multiprocessing exception: No Child processes

[jeffforbes]

I recently modified the logging in a recent version of websocket.py so that the all of the loggeded information would go to a log file. I am not sure if my changes have caused a recurrence of the multiprocessing exception that was fixed in 2013. Below in the error trace :

2015-08-20 03:00:58,182 exception
Traceback (most recent call last):
File "/opt/websockify/websocket.py", line 977, in start_server
child_count = len(multiprocessing.active_children())
File "/usr/lib64/python2.4/site-packages/multiprocessing/process.py", line 48, in active_children
_cleanup()
File "/usr/lib64/python2.4/site-packages/multiprocessing/process.py", line 58, in _cleanup
if p._popen.poll() is not None:
File "/usr/lib64/python2.4/site-packages/multiprocessing/forking.py", line 106, in poll
pid, sts = os.waitpid(self.pid, flag)
OSError: [Errno 10] No child processes
2015-08-20 03:00:58,182 handler exception: [Errno 10] No child processes

The error only shows up on a busy site which is spawning many child processes.
When this error occurs, the parent process CPU eventually goes to 100% and the log file get filled with these messages. if verbose is off, then only the "OSError: [Errno 10] No child processes" is recorded.

Please advise on any possible solutions.

Below in the diff between my modified version and the most recent version from the GitHub site:

# diff /opt/websockify/websocket.py websocket.py 
107a108
>         self.strict_mode = getattr(server, "strict_mode", True)
112d112
<         self.log_file = getattr(server, "log_file", False)
181c181
<     def decode_hybi(buf, base64=False, logger=None):

---
>     def decode_hybi(buf, base64=False, logger=None, strict=True):
246a247,250
> 
>             if strict:
>                 raise WebSocketRequestHandler.CClose(1002, "The client sent an unmasked frame.")
> 
355c359,360
<                                      logger=self.logger)

---
>                                      logger=self.logger,
>                                      strict=self.strict_mode)
499c504
<             self.msg("%s: %s WebSocket connection", client_addr,

---
>             self.log_message("%s: %s WebSocket connection", client_addr,
501c506
<             self.msg("%s: Version %s, base64: '%s'", client_addr,

---
>             self.log_message("%s: Version %s, base64: '%s'", client_addr,
504c509
<                 self.msg("%s: Path: '%s'", client_addr, self.path)

---
>                 self.log_message("%s: Path: '%s'", client_addr, self.path)
510c515
<                 self.msg("opening record file: %s", fname)

---
>                 self.log_message("opening record file: %s", fname)
592c597
<             file_only=False, log_file=False, log_file_name='',

---
>             file_only=False,
595c600
<             tcp_keepintvl=None, auto_pong=False):

---
>             tcp_keepintvl=None, auto_pong=False, strict_mode=True):
608a614,615
>         self.file_only      = file_only
>         self.strict_mode    = strict_mode
615d621
<         self.log_file       = log_file
648c654,657
<             self.msg("  - Web server. Web root: %s", self.web)

---
>             if self.file_only:
>                 self.msg("  - Web server (no directory listings). Web root: %s", self.web)
>             else:
>                 self.msg("  - Web server. Web root: %s", self.web)
730c739
<     def daemonize(keepfd=[], chdir='/', stdStream=None):

---
>     def daemonize(keepfd=None, chdir='/'):
753c762
<                 if (fd not in keepfd ):

---
>                 if fd != keepfd:
761,766c770,771
<         if stdStream :
<             sys.stdout = stdStream
<             sys.stderr = stdStream
<         else:
<             os.dup2(os.open(os.devnull, os.O_RDWR), sys.stdout.fileno())
<             os.dup2(os.open(os.devnull, os.O_RDWR), sys.stderr.fileno())

---
>         os.dup2(os.open(os.devnull, os.O_RDWR), sys.stdout.fileno())
>         os.dup2(os.open(os.devnull, os.O_RDWR), sys.stderr.fileno())
795c800
<         if handshake == "":

---
>         if not handshake:
939,946c944
<             if self.log_file:
< # Get the stream for the log file so that it can be used for logging in the daemon mode
<                 logStream = self.logger.parent.handlers[0].stream
<                 files_preserve = [lsock.fileno(), logStream.fileno()]
<                 self.daemonize(files_preserve, self.web, logStream)
<             else:
<                 files_preserve =  [lsock.fileno()]
<                 self.daemonize(files_preserve, self.web)

