PATCH: Fix (make it less likely to happen) race in nagios init script

Hi,

 there is apparently a race in the stop/restart
functionality of the
nagios init script.

 When doing stop or restart, the "$NagiosRunFile"
can disappear between
the check for existence and the "head" command in
the status_nagios
function. As a result one gets a nasty usage message from
"ps".

 Observed on RHEL4/x86_64 with Nagios 2.6 and 2.7. The
following patch
seems to scare away the problem. It does not fix the race,
but the
problem does no longer occur.

 For me the additional 2 sec delay in stop/restart is
acceptable.

# diff -pu daemon-init daemon-init-new
--- daemon-init 2007-03-08 11:11:50.000000000 +0100
+++ daemon-init-new     2007-03-28 10:23:22.000000000 +0200
 -37,6
+37,10  status_nagios ()
                return 1
        fi

+#
+# There is a race between here and the check above !!!
+# Fixed by a "sleep 2" in the "stop"
case
+#
        NagiosPID=`head -n 1 $NagiosRunFile`
        if test -x $NagiosCGI/daemonchk.cgi; then
                if $NagiosCGI/daemonchk.cgi -l
$NagiosRunFile; then
 -139,6
+143,10  case "$1" in
                # new NagiosRunFile, allowing multiple
nagios daemons
                # to (sooner or later) run - John Sellens
                echo -n 'Waiting for nagios to exit .'
+#
+# Sleep first to minimize risk of race in status_nagios
+#
+               sleep 2
                for i in 1 2 3 4 5 6 7 8 9 10 ; do
                    if status_nagios > /dev/null; then
                        echo -n ' .'


------------------------------------------------------
Martin Knoblauch
email: k n o b i AT knobisoft DOT de
www:   http://www.knobisoft.de

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Martin Knoblauch wrote:
> Hi,
> 
>  there is apparently a race in the stop/restart
functionality of the
> nagios init script.
> 
>  When doing stop or restart, the
"$NagiosRunFile" can disappear between
> the check for existence and the "head"
command in the status_nagios
> function. As a result one gets a nasty usage message
from "ps".
> 
>  Observed on RHEL4/x86_64 with Nagios 2.6 and 2.7. The
following patch
> seems to scare away the problem. It does not fix the
race, but the
> problem does no longer occur.
> 
>  For me the additional 2 sec delay in stop/restart is
acceptable.
> 

I rewrote the init script a bit to help ensure this doesn't
happen.  The 
head command is run to get the pid before it can be deleted
by a 
restart, etc.  Patches are now in CVS for the 2.x and
3(HEAD) branches. 
  Thanks for the note!


Ethan Galstad,
Nagios Developer
---
Email: nagiosnagios.org
Website: http://www.nagios.org

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