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List:       apache-modules
Subject:    Re: [apache-modules] select()ing client sockets (was: Re: Thread)
From:       Christian Parpart <cparpart () surakware ! net>
Date:       2004-01-13 19:53:04
Message-ID: 200401132053.09029.cparpart () surakware ! net
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On Tuesday 13 January 2004 8:26 pm, rm@fabula.de wrote:
> On Tue, Jan 13, 2004 at 06:25:57PM +0100, Christian Parpart wrote:
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> > 
> > On Tuesday 13 January 2004 6:02 pm, Marco Spinetti wrote:
> > > No,
> > > 
> > > I'm starting threads in child process (inside handler function) not
> > > during reading of configuration data.
> > > 
> > > Reading your email it seems that using pthreads inside child process \
> > > in apache 1.3.x gives strange results and it will not work as \
> > > expected, while using apache 2 all is ok.
> > > 
> > > Is it true?
> > 
> > it is not (at all).
> 
> Are you talking about v1.3.x or 2.x.x???

2.0.x

> > I believe this, because I have developed a module that had to watch for
> > I/O events on 2 sockets (web client and backend server). This was done \
> > in a backgroupd thread, so that I could do usual work in the main \
> > handler process. Unfortunately, my error log was flooding me with \
> > thouthends of segfault messages (very often requested module), and \
> > after having removed any thread connection in this module, my segfaults \
> > has been reduced to a very more acceptable minimum.
> 
> Sorry, without any offence, but this doesn't say anything about the
> possibility of threading in Apache per se, or? 

no, it doesn't, just as you say. but this is *my* experience, as well as I 
must experience, that apache doesn't like C++ exceptions at all, too :(
Again, this is *my* experience, nothing definite.

> I'm not a thread advocate at 
> all and try to avoid them but there are a lot of place one can mess up
> (hmm, did you try to 'select' on the _client_ filehandle? That's probably
> not a good idea - that's where apache comes in ...).

Unfortunately I had to, and still have to.
Because I *have* to react as fast as possible on client aborts. (think \
about a  message streaming server, that has to logout the user as soon as \
the client  aborted the connection to apache).
The second file descriptor is the socket connection to the server, that I \
have  to watch on sending events and server side connection closes (or \
server side  crashes, however).
Both are currently select()'ed.

See this URL (and STRG-F for "select"):
http://cvs.surakware.net/viewcvs.cgi/trunk/src/clients/mod_yacs/TChatStreamer.cpp?rev=HEAD&root=YaCS&content-type=text/vnd.viewcvs-markup


> > > What is the right and real answer?
> > 
> > The right thing I believe, is, if you'r coding an apache module, you
> > should try to design it in a flat model, that is, without any threads.
> > For listening for I/O events for example do a select/poll/epoll or even
> > use (that still not yet understood how to use easily) apr_poll API by
> > apache.
> 
> Yes, apr_poll seems to be the 'right' way if one wants to use threads.

is this an explicit if? I mean, I did not yet got rid of apr_poll, except 
knowing of it;
shall I use apr_poll over select/poll/epoll, too? Even if I've eliminated \
any  multi threads in the apache module?

> HTH Ralf Mattes

Greets,
Christian Parpart.

- -- 
 20:41:50 up 7 days,  7:31,  3 users,  load average: 0.85, 0.88, 0.73
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