Briefly, this error occurs when Elasticsearch cannot find the necessary index templates for the Watcher feature, which is used for alerting and monitoring. This could be due to a misconfiguration or an unsuccessful initialization. To resolve this issue, you can try restarting Elasticsearch, as this will force the system to reinitialize and recreate the missing templates. Alternatively, you can manually add the missing templates if you have them. Lastly, ensure that the Watcher feature is properly installed and enabled in your Elasticsearch setup.
This guide will help you check for common problems that cause the log ” missing watcher index templates ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin, index.
Overview
In Elasticsearch, an index (plural: indices) contains 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 the command below:
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
Log Context
Log “missing watcher index templates” classname is WatcherService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
* @param state cluster state; which is needed to find out about local shards
*/
void reload(ClusterState state; String reason) {
boolean hasValidWatcherTemplates = WatcherIndexTemplateRegistry.validate(state);
if (hasValidWatcherTemplates == false) {
logger.warn("missing watcher index templates");
}
// this method contains the only async code block; being called by the cluster state listener
// the reason for this is that loading the watches is done in a sync manner and thus cannot be done on the cluster state listener
// thread
//
