How To Solve Issues Related to Log – Realm is in user-dn-template mode:

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Troubleshooting background

To troubleshoot Elasticsearch log “Realm is in user-dn-template mode:” it’s important to know common problems related to Elasticsearch concepts: 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

Template in Elasticsearch

What it is

A template in Elasticsearch falls into  one of the two following categories and is  indexed inside Elasticsearch using its dedicated endpoint: 

  1. Index Templates, which are a way to define a set of rules including index settings, mappings and an index pattern. The template is applied automatically whenever a new index is created with the matching pattern. Templates are also used to dynamically apply custom mapping for the fields which are not predefined inside existing mapping.
  1. Search Templates, which help in defining templates for search queries using mustache scripting language. These templates act as a placeholder for variables defined inside the search queries.
Examples

Create a dynamic index template

PUT /_template/template_1?pretty
{
  "index_patterns": [
    "logs*",
    "api*"
  ],
  "settings": {
    "number_of_shards": 2
  },
  "mappings": {
    "dynamic_templates": [
      {
        "strings": {
          "match_mapping_type": "string",
          "mapping": {
            "type": "keyword"
          }
        }
      }
    ],
    "properties": {
      "host_name": {
        "type": "keyword"
      },
      "created_at": {
        "type": "date"
      }
    }
  }
}

Create a search template

POST /_scripts/search_template_1?pretty
{
    "script": {
        "lang": "mustache",
        "source": {
            "query": {
                "match": {
                    "description": "{{query_string}}"
                }
            }
        }
    }
}

Executing a search query using search template

GET /_search/template?pretty
{
    "id": "search_template_1", 
    "params": {
        "query_string": "hello world"
    }
}

The search request will be executed by default on all the indices available in the cluster and can be limited to particular indices using an index parameter.

Notes

A dynamic index template is always useful when you do not know the field names in advance and want to control their mapping as per the business use case.


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 :

Uld Not Resolve Placeholder In Stri
stackoverflow.com/questions/20244696/could-not-resolve-placeholder-in-string-value

 

Ring Circular Placeholder Reference
stackoverflow.com/questions/11551083/spring-circular-placeholder-reference-while-running-an-executable-jar

 


Log Context

Log ”Realm is in user-dn-template mode:” classname is LdapSessionFactory.java
We have extracted the following from Elasticsearch source code to get an in-depth context :

         userDnTemplates = LdapSessionFactorySettings.USER_DN_TEMPLATES_SETTING.get(settings).toArray(Strings.EMPTY_ARRAY);
        if (userDnTemplates.length == 0) {
            throw new IllegalArgumentException("missing required LDAP setting ["
                    + RealmSettings.getFullSettingKey(config; LdapSessionFactorySettings.USER_DN_TEMPLATES_SETTING) + "]");
        }
        logger.info("Realm [{}] is in user-dn-template mode: [{}]"; config.name(); userDnTemplates);
        groupResolver = groupResolver(settings);
        metaDataResolver = new LdapMetaDataResolver(settings; ignoreReferralErrors);
    }

    /**






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