feature #27920 Add Zookeeper data store for Lock Component (Ganesh Chandrasekaran)

This PR was merged into the 4.2-dev branch.

Discussion
----------

Add Zookeeper data store for Lock Component

| Q                    | A
| ------------- | ---
| Branch?         | master
| Bug fix?         |   no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | Not applicable
| License       | MIT
| Doc PR        | https://github.com/symfony/symfony-docs/pull/10043

This change adds a new feature to the Lock Component to give the capability to store locks in Zookeeper Data Store. The corresponding documentation PR should describe how this works.

The change here also adds a functional test to make sure all the basic functionality of the lock using this data store works.

Requirements for this to work are having a PHP-Zookeeper extension available to use this.

Commits
-------

c72c297dc3 Add new Zookeeper Data Store. Add functional test for Zookeeper Data Store. Modify Store Factory to support initialization of Zookeeper Data Store.

.travis.yml

@@ -13,6 +13,8 @@ addons:
         - ldap-utils
         - slapd
         - librabbitmq-dev
+        - zookeeperd
+        - libzookeeper-mt-dev
 
 env:
     global:
@@ -161,6 +163,7 @@ before_install:
           tfold ext.mongodb tpecl mongodb-1.5.0 mongodb.so $INI
           tfold ext.amqp tpecl amqp-1.9.3 amqp.so $INI
           tfold ext.igbinary tpecl igbinary-2.0.6 igbinary.so $INI
+          tfold ext.zookeeper tpecl zookeeper-0.5.0 zookeeper.so $INI
       done
 
     - |

phpunit.xml.dist

@@ -19,6 +19,7 @@
         <env name="LDAP_PORT" value="3389" />
         <env name="REDIS_HOST" value="localhost" />
         <env name="MEMCACHED_HOST" value="localhost" />
+        <env name="ZOOKEEPER_HOST" value="localhost" />
     </php>
 
     <testsuites>

src/Symfony/Component/Lock/CHANGELOG.md

@@ -5,6 +5,7 @@ CHANGELOG
 -----
 
  * added the PDO Store
+ * Add a new Zookeeper Data Store for Lock Component.
 
 3.4.0
 -----

src/Symfony/Component/Lock/Store/StoreFactory.php

@@ -22,9 +22,9 @@ use Symfony\Component\Lock\Exception\InvalidArgumentException;
 class StoreFactory
 {
     /**
-     * @param \Redis|\RedisArray|\RedisCluster|\Predis\Client|\Memcached $connection
+     * @param \Redis|\RedisArray|\RedisCluster|\Predis\Client|\Memcached|\Zookeeper $connection
      *
-     * @return RedisStore|MemcachedStore
+     * @return RedisStore|MemcachedStore|ZookeeperStore
      */
     public static function createStore($connection)
     {
@@ -34,6 +34,9 @@ class StoreFactory
         if ($connection instanceof \Memcached) {
             return new MemcachedStore($connection);
         }
+        if ($connection instanceof \Zookeeper) {
+            return new ZookeeperStore($connection);
+        }
 
         throw new InvalidArgumentException(sprintf('Unsupported Connection: %s.', \get_class($connection)));
     }

src/Symfony/Component/Lock/Store/ZookeeperStore.php

@@ -0,0 +1,150 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Lock\Store;
+
+use Symfony\Component\Lock\Exception\LockAcquiringException;
+use Symfony\Component\Lock\Exception\LockConflictedException;
+use Symfony\Component\Lock\Exception\LockReleasingException;
+use Symfony\Component\Lock\Exception\NotSupportedException;
+use Symfony\Component\Lock\Key;
+use Symfony\Component\Lock\StoreInterface;
+
+/**
+ * ZookeeperStore is a StoreInterface implementation using Zookeeper as store engine.
+ *
+ * @author Ganesh Chandrasekaran <gchandrasekaran@wayfair.com>
+ */
+class ZookeeperStore implements StoreInterface
+{
+    private $zookeeper;
+
+    public function __construct(\Zookeeper $zookeeper)
+    {
+        $this->zookeeper = $zookeeper;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function save(Key $key)
+    {
+        if ($this->exists($key)) {
+            return;
+        }
+
+        $resource = $this->getKeyResource($key);
+        $token = $this->getUniqueToken($key);
+
+        $this->createNewLock($resource, $token);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function delete(Key $key)
+    {
+        if (!$this->exists($key)) {
+            return;
+        }
+        $resource = $this->getKeyResource($key);
+        try {
+            $this->zookeeper->delete($resource);
+        } catch (\ZookeeperException $exception) {
+            // For Zookeeper Ephemeral Nodes, the node will be deleted upon session death. But, if we want to unlock
+            // the lock before proceeding further in the session, the client should be aware of this
+            throw new LockReleasingException($exception);
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function exists(Key $key): bool
+    {
+        $resource = $this->getKeyResource($key);
+        try {
+            return $this->zookeeper->get($resource) === $this->getUniqueToken($key);
+        } catch (\ZookeeperException $ex) {
+            return false;
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function waitAndSave(Key $key)
+    {
+        throw new NotSupportedException();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function putOffExpiration(Key $key, $ttl)
+    {
+        throw new NotSupportedException();
+    }
+
+    /**
+     * Creates a zookeeper node.
+     *
+     * @param string $node  The node which needs to be created
+     * @param string $value The value to be assigned to a zookeeper node
+     *
+     * @throws LockConflictedException
+     * @throws LockAcquiringException
+     */
+    private function createNewLock(string $node, string $value)
+    {
+        // Default Node Permissions
+        $acl = array(array('perms' => \Zookeeper::PERM_ALL, 'scheme' => 'world', 'id' => 'anyone'));
+        // This ensures that the nodes are deleted when the client session to zookeeper server ends.
+        $type = \Zookeeper::EPHEMERAL;
+
+        try {
+            $this->zookeeper->create($node, $value, $acl, $type);
+        } catch (\ZookeeperException $ex) {
+            if (\Zookeeper::NODEEXISTS === $ex->getCode()) {
+                throw new LockConflictedException($ex);
+            }
+
+            throw new LockAcquiringException($ex);
+        }
+    }
+
+    private function getKeyResource(Key $key): string
+    {
+        // Since we do not support storing locks as multi-level nodes, we convert them to be stored at root level.
+        // For example: foo/bar will become /foo-bar and /foo/bar will become /-foo-bar
+        $resource = (string) $key;
+
+        if (false !== \strpos($resource, '/')) {
+            $resource = \strtr($resource, array('/' => '-')).'-'.sha1($resource);
+        }
+
+        if ('' === $resource) {
+            $resource = sha1($resource);
+        }
+
+        return '/'.$resource;
+    }
+
+    private function getUniqueToken(Key $key): string
+    {
+        if (!$key->hasState(self::class)) {
+            $token = base64_encode(random_bytes(32));
+            $key->setState(self::class, $token);
+        }
+
+        return $key->getState(self::class);
+    }
+}

