Re: [Users] Question about forking

[Anatoly Pidruchny]

Hi Bogdan,

indeed, there are some grand-children processes created by some 
modules (like cpl-c, mi_fifo, mi_xmlrpc, etc). As far as I know, the 
modules implements the killing of the processes spawned by themselves 
- they keep the pid and kill them as module_destroy.
Well, apparently, at least not all modules do this. I just looked at the 
first module with a fork call that my find/grep command gave me. It 
happened to be xmpp module. It does not save the pid of the child 
process after the fork and it does not kill the child process in the 
module destroy function. But the reason why normally there are no 
left-over openser processes when openser is terminated is because the 
main openser process sends a SIGTERM signal to the whole process group, 
so, the signal is delivered to all the descendant openser processes, not 
only to the children of the main openser process.

I was lurking around your patch, but the thing that prevented me to 
upload it on SVN was the naming of the options :D - yes, it sounds 
stupid, but we need to take care and maintain backward compatibility 
(with the fork option) and in the same time to have some suggestive 
and correct names for the options....
Please modify the patch and use whatever name you think would be 
appropriate for this option. My reasoning for using the name -D is that 
currently -D option is for developers only. Nobody else is using this 
option and so nobody else will be affected if the meaning of the -D 
option changes. But I am OK if you use any other name for the new option 
and leave -D as it is.

Regards,
Anatoly.
Anatoly Pidruchny wrote:
Tim,

I found a difference in signal handling in non-daemonized vs 
daemonized mode. When the main openser process daemonizes itself, it 
also creates a new process group and session, puts itself into the 
new process group and becomes its leader. Then later it can send 
signals to all the processes in the process group. It means the 
signal will be delivered to all the children, children of children 
and so on. In non-daemonized mode it only sends signals to its direct 
children.

I will try to modify code to create a new process group also when -D 
option is used (but only when -F is not used). I will let you know 
when a modified patch is ready.

Thanks,

Anatoly.
Hi Anatoly,

That is what I did in the first example that I sent to you today.
Running manually with the -D option has the same results as when
executing openser with runsv.

thanks,

Tim

On 5/16/07, Anatoly Pidruchny <[EMAIL PROTECTED]> wrote:
Tim,

I can not explain why it behaves differently. But can you also try the
same test with -D option, but without using runsv?

