On 07:27 am, t...@commsecure.com.au wrote: >On 03/16/2010 06:07 PM, Peter Cai wrote: >>I think an init.d script could resolve this problem. >>But I am curious about why "turning off power without shutdown twisted >>server before" could cause such a problem. >> >>Is it a bug or it has some more fundamental reason? > >When twistd starts up, it creates a .pid file as a signal that it's >running. If you try and start it a second time, it notices that the >.pid >file exists, and refuses to run a second time. When twistd is shut down >cleanly, it removes the .pid file so that it can be run again. > >Unfortunately, this means that if twistd is shutdown *uncleanly* (by a >power failure, or SIGKILL, or some other means), the .pid file must be >removed before twistd will start again. > >This isn't really a bug in twistd as such; almost all Unix daemons use >the same fundamental system. Try running "ls /var/run/*.pid" on a Linux >system, for example. > >It's possible to add refinements to the basic .pid system, to make it >more resistant to this kind of problem (off the top of my head, >checking >that the named PID exists,
Actually it does this already. But this is a particularly ineffective check, especially for processes launched at boot time, because of the very high possibility of collisions. > >that it's a process of the right kind, >checking for stale .pid files with exclusive file locks), but all of >them require more code to implement, reduce portability, and still have >corner-cases that would require an admin to manually delete the .pid >file anyway. Jean-Paul _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
