Platonides wrote: I don't know what either of you are talking about. There's no problem with autoincrement in a single-master setup. -- Tim Starling

*regular MySQL replication rather On 7/9/07, Jim Wilson <wilson.jim.r(a)gmail.com> wrote:

Hello again, I found this very informative document on the subject of WP replication: http://dammit.lt/uc/workbook2007.pdf And I'm curious about a passage from page 22: --------------- The solution (hack?) was pretty simple - abusing the flags field by putting 'external' flag into it, and treating old_text as locator rather than text itself, then migrating the data record-by-record into other locations. The easiest way to implement other location was to deploy lots of small mysql replication setups across application servers (which always come with big disks, just in case, ATA/ SATA is cheap anyway): --------------- Is this to say that "other location" is another database? Is there anything outside of the vanilla MW source necessary to produce an identical setup? Thanks in advance, -- Jim On 7/9/07, Brion Vibber <brion(a)wikimedia.org> wrote:

Thanks Brion, I'm trying to wrap my head around that document and portions of the code, please let me know if this sounds right: * The WMF has multiple clusters - a main cluster, and some replication clusters. * Each cluster has a master node and some number of slave nodes. * The main cluster's `text` table uses the `old_flags` parameter to indicate that `old_text` is really a "locator", not the real data. * A "locator" is a string which tells MW in which replication cluster to find the revision. * Upon a revision retrieval request, MW will seek out the appropriate record from the main cluster's `text` cluster and use the locator to ask the correct replication cluster for the revision data. So if one were to attempt to minimally imitate this setup (using the fewest possible nodes), one would need: * A main cluster (one master and one slave) * A replication cluster (one master and one slave) For a total of 4 nodes. Is any of that right? I appreciate all feedback :) Thanks in advance, -- Jim On 7/9/07, Brion Vibber <brion(a)wikimedia.org> wrote:

Thanks Domas, that's very helpful. I have just a few more questions ... I see. So, if one were to create an "external storage" database instance, what schema is needed? Is it the same as vanilla MW? Are there any documents on how to create an external storage node or cluster? Is it as simple as just installing MediaWiki on those nodes? I'm happy to start with just a 'main' instance and a 'text storage' instance - probably as different databases in the same MySQL server on my localhost. I just don't yet understand how to do the following: * Set up the 'text storage' instance (is this just a plain MW install?) * Point the 'main' instance to use the 'text storage' instance. (is this just configuring $wgExternalServers in LocalSettings.php) Thanks for all your help so far. If all of this is already documented somewhere, I'll be happy to read that instead of continuing with these questions. :) -- Jim On 7/9/07, Domas Mituzas <midom.lists(a)gmail.com> wrote: > > Hello Jim, > > > * The WMF has multiple clusters - a main cluster, and some replication > > clusters. > > We don't call them 'replication clusters'. They're 'external > storage'. Probably we could have other names too. Its simply append- > only storage, that for convenience now is mysql with replication. > > > * Each cluster has a master node and some number of slave nodes. > > Yes! > > > * The main cluster's `text` table uses the `old_flags` parameter to > > indicate > > that `old_text` is really a "locator", not the real data. > > Right, otherwise text goes directly into 'text'. > > > > BR, > -- > Domas Mituzas -- http://dammit.lt/ -- [[user:midom]] > > > > _______________________________________________ > Wikitech-l mailing list > Wikitech-l(a)lists.wikimedia.org > http://lists.wikimedia.org/mailman/listinfo/wikitech-l >