{"id":54924,"date":"2022-04-20T12:59:43","date_gmt":"2022-04-20T07:29:43","guid":{"rendered":"https:\/\/www.tothenew.com\/blog\/?p=54924"},"modified":"2022-05-18T13:04:34","modified_gmt":"2022-05-18T07:34:34","slug":"how-to-use-singleton-design-pattern-with-elasticsearch-in-drupal-9","status":"publish","type":"post","link":"https:\/\/www.tothenew.com\/blog\/how-to-use-singleton-design-pattern-with-elasticsearch-in-drupal-9\/","title":{"rendered":"How to use singleton design pattern with Elasticsearch in Drupal 9"},"content":{"rendered":"

Singleton design pattern is really useful to use the same object over multiple calls. For third party softwares for examples like Apache Solr, elastic search, Redis, etc. it is not good practice to create the connection object again and again, rather a single object can be used multiple times. In such cases singleton design patterns can be used.<\/span><\/p>\n

Drupal is flexible enough to integrate with lots of libraries, we are going to pick <\/span>elasticsearch connector<\/b> module integration with Drupal 9 as an example.<\/span><\/p>\n

We will create a simple class which will connect with the elasticsearch server and will return the elasticsearch client object.<\/span><\/p>\n

For elasticsearch, <\/span>ElasticSearch Connector<\/span><\/a> module is used.<\/span><\/p>\n

We will create services for achieving the singleton object of elasticsearch. There are two services which we will use to get the objects, one will be a direct method and other will be an indirect method.<\/span><\/p>\n

As per guidelines a custom module should be created. The files which are mentioned below should be created.<\/span><\/p>\n

 <\/p>\n

File name: module_name.services.yml<\/span><\/p>\n

services<\/span>:<\/span><\/p>\n

\u00a0\u00a0<\/span>elastic_singleton.indirect_object<\/span>:<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0<\/span>class<\/span>: Drupal\\elastic_singleton\\ElasticInitiate<\/span><\/p>\n

\u00a0\u00a0<\/span>elastic_singleton.direct_object<\/span>:<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0<\/span>class<\/span>: Drupal\\elastic_singleton\\ElasticSingleton<\/span><\/p>\n

 <\/p>\n

We will create the first service which supplies direct objects as per demand.<\/span><\/p>\n

 <\/p>\n

File name: src\/ElasticSingleton.php<\/span><\/p>\n

 <\/p>\n

<?php<\/span><\/p>\n

\/**<\/span><\/p>\n

\u00a0* @file<\/span><\/p>\n

\u00a0* Contains ElasticSingleton singleton.<\/span><\/p>\n

\u00a0*\/<\/span><\/p>\n

namespace Drupal\\module_name;<\/span><\/p>\n

use Elasticsearch\\ClientBuilder;<\/span><\/p>\n

class ElasticSingleton {<\/span><\/p>\n

\u00a0\u00a0private static $instance = NULL;<\/span><\/p>\n

\u00a0\u00a0\/**<\/span><\/p>\n

\u00a0\u00a0\u00a0* Checks connectivity with ElasticSearch.<\/span><\/p>\n

\u00a0\u00a0\u00a0*\/<\/span><\/p>\n

\u00a0\u00a0private static function getClient() {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0try {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0$elastic_host = \u2018127.0.0.1\u2019; \/\/ Elasticsearch server.<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0$client = ClientBuilder::create()<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0->setHosts([$elastic_host])<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0->build();<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0$health = $client->cluster()->health();<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0if (empty($health)) {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return FALSE;<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return $client;<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0}<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0catch (\\Exception $e) {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return FALSE;<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0}<\/span><\/p>\n

\u00a0\u00a0}<\/span><\/p>\n

 <\/p>\n

\u00a0\u00a0\/**ElasticSingleton.phpElasticSingleton.php<\/span><\/p>\n

\u00a0\u00a0\u00a0* Check connectivity getInstance.<\/span><\/p>\n

\u00a0\u00a0\u00a0*\/<\/span><\/p>\n

\u00a0\u00a0public static function getInstance() {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0if(self::$instance === NULL) {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0self::$instance = self::getClient();<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0}<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0return self::$instance;<\/span><\/p>\n

\u00a0\u00a0}<\/span><\/p>\n

}<\/span><\/p>\n

 <\/p>\n

Now we will create a second service which will supply the same object but indirectly or using without static property\/without using scope resolution operator.<\/span><\/p>\n

