Laravel 数据库主从分离读写配置

配置范例

'mysql' => [
    'driver'   => 'mysql',  
    'write'    => [  
        'host' => '192.168.1.180',  
    ],  
    'read'     => [
        ['host' => '192.168.1.182'],  
        ['host' => '192.168.1.179'],  
    ],
    ...  
]

或

'mysql' => [
    'driver'   => 'mysql',  
    'write'    => [  
        'host' => '192.168.1.180',  
    ],  
    'read'     => [
        'host' => ［
            '192.168.1.182',
            '192.168.1.179'
        ],  
    ],
    ...  
]

扩展配置范例

'mysql' => [
    'driver'   => 'mysql',  
    'write'    => [  
        'host'      => '192.168.1.180',  
        'username'  => 'write',
        'password'   => 'write',
    ],  
    'read'     => [
        [
            'host' => '192.168.1.182',
            'username'  => 'read1',
            'password'   => 'read1',
        ],  
        [
            'host' => '192.168.1.179',
            'username'  => 'read2',
            'password'   => 'read2',
        ],  
    ],
    ...  
]

//或者

'mysql' => [
    'driver'   => 'mysql',  
    'write'    => [  
        'host'      => '192.168.1.180',  
        'username'  => 'write',
        'password'   => 'write',
    ],  
    'read'     => [
       'host' => ［
           '192.168.1.179',
           '192.168.1.182',
       ],
       'username'  => 'read',
       'password'   => 'read', 
    ],
    ...  
]

代码分析

文件路径：vendor/laravel/framework/src/Illuminate/Database/Connectors/ConnectionFactory.php

代码：

class ConnectionFactory
{
    ...

    /**
     * Get the read configuration for a read / write connection.
     *
     * @param  array  $config
     * @return array
     */
    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);
    }

    ...

    /**
     * Get a read / write level configuration.
     *
     * @param  array   $config
     * @param  string  $type
     * @return array
     */
    protected function getReadWriteConfig(array $config, $type)
    {
        if (isset($config[$type][0])) {
            return $config[$type][array_rand($config[$type])];
        }

        return $config[$type];
    }

    ...

    /**
     * Merge a configuration for a read / write connection.
     *
     * @param  array  $config
     * @param  array  $merge
     * @return array
     */
    protected function mergeReadWriteConfig(array $config, array $merge)
    {
        return Arr::except(array_merge($config, $merge), ['read', 'write']);
    }

    ...
}


class Arr
{
   ...

   /**
    * Get all of the given array except for a specified array of items.
    *
    * @param  array  $array
    * @param  array|string  $keys
    * @return array
    */
   public static function except($array, $keys)
   {
       static::forget($array, $keys);

       return $array;
   }

   ...

   /**
    * Remove one or many array items from a given array using "dot" notation.
    *
    * @param  array  $array
    * @param  array|string  $keys
    * @return void
    */
   public static function forget(&$array, $keys)
   {
       $original = &$array;

       $keys = (array) $keys;

       if (count($keys) === 0) {
           return;
       }

       foreach ($keys as $key) {
           $parts = explode('.', $key);

           while (count($parts) > 1) {
               $part = array_shift($parts);

               if (isset($array[$part]) && is_array($array[$part])) {
                   $array = &$array[$part];
               } else {
                   $parts = [];
               }
           }

           unset($array[array_shift($parts)]);

           // clean up after each pass
           $array = &$original;
       }
   }

   ...
}