[REBOL] Re: REBOL CGI Zombiness on Linux
From: holger:rebol at: 12-Jun-2001 9:33
On Tue, Jun 12, 2001 at 12:55:27PM +0200, Christian Langreiter wrote:
> Since the update to Core 2.5 REBOL CGI processes seem to hang a lot - today
> I killed 57 running REBOL zombies on my Linux machine.
> - This is a 2.5 problem. 2.3 didn't have it.
> - My code is OK (happens even with trivial things which can't hang) ;-)
> - Happened to other people running REBOL/Core 2.5 on Linux as well.
> Is this a known problem?
Yes. What is happening is: the Unix versions of Core 2.5 fork() during
startup to create a background process for asynchronous DNS lookup.
Under certain circumstances web servers brutally "kill" the spawned
process (SIGTERM/SIGINT/SIGHUP), instead of just closing stdin gracefully.
That leaves the DNS child process behind.
We have added some more sophisticated signal handling/trapping to
Command 2.0 (will also be in future Core versions) to handle the
most common problems and shut down child processes in those situations.
The good news is that even with Core 2.5 those zombies are basically
harmless. They take up no CPU time and virtually no RAM.