[6.x] Introduce a locking mechanism for the array cache driver

src/Illuminate/Cache/ArrayLock.php

@@ -0,0 +1,98 @@
+<?php
+
+namespace Illuminate\Cache;
+
+use Carbon\Carbon;
+
+class ArrayLock extends Lock
+{
+    /**
+     * The parent array cache store.
+     *
+     * @var \Illuminate\Cache\ArrayStore
+     */
+    protected $store;
+
+    /**
+     * Create a new lock instance.
+     *
+     * @param  \Illuminate\Cache\ArrayStore  $store
+     * @param  string  $name
+     * @param  int  $seconds
+     * @param  string|null  $owner
+     * @return void
+     */
+    public function __construct($store, $name, $seconds, $owner = null)
+    {
+        parent::__construct($name, $seconds, $owner);
+
+        $this->store = $store;
+    }
+
+    /**
+     * Attempt to acquire the lock.
+     *
+     * @return bool
+     */
+    public function acquire()
+    {
+        $expiration = $this->store->locks[$this->name]['expiresAt'] ?? Carbon::now()->addSecond();
+
+        if ($this->exists() && $expiration->isFuture()) {
+            return false;
+        }
+
+        $this->store->locks[$this->name] = [
+            'owner' => $this->owner,
+            'expiresAt' => $this->seconds === 0 ? null : Carbon::now()->addSeconds($this->seconds),
+        ];
+
+        return true;
+    }
+
+    /**
+     * Determine if the current lock exists.
+     *
+     * @return bool
+     */
+    protected function exists()
+    {
+        return isset($this->store->locks[$this->name]);
+    }
+
+    /**
+     * Release the lock.
+     *
+     * @return bool
+     */
+    public function release()
+    {
+        if (! $this->isOwnedByCurrentProcess()) {
+            return false;
+        }
+
+        $this->forceRelease();
+
+        return true;
+    }
+
+    /**
+     * Returns the owner value written into the driver for this lock.
+     *
+     * @return string
+     */
+    protected function getCurrentOwner()
+    {
+        return $this->store->locks[$this->name]['owner'];
+    }
+
+    /**
+     * Releases this lock in disregard of ownership.
+     *
+     * @return void
+     */
+    public function forceRelease()
+    {
+        unset($this->store->locks[$this->name]);
+    }
+}

src/Illuminate/Cache/ArrayStore.php

@@ -2,9 +2,10 @@
 
 namespace Illuminate\Cache;
 
+use Illuminate\Contracts\Cache\LockProvider;
 use Illuminate\Support\InteractsWithTime;
 
-class ArrayStore extends TaggableStore
+class ArrayStore extends TaggableStore implements LockProvider
 {
     use InteractsWithTime, RetrievesMultipleKeys;
 
@@ -15,6 +16,13 @@ class ArrayStore extends TaggableStore
      */
     protected $storage = [];
 
+    /**
+     * The array of locks.
+     *
+     * @var array
+     */
+    public $locks = [];
+
     /**
      * Retrieve an item from the cache by key.
      *
@@ -162,4 +170,29 @@ protected function toTimestamp($seconds)
     {
         return $seconds > 0 ? $this->availableAt($seconds) : 0;
     }
+
+    /**
+     * Get a lock instance.
+     *
+     * @param  string $name
+     * @param  int $seconds
+     * @param  string|null $owner
+     * @return \Illuminate\Contracts\Cache\Lock
+     */
+    public function lock($name, $seconds = 0, $owner = null)
+    {
+        return new ArrayLock($this, $name, $seconds, $owner);
+    }
+
+    /**
+     * Restore a lock instance using the owner identifier.
+     *
+     * @param  string  $name
+     * @param  string  $owner
+     * @return \Illuminate\Contracts\Cache\Lock
+     */
+    public function restoreLock($name, $owner)
+    {
+        return $this->lock($name, 0, $owner);
+    }
 }

tests/Cache/CacheArrayStoreTest.php

@@ -108,4 +108,77 @@ public function testCacheKey()
         $store = new ArrayStore;
         $this->assertEmpty($store->getPrefix());
     }
+
+    public function testCannotAquireLockTwice()
+    {
+        $store = new ArrayStore;
+        $lock = $store->lock('foo', 10);
+
+        $this->assertTrue($lock->acquire());
+        $this->assertFalse($lock->acquire());
+    }
+
+    public function testCanAquireLockAgainAfterExpiry()
+    {
+        Carbon::setTestNow(Carbon::now());
+        $store = new ArrayStore;
+        $lock = $store->lock('foo', 10);
+        $lock->acquire();
+        Carbon::setTestNow(Carbon::now()->addSeconds(10));
+
+        $this->assertTrue($lock->acquire());
+    }
+
+    public function testLockExpirationLowerBoundary()
+    {
+        Carbon::setTestNow(Carbon::now());
+        $store = new ArrayStore;
+        $lock = $store->lock('foo', 10);
+        $lock->acquire();
+        Carbon::setTestNow(Carbon::now()->addSeconds(10)->subMicrosecond());
+
+        $this->assertFalse($lock->acquire());
+    }
+
+    public function testLockWithNoExpirationNeverExpires()
+    {
+        Carbon::setTestNow(Carbon::now());
+        $store = new ArrayStore;
+        $lock = $store->lock('foo');
+        $lock->acquire();
+        Carbon::setTestNow(Carbon::now()->addYears(100));
+
+        $this->assertFalse($lock->acquire());
+    }
+
+    public function testCanAcquireLockAfterRelease()
+    {
+        $store = new ArrayStore;
+        $lock = $store->lock('foo', 10);
+        $lock->acquire();
+
+        $this->assertTrue($lock->release());
+        $this->assertTrue($lock->acquire());
+    }
+
+    public function testAnotherOwnerCannotReleaseLock()
+    {
+        $store = new ArrayStore;
+        $owner = $store->lock('foo', 10);
+        $wannabeOwner = $store->lock('foo', 10);
+        $owner->acquire();
+
+        $this->assertFalse($wannabeOwner->release());
+    }
+
+    public function testAnotherOwnerCanForceReleaseALock()
+    {
+        $store = new ArrayStore;
+        $owner = $store->lock('foo', 10);
+        $wannabeOwner = $store->lock('foo', 10);
+        $owner->acquire();
+        $wannabeOwner->forceRelease();
+
+        $this->assertTrue($wannabeOwner->acquire());
+    }
 }