Race condition on restart

[Jerry Benton]

If someone will create a pull request on GitHub I will implement it. 

-
Jerry Benton
www.mailborder.com
+1 - 844-436-6245



> On Apr 28, 2017, at 12:54 AM, Paul Scott <sales at edenusa.com> wrote:
> 
> This is exactly what I thought.  Every time I restarted MailScanner, it caused this problem and the system had to be restarted.
> 
> Sincerely,
> 
> Paul Scott, Engineer
> Eden USA, Incorporated
> Event Production Services Since 1995
> Los Angeles-Las Vegas-New York
> sales at edenusa.com OR edenusasales at gmail.com
> Telephone(s): 866.501.3336 OR 951.505.6967
> Fax: 866.502.3336 
> 
> WEBSITE: https://www.edenusa.com
> FACEBOOK: http://www.facebook.com/edenusainc
> 
> -----Original Message-----
> From: MailScanner [mailto:mailscanner-bounces+sales=edenusa.com at lists.mailscanner.info] On Behalf Of David While
> Sent: Wednesday, April 26, 2017 9:39 AM
> To: mailscanner at lists.mailscanner.info
> Subject: Race condition on restart
> 
> There is a bug in MailScanner which leads to a race condition.
> 
> The init script which starts/stops & restarts MailScanner removes the PID file when MailScanner is stopped.
> 
> Unfortunately when MailScanner is issued with a SIGTERM (when issuing a restart or stop) then it also removes the PID file (line 1419 in MailScanner).
> 
> What is happening is that the init script issues the kill and then continues. This doesn't kill MailScanner but simply sends the signal. 
> MailScanner does some processing before dying. Consequently there is now a race as to who will remove the PID file. The worst case is that it is removed after MailScanner has been restarted. This leads to the hourly ms-check constantly restarting MailScanner.
> 
> I fixed this in the init script by:
> 
> 1. Removing the following lines from do_stop
> 
>                     # remove pid file
>                     if [ -f $PIDFILE ] ; then
>                                 rm -f $PIDFILE
>                         fi
> 
> 2. Moving the following lines from restart to do_stop where the above lines were removed
> 
>         s='-\|/';
>         x=0
>         i=0
>         while [ "$x" -lt 300 -a -f $PIDFILE ]; do
>            x=$((x+1));
>            i=$(( (i+1) %4 ));
>            printf "\r${s:$i:1}";
>            sleep .1;
>         done
> 
> What this does is wait for MailScanner to die and remove the PID file before continuing.
> 
> I don't think this is a permament fix as there ought to be a check that it has not timed out before continuing.
> 
> David While
> 
> 
> 
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> 
> 
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