefly, this error occurs when an Elasticsearch unfollow request is not acknowledged by the follower index. This could be due to network issues, heavy load on the follower index, or the follower index being unavailable. To resolve this issue, you can try the following: 1) Check the network connectivity between the leader and follower index. 2) Monitor the load on the follower index and scale up resources if necessary. 3) Ensure the follower index is available and operational. 4) Retry the unfollow request after some time.

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This guide will help you check for common problems that cause the log ” unfollow 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, request.

Log Context

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

 void innerPerformAction(String followerIndex; ClusterState currentClusterState; ActionListener listener) {
 UnfollowAction.Request request = new UnfollowAction.Request(followerIndex).masterNodeTimeout(TimeValue.MAX_VALUE);
 getClient().execute(UnfollowAction.INSTANCE; request; ActionListener.wrap(r -> {
 if (r.isAcknowledged() == false) {
 throw new ElasticsearchException("unfollow request failed to be acknowledged");
 }; exception -> {
 if (exception instanceof ElasticsearchException e && e.getMetadata("es.failed_to_remove_retention_leases") != null) {
 List leasesNotRemoved = e.getMetadata("es.failed_to_remove_retention_leases");


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