Briefly, this error occurs when Elasticsearch is unable to delete a file during the cleanup process of a snapshot. This could be 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.
This guide will help you check for common problems that cause the log ” [{}] [{}] failed to delete file [{}] during snapshot cleanup ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: blobstore, repositories, delete, snapshot.
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.
Overview
DELETE is an Elasticsearch API which removes a document from a specific index. This API requires an index name and _id document to delete the document.
Delete a document
DELETE /my_index/_doc/1
Notes
- A delete request throws 404 error code if the document does not already exist in the index.
- If you want to delete a set of documents that matches a query, you need to use delete by query API.
Log Context
Log “[{}] [{}] failed to delete file [{}] during snapshot cleanup” classname is FileRestoreContext.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
// snapshots of immutable directories either only contain an empty `segments_N` file or no data at all;
// since the data lives elsewhere; and if we restore such a snapshot then the real data is already present
// in the directory and cannot be removed.
assert snapshotFiles.indexFiles().size() <= 1 : snapshotFiles;
} catch (IOException e) {
logger.warn("[{}] [{}] failed to delete file [{}] during snapshot cleanup"; shardId; snapshotId; storeFile);
}
}
} catch (IOException e) {
logger.warn("[{}] [{}] failed to list directory - some of files might not be deleted"; shardId; snapshotId);
}
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