Briefly, this error occurs when Elasticsearch tries to access a field that doesn’t exist in the index. This could be due to a typo in the field name or the field not being defined in the mapping. To resolve this issue, you can check the field name for typos, ensure the field exists in the index mapping, or add the field to the index mapping if it’s missing. If the field is not required, you can also handle the error in your application code to ignore the field.
This guide will help you check for common problems that cause the log ” unknown field name [” + field + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: 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 “unknown field name [” + field + “]” class name is RepositoryData.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :
throw new ElasticsearchParseException("version string expected [min_version]");
}
final Version version = Version.fromString(parser.text());
assert SnapshotsService.useShardGenerations(version);
} else {
throw new ElasticsearchParseException("unknown field name [" + field + "]");
}
}
} else {
throw new ElasticsearchParseException("start object expected");
}
