Briefly, this error occurs when Elasticsearch tries to restore a snapshot but can’t find the segments file. The segments file is crucial as it contains information about the index segments. This error can be caused by a corrupted snapshot or issues with the storage system. To resolve this, you can try to restore from a different snapshot, ensure the storage system is functioning properly, or recreate the snapshot if possible. If the error persists, you may need to rebuild the index from your original data source.
This guide will help you check for common problems that cause the log ” Snapshot has no segments file ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: blobstore, snapshot, repositories.
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.
Log Context
Log “Snapshot has no segments file” class name is FileRestoreContext.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :
final Store.MetadataSnapshot sourceMetadata = new Store.MetadataSnapshot(unmodifiableMap(snapshotMetadata); emptyMap(); 0); final StoreFileMetadata restoredSegmentsFile = sourceMetadata.getSegmentsFile();
if (restoredSegmentsFile == null) {
throw new IndexShardRestoreFailedException(shardId; "Snapshot has no segments file");
} final Store.RecoveryDiff diff = sourceMetadata.recoveryDiff(recoveryTargetMetadata);
for (StoreFileMetadata md : diff.identical) {
BlobStoreIndexShardSnapshot.FileInfo fileInfo = fileInfos.get(md.name());
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