Add a cache layer on top of SSM (#580)

* Add a cache layer on top of SSM

* Fix CI

* Use cache.system as default value

Author: jderusse

composer.json

@@ -24,7 +24,8 @@
         "async-aws/sqs": "^1.0",
         "async-aws/ssm": "^0.1",
         "matthiasnoback/symfony-config-test": "^4.1",
-        "nyholm/symfony-bundle-test": "^1.6.1"
+        "nyholm/symfony-bundle-test": "^1.6.1",
+        "symfony/cache": "^4.4 || ^5.0"
     },
     "extra": {
         "branch-alias": {

src/DependencyInjection/AsyncAwsExtension.php

@@ -4,13 +4,15 @@
 
 namespace AsyncAws\Symfony\Bundle\DependencyInjection;
 
+use AsyncAws\Symfony\Bundle\Secrets\CachedEnvVarLoader;
 use AsyncAws\Symfony\Bundle\Secrets\SsmVault;
 use Symfony\Component\Config\Definition\Exception\InvalidConfigurationException;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\DependencyInjection\Definition;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\HttpKernel\DependencyInjection\Extension;
+use Symfony\Contracts\Cache\CacheInterface;
 
 class AsyncAwsExtension extends Extension
 {
@@ -137,6 +139,20 @@ private function registerEnvLoader(ContainerBuilder $container, array $config):
                 $config['secrets']['path'],
                 $config['secrets']['recursive'],
             ]);
+
+        if ($config['secrets']['cache']['enabled']) {
+            if (!\interface_exists(CacheInterface::class)) {
+                throw new InvalidConfigurationException(sprintf('You have enabled "async_aws.secrets.cache" but the "symfony/cache" package is not installed. Try running "composer require symfony/cache"'));
+            }
+
+            $container->Register(CachedEnvVarLoader::class)
+                ->setDecoratedService(SsmVault::class)
+                ->setArguments([
+                    new Reference(CachedEnvVarLoader::class . '.inner'),
+                    new Reference($config['secrets']['cache']['pool']),
+                    $config['secrets']['cache']['ttl'],
+                ]);
+        }
     }
 
     private function autowireServices(ContainerBuilder $container, array $usedServices): void

src/DependencyInjection/Configuration.php

@@ -48,6 +48,13 @@ public function getConfigTreeBuilder()
                         ->scalarNode('path')->info('Path to the parameters.')->defaultNull()->end()
                         ->booleanNode('recursive')->info('Retrieve all parameters within a hierarchy.')->defaultValue(true)->end()
                         ->scalarNode('client')->info('Name of the SSM client. When null, use the default SSM configuration.')->defaultNull()->end()
+                        ->arrayNode('cache')
+                            ->canBeEnabled()
+                            ->children()
+                                ->scalarNode('pool')->info('Identifier of the Symfony Cache Pool.')->defaultValue('cache.system')->end()
+                                ->integerNode('ttl')->info('Duration of cache in seconds')->min(0)->defaultValue(600)->end()
+                            ->end()
+                        ->end()
                     ->end()
                 ->end()
             ->end();

src/Secrets/CachedEnvVarLoader.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace AsyncAws\Symfony\Bundle\Secrets;
+
+use Symfony\Component\DependencyInjection\EnvVarLoaderInterface;
+use Symfony\Contracts\Cache\CacheInterface;
+use Symfony\Contracts\Cache\ItemInterface;
+
+class CachedEnvVarLoader implements EnvVarLoaderInterface
+{
+    private $decorated;
+
+    private $cache;
+
+    private $ttl;
+
+    public function __construct(EnvVarLoaderInterface $decorated, CacheInterface $cache, int $ttl)
+    {
+        $this->decorated = $decorated;
+        $this->cache = $cache;
+        $this->ttl = $ttl;
+    }
+
+    public function loadEnvVars(): array
+    {
+        return $this->cache->get('AsyncAws.Secrets', function (ItemInterface $item) {
+            $item->expiresAfter($this->ttl);
+
+            return $this->decorated->loadEnvVars();
+        });
+    }
+}

tests/Unit/DependencyInjection/ConfigurationTest.php

@@ -33,6 +33,11 @@ public function testDefaultValues(): void
                 'path' => null,
                 'recursive' => true,
                 'client' => null,
+                'cache' => [
+                    'enabled' => false,
+                    'pool' => 'cache.system',
+                    'ttl' => 600,
+                ],
             ],
         ]);
     }

tests/Unit/Secrets/CachedEnvVarLoaderTest.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace AsyncAws\Symfony\Bundle\Tests\Unit\Secrets;
+
+use AsyncAws\Symfony\Bundle\Secrets\CachedEnvVarLoader;
+use AsyncAws\Symfony\Bundle\Secrets\SsmVault;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Cache\Adapter\ArrayAdapter;
+
+class CachedEnvVarLoaderTest extends TestCase
+{
+    public function testLoadEnvVars()
+    {
+        $env = ['FOO' => 'bar'];
+        $decorated = $this->createMock(SsmVault::class);
+        $decorated->expects(self::once())
+            ->method('loadEnvVars')
+            ->willReturn($env);
+
+        $envLoader = new CachedEnvVarLoader($decorated, new ArrayAdapter(), 5);
+
+        self::assertSame($env, $envLoader->loadEnvVars());
+        // call it twice to assert decorated is called once
+        self::assertSame($env, $envLoader->loadEnvVars());
+    }
+}