patch to force cyrus to reload its configuration in a more rigorous way

[Alain Spineux]

On Wed, Apr 2, 2008 at 10:30 AM, Simon Matter <simon.matter at invoca.ch> wrote:
> > Before this patch, cyrus was already able to detect a configuration
>  > file change,
>  > but only at the end of a connection. And any process waiting for a
>  > new connection was ignoring the change during the next connection,
>  > until they have finished.
>  > In other word, after a configuration change, any waiting process can
>  > still serve a new
>  > connection with the old configuration and let the administrator
>  > believe its change is not
>  > working.
>  >
>  > My patch force cyrmaster to send a SIGHUP to all its children when it
>  > detect a configuration change:
>  > - any working process will ignore the SIGHUP when processing a
>  > connection (what my patch does)
>  > and at the end of the connection, it will detect the configuration
>  > change and terminate
>  > (this is what is doing the original code).
>  > - any waiting process, will catch the SIGHUP and handle it like SIGALARM
>  > (what my patch does) and make the process believe its waiting period
>  > (-T option of imapd command) is expired and then terminate. (like was
>  > doing the original code)
>
>  Hi Alain,
>
>  Thanks for the patch, I'll try it out and may include it in my rpms later.
>  If I understand this correctly one drawback could be that on a heavy
>  loaded server sending SIGHUP will resuilt in much more newly created
>  processes after the SIGHUP has been sent. Could that be a problem somehow?

The only difference, is that without the patch,
any waiting process can still serve one connection before to terminate
and this during the timeout
period of 60sec (the cyrus default)
Then, it should not impact the load, this should not be measurable.

Some more details, because your question was a little unclear :

- After having made change, you have to SIGHUP cyrmaster only, like
before! Not all imapd, pop3, ... processes.
- When an inactive imapd nor pop3d, ... process get the SIGHUP, it
will terminate immediately. Their
is no reasons to terminate an active process. Active process, will
detect the configuartion change by temself
at the end of the connection and terminate.
- cyrmaster will start a new process when new connections arrive or to
match "prefork" in cyrus.conf.

Regards


>
>  Simon
>
>
>
>  >
>  > Here is the patch and also in attachment.
>  >
>  > Regards
>  >
>  > --- cyrus-imapd-2.3.11/imap/signals.c.orig      2006-11-30
>  > 18:11:20.000000000 +0100
>  > +++ cyrus-imapd-2.3.11/imap/signals.c   2008-03-23 17:24:54.000000000
>  > +0100
>  > @@ -79,6 +79,12 @@
>  >         fatal("unable to install signal handler for %d: %m", SIGALRM);
>  >      }
>  >
>  > +    /* ASX: SIGHUP is used to force a configuration reload, and the
>  > waiting
>  > +     * period is a privileged moment, so we don't set SA_RESTART */
>  > +    if (alarm && sigaction(SIGHUP, &action, NULL) < 0) {
>  > +       fatal("unable to install signal handler for %d: %m", SIGHUP);
>  > +    }
>  > +
>  >  #ifdef SA_RESTART
>  >      action.sa_flags |= SA_RESTART;
>  >  #endif
>  > --- cyrus-imapd-2.3.11/master/master.c.orig     2007-10-10
>  > 15:59:48.000000000 +0200
>  > +++ cyrus-imapd-2.3.11/master/master.c  2008-03-23 17:29:33.000000000
>  > +0100
>  > @@ -1568,6 +1568,23 @@
>  >                 syslog(LOG_DEBUG, "init: service %s socket %d pipe %d %d",
>  >                        Services[i].name, Services[i].socket,
>  >                        Services[i].stat[0], Services[i].stat[1]);
>  > +        } else if (Services[i].exec && Services[i].socket) {
>  > +            /* refresh the old one */
>  > +            syslog(LOG_DEBUG, "ASX SOMETHING TO DO service %s socket
>  > %d pipe %d %d %d",
>  > +                      Services[i].name, Services[i].socket,
>  > +                      Services[i].stat[0], Services[i].stat[1],
>  > +                       Services[i].exec ? 1:0);
>  > +            /* send SIGHUP to all children */
>  > +            for (j = 0 ; j < child_table_size ; j++ ) {
>  > +                c = ctable[j];
>  > +                while (c != NULL) {
>  > +                    if ((c->si == i) && (c->service_state !=
>  > SERVICE_STATE_DEAD)) {
>  > +                        syslog(LOG_DEBUG, "ASX send SIGHUP to %d",
>  > c->pid);
>  > +                        kill(c->pid, SIGHUP);
>  > +                    }
>  > +                    c = c->next;
>  > +                }
>  > +            }
>  >         }
>  >      }
>  >
>  > --- cyrus-imapd-2.3.11/master/service.c.orig    2007-09-27
>  > 22:10:39.000000000 +0200
>  > +++ cyrus-imapd-2.3.11/master/service.c 2008-03-23 17:32:46.000000000
>  > +0100
>  > @@ -460,7 +460,12 @@
>  >                             notify_master(STATUS_FD,
>  > MASTER_SERVICE_UNAVAILABLE);
>  >                         service_abort(EX_OSERR);
>  >                     }
>  > -               }
>  > +                } else {
>  > +                     /* fd >= 0 */
>  > +                     /* ASX we dont want SIGHUP to disrupt a connection
>  > +                      * before the end */
>  > +                     signals_add_handlers(0);
>  > +                }
>  >             } else {
>  >                 /* udp */
>  >                 struct sockaddr_storage from;
>  >
>  >
>  > --
>  > Alain Spineux
>  > aspineux gmail com
>  > May the sources be with you
>  > ----
>  > Cyrus Home Page: http://cyrusimap.web.cmu.edu/
>  > Cyrus Wiki/FAQ: http://cyrusimap.web.cmu.edu/twiki
>  > List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html
>
>
>



-- 
Alain Spineux
aspineux gmail com
May the sources be with you