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 current Elasticsearch version. If the snapshot files are corrupted, try restoring from a different snapshot. Also, check the Elasticsearch logs for more specific error messages that can guide you to the root cause.
This guide will help you check for common problems that cause the log ” [” + snapshot + “] failed to restore snapshot ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: snapshot, restore.
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 “[” + snapshot + “] failed to restore snapshot” classname is RestoreService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
}
}
@Override
public void onFailure(Exception e) {
logger.warn(() -> "[" + snapshot + "] failed to restore snapshot"; e);
listener.clusterStateUpdate().onFailure(e);
}
@Override
public void clusterStateProcessed(ClusterState oldState; ClusterState newState) {
