Failed to delete unassigned index reason – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-1.1

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Briefly, this error occurs when OpenSearch fails to delete an unassigned index due to a specific reason, which should be indicated in the error message. This could be due to insufficient permissions, a locked index, or a network issue. To resolve this, you can try the following: 1) Ensure the user has the necessary permissions to delete indices. 2) Check if the index is locked and unlock it if necessary. 3) Investigate for any network connectivity issues. 4) If the index is not needed, manually delete it using the Delete Index API.

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This guide will help you check for common problems that cause the log ” [{}] failed to delete unassigned index (reason [{}]) ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: indices, delete, index.

Log Context

Log “[{}] failed to delete unassigned index (reason [{}])” classname is
We extracted the following from OpenSearch source code for those seeking an in-depth context :

                    throw new IllegalStateException("Can't delete unassigned index store for [" + indexName + "] - it's still part of " +
                                                    "the cluster state [" + index.getIndexUUID() + "] [" + metadata.getIndexUUID() + "]");
                deleteIndexStore(reason; metadata);
            } catch (Exception e) {
                logger.warn(() -> new ParameterizedMessage("[{}] failed to delete unassigned index (reason [{}])";
                    metadata.getIndex(); reason); e);


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