我写了一个 Laravel 命令，它会派生出一些子进程。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 Eloquent 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派生的相同 MySQL 连接。

如果我在调用 fork() 之前不在父进程中调用 Item::first()，它会运行良好。 (在我的实际用例中，我不能那样做......在 fork 子进程之前，父进程将对 MySQL 做很多事情。)

因为在那种情况下，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一个连接。

那么，如果是这样的话，forked之后如何为每个子进程初始化一个新的MySQL连接呢？

最佳答案

因为这都是关于连接死亡的，你可以通过简单地重新连接到数据库来解决这个问题。

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 中对此进行了测试并且它有效。

关于php - Laravel:如何在子进程中通过 Eloquent 更新 MySQL？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/51437882/