Anatoly.
> Hi Anatoly,
>
> Thanks for your work-around - I'll try it. However, I did try the 
test
> you described without the -D option and here are the results:
>
> [EMAIL PROTECTED]:/# ps -ef | grep openser
> sipproxy 29793 29786   0 12:52:24 ?           0:00 openser
> sipproxy 29788 29786   0 12:52:24 ?           0:00 openser
> sipproxy 29791 29786   0 12:52:24 ?           0:00 openser
> sipproxy 29789 29786   0 12:52:24 ?           0:00 openser
> root 29797 29266   0 12:52:28 pts/1       0:00 grep openser
> sipproxy 29795 29786   0 12:52:24 ?           0:00 openser
> sipproxy 29786     1   0 12:52:24 ?           0:00 openser
> sipproxy 29794 29786   0 12:52:24 ?           0:00 openser
> sipproxy 29792 29786   0 12:52:24 ?           0:00 openser
> sipproxy 29790 29787   0 12:52:24 ?           0:00 openser
> sipproxy 29787 29786   0 12:52:24 ?           0:00 openser
>
> [EMAIL PROTECTED]:/# kill 29786
> [EMAIL PROTECTED]:/# ps -ef | grep openser
>    root 29799 29266   0 12:52:50 pts/1       0:00 grep openser
>
> As you can see, the child (29787) kills the grandchild (29790) when
> the parent (29786) is killed. I'm not sure why it behaves 
differently.
>
> Tim
>
> On 5/16/07, Anatoly Pidruchny <[EMAIL PROTECTED]> wrote:
>> Hi Tim,
>>
>> As far as I know, the problem with the left over openser process 
that
>> you described is not caused by the patch. If you run openser 
manually
>> without -D option, then kill the main process, you will get 
exactly the
>> same result. The main openser process will kill all its 
children, but
>> will not kill its grandchildren. The reason is that the main 
openser
>> process does not know anything about its grandchildren. 
Theoretically,
>> the process that forked a child (for example, your process with PID
>> 29744) is supposed to kill its children (for example, your 
process with
>> PID 29747) when it is terminated. But this does not happen. I 
think it
>> is a known issue (bug?) with openser. May be if you open a 
feature (or
>> bug?) request then this issue will be resolved.
>>
>> By the way, we do not have this problem. I think the reason is 
that you
>> use some module that we do not use. I grepped the openser 
sources and
>> found a number of places in modules where a child process is 
forked. In
>> our case, I think we never hit code that creates any of the 
"child of a
>> child" processes.
>>
>> As a workaround, did you try to kill all the left over openser 
processes
>> from the ./finish file?
>>
>> Regards,
>>
>> Anatoly.
>> > Hey Anatoly,
>> >
>> > I've been running with your patch and it works, but there is 
one issue
>> > that I want to bring up. After openser forks, it creates 
processes as
>> > follows:
>> >
>> > sipproxy 29745 29743   0 11:32:38 pts/2       0:00 openser -D
>> > sipproxy 29751 29743   0 11:32:38 pts/2       0:00 openser -D
>> > sipproxy 29748 29743   0 11:32:38 pts/2       0:00 openser -D
>> > sipproxy 29750 29743   0 11:32:38 pts/2       0:00 openser -D
>> > sipproxy 29743 29432   0 11:32:37 pts/2       0:00 openser -D
>> > sipproxy 29752 29743   0 11:32:38 pts/2       0:00 openser -D
>> > sipproxy 29744 29743   0 11:32:38 pts/2       0:00 openser -D
>> > sipproxy 29746 29743   0 11:32:38 pts/2       0:00 openser -D
>> > sipproxy 29749 29743   0 11:32:38 pts/2       0:00 openser -D
>> > sipproxy 29747 29744   0 11:32:38 pts/2       0:00 openser -D
>> >
>> > You can note that the parent PID is 29743 and has several 
children,
>> > but for some reason, process 29744 also spawns the child process
>> > 29747. When I use runsv to start the process, it notes the 
process
>> > that it creates is 29743. Then when I terminate with runsv, it 
kills
>> > 29743 - which kills all of it's children, but leaves PID 29747
>> > running. Since it's parent was killed, PID 29747 is adopted by 
the
>> > init process (PID 1). Here is an example of this done by hand 
(with a
>> > kill of 29743):
>> >
>> > [EMAIL PROTECTED]:/# kill 29743
>> > [EMAIL PROTECTED]:/# ps -ef | grep openser
>> >    root 29756 29266   0 11:35:19 pts/1       0:00 grep openser
>> > sipproxy 29747     1   0 11:32:38 pts/2       0:00 openser -D
>> >
>> > Please let me know if you can assist here.
>> >
>> > thanks much,
>> > Tim
>> >
>> > On 5/7/07, Anatoly Pidruchny <[EMAIL PROTECTED]> wrote:
>> >> Hi, Tim,
>> >>
>> >> there is a patch (that I submitted) that allows to run the main
>> openser
>> >> process in foreground and fork child processes as usual. No 
developer
>> >> has reviewed the patch yet. I hope this patch will be accepted
>> soon. The
>> >> patch is simple and we use it for a long time now. You can also
>> take the
>> >> patch and use it.
>> >>
>> >> The patch is:
>> >>
>> 
http://sourceforge.net/tracker/index.php?func=detail&aid=1689998&group_id=139143&atid=743022 

>>
>> >>
>> >>
>> >> Anatoly
>> >> > Hi,
>> >> >
>> >> > I want to start openser with runsv which requires that the 
starting
>> >> > process run in the foreground. My problem is that I also 
want to
>> >> > listen on a couple of different ports. When I set forking = 
yes, it
>> >> > will listen on multiple ports, but runsv won't work. When I 
set
>> >> > forking=no, then openser will only listen on the first 
specified
>> port.
>> >> >
>> >> > Is there any way around this? Can I have the starting process
>> run in
>> >> > the foreground and fork other processes that listen to the 
ports in
>> >> > the background?
>> >> >
>> >> > Here is the error message:
>> >> >
>> >> > WARNING: no fork mode  and more than one listen address
>> found(will use
>> >> > only the the first one)
>> >> >
>> >> > Here are the associated configuration lines:
>> >> >
>> >> > fork=no
>> >> >
>> >> > children=32
>> >> >
>> >> > # Local IP address/port pairs to listen to
>> >> > listen=65.185.233.55:5061
>> >> > listen=65.185.233.55:5062
>> >> >
>> >> > # Alias IP address/port pairs
>> >> > alias=65.185.233.104:5061
>> >> > alias=65.185.233.104:5062
>> >> >
>> >> > thanks,
>> >> > Tim
>> >> >




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