Recently I have upgraded the one data node , Node got successfully upgraded but there are some unassigned shards which are not being replicated to other nodes because of below error:
"explanation" : "cannot allocate replica shard to a node with version [7.13.4] since this is older than the primary version [7.16.3]"
After upgrading the few nodes, I can see logstash service got failed inside the machines. And we are unable to restart the service.
Please refer below logs:
[2022-03-17T07:44:42,432][ERROR][logstash.outputs.Elasticsearch][main][db1af4057ae53eec4aebe1d43e3d39bc64c27408ff34e47b0e3370f6927d375f] Attempted to send a bulk request but Elasticsearch appears to be unreachable or down {:message=>"Elasticsearch Unreachable: [https://logstash_writer:xxxxxx@elasticsearch.mgmt.aws.uk.tsb:9200/][Manticore::SocketException] Connection reset by peer (Write failed)", :exception=>LogStash::Outputs::Elasticsearch::HttpClient::Pool::HostUnreachableError, :will_retry_in_seconds=>2}
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