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Distributed spam filtering

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gillonba View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gillonba Quote  Post ReplyReply Direct Link To This Post Topic: Distributed spam filtering
    Posted: 20 July 2010 at 12:09pm

Currently we are hosting Spam Filter ISP on 2 servers within our office, with a single MS SQL server hosting the quarantine database.  We are happy with the filter, but are looking for a bit more in the way of redundancy.  The plan is to move one of the servers to an off-site data center.  Can we expect problems caused by a slower, less reliable connection between one of the spam servers and the SQL server?  I did find this thread

http://www.logsat.com/SpamFilter/Forums/forum_posts.asp?TID=6770&title=quarantine-folder

which seems to indicate that quarantine messages are cached so that a break in the connection will not cause permanent damage.  Is anyone else hosting multiple spam servers in separate locations, and if so, what sort of issues should we be anticipating?  Thanks

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yapadu View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote yapadu Quote  Post ReplyReply Direct Link To This Post Posted: 20 July 2010 at 6:16pm
We host our servers in two different countries, one data center in Canada & Japan right now.  Our connection is stable with a 10mb connection between the two, no issues so far.

We are actually looking to take it a step further and use multi-master mysql replication between the sites to provide redundancy.  We have not achieved that yet, but we do have master/slave replication setup between the two data centers which does make it easier to do backups from the slave without causing any issues on the primary.

A master-master database configuration would be the ultimate ;-)
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I am a user of SF, not an employee. Use any advice offered at your own risk.
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gillonba View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gillonba Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2010 at 10:43am

Thanks for the reply yapadu!  That does sound encouraging.  

Please forgive the noobish question but I'm not a DBA and we use MS SQL in any case, but: if you're using master/slave replication, doesn't that mean you can only write to the database at one physical location?  So if the link between the data centers fails, one site will be unable to write to quarantine?  Or does mysql allow table-level replication so you can replicate settings but both sites maintain separate quarantines?  Thanks, for the input though!

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yapadu View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote yapadu Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2010 at 9:04pm
Yes, you are correct.  You can only make updates in 1 location with master/slave.  For us there are already a couple of advantages

1) We can do backups from the slave and have no impact on the master where the updates are happening.  When doing a backup on the live server it locks things while doing the backup.

2) We are working on a distributed website as well as distributed servers, so users access the closest server to them for fastest access.  We don't have master/master yet, but even with a local read only copy we can do reads from the quarantine table and show them to users much faster.

If our write database is unavailable to place new quarantine emails into, spamfilter writes them to a quarantine folder.  When the database is again available, it writes them to the database.  So having a server that is quite a distance away, where the link could go down is not so much of an issue.

That is how spamfilter was designed, and why all configuration information is read from the database and then stored locally.  So if the database is not available the system can still perform with little impact.
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I am a user of SF, not an employee. Use any advice offered at your own risk.
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