src/Symfony/Component/Lock/StoreInterface.php

@@ -11,7 +11,9 @@
 
 namespace Symfony\Component\Lock;
 
+use Symfony\Component\Lock\Exception\LockAcquiringException;
 use Symfony\Component\Lock\Exception\LockConflictedException;
+use Symfony\Component\Lock\Exception\LockReleasingException;
 use Symfony\Component\Lock\Exception\NotSupportedException;
 
 /**
@@ -24,6 +26,7 @@ interface StoreInterface
     /**
      * Stores the resource if it's not locked by someone else.
      *
+     * @throws LockAcquiringException
      * @throws LockConflictedException
      */
     public function save(Key $key);
@@ -52,6 +55,8 @@ interface StoreInterface
 
     /**
      * Removes a resource from the storage.
+     *
+     * @throws LockReleasingException
      */
     public function delete(Key $key);
 

src/Symfony/Component/Lock/Tests/Store/ZookeeperStoreTest.php

@@ -0,0 +1,108 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Lock\Tests\Store;
+
+use Symfony\Component\Lock\Key;
+use Symfony\Component\Lock\Store\StoreFactory;
+use Symfony\Component\Lock\Store\ZookeeperStore;
+
+/**
+ * @author Ganesh Chandrasekaran <gchandrasekaran@wayfair.com>
+ *
+ * @requires extension zookeeper
+ */
+class ZookeeperStoreTest extends AbstractStoreTest
+{
+    public function getStore(): ZookeeperStore
+    {
+        $zookeeper_server = getenv('ZOOKEEPER_HOST').':2181';
+
+        $zookeeper = new \Zookeeper(implode(',', array($zookeeper_server)));
+
+        return StoreFactory::createStore($zookeeper);
+    }
+
+    public function testSaveSucceedsWhenPathContainsMoreThanOneNode()
+    {
+        $store = $this->getStore();
+        $resource = '/baseNode/lockNode';
+        $key = new Key($resource);
+
+        $store->save($key);
+        $this->assertTrue($store->exists($key));
+
+        $store->delete($key);
+        $this->assertFalse($store->exists($key));
+    }
+
+    public function testSaveSucceedsWhenPathContainsOneNode()
+    {
+        $store = $this->getStore();
+        $resource = '/baseNode';
+        $key = new Key($resource);
+
+        $store->save($key);
+        $this->assertTrue($store->exists($key));
+
+        $store->delete($key);
+        $this->assertFalse($store->exists($key));
+    }
+
+    public function testSaveSucceedsWhenPathsContainSameFirstNode()
+    {
+        $store = $this->getStore();
+        $resource = 'foo/bar';
+        $key = new Key($resource);
+
+        $store->save($key);
+        $this->assertTrue($store->exists($key));
+
+        $resource2 = 'foo';
+        $key2 = new Key($resource2);
+
+        $this->assertFalse($store->exists($key2));
+        $store->save($key2);
+        $this->assertTrue($store->exists($key2));
+
+        $store->delete($key2);
+        $this->assertFalse($store->exists($key2));
+
+        $store->delete($key);
+        $this->assertFalse($store->exists($key));
+    }
+
+    public function testRootPathIsLockable()
+    {
+        $store = $this->getStore();
+        $resource = '/';
+        $key = new Key($resource);
+
+        $store->save($key);
+        $this->assertTrue($store->exists($key));
+
+        $store->delete($key);
+        $this->assertFalse($store->exists($key));
+    }
+
+    public function testEmptyStringIsLockable()
+    {
+        $store = $this->getStore();
+        $resource = '';
+        $key = new Key($resource);
+
+        $store->save($key);
+        $this->assertTrue($store->exists($key));
+
+        $store->delete($key);
+        $this->assertFalse($store->exists($key));
+    }
+}

src/Symfony/Component/Lock/phpunit.xml.dist

@@ -12,6 +12,7 @@
         <ini name="error_reporting" value="-1" />
         <env name="REDIS_HOST" value="localhost" />
         <env name="MEMCACHED_HOST" value="localhost" />
+        <env name="ZOOKEEPER_HOST" value="localhost" />
     </php>
 
     <testsuites>