Briefly, this error occurs when Elasticsearch tries to access a blob (binary large object) in the repository that doesn’t exist or is not recognized. This could be due to a corrupted or deleted blob, or a synchronization issue between nodes. To resolve this, you can try to restore the blob if you have a backup, recreate the repository, or perform a resynchronization of your Elasticsearch nodes. Always ensure that your blobs are properly managed and backed up to prevent such issues.
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 Elasticsearch concepts: blobstore, repositories.
Overview
An Elasticsearch snapshot provides a backup mechanism that takes the current state and data in the cluster and saves it to a repository (read snapshot for more information). The backup process requires a repository to be created first. The repository needs to be registered using the _snapshot endpoint, and multiple repositories can be created per cluster. The following repository types are supported:
Repository types
| Repository type | Configuration type |
|---|---|
| Shared file system | Type: “fs” |
| S3 | Type : “s3” |
| HDFS | Type :“hdfs” |
| Azure | Type: “azure” |
| Google Cloud Storage | Type : “gcs” |
Examples
To register an “fs” repository:
PUT _snapshot/my_repo_01
{
"type": "fs",
"settings": {
"location": "/mnt/my_repo_dir"
}
}Notes and good things to know
- S3, HDFS, Azure and Google Cloud require a relevant plugin to be installed before it can be used for a snapshot.
- The setting, path.repo: /mnt/my_repo_dir needs to be added to elasticsearch.yml on all the nodes if you are planning to use the repo type of file system. Otherwise, it will fail.
- When using remote repositories, the network bandwidth and repository storage throughput should be high enough to complete the snapshot operations normally, otherwise you will end up with partial snapshots.
Log Context
Log “[{}] Unknown blob in the repository: {}” classname is BlobStoreRepository.java.
We extracted the following from Elasticsearch 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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