Laravel：如何在子进程中通过Eloquent更新MySQL？

Question

我编写了一个Laravel命令，它将派生一些子进程。子进程将通过Eloquent更新数据库。

代码:

<?php

namespace App\Console\Commands;

use App\Console\BaseCommand;
use App\Item;
use Illuminate\Console\Command;

class Test extends Command
{
    /**
     * The name and signature of the console command.
     *
     * @var string
     */
    protected $signature = 'test';

    /**
     * The console command description.
     *
     * @var string
     */
    protected $description = 'Command description';

    /**
     * Create a new command instance.
     *
     * @return void
     */
    public function __construct()
    {
        parent::__construct();
    }

    /**
     * Execute the console command.
     *
     * @return mixed
     */
    public function handle()
    {
        Item::first();
        $children = [];
        for($i = 0; $i < 5; $i++) {
            $pid = pcntl_fork();
            if ($pid == -1) {
                die('pmap fork error');
            } else {
                if ($pid) {
                    $children[] = $pid;
                } else {
                    Item::first(); exit;
                }
            }
        }
        foreach ($children as $child) {
            pcntl_waitpid($child, $status);
        }
    }
}

运行我的代码：

vagrant@homestead:~/ECAME$ php artisan test


  [Illuminate\Database\QueryException]
  Packets out of order. Expected 1 received 116. Packet size=6255201 (SQL: select * from `items` where `items`.`deleted_at` is null limit 1)



  [Illuminate\Database\QueryException]
  Packets out of order. Expected 1 received 100. Packet size=6238815 (SQL: select * from `items` where `items`.`deleted_at` is null limit 1)



  [Illuminate\Database\QueryException]
  Packets out of order. Expected 1 received 0. Packet size=2816 (SQL: select * from `items` where `items`.`deleted_at` is null limit 1)



  [Illuminate\Database\QueryException]
  Packets out of order. Expected 1 received 116. Packet size=6381412 (SQL: select * from `items` where `items`.`deleted_at` is null limit 1)



  [ErrorException]
  Packets out of order. Expected 1 received 100. Packet size=6238815



  [ErrorException]
  Packets out of order. Expected 1 received 116. Packet size=6381412



  [ErrorException]
  Packets out of order. Expected 1 received 116. Packet size=6255201



  [ErrorException]
  Packets out of order. Expected 1 received 0. Packet size=2816

这背后的原因是什么？以及如何在子进程中通过口才更新MySQL？

附言：

我认为这个问题的原因是，所有子进程都使用从父进程分叉的相同MySQL连接。

如果我在调用fork（）之前没有在父进程中调用Item：：first（），那么它运行良好。（在我的实际用例中，我不能这样做...父进程将在分叉子进程之前使用MySQL做很多事情。

因为在这种情况下，MySQL连接不会在父进程中初始化，所以每个子进程都会自己初始化连接。

那么，如果是这种情况，如何在分叉后为每个子进程初始化新的MySQL连接？

Answer 1

在Laravel中进行进程分叉后，将以下代码放入子进程中，在Laravel 4.2中为我创建了一个稳定的mysql客户端连接：

DB::disconnect();

// we need to clone the database connection of the parent and
// create a new connection as using the original causes protocol errors

$dbconn_child = 
    [
        'driver'    => DB::connection()->getConfig('driver'),
        'host'      => DB::connection()->getConfig('host'),
        'port'      => DB::connection()->getConfig('port'),
        'database'  => DB::connection()->getConfig('database'),
        'username'  => DB::connection()->getConfig('username'),
        'password'  => DB::connection()->getConfig('password'),
        'charset'   => DB::connection()->getConfig('charset'),
        'collation' => DB::connection()->getConfig('collation'),
        'prefix'    => DB::connection()->getConfig('prefix'),
        'modes'     => DB::connection()->getConfig('modes'),
        'options'   => DB::connection()->getConfig('options'),
    ];

Config::set('database.connections.DB_CONFIG_CHILD', $dbconn_child);

DB::setDefaultConnection('DB_CONFIG_CHILD');

DB::reconnect();

这将使用与原始连接相同的参数动态创建新连接，然后将子进程切换到新连接并进行连接。

简单地断开并重新连接默认连接会导致类似于OPs结果的各种mysql协议错误。

Answer 2

如果您在database.php中定义了一个具有相等参数的第二个ddbb，并且您在第二个连接中启动了项目::first？

# Primary database connection
            'mysql' => [
                'driver'    => 'mysql',
                'host'      => 'localhost',
                'database'  => 'myddbb',
                'username'  => 'root',
                'password'  => '',
                'charset'   => 'utf8',
                'collation' => 'utf8_unicode_ci',
                'prefix'    => '',
            ],
  # Secondary database connection
        'mysql_forConnectChildren' => [
            'driver'    => 'mysql',
            'host'      => 'localhost',
            'database'  => 'myddbb',
            'username'  => 'root',
            'password'  => '',
            'charset'   => 'utf8',
            'collation' => 'utf8_unicode_ci',
            'prefix'    => '',
        ],

后来

 $item = \DB::connection('mysql_forConnectChildren')->select('select * from Item')->get(1);

我没有测试，但我认为可以工作

Answer 3

由于这一切都是关于连接死亡的，因此只需重新连接到数据库即可解决此问题。

use Illuminate\Support\Facades\DB;

[...]

public function handle()
{
    User::first();

    $children = [];

    for ($i = 0; $i < 5; $i++) 
    {
        $pid = pcntl_fork();

        if ($pid == -1) 
        {
            die('pmap fork error');
        } 
        else 
        {
            if ($pid) 
            {
                $children[] = $pid;
            } 
            else
            {
                DB::connection()->reconnect(); // <----- add this
                User::first(); exit;
            }
        }
    }

    foreach ($children as $child) 
    {
        pcntl_waitpid($child, $status);
    }
}

我在Laravel 5.6中测试了这一点，它工作正常。