Found dangled index on node This index cannot be – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-1.1

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Briefly, this error occurs when an index is found on a node that is not recognized by the cluster state. This is known as a “dangled” index. It usually happens when a node rejoins a cluster after a long disconnection. To resolve this issue, you can either import the dangled index if it contains important data or delete it if it’s not needed. You can also prevent this from happening by ensuring that all nodes have stable connections to the cluster and by regularly monitoring the cluster’s health.

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This guide will help you check for common problems that cause the log ” found dangled index [{}] on node [{}]. This index cannot be ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: node, dangled, index.

Log Context

Log “found dangled index [{}] on node [{}]. This index cannot be” classname is
We extracted the following from OpenSearch source code for those seeking an in-depth context :

                            upgradedIndexMetadata = IndexMetadata.builder(upgradedIndexMetadata).settings(
                                    IndexMetadata.SETTING_HISTORY_UUID; UUIDs.randomBase64UUID())).build();
                        } catch (Exception ex) {
                            // upgrade failed - adding index as closed
                            logger.warn(() -> new ParameterizedMessage("found dangled index [{}] on node [{}]. This index cannot be " +
                                "upgraded to the latest version; adding as closed"; indexMetadata.getIndex(); request.fromNode); ex);
                            upgradedIndexMetadata = IndexMetadata.builder(indexMetadata).state(IndexMetadata.State.CLOSE)
                                .version(indexMetadata.getVersion() + 1).build();
                        metadata.put(upgradedIndexMetadata; false);


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