Route backend jobs to use correct image

This selects a pod that matches the selector[1]
for the appropriate backend service rather than
any random backend MediaWiki pod

[1] https://kubernetes.io/docs/concepts/services-networking/service/#services-in-kubernetes
Bug: T408624

Author: tarrow

app/Jobs/ProcessMediaWikiJobsJob.php

@@ -2,6 +2,7 @@
 
 namespace App\Jobs;
 
+use App\Services\MediaWikiHostResolver;
 use Illuminate\Bus\Queueable;
 use Illuminate\Contracts\Queue\ShouldBeUnique;
 use Illuminate\Contracts\Queue\ShouldQueue;
@@ -27,14 +28,28 @@ public function uniqueId(): string {
         return $this->wikiDomain;
     }
 
-    public function handle(Client $kubernetesClient): void {
+    public function handle(Client $kubernetesClient, MediaWikiHostResolver $resolver): void {
+        $domain = $resolver->getBackendHostForDomain($this->wikiDomain);
+        $serviceName = $domain;
         $kubernetesClient->setNamespace('default');
+        $backendService = $kubernetesClient->services()->setLabelSelector([
+            'name' => $serviceName,
+        ])->first();
+
+        if ($backendService === null) {
+            $this->fail(
+                new \RuntimeException(
+                    'Unable to find a matching MediaWiki backend service in the cluster'
+                )
+            );
+
+            return;
+        }
+
+        $MWPodSelector = $backendService->toArray()['spec']['selector'];
         $mediawikiPod = $kubernetesClient->pods()->setFieldSelector([
             'status.phase' => 'Running',
-        ])->setLabelSelector([
-            'app.kubernetes.io/name' => 'mediawiki',
-            'app.kubernetes.io/component' => 'app-backend',
-        ])->first();
+        ])->setLabelSelector($MWPodSelector)->first();
 
         if ($mediawikiPod === null) {
             $this->fail(

tests/Jobs/ProcessMediaWikiJobsJobTest.php

@@ -3,6 +3,7 @@
 namespace Tests\Jobs;
 
 use App\Jobs\ProcessMediaWikiJobsJob;
+use App\Services\MediaWikiHostResolver;
 use GuzzleHttp\Handler\MockHandler;
 use GuzzleHttp\HandlerStack;
 use GuzzleHttp\Psr7\Response;
@@ -16,6 +17,9 @@ class ProcessMediaWikiJobsJobTest extends TestCase {
     use RefreshDatabase;
 
     public function testJobFailOnNoMediaWikiPod() {
+
+        $mockResolver = $this->createMock(MediaWikiHostResolver::class);
+
         $mockJob = $this->createMock(Job::class);
         $mockJob->expects($this->once())->method('fail');
 
@@ -24,6 +28,7 @@ public function testJobFailOnNoMediaWikiPod() {
 
         $mock = new MockHandler([
             new Response(200, [], json_encode(['items' => []])),
+            new Response(200, [], json_encode(['items' => []])),
         ]);
 
         $handlerStack = HandlerStack::create($mock);
@@ -35,17 +40,30 @@ public function testJobFailOnNoMediaWikiPod() {
         $job->handle(new Client([
             'master' => 'https://kubernetes.default.svc',
             'token' => '/var/run/secrets/kubernetes.io/serviceaccount/token',
-        ], null, $mockGuzzle));
+        ], null, $mockGuzzle), $mockResolver);
     }
 
     public function testJobDoesNotFail() {
+        $mockResolver = $this->createMock(MediaWikiHostResolver::class);
         $mockJob = $this->createMock(Job::class);
         $mockJob->expects($this->never())->method('fail');
 
         $job = new ProcessMediaWikiJobsJob('test.wikibase.cloud');
         $job->setJob($mockJob);
 
         $mock = new MockHandler([
+            new Response(200, [], json_encode(['items' => [
+                [
+                    'kind' => 'Service',
+                    'spec' => [
+                        'selector' => [
+                            'app.kubernetes.io/component' => 'app-backend',
+                            'app.kubernetes.io/instance' => 'mediawiki-143',
+                            'app.kubernetes.io/name' => 'mediawiki',
+                        ],
+                    ],
+                ],
+            ]])),
             new Response(200, [], json_encode(['items' => [
                 [
                     'kind' => 'Pod',
@@ -75,9 +93,12 @@ public function testJobDoesNotFail() {
             'verify' => '/var/run/secrets/kubernetes.io/serviceaccount/ca.crt',
         ]);
 
-        $job->handle(new Client([
-            'master' => 'https://kubernetes.default.svc',
-            'token' => '/var/run/secrets/kubernetes.io/serviceaccount/token',
-        ], null, $mockGuzzle));
+        $job->handle(
+            new Client([
+                'master' => 'https://kubernetes.default.svc',
+                'token' => '/var/run/secrets/kubernetes.io/serviceaccount/token',
+            ], null, $mockGuzzle),
+            $mockResolver
+        );
     }
 }