Unless you can be certain that nobody else might run their own rsync, it's
not quite ready.
I'd suggest more like
++++++++++++++++++++++++++++++++++++
#!/bin/sh
pidfile=/var/tmp/ourproceduresrsync.pid
#get the content. will be blank if nonexistent... saves a stat.
oldpid=`cat $pidfile 2>/dev/null`
#verify that it's numeric
if [ "`expr $oldpid / $oldpid 2>/dev/null`" -eq 1 ]
then
#see if it represents a running rsync... unlikely to randomly get another
rsync on the same pid
if ps -p $oldpid |grep rsync >/dev/null
then
#and if it's running, that's all we need to know.. maybe next time
exit 0
fi
fi
#fire off the rsync in the background
rsync -options source destination &
#save its pid for the next run, in case we're not done when he starts
echo $! > $pidfile
#wait for it to finish (this is kid of like a "fg"
wait $!
#and get rid of the pid file
rm $pidfile
++++++++++++++++++++++++++++++++++++
fix the ps for however your system works.
Now, there are still two vulnerabilities here. If it takes more than 5
minutes to cat the file, do the expr, do the ps and grep call rsync, and
echo the rsync pid into the pidfile, you could possibly get a race
condition. If it takes that long, though, you've got bigger problems.
Frankly, you should be safe all the way down to an every-minute run,
though that would probably be wasteful.
I don't know if the setlock thing is completely immune to racing. It
might be better.
Tim Conway
[EMAIL PROTECTED]
303.682.4917 office, 3039210301 cell
Philips Semiconductor - Longmont TC
1880 Industrial Circle, Suite D
Longmont, CO 80501
Available via SameTime Connect within Philips, n9hmg on AIM
perl -e 'print pack(nnnnnnnnnnnn,
19061,29556,8289,28271,29800,25970,8304,25970,27680,26721,25451,25970),
".\n" '
"There are some who call me.... Tim?"
[EMAIL PROTECTED]
Sent by: [EMAIL PROTECTED]
06/20/2002 08:03 AM
To: [EMAIL PROTECTED]
cc: (bcc: Tim Conway/LMT/SC/PHILIPS)
Subject: RE: cronning rsync
Classification:
Thanks for all your swift replies. I can't believe that I didn't even see
the obvious solution of checking to see if rsync was running before-hand.
I've essentially rolled up my call to rsync in a shell-script as below:
---begin script---
#!/bin/sh
#is a previous rsync process still running?
ps -ef | grep 'rsync' | grep -v 'grep rsync' | grep -v 'rsync.sh' >
/dev/null
if [ $? -eq 1 ]; then #rsync isn't running - let's launch it now
rsync [opts] user@host::/module/* .
else
echo "Rsync is still running...please wait and try again later"
fi
---end script---
Thanks for all of your suggestions,
Matt Burgess
British Telecommunications plc
Registered office: 81 Newgate Street London EC1A 7AJ
Registered in England no. 1800000
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-----Original Message-----
From: Adrian Ho [mailto:[EMAIL PROTECTED]]
Sent: Thursday, June 20, 2002 14:19
To: [EMAIL PROTECTED]
Subject: Re: cronning rsync
On Thu, Jun 20, 2002 at 12:51:14PM +0100, [EMAIL PROTECTED] wrote:
> We're thinking about putting rsync to use in our production environment.
> What we want to do is have a cron job running on a client that
replicates
> files on the host every five minutes. We believe that some of the files
> will take longer than five minutes to complete.
Then you'll want to ensure that only one rsync instance is active
at a time. This is best done with an external locking mechanism.
My personal favorite is setlock, part of Dan Bernstein's daemontools
package <http://cr.yp.to/daemontools.html>, and your setlock'd cron job
might look like this:
0-55/5 * * * * setlock -n /tmp/.rsync.lock rsync <blah blah blah>
Your OS may have similar functionality already available, and other
3rd-party packages may also have rolled their own equivalents (I know
both procmail and maildrop did) -- "man -k lock" to see for yourself.
- Adrian
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