Re: Who actually gets the TERM signal in "runsvctrl down"?

[Lloyd Zusman <ljz@asfast.com>]

Charlie Brady <charlieb-smarden-supervision@budge.apana.org.au> writes:

> On Fri, 25 Jun 2004, Lloyd Zusman wrote:
>
> [ ... ]
>
>> Therefore, an "apachectl stop" causes "httpd -k stop" to be invoked.
>> Does passing "-k stop" to httpd cause it to signal itself with
>> TERM?
>
> I don't know. strace it, or check the source. I guess that's what it does, 
> after finding the right process id, by searching for a pid file. The docs 
> suggest I'm right:
>
> http://httpd.apache.org/docs/stopping.html

This one applies to Apache 2:

  http://httpd.apache.org/docs-2.0/stopping.html

It also documents that the signals will work.  But I want to use the
command line options, in case some future version of apache kills the
daemons in a different way, or perhaps does some cleanup before sending
the signal.


> [Note - the "itself" you use isn't accurate. You pass "-k stop" to a new 
> httpd process, not one of the ones which is running. This new process 
> tries to pick the parent httpd process from all the ones which are 
> running, and sends it a TERM signal.]

Yes, I was imprecise in using the word "itself".  I should have said
this:  "the running instance(s) of itself".


>> > Why do you want this extra shell process between runsv and apache, and
>> > why do you want to run apachectl?
>> 
>> Because I want to use the software's own recommended startup and
>> shutdown procedures when I invoke it and kill it.
>
> In that case why use runit at all?

Because I want the apache daemon to automatically be restarted in case
it dies.


> You need to craft a suitable run script for each service. Unless the 
> service that you start mishandles signals when given them, that's probably 
> all you need. You need to determine what "suitable" means. Google and a 
> cast of hundreds will probably help you there.

Based on this discussion, I have crafted a run script that is a
compromise between a pure invocation of httpd and the apachectl-based
version that I was previously advocating.  It causes "httpd -k stop",
"httpd -k restart", and "httpd -k graceful" to be invoked when
appropriate signals are received, in case a future version of apache
needs this to be done for cleanup purposes, or whatever.

The script is attached below.


>> I'd rather rely on startup and shutdown scripts that are supplied with
>> the various software packages that I use.  But I want to control them
>> via runit mechanisms.
>
> You probably can't do both. And if you can, I doubt it's worth it.

You're right.  The normal startup script does not make use of the
-DNO_DETACH option to httpd, which is needed in order for runit to work.


>> The amount of extra time that is used to start up and stop a
>> long-running daemon like apache by invoking its recommended wrapper
>> script inside of "run" is infinitessimal in relation to the daemon's
>> lifetime.
>
> So?
>
> If you're like me, you want to use runit to increase the reliability
> of your system. That means running as little software as possible. To
> shut down apache, you need to give one of the running apache processes
> (the right one) a TERM signal. runsv can do that. Why do you want to
> give a (putative) bug in apachectl or httpd a chance to be executed?

For the same reason that I would want to ensure that cleanup is
performed by the daemon before shutdown, which might not occur when a
signal is received.  One might find daemons who don't properly clean up
external resources when a SIGTERM is received; that also is a putative
bug.

For now, I'll take my chances with "httpd -k stop".

De gustibus non disputandum est.


Here's my script, which seems to be working just fine:

#!/bin/sh

exec 2>&1

ApacheHome='/home/services/apache'
ApachePort='80'
HasSSL=1
Command='start'

stopfunc () {
  Command='stop'
}
gracefulfunc () {
  Command='graceful'
}
restartfunc () {
  Command='restart'
}
trap "stopfunc"     15
trap "gracefulfunc" 30
trap "restartfunc"  31

if [ -n "${HasSSL:-}" ]
then
  [ "${Command}" = "start" ] && {
    Command='startssl'
    echo "overriding: start => startssl"
  }
else
  [ "${Command}" = "startssl" ] && {
    Command='start'
    echo "overriding: startssl => start"
  }
fi

echo "invoking $Command"

set -- "${Command}" "$@"

### This stuff is borrowed from the default apachectl script:
#
# The exit codes returned are:
#   XXX this doc is no longer correct now that the interesting
#   XXX functions are handled by httpd
#	0 - operation completed successfully
#	1 - 
#	2 - usage error
#	3 - httpd could not be started
#	4 - httpd could not be stopped
#	5 - httpd could not be started during a restart
#	6 - httpd could not be restarted during a restart
#	7 - httpd could not be restarted during a graceful restart
#	8 - configuration syntax error
#
# When multiple arguments are given, only the error from the _last_
# one is reported.  Run "apachectl help" for usage info
#
ARGV="$@"
#
# |||||||||||||||||||| START CONFIGURATION SECTION  ||||||||||||||||||||
# --------------------                              --------------------
# 
# the path to your httpd binary, including options if necessary
HTTPD="${ApacheHome}/bin/httpd"
#
# pick up any necessary environment variables
if test -f ${ApacheHome}/bin/envvars; then
  . ${ApacheHome}/bin/envvars
fi
#
# Set this variable to a command that increases the maximum
# number of file descriptors allowed per child process. This is
# critical for configurations that use many file descriptors,
# such as mass vhosting, or a multithreaded server.
ULIMIT_MAX_FILES="ulimit -S -n `ulimit -H -n`"
# --------------------                              --------------------
# ||||||||||||||||||||   END CONFIGURATION SECTION  ||||||||||||||||||||
#
### End of stuff that's borrowed from the default apachectl script.

invoke () {
  exec /usr/bin/env -i PATH='/usr/bin:/bin' CHARSET='iso-8859-1' \
       /command/pgrphack $HTTPD "$@"
}

case $ARGV in
start*|restart)

  # Do my own initialization during start or restart.

  # Preprocess the vhosts include file.
  vhostsInc="${ApacheHome}/conf/.vhosts.inc"
  /root/bin/expandVhosts ${ApachePort} >${vhostsInc}
  {
    # Do other initialization
    /bin/rm -rf /tmp/php /tmp/mp
    /bin/mkdir /tmp/php
    /bin/mkdir /tmp/mp
  } 1>/dev/null 2>&1

  # Set the maximum number of file descriptors allowed per child process.
  # (borrowed from default apachectl script)
  if [ "x$ULIMIT_MAX_FILES" != "x" ] ; then
    $ULIMIT_MAX_FILES
  fi
  ;;
esac

case $ARGV in
start|stop|restart|graceful)
    invoke -k $ARGV -DNO_DETACH
    ;;
startssl)
    invoke -k start -DNO_DETACH -DSSL
    ;;
esac

# We should never get here.
exit 2


-- 
 Lloyd Zusman
 ljz@asfast.com
 God bless you.