Hi, Generally it can take a couple of seconds before a schema change has propagated to all nodes. The schema will in most cases converge, but as far as I've understood, concurrent schema changes are considered a bad practise and can lead to inconsistent schemas down the road. IIRC if one executes all schema changes from the same node one can be certain that the schema changes will converge. After executing a schema change you can execute `nodetool describecluster` to make sure all nodes have the same schema.
What I'd suggest is that you either - introduce a queue to execute the schema changes from a single node; or - come up with the schema that works generically over time; or - somehow introduce a global lock if you are to programatically alter schema. Lock, make change, poll until all nodes have the same schema, release lock. Those are mu 5 cents. There are probably other solutions. Cheers, Jens On Mon, May 25, 2015 at 10:58 AM, Magnus Vojbacke < magnus.vojba...@digitalroute.com> wrote: > I have a lot of clients that will try to create the same schema (a > keyspace with multiple tables) concurrently during application startup. The > idea is that the first time the application starts, the clients will create > the schema needed to run (create if not exists, etc...) > > From what I’ve read, I think that Cassandra has support for concurrent > schema creation and modification, but I assume there will be conflicts of > some sort. > > > Is there any known strategy for handling this? Specifically considering > conflicts. > > In case of a conflict (e.g., two clients trying to create the exact same > table), will the client call return with an error? (Datastax driver) > > Would a plausible strategy be (for each client) 1) try to create the > table, 2) examine any error coming back to determine if a conflict > happened, 3) if conflict, move on to next table? > > Or is it just better to add a separate step to create the schema at some > point in time before the clients can be allowed to work (i.e. move schema > creation out of the clients)? > > > > > Thanks > /Magnus > > -- Jens Rantil Backend engineer Tink AB Email: jens.ran...@tink.se Phone: +46 708 84 18 32 Web: www.tink.se Facebook <https://www.facebook.com/#!/tink.se> Linkedin <http://www.linkedin.com/company/2735919?trk=vsrp_companies_res_photo&trkInfo=VSRPsearchId%3A1057023381369207406670%2CVSRPtargetId%3A2735919%2CVSRPcmpt%3Aprimary> Twitter <https://twitter.com/tink>
