6、通过更改配置文件来控制nginx-阅读官方文档

官网：Controlling nginx

翻译部分：Changing Configuration

开始！

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In order for nginx to re-read the configuration file, a HUP signal should be sent to the master process.

 为了让nginx重读配置文件，需要发送一个HUP信号给主进程。

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The master process first checks the syntax validity, then tries to apply new configuration, that is, to open log files and new listen sockets.

 主进程先检查配置文件的语法合法性，然后尝试应用新的配置，也就是说，打开日志文件和新的监听套接字。

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If this fails, it rolls back changes and continues to work with old configuration.

如果失败了，nginx会回滚新配置的修改，继续用就配置工作。 

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If this succeeds, it starts new worker processes, and sends messages to old worker processes requesting them to shut down gracefully.

如果成功了，nginx开启一个新的工作进程 ，并且发消息给旧的工作进程请求它们正常关闭。

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Old worker processes close listen sockets and continue to service old clients.

 旧进程关闭监听套接字，继续为旧客户端服务。

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After all clients are serviced, old worker processes are shut down.

 当服务完所有客户端，旧工作进程才会被关闭。

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Let’s illustrate this by example.

 让我们用一个例子来验证一下。

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Imagine that nginx is run on FreeBSD and the command

 假设nginx跑在FreeBSD操作系统(一种类UNIX操作系统)上，执行下面的命令：

ps axw -o pid,ppid,user,%cpu,vsz,wchan,command | egrep '(nginx|PID)'

produces the following output:

 会得到下面的内容：

  PID  PPID USER    %CPU   VSZ WCHAN  COMMAND
33126     1 root     0.0  1148 pause  nginx: master process /usr/local/nginx/sbin/nginx
33127 33126 nobody   0.0  1380 kqread nginx: worker process (nginx)
33128 33126 nobody   0.0  1364 kqread nginx: worker process (nginx)
33129 33126 nobody   0.0  1364 kqread nginx: worker process (nginx)

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If HUP is sent to the master process, the output becomes:

 如果发送HUP给主进程，输出内容变成：

  PID  PPID USER    %CPU   VSZ WCHAN  COMMAND
33126     1 root     0.0  1164 pause  nginx: master process /usr/local/nginx/sbin/nginx
33129 33126 nobody   0.0  1380 kqread nginx: worker process is shutting down (nginx)
33134 33126 nobody   0.0  1368 kqread nginx: worker process (nginx)
33135 33126 nobody   0.0  1368 kqread nginx: worker process (nginx)
33136 33126 nobody   0.0  1368 kqread nginx: worker process (nginx)

One of the old worker processes with PID 33129 still continues to work.

其中一个id为33129的旧工作进程 依然在继续工作，还没有关闭。

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After some time it exits:

 过了一段时间后，33129进程才退出了：

  PID  PPID USER    %CPU   VSZ WCHAN  COMMAND
33126     1 root     0.0  1164 pause  nginx: master process /usr/local/nginx/sbin/nginx
33134 33126 nobody   0.0  1368 kqread nginx: worker process (nginx)
33135 33126 nobody   0.0  1368 kqread nginx: worker process (nginx)
33136 33126 nobody   0.0  1368 kqread nginx: worker process (nginx)