Briefly, this error occurs when Elasticsearch is unable to delete a snapshot file due to insufficient permissions, a locked file, or a network issue. To resolve this, you can try the following: 1) Check and adjust the file permissions to ensure Elasticsearch has the necessary access. 2) Ensure the file is not being used or locked by another process. 3) If the snapshot is stored on a remote server, verify the network connection and the server’s status. 4) If the snapshot is corrupted, you may need to manually delete it from the filesystem.
This guide will help you check for common problems that cause the log ” [{}] Unable to delete snapshot file [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: repositories, snapshot, blobstore, delete.
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 “[{}] Unable to delete snapshot file [{}]” classname is BlobStoreRepository.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
private void deleteSnapshotBlobIgnoringErrors(final SnapshotInfo snapshotInfo; final String blobId) {
try {
snapshotFormat.delete(blobContainer(); blobId);
} catch (IOException e) {
if (snapshotInfo != null) {
logger.warn(() -> new ParameterizedMessage("[{}] Unable to delete snapshot file [{}]";
snapshotInfo.snapshotId(); blobId); e);
} else {
logger.warn(() -> new ParameterizedMessage("Unable to delete snapshot file [{}]"; blobId); e);
}
}
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