Add support for failover cache (#23)

- Changes cache TTL default to 15s, the standard default
- Add unleash.cache.failover option that will pull the last successful result from the cache
  - This setting is independent of regular caching
  - The cache is always stored, to allow enabling the feature during a failure incidence
- This change also moves the requests for features out of the constructor
  - Possible to use in Facades
  - Still "cached" for the lifetime of the Unleash object

Author: dshafik

composer.json

@@ -3,7 +3,7 @@
     "description": "An Unleash client for Laravel",
     "type": "library",
     "require": {
-        "guzzlehttp/guzzle": "^6.3",
+        "guzzlehttp/guzzle": "^6.3|^7.0",
         "illuminate/support": "^5.8|^6|^7|^8",
         "illuminate/http": "^5.8|^6|^7|^8"
     },

config/unleash.php

@@ -11,9 +11,13 @@
   'isEnabled' => env('UNLEASH_ENABLED', true),
 
   // Allow the Unleash API response to be cached.
+  // Default TTL is 15s
+  // Failover caching will use the last successful result from Unleash if it down.
+  // Failover is independent of regular caching.
   'cache' => [
-    'isEnabled' => false,
-    'ttl' => 3600,
+    'isEnabled' => env('UNLEASH_CACHE_ENABLED', false),
+    'ttl' => env('UNLEASH_CACHE_TTL', 15),
+    'failover' => env('UNLEASH_CACHE_FAILOVER', true),
   ],
 
   // Mapping of strategies used to guard features on Unleash. The default strategies are already

src/Unleash.php

@@ -2,55 +2,52 @@
 
 namespace MikeFrancis\LaravelUnleash;
 
-use function GuzzleHttp\json_decode;
-
 use GuzzleHttp\ClientInterface;
+use GuzzleHttp\Exception\InvalidArgumentException;
+use GuzzleHttp\Exception\TransferException;
 use Illuminate\Contracts\Cache\Repository as Cache;
 use Illuminate\Contracts\Config\Repository as Config;
 use Illuminate\Http\Request;
 use Illuminate\Support\Arr;
 use MikeFrancis\LaravelUnleash\Strategies\Contracts\DynamicStrategy;
 use MikeFrancis\LaravelUnleash\Strategies\Contracts\Strategy;
+use Symfony\Component\HttpFoundation\Exception\JsonException;
+use function GuzzleHttp\json_decode;
 
 class Unleash
 {
-    protected $client;
+    const DEFAULT_CACHE_TTL = 15;
 
+    protected $client;
     protected $cache;
-
     protected $config;
-
     protected $request;
-
-    protected $features = [];
+    protected $features;
 
     public function __construct(ClientInterface $client, Cache $cache, Config $config, Request $request)
     {
         $this->client = $client;
         $this->cache = $cache;
         $this->config = $config;
         $this->request = $request;
-
-        if (!$this->config->get('unleash.isEnabled')) {
-            return;
-        }
-
-        if ($this->config->get('unleash.cache.isEnabled')) {
-            $this->features = $this->cache->remember(
-                'unleash',
-                $this->config->get('unleash.cache.ttl'),
-                function () {
-                    return $this->fetchFeatures();
-                }
-            );
-        } else {
-            $this->features = $this->fetchFeatures();
-        }
     }
 
     public function getFeatures(): array
     {
-        return $this->features;
+        try {
+            $features = $this->getCachedFeatures();
+
+            // Always store the failover cache, in case it is turned on during failure scenarios.
+            $this->cache->forever('unleash.features.failover', $features);
+
+            return $features;
+        } catch (TransferException | JsonException $e) {
+            if ($this->config->get('unleash.cache.failover') === true) {
+                return $this->cache->get('unleash.features.failover', []);
+            }
+        }
+
+        return [];
     }
 
     public function getFeature(string $name)
@@ -109,16 +106,36 @@ public function isFeatureDisabled(string $name, ...$args): bool
         return !$this->isFeatureEnabled($name, ...$args);
     }
 
+    protected function getCachedFeatures(): array
+    {
+        if (!$this->config->get('unleash.isEnabled')) {
+            return [];
+        }
+
+        if ($this->config->get('unleash.cache.isEnabled')) {
+            return $this->cache->remember(
+                'unleash',
+                $this->config->get('unleash.cache.ttl', self::DEFAULT_CACHE_TTL),
+                function () {
+                    return $this->fetchFeatures();
+                }
+            );
+        }
+
+        return $this->features ?? $this->features = $this->fetchFeatures();
+    }
+
     protected function fetchFeatures(): array
     {
-        try {
-            $response = $this->client->get($this->getFeaturesApiUrl(), $this->getRequestOptions());
-            $data = json_decode((string) $response->getBody(), true);
+        $response = $this->client->get($this->getFeaturesApiUrl(), $this->getRequestOptions());
 
-            return $this->formatResponse($data);
-        } catch (\InvalidArgumentException $e) {
-            return [];
+        try {
+            $data = json_decode((string)$response->getBody(), true, 512, \JSON_BIGINT_AS_STRING);
+        } catch (InvalidArgumentException $e) {
+            throw new JsonException('Could not decode unleash response body.', $e->getCode(), $e);
         }
+
+        return $this->formatResponse($data);
     }
 
     protected function getFeaturesApiUrl(): string

tests/Strategies/DynamicStrategyTest.php

@@ -114,6 +114,14 @@ protected function getMockConfig(\PHPUnit\Framework\MockObject\MockObject $strat
                 ]
             );
         $config->expects($this->at(3))
+            ->method('get')
+            ->with('unleash.isEnabled')
+            ->willReturn(true);
+        $config->expects($this->at(4))
+            ->method('get')
+            ->with('unleash.cache.isEnabled')
+            ->willReturn(false);
+        $config->expects($this->at(5))
             ->method('get')
             ->with('unleash.strategies')
             ->willReturn(