How To Solve Issues Related to Log – Adding template for index patterns

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Updated: Jan-20

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Troubleshooting background

To troubleshoot Elasticsearch log “Adding template for index patterns” it’s important to understand common problems related to Elasticsearch concepts: cluster, index, metadata, template. See detailed explanations below complete with common problems, examples and useful tips.

Index in Elasticsearch

What it is

In Elasticsearch, an index (indices in plural) can be thought of as a table inside a database that has a schema and can have one or more shards and replicas. An Elasticsearch index is divided into shards and each shard is an instance of a Lucene index.

Indices are used to store the documents in dedicated data structures corresponding to the data type of fields. For example, text fields are stored inside an inverted index whereas numeric and geo fields are stored inside BKD trees.

Examples
Create Index

The following example is based on Elasticsearch version 5.x onwards. An index with two shards, each having one replica will be created with the name test_index1

PUT /test_index1?pretty
{
    "settings" : {
        "number_of_shards" : 2,
        "number_of_replicas" : 1
    },
    "mappings" : {
        "properties" : {
            "tags" : { "type" : "keyword" },
            "updated_at" : { "type" : "date" }
        }
    }
}
List Indices

All the index names and their basic information can be retrieved using the following command:

GET _cat/indices?v
Index a document

Let’s add a document in the index with below command:

PUT test_index1/_doc/1
{
  "tags": [
    "opster",
    "elasticsearch"
  ],
  "date": "01-01-2020"
}
Query an index
GET test_index1/_search
{
  "query": {
    "match_all": {}
  }
}
Query Multiple Indices

It is possible to search multiple indices with a single request. If it is a raw HTTP request, Index names should be sent in comma-separated format, as shown in the example below, and in the case of a query via a programming language client such as python or Java, index names are to be sent in a list format.

GET test_index1,test_index2/_search
Delete Indices
DELETE test_index1
Common Problems
  • It is good practice to define the settings and mapping of an Index wherever possible because if this is not done, Elasticsearch tries to automatically guess the data type of fields at the time of indexing. This automatic process may have disadvantages, such as mapping conflicts, duplicate data and incorrect data types being set in the index. If the fields are not known in advance, it’s better to use dynamic index templates.
  • Elasticsearch supports wildcard patterns in Index names, which sometimes aids with querying multiple indices, but can also be very destructive too. For example, It is possible to delete all the indices in a single command using the following commands:
DELETE /*

To disable this, you can add the following lines in the elasticsearch.yml:

action.destructive_requires_name: true

Metadata in Elasticsearch

What it is

Metadata in Elasticsearch refers to storing some additional information for each document. This is achieved using the specific metadata fields available in Elasticsearch. 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
  • In version 2.x, Elasticsearch had a total 13 meta fields available, which are: _index, _uid, _type, _id, _source, _size, _all, _field_names, _timestamp, _ttl, _parent, _routing, _meta
  • In version 5.x, _timestamp and _ttl meta fields were removed.
  • In version 6.x, the _parent meta field was removed.
  • In version 7.x, _uid and _all meta fields were removed.

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 Elasticsearch index-patterns on template without wildcards ✔ – 0.05 K 

2 ElasticSearch – what is the difference between an index template and an index pattern ✔   1 2.10 K 

Log Context

Log ”Adding template [{}] for index patterns {}” classname is MetaDataIndexTemplateService.java
We have extracted the following from Elasticsearch source code to get an in-depth context : 

                 }
                IndexTemplateMetaData template = templateBuilder.build();

                MetaData.Builder builder = MetaData.builder(currentState.metaData()).put(template);

                logger.info("adding template [{}] for index patterns {}"; request.name; request.indexPatterns);
                return ClusterState.builder(currentState).metaData(builder).build();
            }

            
Override
            public void clusterStateProcessed(String source; ClusterState oldState; ClusterState newState) {
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