#66 distribute the read operation on Redis Cache

CHANGELOG.md

@@ -4,7 +4,7 @@ Yii Framework 2 redis extension Change Log
 2.0.8 under development
 -----------------------
 
-- no changes in this release.
+- Enh #66: Cache component can be configured to read / get from replicas (ryusoft)
 
 
 2.0.7 December 11, 2017

Cache.php

@@ -53,6 +53,28 @@
  * ]
  * ~~~
  *
+ * If you have multiple redis replicas (e.g. AWS ElasticCache Redis) you can configure the cache to
+ * send read operations to the replicas. If no replicas are configured, all operations will be performed on the
+ * master connection configured via the [[redis]] property.
+ *
+ * ~~~
+ * [
+ * 'components' => [
+ * 'cache' => [
+ * 'class' => 'yii\redis\Cache',
+ * 'enableReplicas' => true,
+ * 'replicas' => [
+ * // config for replica redis connections, (default class will be yii\redis\Connection if not provided)
+ * // you can optionally put in master as hostname as well, as all GET operation will use replicas
+ * 'redis',//id of Redis [[Connection]] Component
+ * ['hostname' => 'redis-slave-002.xyz.0001.apse1.cache.amazonaws.com'],
+ * ['hostname' => 'redis-slave-003.xyz.0001.apse1.cache.amazonaws.com'],
+ * ],
+ * ],
+ * ],
+ * ]
+ * ~~~
+ *
  * @author Carsten Brandt <mail@cebe.cc>
  * @since 2.0
  */
@@ -66,6 +88,36 @@ class Cache extends \yii\caching\Cache
  * with a Redis [[Connection]] object.
  */
  public $redis = 'redis';
+ /**
+ * @var bool whether to enable read / get from redis replicas.
+ * @since 2.0.8
+ * @see $replicas
+ */
+ public $enableReplicas = false;
+ /**
+ * @var array the Redis [[Connection]] configurations for redis replicas.
+ * Each entry is a class configuration, which will be used to instantiate a replica connection.
+ * The default class is [[Connection|yii\redis\Connection]]. You should at least provide a hostname.
+ * 
+ * Configuration example:
+ *
+ * ```php
+ * 'replicas' => [
+ * 'redis',
+ * ['hostname' => 'redis-slave-002.xyz.0001.apse1.cache.amazonaws.com'],
+ * ['hostname' => 'redis-slave-003.xyz.0001.apse1.cache.amazonaws.com'],
+ * ],
+ * ```
+ *
+ * @since 2.0.8
+ * @see $enableReplicas
+ */
+ public $replicas = [];
+
+ /**
+ * @var Connection currently active connection.
+ */
+ private $_replica;
 
 
  /**
@@ -99,15 +151,15 @@ public function exists($key)
  */
  protected function getValue($key)
  {
- return $this->redis->executeCommand('GET', [$key]);
+ return $this->getReplica()->executeCommand('GET', [$key]);
  }
 
  /**
  * @inheritdoc
  */
  protected function getValues($keys)
  {
- $response = $this->redis->executeCommand('MGET', $keys);
+ $response = $this->getReplica()->executeCommand('MGET', $keys);
  $result = [];
  $i = 0;
  foreach ($keys as $key) {
@@ -195,4 +247,32 @@ protected function flushValues()
  {
  return $this->redis->executeCommand('FLUSHDB');
  }
+
+ /**
+ * It will return the current Replica Redis [[Connection]], and fall back to default [[redis]] [[Connection]]
+ * defined in this instance. Only used in getValue() and getValues().
+ * @since 2.0.8
+ * @return array|string|Connection
+ * @throws \yii\base\InvalidConfigException
+ */
+ protected function getReplica()
+ {
+ if ($this->enableReplicas === false) {
+ return $this->redis;
+ }
+
+ if ($this->_replica !== null) {
+ return $this->_replica;
+ }
+
+ if (empty($this->replicas)) {
+ return $this->_replica = $this->redis;
+ }
+
+ $replicas = $this->replicas;
+ shuffle($replicas);
+ $config = array_shift($replicas);
+ $this->_replica = Instance::ensure($config, Connection::className());
+ return $this->_replica;
+ }
 }

tests/RedisCacheTest.php

@@ -2,6 +2,7 @@
 
 namespace yiiunit\extensions\redis;
 
+use yii\base\InvalidConfigException;
 use yii\redis\Cache;
 use yii\redis\Connection;
 use yiiunit\framework\caching\CacheTestCase;
@@ -39,6 +40,12 @@ protected function getCacheInstance()
  return $this->_cacheInstance;
  }
 
+ protected function resetCacheInstance()
+ {
+ $this->getCacheInstance()->flush();
+ $this->_cacheInstance = null;
+ }
+
  public function testExpireMilliseconds()
  {
  $cache = $this->getCacheInstance();
@@ -120,4 +127,61 @@ public function testMultiByteGetAndSet()
  $cache->set($key, $data);
  $this->assertSame($cache->get($key), $data);
  }
+
+ public function testReplica()
+ {
+ $this->resetCacheInstance();
+
+ $cache = $this->getCacheInstance();
+ $cache->enableReplicas = true;
+
+ $key = 'replica-1';
+ $value = 'replica';
+
+ //No Replica listed
+ $this->assertFalse($cache->get($key));
+ $cache->set($key, $value);
+ $this->assertSame($cache->get($key), $value);
+
+ $cache->replicas = [
+ ['hostname' => 'localhost'],
+ ];
+ $this->assertSame($cache->get($key), $value);
+
+ //One Replica listed
+ $this->resetCacheInstance();
+ $cache = $this->getCacheInstance();
+ $cache->enableReplicas = true;
+ $cache->replicas = [
+ ['hostname' => 'localhost'],
+ ];
+ $this->assertFalse($cache->get($key));
+ $cache->set($key, $value);
+ $this->assertSame($cache->get($key), $value);
+
+ //Multiple Replicas listed
+ $this->resetCacheInstance();
+ $cache = $this->getCacheInstance();
+ $cache->enableReplicas = true;
+
+ $cache->replicas = [
+ ['hostname' => 'localhost'],
+ ['hostname' => 'localhost'],
+ ];
+ $this->assertFalse($cache->get($key));
+ $cache->set($key, $value);
+ $this->assertSame($cache->get($key), $value);
+
+ //invalid config
+ $this->resetCacheInstance();
+ $cache = $this->getCacheInstance();
+ $cache->enableReplicas = true;
+
+ $cache->replicas = ['redis'];
+ $this->assertFalse($cache->get($key));
+ $cache->set($key, $value);
+ $this->assertSame($cache->get($key), $value);
+
+ $this->resetCacheInstance();
+ }
 }