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From Victor Danilchenko <vic...@askonline.net>
Subject Re: Help -- how to fork an Apache process in mod_perl safely? Not Apache2:Subprocess...
Date Sat, 12 Sep 2009 22:11:15 GMT
William T wrote:
> There are all kinds of problems that you'll encounter and have to solve 
> if you fork.  I found it's better to call at(1) to start another 
> seperate process immediatly.  If you need to pass data JSON worked 
> really well for me.

	Thanks, that's what I ended up doing. First I ended up having to move 
the processing into an external script call anyway, and then I tried 
Apache2::SubProcess, and it ended up working, but my script was randomly 
receiving TERM signals... it's handleable of course, but I decided to go 
with the 'at' technique, it's safer that way, I suppose.



>> On Aug 25, 2009 5:12 AM, "Victor Danilchenko" <victor@askonline.net 
>> <mailto:victor@askonline.net>> wrote:
>>
>>        Hi all,
>>
>>        I need to be able to fork an Apache process in daemon form, to 
>> do some housekeeping which might potentially take a few seconds. 
>> However, when I do that, I start getting SQL errors (of the 
>> "connection lost" type) in the browser. I do the fairly standard 
>> cleanup to daemonize the child process, but of course it needs to 
>> retain the SQL socket open. Here is my forking code:
>>
>> sub modperl_kamikaze_fork () {
>>    # You will have to do CORE::exit(0) at the end of the execution.
>>
>>    $SIG{CHLD} = 'IGNORE';
>>    get_m->flush_buffer;
>>    defined (my $kid = fork) or die "Cannot fork: $!\n";
>>    return $kid if $kid;
>>
>>    my $r = get_r;
>>    close STDIN; open STDIN, '/dev/null'
>>        or die "Can't read /dev/null: $!";
>>    close STDOUT; open STDOUT, '>/dev/null'
>>        or die "Can't write to /dev/null: $!";
>>    close STDERR; open STDERR, '>>/tmp/form.log'
>>        or die "Cannot open /tmp/fork.log\n";
>>    setsid
>>        or die "Can't start a new session: $!";
>>
>>    my $oldfh = select STDERR;
>>    local $| = 1;
>>    select $oldfh;
>>    warn "Child (PID $$) spawned.\n";
>>
>>    $r->child_terminate;
>> }
>>
>>
>>        The Apache2:Subprocess doesn't help me, because I need not to 
>> spawn an external process, but to finish processing in mod_perl 
>> context -- just without bugging the user with it.
>>
>>        Any ideas on how to either fork better, or how to solve this 
>> without forking (e.g. is there a way to 'append' a function call to 
>> the request after the rest of the request is completed)?
>>
>>        Many thanks in advance.
>>
>> -- 
>>        Victor Danilchenko
>>        Senior Software Engineer, AskOnline.net
>>        victor@askonline.net <mailto:victor@askonline.net> - 617-273-0119
> 


-- 
	Victor Danilchenko
	Senior Software Engineer, AskOnline.net
	victor@askonline.net - 617-273-0119

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