gunicorn 信号处理（SIGHUP，SIGUSR2）

来源：互联网发布：邮箱数据购买编辑：程序博客网时间：2024/06/06 08:41

在这篇文章中，提到了Master进程对信号的处理函数，其中有两个信号比较有意思。

SIGHUP：用来热更新（Reload）应用

SIGUSR2：用来在线升级（upgrade on the fly）gunicorn

下面来详细看一下：

SIGHUP:

Reload the configuration, start the new worker processes with a new configuration and gracefully shutdown older workers.

SIGUP对应的信号处理函数是Arbiter.reload。简化后的核心代码如下：

 1     def reload(self): 2         old_address = self.cfg.address 3   4         # reload conf，重新加载配置 5         self.app.reload() 6         self.setup(self.app) 7   8         # reopen log files 9         self.log.reopen_files()10  11         # do we need to change listener ?，处理监听端口变化的情况12         if old_address != self.cfg.address:13             # close all listeners14             [l.close() for l in self.LISTENERS]15             # init new listeners16             self.LISTENERS = create_sockets(self.cfg, self.log)17             listeners_str = ",".join([str(l) for l in self.LISTENERS])18             self.log.info("Listening at: %s", listeners_str)19  20         # spawn new workers，启动新的Worker（数量和类型来自新的配置）21         for i in range(self.cfg.workers):22             self.spawn_worker()23  24         # manage workers，这里会kill掉原来的Worker25         self.manage_workers()

　　在上面的引用中提到，会“优雅”（graceful）地kill掉老的worker进程。实现也很简单，Arbiter为每一个fork出的worker进程设置一个自增的“worker_age”，worker中这个属性越小，表明这个worker越老。在manage_workers中，如果已经启动的worker进程数量大于配置中的数量，那么会kill掉比较老的worker进程。代码如下

 1     def manage_workers(self): 2         """\ 3         Maintain the number of workers by spawning or killing 4         as required. 5         """ 6         if len(self.WORKERS.keys()) < self.num_workers: 7             self.spawn_workers() 8   9         workers = self.WORKERS.items()10         workers = sorted(workers, key=lambda w: w[1].age) # 按worker的age顺序排序11         while len(workers) > self.num_workers: # num_workers是配置的worker数量12             (pid, _) = workers.pop(0)13             self.kill_worker(pid, signal.SIGTERM)

SIGUSR2

Upgrade the Gunicorn on the fly. A separate TERM signal should be used to kill the old process.

　对应的信号处理函数是Arbiter.reexec，该函数会重新fork出新的master-workers进程，但不会影响到原来的master，worker进程，所以上面提到需要将原来的进程kill掉。

 1     def reexec(self): 2         """\ 3         Relaunch the master and workers. 4         """ 5         if self.reexec_pid != 0: 6             self.log.warning("USR2 signal ignored. Child exists.") 7             return 8   9         if self.master_pid != 0:10             self.log.warning("USR2 signal ignored. Parent exists")11             return12  13         master_pid = os.getpid()14         self.reexec_pid = os.fork()15         if self.reexec_pid != 0:16             return17  18         self.cfg.pre_exec(self)19  20         environ = self.cfg.env_orig.copy()21         fds = [l.fileno() for l in self.LISTENERS]22         environ['GUNICORN_FD'] = ",".join([str(fd) for fd in fds]) # 设置了一些环境变量，用来区分是正常启动gunicorn还是通过fork重新启动。23         environ['GUNICORN_PID'] = str(master_pid)24  25         os.chdir(self.START_CTX['cwd'])26  27         # exec the process using the original environnement28         os.execvpe(self.START_CTX[0], self.START_CTX['args'], environ)

下面做一下实验，两个终端，1号终端运行代码，2号终端发送信号。

step1：

1号终端启动gunirorn： gunicorn -w 2 gunicorn_app:app ，

2号终端查看python进程： ps -ef | grep python,

1号终端输出

[2017-01-19 15:21:23 +0000] [6166] [INFO] Starting gunicorn 19.6.0

[2017-01-19 15:21:23 +0000] [6166] [INFO] Listening at: http://127.0.0.1:8000 (6166)

[2017-01-19 15:21:23 +0000] [6166] [INFO] Using worker: sync

[2017-01-19 15:21:23 +0000] [6171] [INFO] Booting worker with pid: 6171

[2017-01-19 15:21:23 +0000] [6172] [INFO] Booting worker with pid: 6172

2号终端输出

hzliumi+ 6166 5721 0 15:21 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

hzliumi+ 6171 6166 0 15:21 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

hzliumi+ 6172 6166 0 15:21 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

可以看到，master进程的PID是6166，然后两个worker进程的pid分别是6171、6172. 下面需要用到master进程的PID

step2：

2号终端发送信号：kill -SIGUSR2 6166 ，然后查看python进程

1号终端追加输出

[2017-01-19 15:27:08 +0000] [6166] [INFO] Handling signal: usr2

[2017-01-19 15:27:08 +0000] [6629] [INFO] Starting gunicorn 19.6.0

[2017-01-19 15:27:08 +0000] [6629] [INFO] Listening at: http://127.0.0.1:8000 (6629)

[2017-01-19 15:27:08 +0000] [6629] [INFO] Using worker: sync

[2017-01-19 15:27:08 +0000] [6634] [INFO] Booting worker with pid: 6634

[2017-01-19 15:27:08 +0000] [6635] [INFO] Booting worker with pid: 6635

2号终端输出

hzliumi+ 6166 5721 0 15:21 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

hzliumi+ 6171 6166 0 15:21 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

hzliumi+ 6172 6166 0 15:21 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

hzliumi+ 6629 6166 3 15:27 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

hzliumi+ 6634 6629 0 15:27 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

hzliumi+ 6635 6629 0 15:27 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

从1号终端可以看出，基本是重新启动了gunicorn，不过从2号终端输出可以看到，新的master进程（pid 6629）是老的master进程（pid 6166）的子进程

step3：

2号终端发送信号：kill -SIGTERM 6166 ，稍等几秒后查看python进程：

1号终端追加输出

[2017-01-19 15:29:42 +0000] [6166] [INFO] Handling signal: term

[2017-01-19 15:29:42 +0000] [6171] [INFO] Worker exiting (pid: 6171)

[2017-01-19 15:29:42 +0000] [6172] [INFO] Worker exiting (pid: 6172)

[2017-01-19 15:29:42 +0000] [6166] [INFO] Shutting down: Master

[2017-01-19 15:29:42 +0000] [6629] [INFO] Master has been promoted.

2号终端输出

hzliumi+ 6629 1 0 15:27 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

hzliumi+ 6634 6629 0 15:27 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

hzliumi+ 6635 6629 0 15:27 pts/0 00:00:00 /usr/bin/python /usr/local/bin/gunicorn -w 2 gunicorn_app:app

可以看到，老的master进程（6166）及其fork出的worker子进程（pid分别是6171、6172）已经被kill掉了

references：

http://docs.gunicorn.org/en/stable/signals.html

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