Merge pull request #24 from guywithnose/master

TCG-2460 - Automatically refresh frequently used keys before they expire

Author: Robert Bittle

src/Predis.php

@@ -23,16 +23,37 @@ class Predis implements Memoize
      */
     private $refresh;
 
+    /**
+     * The percentage of requests that check for refreshes
+     *
+     * @var int
+     */
+    private $refreshPercent;
+
+    /**
+     * The multiplier to use on runtime when deciding to do a refresh
+     *
+     * @var float
+     */
+    private $runtimeMultiplier;
+
     /**
      * Sets the predis client.
      *
-     * @param ClientInterface $client  The predis client to use
-     * @param boolean         $refresh If true we will always overwrite cache even if it is already set
+     * @param ClientInterface $client         The predis client to use
+     * @param boolean         $refresh        If true we will always overwrite cache even if it is already set
+     * @param int             $refreshPercent The percentage of requests that check for refreshes
      */
-    public function __construct(ClientInterface $client, bool $refresh = false)
-    {
+    public function __construct(
+        ClientInterface $client,
+        bool $refresh = false,
+        int $refreshPercent = 0,
+        float $runtimeMultiplier = 3
+    ) {
         $this->client = $client;
         $this->refresh = $refresh;
+        $this->refreshPercent = $refreshPercent;
+        $this->runtimeMultiplier = $runtimeMultiplier;
     }
 
     /**
@@ -51,19 +72,37 @@ public function memoizeCallable(string $key, callable $compute, int $cacheTime =
     {
         if (!$this->refresh) {
             try {
+                if (rand(1, 100) <= $this->refreshPercent) {
+                    // {$refreshPercent}% of requests should check to see if this key is almost expired.
+                    // We don't want to check this on every call to preserve performance.
+                    // Also, this functionality is only important for requests that have many concurrent calls.
+                    $runtime = $this->client->get("{$key}.runtime");
+                    $ttl = $this->client->pttl($key) / 1000;
+                    if ($runtime && $runtime * $this->runtimeMultiplier > $ttl) {
+                        return $this->getData($key, $compute, $cacheTime);
+                    }
+                }
+
                 $cached = $this->client->get($key);
                 if ($cached !== null) {
                     $data = json_decode($cached, true);
                     return $data['result'];
                 }
             } catch (\Exception $e) {
-                return call_user_func($compute);
+                return $this->getData($key, $compute, $cacheTime);
             }
         }
 
+        return $this->getData($key, $compute, $cacheTime);
+    }
+
+    private function getData(string $key, callable $compute, int $cacheTime = null)
+    {
+        $start = microtime(true);
         $result = call_user_func($compute);
+        $runtime = microtime(true) - $start;
 
-        $this->cache($key, json_encode(['result' => $result]), $cacheTime);
+        $this->cache($key, json_encode(['result' => $result]), $cacheTime, $runtime);
 
         return $result;
     }
@@ -77,10 +116,11 @@ public function memoizeCallable(string $key, callable $compute, int $cacheTime =
      *
      * @return void
      */
-    private function cache(string $key, string $value, int $cacheTime = null)
+    private function cache(string $key, string $value, int $cacheTime = null, float $runtime)
     {
         try {
             $this->client->set($key, $value);
+            $this->client->set("{$key}.runtime", $runtime);
 
             if ($cacheTime !== null) {
                 $this->client->expire($key, $cacheTime);

tests/PredisTest.php

@@ -69,6 +69,39 @@ public function memoizeCallableWithExceptionOnGet()
         $this->assertSame(1, $count);
     }
 
+    /**
+     * @test
+     * @covers ::__construct
+     * @covers ::memoizeCallable
+     */
+    public function memoizeCallableRefreshRequest()
+    {
+        $count = 0;
+        $key = 'foo';
+        $value = 'bar';
+        $cachedValue = json_encode(['result' => $value]);
+        $cacheTime = 1234;
+        $compute = function () use (&$count, $value) {
+            $count++;
+
+            return $value;
+        };
+
+        $client = $this->getPredisMock();
+        $client->expects($this->at(0))->method('get')->with(
+            $this->equalTo("{$key}.runtime")
+        )->will($this->returnValue(.2));
+        $client->expects($this->at(1))->method('pttl')->with($this->equalTo($key))->will($this->returnValue(10));
+        $client->expects($this->at(2))->method('set')->with($this->equalTo($key), $this->equalTo($cachedValue));
+        $client->expects($this->at(3))->method('set')->with($this->equalTo("{$key}.runtime"), $this->lessThan(1));
+        $client->expects($this->at(4))->method('expire')->with($this->equalTo($key), $this->equalTo($cacheTime));
+
+        $memoizer = new Predis($client, false, 100);
+
+        $this->assertSame($value, $memoizer->memoizeCallable($key, $compute, $cacheTime));
+        $this->assertSame(1, $count);
+    }
+
     /**
      * @test
      * @covers ::__construct
@@ -88,9 +121,10 @@ public function memoizeCallableWithUncachedKey()
         };
 
         $client = $this->getPredisMock();
-        $client->expects($this->once())->method('get')->with($this->equalTo($key))->will($this->returnValue(null));
-        $client->expects($this->once())->method('set')->with($this->equalTo($key), $this->equalTo($cachedValue));
-        $client->expects($this->once())->method('expire')->with($this->equalTo($key), $this->equalTo($cacheTime));
+        $client->expects($this->at(0))->method('get')->with($this->equalTo($key))->will($this->returnValue(null));
+        $client->expects($this->at(1))->method('set')->with($this->equalTo($key), $this->equalTo($cachedValue));
+        $client->expects($this->at(2))->method('set')->with($this->equalTo("{$key}.runtime"), $this->lessThan(1));
+        $client->expects($this->at(3))->method('expire')->with($this->equalTo($key), $this->equalTo($cacheTime));
 
         $memoizer = new Predis($client);
 
@@ -132,6 +166,8 @@ public function memoizeCallableWithUncachedKeyWithExceptionOnSet()
 
     private function getPredisMock() : ClientInterface
     {
-        return $this->getMockBuilder('\Predis\Client')->setMethods(['get', 'set', 'expire'])->getMock();
+        return $this->getMockBuilder('\Predis\Client')->setMethods(
+            ['get', 'set', 'expire', 'del', 'exec', 'unwatch', 'pttl']
+        )->getMock();
     }
 }