How To Solve Issues Related to Log – Starting template upgrade to version ; templates will be updated and will be removed

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Updated: Jan-20

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Troubleshooting background

To troubleshoot Elasticsearch log “Starting template upgrade to version ; templates will be updated and will be removed” it’s important to understand common problems related to Elasticsearch concepts: cluster, metadata, template, upgrade, version. See detailed explanations below complete with common problems, examples and useful tips.

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.

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 :

1 Github Issue Number 26673  

2Cannot Update Templates Template Up  


Log Context

Log ”Starting template upgrade to version {}; {} templates will be updated and {} will be removed” classname is TemplateUpgradeService.java
We have extracted the following from Elasticsearch source code to get an in-depth context :

<pre class="wp-block-syntaxhighlighter-code"> 
        lastTemplateMetaData = templates;
        Optional<Tuple<Map<String; BytesReference>; Set<String>>> changes = calculateTemplateChanges(templates);
        if (changes.isPresent()) {
            if (upgradesInProgress.compareAndSet(0; changes.get().v1().size() + changes.get().v2().size() + 1)) {
                logger.info("Starting template upgrade to version {}; {} templates will be updated and {} will be removed";
                    Version.CURRENT;
                    changes.get().v1().size();
                    changes.get().v2().size());

                final ThreadContext threadContext = threadPool.getThreadContext();




</pre>


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