<br><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Nov 27, 2012 at 8:59 AM, Frank McGeough <span dir="ltr"><<a href="mailto:Frank.Mcgeough@vocalocity.com" target="_blank">Frank.Mcgeough@vocalocity.com</a>></span> wrote:<br>
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<div>I'm writing to ask about using Slony switchover capability. I've never actually been able to make this work. I'm curious about whether this is a common experience or if, perhaps, there is something that I don't understand about how this should function.
The environment that I have is a database that is in constant use. That is, there is always at least a low level of DML (inserts for the most part) occurring 24 x 7, 365 days a year. I've found that Slony will never be able to get a lock in order to perform
the switchover and thus I'm left with tearing replication completely down and rebuilding from scratch if I have to perform maintenance on the primary. Do people find this unusual or is this somewhat expected — and the only time this actually functions as described
in the documentation is if you are able to shutdown all database operations for a short period of time ( a few seconds even)? </div>
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<div>What I do currently is use a VIP ( <a href="http://en.wikipedia.org/wiki/Virtual_IP_address" target="_blank">
http://en.wikipedia.org/wiki/Virtual_IP_address</a> ) to control how the various app servers are connecting to the primary database. I modify this to go to what was the slave, stop the slony processes, drop the slony schema and then restart replication from
scratch. </div>
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<br></blockquote><div><br>Slony is designed to do exactly what you are stating it's not able to. We run a very busy site and switchover's "albeit one of those moments where you hold your breath", work without an issue (knocks on wood). We too use a virtual for our insert DB's and Query db's (inserts are the master/slave) . As part of the switchover we hit the switchover button (script) and at about the same time, we move the slave into the vip. We have 3 sets that have to move, but 99.9% of the time the switchover works without a hitch (the .1% is when we have done changes, or schema modifications or other and didn't clean up after ourselves properly).<br>
<br>So this works and has worked for many many versions now.<br><br>Not sure why it can't get a lock, at some point it's request has to take priority over a later request.<br><br>Tory<br></div></div><br></div>