[5.3] Added database slave failover

src/Illuminate/Database/Connectors/ConnectionFactory.php

@@ -96,8 +96,56 @@ protected function createReadPdo(array $config)
      */
     protected function createPdoResolver(array $config)
     {
+        if (array_key_exists('host', $config)) {
+            return $this->createPdoResolverWithHosts($config);
+        }
+        else{
+            return $this->createPdoResolverWithoutHosts($config);
+        }
+    }
+
+    /**
+     * Create a new Closure that resolves to a PDO instance with a specific host or an array of hosts.
+     *
+     * @param  array  $config
+     * @return \Closure
+     */
+    protected function createPdoResolverWithHosts(array $config){
+        return function () use ($config) {
+            if (!is_array($config['host'])) {
+                $hosts = [$config['host']];
+            } else {
+                $hosts = $config['host'];
+                shuffle($hosts);
+            }
+
+            foreach($hosts as $host){
+                $config['host'] = $host;
+
+                try{
+                    return $this->createConnector($config)->connect($config);
+                }
+                catch(\PDOException $e){
+                }
+            }
+
+            if (empty($hosts)) {
+                throw new InvalidArgumentException("Database hosts array cannot be empty");
+            }
+
+            throw $e;
+        };
+    }
+
+    /**
+     * Create a new Closure that resolves to a PDO instance where there is no configured host
+     *
+     * @param  array  $config
+     * @return \Closure
+     */
+    protected function createPdoResolverWithoutHosts(array $config){
         return function () use ($config) {
-            return $this->createConnector($config)->connect($config);
+                return $this->createConnector($config)->connect($config);
         };
     }
 
@@ -111,12 +159,6 @@ protected function getReadConfig(array $config)
     {
         $readConfig = $this->getReadWriteConfig($config, 'read');
 
-        if (isset($readConfig['host']) && is_array($readConfig['host'])) {
-            $readConfig['host'] = count($readConfig['host']) > 1
-                ? $readConfig['host'][array_rand($readConfig['host'])]
-                : $readConfig['host'][0];
-        }
-
         return $this->mergeReadWriteConfig($config, $readConfig);
     }