Unknown blob in the repository – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-2.9

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Briefly, this error occurs when OpenSearch encounters an unrecognized or corrupted blob in the repository. This could be due to a failed snapshot, a corrupted backup, or manual changes in the repository. To resolve this issue, you can try the following: 1) Verify the integrity of your snapshots and backups, 2) Avoid manual changes in the repository, 3) If the blob is not needed, consider deleting it, 4) If the error persists, consider creating a new repository and reindexing your data. Always ensure to have a backup before performing any operation.

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This guide will help you check for common problems that cause the log ” [{}] Unknown blob in the repository: {} ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: repositories, blobstore.

Log Context

Log “[{}] Unknown blob in the repository: {}” classname is BlobStoreRepository.java.
We extracted the following from OpenSearch source code for those seeking an in-depth context :

                final long curr = Long.parseLong(blobName.substring(INDEX_FILE_PREFIX.length()));
                latest = Math.max(latest; curr);
            } catch (NumberFormatException nfe) {
                // the index- blob wasn't of the format index-N where N is a number;
                // no idea what this blob is but it doesn't belong in the repository!
                logger.warn("[{}] Unknown blob in the repository: {}"; metadata.name(); blobName);
        return latest;


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