Implemented metadata caching for Elasticsearch.

classes/engine.php

@@ -60,6 +60,11 @@ class engine extends \core_search\engine {
      */
     protected $count = 0;
 
+    /**
+     * @var cache_application|cache_session|cache_store The cache storage.
+     */
+    protected $cache = null;
+
     /**
      *
      * @var array Configuration defaults.
@@ -87,6 +92,8 @@ public function __construct() {
             set_config($name, $value, 'search_elastic');
         }
 
+        $this->cache = \cache::make('search_elastic', 'elasticserver');
+
     }
 
     /**
@@ -181,12 +188,19 @@ public function validate_index() {
      * @return object Apache Lucene version details.
      */
     private function get_es_version_details() {
-        $url = $this->get_url();
-        $client = new \search_elastic\esrequest();
-        $response = $client->get($url);
-        $responsebody = json_decode($response->getBody());
+        $data = $this->cache->get('es_version');
+
+        if ($data === false) {
+            $url = $this->get_url();
+            $client = new \search_elastic\esrequest();
+            $response = $client->get($url);
+            $responsebody = json_decode($response->getBody());
+
+            $data = $responsebody->version;
+            $this->cache->set('es_version', $responsebody->version);
+        }
 
-        return $responsebody->version;
+        return $data;
     }
 
     /**

db/caches.php

@@ -0,0 +1,32 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Elasticsearch web service external functions and service definitions.
+ *
+ * @package    search_elastic
+ * @copyright  2017 Matt Porritt <mattp@catalyst-au.net>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+$definitions = [
+    'elasticserver' => [
+        'mode' => cache_store::MODE_APPLICATION,
+        'ttl' => 5 * MINSECS,
+    ]
+];

lang/en/search_elastic.php

@@ -24,6 +24,7 @@
 
 $string['pluginname'] = 'Elastic';
 $string['pluginname_help'] = 'Search backend for the Elasticsearch search engine';
+$string['cachedef_elasticsearch'] = 'Cache server\'s metadata';
 
 $string['addfail'] = 'Failed to add document to index';
 $string['advsettings'] = 'Advanced settings';