search-backend-module-elasticsearch: add support for reading index templates from options

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

plugins/search-backend-module-elasticsearch/config.d.ts

@@ -43,6 +43,33 @@ export interface Config {
          */
         fragmentDelimiter?: string;
       };
+
+      /** Elasticsearch specific index template bodies */
+      indexTemplates?: Array<{
+        name: string;
+        body: {
+          /**
+           * Array of wildcard (*) expressions used to match the names of data streams and indices during creation.
+           */
+          index_patterns: string[];
+
+          /**
+           * An ordered list of component template names.
+           * Component templates are merged in the order specified,
+           * meaning that the last component template specified has the highest precedence.
+           */
+          composed_of?: string[];
+
+          /**
+           * See available properties of template
+           * https://www.elastic.co/guide/en/elasticsearch/reference/7.15/indices-put-template.html#put-index-template-api-request-body
+           */
+          template?: {
+            [key: string]: unknown;
+          };
+        };
+      }>;
+
       /** Miscellaneous options for the client */
       clientOptions?: {
         ssl?: {
@@ -128,7 +155,7 @@ export interface Config {
                 };
             /* TODO(kuangp): unsupported until @elastic/elasticsearch@7.14 is released
     | {
- 
+
       /**
        * Bearer authentication token to connect to the cluster.
        * See: https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-create-service-token.html

plugins/search-backend-module-elasticsearch/src/engines/ElasticSearchSearchEngine.ts

@@ -165,7 +165,7 @@ export class ElasticSearchSearchEngine implements SearchEngine {
       logger.info('Initializing ElasticSearch search engine.');
     }
 
-    return new ElasticSearchSearchEngine(
+    const engine = new ElasticSearchSearchEngine(
       clientOptions,
       aliasPostfix,
       indexPrefix,
@@ -176,6 +176,14 @@ export class ElasticSearchSearchEngine implements SearchEngine {
         'search.elasticsearch.highlightOptions',
       ),
     );
+
+    for (const indexTemplate of this.readIndexTemplateConfig(
+      config.getConfig('search.elasticsearch'),
+    )) {
+      await engine.setIndexTemplate(indexTemplate);
+    }
+
+    return engine;
   }
 
   /**
@@ -518,6 +526,24 @@ export class ElasticSearchSearchEngine implements SearchEngine {
         : {}),
     };
   }
+
+  private static readIndexTemplateConfig(
+    config: Config,
+  ): ElasticSearchCustomIndexTemplate[] {
+    return (
+      config.getOptionalConfigArray('indexTemplates')?.map(templateConfig => {
+        const bodyConfig = templateConfig.getConfig('body');
+        return {
+          name: templateConfig.getString('name'),
+          body: {
+            index_patterns: bodyConfig.getStringArray('index_patterns'),
+            composed_of: bodyConfig.getOptionalStringArray('composed_of'),
+            template: bodyConfig.getOptionalConfig('template')?.get(),
+          },
+        };
+      }) ?? []
+    );
+  }
 }
 
 /**