Briefly, this error occurs when Elasticsearch is unable to synchronize the restore state after a master node switch. This could be due to network issues, node failures, or configuration problems. To resolve this issue, you can try the following: 1) Check the network connectivity between the nodes. 2) Verify the health of the nodes and replace any failed ones. 3) Review and correct any misconfigurations in your Elasticsearch setup. 4) Ensure that the master node has sufficient resources to handle the cluster operations.
This guide will help you check for common problems that cause the log ” failed to sync restore state after master switch ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: master and 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 “failed to sync restore state after master switch” classname is RestoreService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
return resyncRestoreInProgressWithRoutingTable(currentState);
}
Override
public void onFailure(String source; Exception e) {
logger.warn("failed to sync restore state after master switch"; e);
}
});
}
}
}
