Cluster UUID set to – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-2.9

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Briefly, this error occurs when OpenSearch cannot identify the cluster’s unique identifier (UUID). This could be due to a new cluster being formed, a node rejoining after a long disconnection, or data directory issues. To resolve this, ensure all nodes are properly connected and communicating. If it’s a new cluster, this is normal as the UUID is being set for the first time. For data directory issues, check permissions and paths. Always ensure to have a backup of your data to prevent loss during troubleshooting.

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This guide will help you check for common problems that cause the log ” cluster UUID set to [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: cluster.

Log Context

Log “cluster UUID set to [{}]” classname is
We extracted the following from OpenSearch source code for those seeking an in-depth context :

                if (lastAcceptedState.term() != ZEN1_BWC_TERM) {
                    // Zen1 cluster-managers never publish a committed cluster UUID so if we logged this it'd happen on on every update.
                    // Let's just
                    // not log it at all in a 6.8/7.x rolling upgrade.
          "cluster UUID set to [{}]"; lastAcceptedState.metadata().clusterUUID());
            if (metadataBuilder != null) {


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