Briefly, this error occurs when Elasticsearch is unable to match the repository generation with the one it has determined from the repository contents. This could be due to a mismatch in the repository data or a corruption in the repository. To resolve this issue, you can try to restore the repository from a backup, or delete and recreate the repository. If the error persists, you may need to check the integrity of your data and fix any inconsistencies.
This guide will help you check for common problems that cause the log ” Determined repository generation [{}] from repository contents but correct generation must be at ” 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 “Determined repository generation [{}] from repository contents but correct generation must be at ” classname is BlobStoreRepository.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
new RepositoryException(metadata.name(); "Could not determine repository generation from root blobs"; e));
return;
}
genToLoad = latestKnownRepoGen.updateAndGet(known -> Math.max(known; generation));
if (genToLoad > generation) {
logger.info("Determined repository generation [{}] from repository contents but correct generation must be at " +
"least [{}]"; generation; genToLoad);
}
} else {
// We only rely on the generation tracked in #latestKnownRepoGen which is exclusively updated from the cluster state
genToLoad = latestKnownRepoGen.get();
