Briefly, this error occurs when Elasticsearch is unable to restore a snapshot due to reasons like insufficient disk space, incompatible versions between the snapshot and the current Elasticsearch, or corrupted snapshot files. To resolve this, ensure you have enough disk space and that the snapshot version is compatible with your Elasticsearch version. If the snapshot files are corrupted, try restoring from a different snapshot. If the issue persists, consider reindexing your data.
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: blobstore, restore, snapshot, repositories.
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 + “]” class name 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()) {
