Failed send response for allocating dangled – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 6.8-8.5

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Briefly, this error occurs when Elasticsearch tries to allocate a dangled index but fails to send a response. A dangled index is an index that exists on disk but is not part of the cluster state. This could be due to network issues, insufficient disk space, or a problem with the cluster state. To resolve this issue, you can try restarting the Elasticsearch node, checking the network connection, ensuring there is enough disk space, or manually adding the dangled index to the cluster state.

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This guide will help you check for common problems that cause the log ” failed send response for allocating dangled ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: dangled, response.

Log Context

Log “failed send response for allocating dangled” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

                    logger.error(() -> "unexpected failure during [" + source + "]"; e);
                    try {
                    } catch (Exception inner) {
                        logger.warn("failed send response for allocating dangled"; inner);

                public void clusterStateProcessed(ClusterState oldState; ClusterState newState) {


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