PHP的popen命令失败的原因
我有一个批量电子邮件流程，可发送大约 30,000 封电子邮件。我遇到了一个奇怪的问题，该过程完成了大约 85%，然后电子邮件开始失败，并显示消息 无法执行：/usr/sbin/sendmail 我正在使用一个名为的库PHPMailer 1.73 以及错误消息来自的相关代码是
if(!@$mail = popen($sendmail, "w"))
{
$this->SetError($this->Lang("execute") . $this->Sendmail);
return false;
}
$sendmail 的值的形式为： /usr/sbin/sendmail -oi -f [电子邮件受保护] -t
我有 set_time_limit(0); 这样脚本就不会超时。
无论如何，有没有办法弄清楚为什么 popen() 突然开始失败？操作系统是否会耗尽文件描述符或达到其他限制？
我应该如何解决这个问题？我应该让它休眠，然后在失败之前重试 popen() 几次吗？
更新：感谢 Marko 的建议，查看我在 proc_open 文档 一条注释，如果它返回 FALSE ，则可能意味着您用完了文件描述符，或者您内存不足。我发现我的进程占用了 20G 内存。但是，如果将 memory_limit 设置为 64M，怎么会占用那么多内存呢？好吧，看来使用 exec()、popen() 或 proc_open() 运行外部程序并不会计入 PHP 的内存限制。有关详细信息，请参阅此问题，调试 mod_php 中的内存使用情况。我仍然不确定这是如何发生的，但我怀疑存在某种内存泄漏。
总之，如果文件描述符或内存不足，popen() 和 proc_open() 可能会返回 FALSE。
I have a batch email process that sends about 30,000 email messages. I have ran into a strange problem where it gets to about 85% completion of the process and then the email start failing with the message Could not execute: /usr/sbin/sendmail I am using a library called PHPMailer 1.73 and the relevant code where the error message comes from is
if(!@$mail = popen($sendmail, "w"))
{
$this->SetError($this->Lang("execute") . $this->Sendmail);
return false;
}
The value of $sendmail is of the form: /usr/sbin/sendmail -oi -f [email protected] -t
I have set_time_limit(0); so the script will not timeout.
Is there anyway to figure out why all of a sudden popen() starts failing? Could the OS be running out of file descriptors or some other limit being reached?
How should I resolve this? Should I have it sleep and then retry the popen() several times before failing?
Update: Thanks to the suggestion of Marko to check out proc_open() I found on the proc_open documentation a comment that if it returns FALSE it probably means that you ran out of file descriptors or you are out of memory. I found that my process was taking 20G of memory. But how could it take that much memory if memory_limit is set at 64M? Well, it seems that running external programs with exec(), popen() or proc_open() do NOT count against PHP's memory limit. See this SO question for more info on that, Debugging memory usage in mod_php. I'm still not sure how this is happening but I suspect some sort of memory leak.
In summary, popen() and proc_open() can return FALSE if you are out of file descriptors or out of memory.
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我建议使用 proc_open 代替。它使用起来稍微复杂一些，但是可以让您访问 stdout 和 stderr。这两个管道上的消息将为您节省大量调试时间。
如何使用，只需阅读PHP文档中的示例和注释即可。
I would recommend to use proc_open instead. It is slightly more complex to use, but gives you access to stdout and stderr. The messages on this two pipes will save you a lot of debugging time.
How to use, just read the examples and comments in the PHP documentation.