Briefly, this error occurs when an attempt is made to perform a snapshot on a non-primary shard in Elasticsearch. Snapshots are backups of a cluster’s indices and should only be performed on primary shards to ensure data consistency. To resolve this issue, ensure that the snapshot operation is performed on the primary shard. If the error persists, check the cluster health and ensure all primary shards are correctly allocated. If necessary, you may need to manually reassign the primary shard or perform a cluster reroute operation.
This guide will help you check for common problems that cause the log ” snapshot should be performed only on primary ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: snapshot.
Log Context
Log “snapshot should be performed only on primary” class name is SnapshotShardsService.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :
) {
ActionListener.run(resultListener; listener -> {
snapshotStatus.ensureNotAborted();
final IndexShard indexShard = indicesService.indexServiceSafe(shardId.getIndex()).getShard(shardId.id());
if (indexShard.routingEntry().primary() == false) {
throw new IndexShardSnapshotFailedException(shardId; "snapshot should be performed only on primary");
}
if (indexShard.routingEntry().relocating()) {
// do not snapshot when in the process of relocation of primaries so we won't get conflicts
throw new IndexShardSnapshotFailedException(shardId; "cannot snapshot while relocating");
}