---
>             self.daemonize(keepfd=lsock.fileno(), chdir=self.web)
1052d1049
<                         _, exc, _ = sys.exc_info()
[root@rndgw tmp]# diff /opt/websockify/websocket.py websocket.py  | less
[root@rndgw tmp]# less  websocket.py                                   
[root@rndgw tmp]# diff /opt/websockify/websocket.py websocket.py  | less
[root@rndgw tmp]# diff /opt/websockify/websocket.py websocket.py  
107a108
>         self.strict_mode = getattr(server, "strict_mode", True)
112d112
<         self.log_file = getattr(server, "log_file", False)
181c181
<     def decode_hybi(buf, base64=False, logger=None):

---
>     def decode_hybi(buf, base64=False, logger=None, strict=True):
246a247,250
> 
>             if strict:
>                 raise WebSocketRequestHandler.CClose(1002, "The client sent an unmasked frame.")
> 
355c359,360
<                                      logger=self.logger)

---
>                                      logger=self.logger,
>                                      strict=self.strict_mode)
499c504
<             self.msg("%s: %s WebSocket connection", client_addr,

---
>             self.log_message("%s: %s WebSocket connection", client_addr,
501c506
<             self.msg("%s: Version %s, base64: '%s'", client_addr,

---
>             self.log_message("%s: Version %s, base64: '%s'", client_addr,
504c509
<                 self.msg("%s: Path: '%s'", client_addr, self.path)

---
>                 self.log_message("%s: Path: '%s'", client_addr, self.path)
510c515
<                 self.msg("opening record file: %s", fname)

---
>                 self.log_message("opening record file: %s", fname)
592c597
<             file_only=False, log_file=False, log_file_name='',

---
>             file_only=False,
595c600
<             tcp_keepintvl=None, auto_pong=False):

---
>             tcp_keepintvl=None, auto_pong=False, strict_mode=True):
608a614,615
>         self.file_only      = file_only
>         self.strict_mode    = strict_mode
615d621
<         self.log_file       = log_file
648c654,657
<             self.msg("  - Web server. Web root: %s", self.web)

---
>             if self.file_only:
>                 self.msg("  - Web server (no directory listings). Web root: %s", self.web)
>             else:
>                 self.msg("  - Web server. Web root: %s", self.web)
730c739
<     def daemonize(keepfd=[], chdir='/', stdStream=None):

---
>     def daemonize(keepfd=None, chdir='/'):
753c762
<                 if (fd not in keepfd ):

---
>                 if fd != keepfd:
761,766c770,771
<         if stdStream :
<             sys.stdout = stdStream
<             sys.stderr = stdStream
<         else:
<             os.dup2(os.open(os.devnull, os.O_RDWR), sys.stdout.fileno())
<             os.dup2(os.open(os.devnull, os.O_RDWR), sys.stderr.fileno())

---
>         os.dup2(os.open(os.devnull, os.O_RDWR), sys.stdout.fileno())
>         os.dup2(os.open(os.devnull, os.O_RDWR), sys.stderr.fileno())
795c800
<         if handshake == "":

---
>         if not handshake:
939,946c944
<             if self.log_file:
< # Get the stream for the log file so that it can be used for logging in the daemon mode
<                 logStream = self.logger.parent.handlers[0].stream
<                 files_preserve = [lsock.fileno(), logStream.fileno()]
<                 self.daemonize(files_preserve, self.web, logStream)
<             else:
<                 files_preserve =  [lsock.fileno()]
<                 self.daemonize(files_preserve, self.web)

---
>             self.daemonize(keepfd=lsock.fileno(), chdir=self.web)
1052d1049
<                         _, exc, _ = sys.exc_info()

[DirectXMan12]

This actually looks like a websockify issue. Also, you shouldn't need to make many changes to log to a file -- websockify now uses the python logging module from the standard library, so it should be a pretty simple change to log to a file (replace the StreamHandler with a FileHandler in websocketproxy.py if you're running websocketproxy.py directly, or use logging.basicConfig at the top of your application if you're using websockify as a library)