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Briefly, this error occurs when OpenSearch is unable to retrieve metadata for the specified placement or availability zone. This could be due to network issues, incorrect configuration, or the specified zone may not exist. To resolve this, ensure that your network connectivity is stable and check your configuration settings. Make sure the specified availability zone is correct and exists. If the problem persists, consider seeking assistance from your service provider or the OpenSearch community.
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This guide will help you check for common problems that cause the log ” failed to get metadata for [placement/availability-zone] ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: plugins, discovery-ec2, metadata, discovery.
Overview
A plugin is used to enhance the core functionalities of OpenSearch. OpenSearch provides some core plugins as a part of their release installation. In addition to those core plugins, it is possible to write your own custom plugins as well. There are several community plugins available on GitHub for various use cases.
Examples
Get all of the instructions for the plugin:
sudo bin/opensearch-plugin -h
Installing the S3 plugin for storing OpenSearch snapshots on S3:
sudo bin/opensearch-plugin install repository-s3
Removing a plugin:
sudo bin/opensearch-plugin remove repository-s3
Installing a plugin using the file’s path:
sudo bin/opensearch-plugin install file:///path/to/plugin.zip
Notes and good things to know
- Plugins are installed and removed using the opensearch-plugin script, which ships as a part of the OpenSearch installation and can be found inside the bin/ directory of the OpenSearch installation path.
- A plugin has to be installed on every node of the cluster and each of the nodes has to be restarted to make the plugin visible.
- You can also download the plugin manually and then install it using the opensearch-plugin install command, providing the file name/path of the plugin’s source file.
- When a plugin is removed, you will need to restart every OpenSearch node in order to complete the removal process.
Common issues
- Managing permission issues during and after plugin installation is the most common problem. If OpenSearch was installed using the DEB or RPM packages then the plugin has to be installed using the root user. Otherwise you can install the plugin as the user that owns all of the OpenSearch files.
- In the case of DEB or RPM package installation, it is important to check the permissions of the plugins directory after you install it. You can update the permission if it has been modified using the following command:
chown -R opensearch:opensearch path_to_plugin_directory
- If your OpenSearch nodes are running in a private subnet without internet access, you cannot install a plugin directly. In this case, you can simply download the plugins and copy the files inside the plugins directory of the OpenSearch installation path on every node. The node has to be restarted in this case as well.
Overview
Metadata in OpenSearch refers to additional information stored for each document. This is achieved using the specific metadata fields available in OpenSearch. The default behavior of some of these metadata fields can be customized during mapping creation.
Examples
Using _meta meta-field for storing application-specific information with the mapping:
PUT /my_index?pretty
{
"mappings": {
"_meta": {
"domain": "security",
"release_information": {
"date": "18-01-2020",
"version": "7.5"
}
}
}
}Notes
- Meta fields available include: _index, _type, _id, _source, _size, and _field_name.
Log Context
Log “failed to get metadata for [placement/availability-zone]” classname is Ec2DiscoveryPlugin.java.
We extracted the following from OpenSearch source code for those seeking an in-depth context :
} else {
attrs.put(Node.NODE_ATTRIBUTES.getKey() + "aws_availability_zone"; metadataResult);
}
} catch (final IOException e) {
// this is lenient so the plugin does not fail when installed outside of ec2
logger.error("failed to get metadata for [placement/availability-zone]"; e);
}
return attrs.build();
}
