feature symfony#17734 [Cache] Count cache hits/misses in ProxyAdapter (nicolas-grekas)

This PR was merged into the 3.1-dev branch.

Discussion
----------

[Cache] Count cache hits/misses in ProxyAdapter

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#17537 partially
| License       | MIT
| Doc PR        | -

I propose to add this subset of the `Doctrine\Common\Cache\Cache` interface so that we can build data collectors on top and show these stats in the web profiler.
ping @javiereguiluz

Commits
-------

e6f21f9 [Cache] Count cache hits/misses in ProxyAdapter

Author: fabpot

src/Symfony/Component/Cache/Adapter/ProxyAdapter.php

@@ -22,6 +22,8 @@ class ProxyAdapter implements CacheItemPoolInterface
 {
     private $pool;
     private $createCacheItem;
+    private $hits = 0;
+    private $misses = 0;
 
     public function __construct(CacheItemPoolInterface $pool)
     {
@@ -47,8 +49,13 @@ public function getItem($key)
     {
         $f = $this->createCacheItem;
         $item = $this->pool->getItem($key);
+        if ($isHit = $item->isHit()) {
+            ++$this->hits;
+        } else {
+            ++$this->misses;
+        }
 
-        return $f($key, $item->get(), $item->isHit());
+        return $f($key, $item->get(), $isHit);
     }
 
     /**
@@ -134,7 +141,33 @@ private function generateItems($items)
         $f = $this->createCacheItem;
 
         foreach ($items as $key => $item) {
-            yield $key => $f($key, $item->get(), $item->isHit());
+            if ($isHit = $item->isHit()) {
+                ++$this->hits;
+            } else {
+                ++$this->misses;
+            }
+
+            yield $key => $f($key, $item->get(), $isHit);
         }
     }
+
+    /**
+     * Returns the number of cache read hits.
+     *
+     * @return int
+     */
+    public function getHits()
+    {
+        return $this->hits;
+    }
+
+    /**
+     * Returns the number of cache read misses.
+     *
+     * @return int
+     */
+    public function getMisses()
+    {
+        return $this->misses;
+    }
 }

src/Symfony/Component/Cache/Tests/Adapter/ProxyAdapterTest.php

@@ -29,4 +29,21 @@ public function createCachePool()
     {
         return new ProxyAdapter(new ArrayAdapter());
     }
+
+    public function testGetHitsMisses()
+    {
+        $pool = $this->createCachePool();
+
+        $this->assertSame(0, $pool->getHits());
+        $this->assertSame(0, $pool->getMisses());
+
+        $bar = $pool->getItem('bar');
+        $this->assertSame(0, $pool->getHits());
+        $this->assertSame(1, $pool->getMisses());
+
+        $pool->save($bar->set('baz'));
+        $bar = $pool->getItem('bar');
+        $this->assertSame(1, $pool->getHits());
+        $this->assertSame(1, $pool->getMisses());
+    }
 }