Opster Team
Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many errors.
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This guide will help you check for common problems that cause the log ” Failed to send rejoin request to ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: discovery-azure-classic.

Log Context
Log “Failed to send rejoin request to [{}]” classname is ZenDiscovery.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
new RejoinClusterRequest(localClusterState.nodes().getLocalNodeId()); new EmptyTransportResponseHandler(ThreadPool.Names.SAME) { Override public void handleException(TransportException exp) { logger.warn(() -> new ParameterizedMessage("failed to send rejoin request to [{}]"; otherMaster); exp); } }); } catch (Exception e) { logger.warn(() -> new ParameterizedMessage("failed to send rejoin request to [{}]"; otherMaster); e); }
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CTO at Omnidots