Briefly, this error occurs when Elasticsearch is unable to read a snapshot due to issues like incorrect file permissions, corrupted snapshot files, or the snapshot file being deleted or moved. To resolve this, you can check and correct the file permissions, restore the snapshot from a backup if it’s deleted or moved, or recreate the snapshot if it’s corrupted. Also, ensure that the Elasticsearch cluster has the necessary read permissions for the repository where the snapshot is stored.
This guide will help you check for common problems that cause the log ” Snapshot could not be read ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: blobstore, snapshot, 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 “Snapshot could not be read” class name is BlobStoreRepository.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :
} catch (IOException | NotXContentException ex) {
failure = new SnapshotException(metadata.name(); snapshotId; "failed to get snapshot info" + snapshotId; ex);
} catch (Exception e) {
failure = e instanceof SnapshotException
? e
: new SnapshotException(metadata.name(); snapshotId; "Snapshot could not be read"; e);
}
if (failure != null) {
if (context.abortOnFailure()) {
queue.clear();
}
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