gunicorn Arbiter 源码解析

 1 # prefork.py
 2 import sys
 3 import socket
 4 import select
 5 import os
 6 import time
 7  
 8 def do_sub_process():
 9     pid = os.fork()
10     if pid < 0:
11         print ‘fork error‘
12         sys.exit(-1)
13     elif pid > 0:
14         print ‘fork sub process %d‘  % pid
15         return
16  
17     # must be child process
18     time.sleep(1)
19     print ‘sub process will exit‘, os.getpid(), os.getppid()
20     sys.exit(0)
21  
22 def main():
23     sub_num = 2
24     for i in range(sub_num):
25         do_sub_process()
26     time.sleep(10)
27     print ‘main process will exit‘, os.getpid()
28  
29 if __name__ == ‘__main__‘:
30     main()

        def sleep(self):
        """        Sleep until PIPE is readable or we timeout.
        A readable PIPE means a signal occurred.
        """
            ready = select.select([self.PIPE[0]], [], [], 1.0) # self.PIPE = os.pipe()
            if not ready[0]: 
                return
            while os.read(self.PIPE[0], 1):
                pass

　　代码里面的注释写得非常清楚，要么PIPE可读立即返回，要么等待超时。管道可读是因为有信号发生。这里看看pipe函数

　　os.pipe()

Create a pipe. Return a pair of file descriptors (r,w) usable for reading and writing, respectively.

        def wakeup(self):
            """
            Wake up the arbiter by writing to the PIPE
            """
            os.write(self.PIPE[1], b‘.‘)

最后附上Arbiter的信号处理：

• QUIT, INT: Quick shutdown
• TERM: Graceful shutdown. Waits for workers to finish their current requests up to the graceful timeout.
• HUP: Reload the configuration, start the new worker processes with a new configuration and gracefully shutdown older workers. If the application is not preloaded (using the --preloadoption), Gunicorn will also load the new version.
• TTIN: Increment the number of processes by one
• TTOU: Decrement the number of processes by one
• USR1: Reopen the log files
• USR2: Upgrade the Gunicorn on the fly. A separate TERM signal should be used to kill the old process. This signal can also be used to use the new versions of pre-loaded applications.
• WINCH: Gracefully shutdown the worker processes when Gunicorn is daemonized.