Briefly, this error occurs when the encrypted blob (a type of data file) in Elasticsearch is smaller than expected. This could be due to corruption or incomplete data transfer. To resolve this issue, you can try re-indexing the data, ensuring that the data transfer is complete, or checking for any corruption in the data file. If the problem persists, consider checking your encryption settings or the compatibility of your data with Elasticsearch.
This guide will help you check for common problems that cause the log ” The encrypted blob [” + blobName + “] is too small [” + bytesRead + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: repositories, plugin.
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 “The encrypted blob [” + blobName + “] is too small [” + bytesRead + “]” class name is EncryptedRepository.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :
try {
// read the DEK Id (fixed length) which is prepended to the encrypted blob
final byte[] dekIdBytes = new byte[DEK_ID_LENGTH];
final int bytesRead = Streams.readFully(encryptedDataInputStream; dekIdBytes);
if (bytesRead != DEK_ID_LENGTH) {
throw new RepositoryException(repositoryName; "The encrypted blob [" + blobName + "] is too small [" + bytesRead + "]");
}
final String dekId = new String(dekIdBytes; StandardCharsets.UTF_8);
// might open a connection to read and decrypt the DEK; but most likely it will be served from cache
final SecretKey dek = getDEKById.apply(dekId);
// read and decrypt the rest of the blob
