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Old 12-29-2012, 04:52 AM   #1
shaik_rafi2009
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Cronjob


Iam using 2 Redhat linux 5.8 servers with a Tomcat application, I run a cronjob for directory replication from A server to B server with rsync. Now the problem is i need to execute this cronjob when the B server directory modified or A server modified.

Thanks
Rafi

Last edited by shaik_rafi2009; 12-29-2012 at 05:00 AM.
 
Old 12-29-2012, 08:45 AM   #2
divyashree
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From A and B which is your master ? You should run the cronjob in the master server, which is easy to detect the modification and then run rsync to replicate. But you can run the cronjob in any system as the cronjob runs at particular interval and your cron script should be modified to work like that.
 
Old 12-29-2012, 10:23 AM   #3
jpollard
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And if you are trying to do distributed servers on the cheap, then use a filesystem (gluster) to do that instead.

You can't have two master file servers and use rsync to distribute the modifications... No matter what you do, one or the other will delete/overwrite files you don't want destroyed. These are known race conditions that can't be easily fixed.
 
Old 12-31-2012, 10:56 AM   #4
shaik_rafi2009
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Can anyone know configuration of inotify-tools with rsync. Is this helpful replication between servers.
 
Old 12-31-2012, 11:57 AM   #5
jpollard
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only from master to slave.

One of the problems with inotify is that it doesn't scale well. It is designed to watch single files/single directories. When you try to add an entire filesystem, you have to have it watch every single file and directory in the filesystem. And that just doesn't work well.

That is why I recommend using a distributed filesystem, and one that is designed for that.

The major problem is trying use parallel distributed use - inotify cannot cover race conditions. It wasn't designed for that.

I recommend gluster for its ease of configuration though I haven't used it myself (single server system). I have used luster which it is based on. Luster uses a master/slave metadata server to resolve race conditions. The actual data is stored/replicated among multiple servers. When a luster based storage cluster boots, each node joing the group becomes a slave - the startup node (first one up I think) becomes the designated master.

Last edited by jpollard; 12-31-2012 at 12:03 PM. Reason: fixing paragraphing error.
 
Old 01-01-2013, 03:36 AM   #6
shaik_rafi2009
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I will try distributed filesystem, Thanks to jpollard and divyasree.
 
Old 01-02-2013, 08:30 PM   #7
chrism01
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It sounds like you want to sync 2 systems bi-directionally, in which case have a look at unison http://linux.die.net/Mobile-Guide/mo...transport.html Sect 15.4.2.3.
 
Old 01-03-2013, 07:39 AM   #8
jpollard
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Unison is a manual process ("Conflicting updates are detected and displayed.") and is too slow for web servers anyway. It doesn't look like it can handle updates while it is running either.

Last edited by jpollard; 01-03-2013 at 07:42 AM.
 
Old 01-07-2013, 09:44 AM   #9
shaik_rafi2009
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Thanks to all, I added rsync in cronjob which will run every 15min on both servers. Its working fine now.

Last edited by shaik_rafi2009; 01-07-2013 at 09:47 AM.
 
  


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