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This guide will help you check for common problems that cause the log ” failed to restore snapshot ” + snapshotId + ” ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: repositories, restore, snapshot, blobstore.
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
In Elasticsearch, restore refers to the snapshot restore mechanism, which returns indices or clusters to a previous, saved state. You can restore the entire cluster from the snapshot or restore an individual index or selected indices.
Examples
To restore the whole snapshot:
POST /_snapshot/my_backup/snapshot-01-11-2019/_restore
To restore an individual index:
POST /_snapshot/my_backup/snapshot-01-11-2019/_restore
{
"indices": "my_index"
}Notes
- If you are using a security tool like Searchguard, the snapshot restore capability must be enabled in elasticsearch.yml. Otherwise, it will throw a security exception.
Common issues
- If an index or indices already exist with the same names as those you are going to restore, they need to either be closed or deleted before you can restore from a snapshot. Otherwise, the restore operation will fail due to an error that the index already exists.
Log Context
Log “failed to restore snapshot [” + snapshotId + “]”classname is BlobStoreRepository.java We extracted the following from Elasticsearch source code for those seeking an in-depth context :
RecoveryState recoveryState; ActionListenerlistener ) { final ShardId shardId = store.shardId(); final ActionListener restoreListener = listener.delegateResponse( (l; e) -> l.onFailure(new IndexShardRestoreFailedException(shardId; "failed to restore snapshot [" + snapshotId + "]"; e)) ); final Executor executor = threadPool.executor(ThreadPool.Names.SNAPSHOT); final BlobContainer container = shardContainer(indexId; snapshotShardId); synchronized (ongoingRestores) { if (store.isClosing()) {
