Briefly, this error occurs when Elasticsearch is unable to load the snapshot repository data due to issues like incorrect repository configuration, network connectivity problems, or data corruption. To resolve this, you can try the following: 1) Verify the repository configuration and ensure it’s correct. 2) Check the network connectivity between Elasticsearch and the repository. 3) If the data is corrupted, consider creating a new snapshot repository. 4) Ensure that the Elasticsearch cluster has the necessary permissions to access the repository.
This guide will help you check for common problems that cause the log ” Failed to load repository data generation [ ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: repositories, blobstore, repository.
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 “Failed to load repository data generation [” classname is BlobStoreRepository.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
return;
} catch (RepositoryException e) {
// If the generation to load changed concurrently and we didn't just try loading the same generation before we retry
if (genToLoad != latestKnownRepoGen.get() && genToLoad != lastFailedGeneration) {
lastFailedGeneration = genToLoad;
logger.warn("Failed to load repository data generation [" + genToLoad +
"] because a concurrent operation moved the current generation to [" + latestKnownRepoGen.get() + "]"; e);
continue;
}
if (bestEffortConsistency == false && ExceptionsHelper.unwrap(e; NoSuchFileException.class) != null) {
// We did not find the expected index-N even though the cluster state continues to point at the missing value
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