How To Solve Issues Related to Log – Isolating datafeeds:

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Updated: Jan-20

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Troubleshooting background

To troubleshoot Elasticsearch log “Isolating datafeeds:” it’s important to understand common problems related to Elasticsearch concepts: plugin, upgrade. See detailed explanations below complete with common problems, examples and useful tips.

Plugin in Elasticsearch

What it is

A plugin is used to enhance the core functionalities of Elasticsearch. Elasticsearch 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 the instructions for the plugin usage
sudo bin/elasticsearch-plugin -h
  • Installing S3 plugin using URL for storing Elasticsearch snapshots on S3
sudo bin/elasticsearch-plugin install repository-s3
  • Removing a plugin
sudo bin/elasticsearch-plugin remove repository-s3
  • Installing a plugin using the file path
sudo bin/elasticsearch-plugin install file:///path/to/plugin.zip

Notes:
  • Plugins are installed and removed using the elasticsearch-plugin script, which ships as a part of Elasticsearch installation and can be found inside the bin/ directory of the Elasticsearch 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 elasticsearch-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 elasticsearch node in order to complete the removal process.

Common Problems:
  • Managing permission issues during and after plugin installation is the most common problem. If Elasticsearch was installed using the deb or rpm package then the plugin has to be installed using the root user, or else you can install the plugin as the user that owns all of the Elasticsearch files.
  • In case of deb or rpm package installation, it is important to check the permission of the plugins directory after plugin installation and update the permission if it has been modified using the following command:
chown -R elasticsearch:elasticsearch path_to_plugin_directory 
  • If your Elasticsearch 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 at once and copy the files inside the plugins directory of the Elasticsearch installation path on every node. The node has to be restarted in this case as well.

Upgrade in Elasticsearch

What is it

Upgrade refers to migrating your Elasticsearch version to a newer version. An upgrade of an existing cluster can be done in two ways: through a rolling upgrade and through a  full cluster restart. The benefit of a rolling upgrade is having zero downtime.

Commos problems and important points
  • The major problem with upgrades is version incompatibility between upgrades. Elasticsearch supports rolling upgrades only between minor versions. You need to make sure to go through the official documentation to see if your cluster can support a rolling upgrade, otherwise a complete reindexing is required.
    Once you upgrade an Elasticsearch node, a rollback can not be done. You need to make sure to take data backups before an upgrade.
  • Elasticsearch continuously removes or deprecates some of the features with every release, so  keep an eye on the change logs of each version before planning an upgrade. 
  • While doing a rolling upgrade, it is important to disable shard allocation before stopping a node and enable the shard allocation when node is upgraded and restarted. This process helps in avoiding unnecessary IO load in the cluster.


To help troubleshoot related issues we have gathered selected Q&A from the community and issues from Github , please review the following for further information :

1 Struggling To Understand The Value  

2Github Issue Number 30456  

Github Issue Number 46437


Log Context

Log ”Isolating datafeeds:” classname is TransportSetUpgradeModeAction.java
We have extracted the following from Elasticsearch source code to get an in-depth context :

<pre class="wp-block-syntaxhighlighter-code"> 
    private void isolateDatafeeds(PersistentTasksCustomMetaData tasksCustomMetaData;
                                  ActionListener<List<IsolateDatafeedAction.Response>> listener) {
        Set<String> datafeedsToIsolate = MlTasks.startedDatafeedIds(tasksCustomMetaData);

        logger.info("Isolating datafeeds: " + datafeedsToIsolate.toString());
        TypedChainTaskExecutor<IsolateDatafeedAction.Response> isolateDatafeedsExecutor =
            new TypedChainTaskExecutor<>(client.threadPool().executor(executor()); r -> true; ex -> true);

        datafeedsToIsolate.forEach(datafeedId -> {
            IsolateDatafeedAction.Request isolationRequest = new IsolateDatafeedAction.Request(datafeedId);




</pre>


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