 <\/p>\n

<?php<\/span><\/p>\n

\/**<\/span><\/p>\n

\u00a0* @file<\/span><\/p>\n

\u00a0* Provides indirect object of elasticsearch.<\/span><\/p>\n

\u00a0*\/<\/span><\/p>\n

namespace<\/span> Drupal\\elastic_singleton;<\/span><\/p>\n

use<\/span> Drupal\\elastic_singleton\\ElasticSingleton;<\/span><\/p>\n

class<\/span> ElasticInitiate {<\/span><\/p>\n

\u00a0\u00a0<\/span>\/**<\/span><\/p>\n

\u00a0\u00a0\u00a0* Checks connectivity with ElasticSearch.<\/span><\/p>\n

\u00a0\u00a0\u00a0*\/<\/span><\/p>\n

\u00a0\u00a0<\/span>public<\/span> function<\/span> getInstance() {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0<\/span>return<\/span> ElasticSingleton::getInstance();<\/span><\/p>\n

\u00a0\u00a0}<\/span><\/p>\n

}<\/span><\/p>\n

 <\/p>\n

 <\/p>\n

For testing we can create an entry in the routing.yml file.<\/span><\/p>\n

File: modulename.routing.yml<\/span><\/p>\n

elastic.test_singleton<\/span>:<\/span><\/p>\n

\u00a0\u00a0<\/span>path<\/span>: <\/span>‘\/test\/elastic\/singleton’<\/span><\/p>\n

\u00a0\u00a0<\/span>defaults<\/span>:<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0<\/span>_controller<\/span>: <\/span>‘\\Drupal\\elastic_singleton\\Controller\\ElasticController::test’<\/span><\/p>\n

\u00a0\u00a0<\/span>requirements<\/span>:<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0<\/span>_permission<\/span>: <\/span>‘access content’<\/span><\/p>\n

 <\/p>\n

 <\/p>\n

Let’s create a controller in the src\/Controller folder.<\/span><\/p>\n

File Name: ElasticController.php<\/span><\/p>\n

<?php<\/span><\/p>\n

namespace<\/span> Drupal\\elastic_singleton\\Controller;<\/span><\/p>\n

use<\/span> Drupal\\Core\\Controller\\ControllerBase;<\/span><\/p>\n

\/**<\/span><\/p>\n

\u00a0* An Elasticsearch singleton testing controller.<\/span><\/p>\n

\u00a0*\/<\/span><\/p>\n

class<\/span> ElasticController <\/span>extends<\/span> ControllerBase {<\/span><\/p>\n

\u00a0\u00a0<\/span>\/**<\/span><\/p>\n

\u00a0\u00a0\u00a0* Returns a render-able array for a test page.<\/span><\/p>\n

\u00a0\u00a0\u00a0*\/<\/span><\/p>\n

\u00a0\u00a0<\/span>public<\/span> function<\/span> test() {<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0$client = \\Drupal::service(<\/span>‘elastic_singleton.direct_object’<\/span>)::getInstance();<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0var_dump($client);<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0$client1 = \\Drupal::service(<\/span>‘elastic_singleton.indirect_object’<\/span>)->getInstance();<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0var_dump($client);<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0<\/span>\/\/ exit(); \/\/ Uncomment this line to check both the client objects.<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0$build = [<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>‘#markup’<\/span> => <\/span>$this<\/span>->t(<\/span>‘Elasticsearch Singleton example.’<\/span>),<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0];<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0<\/span>return<\/span> $build;<\/span><\/p>\n

\u00a0\u00a0}<\/span><\/p>\n

}<\/span><\/p>\n

 <\/p>\n

We can call the service at desired places and we can notice that the same object is returned multiple times.<\/span><\/p>\n

<\/div>","protected":false},"excerpt":{"rendered":"

Singleton design pattern is really useful to use the same object over multiple calls. For third party softwares for examples like Apache Solr, elastic search, Redis, etc. it is not good practice to create the connection object again and again, rather a single object can be used multiple times. In such cases singleton design patterns […]<\/p>\n","protected":false},"author":1430,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"iawp_total_views":22},"categories":[3602],"tags":[4964],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/posts\/54924"}],"collection":[{"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/users\/1430"}],"replies":[{"embeddable":true,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/comments?post=54924"}],"version-history":[{"count":2,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/posts\/54924\/revisions"}],"predecessor-version":[{"id":54989,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/posts\/54924\/revisions\/54989"}],"wp:attachment":[{"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/media?parent=54924"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/categories?post=54924"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/tags?post=54924"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}