Unexpected exception in multicast receiver – Elasticsearch Log Diagnostic

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Troubleshooting Background – start here to get the full picture       
Log Context – usefull for experts
Related Issues – selected resources from the community  
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Troubleshooting background

To troubleshoot Elasticsearch log “Unexpected exception in multicast receiver” it’s important to know common problems related to Elasticsearch concepts: discovery, discovery-multicast, Plugin. See below-detailed explanations complete with common problems, examples and useful tips.

Plugin in Elasticsearch

What it is

Plugins are used to extend the functionality of Elasticsearch. In addition to the core plugins available to you, it is possible to write custom plugins as well. Plugins are generated in a zip format with the mandatory file structure.

Examples:
  • Core Plugins: Xpack for Security and monitoring, Discovery plugins for EC2
  • Adding S3 plugin for storing snapshots on S3
sudo bin/elasticsearch-plugin install repository-s3
  • Adding HDFS plugin for storing snapshots on HDFS
sudo bin/elasticsearch-plugin install repository-hdfs
  • Removing a plugin
sudo bin/elasticsearch-plugin remove repository-hdfs
Notes:
  • Plugins are installed using the Elasticsearch-plugin script, which enables actions such as  listing, removing and installing plugins.
  • Core plugins can be installed simply by providing the name of the plugin to the Elasticsearch-plugin command.
  • 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 the elasticsearch node(s) in order to complete the removal process.
Common Problems:
  • You need to install the required plugins in your Elasticsearch deployment before moving it to production machines. (as it’s likely your production machines are behind a proxy and it’s very hard to get plugins installed behind a proxy).
  • The same is true when you are going to deploy elasticsearch using Docker images, you will most likely be rebuilding the standard image and including your required plugins in the custom docker build. Make sure the docker build is run on a build machine that is not behind a proxy, otherwise the plugin installation will fail during docker build.

Click here to get to our list of the Most frequent issues caused by Elasticsearch Plugins


Log Context

Log ”Unexpected exception in multicast receiver” classname is MulticastChannel.java
To help get the right context about this log, we have extracted the following from Elasticsearch source code

                         if (datagramPacketReceive.getData().length > 0) {
                            listener.onMessage(new BytesArray(datagramPacketReceive.getData()); datagramPacketReceive.getSocketAddress());
                        }
                    } catch (Throwable e) {
                        if (running) {
                            logger.warn("unexpected exception in multicast receiver"; e);
                        }
                    }
                }
            }
        }






To help troubleshoot related issues we have gathered selected answers from STOF & Discuss and issues from Github, please review the following for further information :

Elasticsearch Always Crashes With Q
discuss.elastic.co/t/elasticsearch-always-crashes-with-query-aggregations/62482

 

Github Issue Number 22909
github.com/elastic/elasticsearch/issues/22909

 


About Opster

Incorporating deep knowledge and broad history of Elasticsearch issues. Opster’s solution identifies and predicts root causes of Elasticsearch problems, provides recommendations and can automatically perform various actions to manage, troubleshoot and prevent issues

We are constantly updating our analysis of Elasticsearch logs, errors, and exceptions. Sharing best practices and providing troubleshooting guides.

Learn more: Glossary | Blog| Troubleshooting guides | Error Repository

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