Great, that is perfect (I think :)). The only thing it appears to be missing is the ability to change multiple listeners together, but that would be a relatively simple patch.
Thanks for pointing me to it! From: Ashutosh Chauhan <hashut...@apache.org> To: "dev@hive.apache.org" <dev@hive.apache.org> Date: 05/27/2015 01:25 AM Subject: Re: Caching metastore objects Siva / Scott, Such a framework exists in some form : https://issues.apache.org/jira/browse/HIVE-2038 To make it even more generic there was a proposal https://issues.apache.org/jira/browse/HIVE-2147 But there was a resistance from a community for it. May be now community is ready for it : ) Ashutosh On Tue, May 26, 2015 at 10:12 PM, Sivaramakrishnan Narayanan < tarb...@gmail.com> wrote: > Thanks for the replies. > > @Ashutosh - thanks for the pointer! Yes I was running 0.11 metastore. Let > me try with 0.13 metastore! Maybe my woes will be gone. If they don't then > I'll continue working along these lines. > > @Alan - agreed. Caching MTables seems like a better approach if 0.13 > metastore perf is not as good as I'd like. > > @Scott - a pluggable hook for metastore calls would be super useful. If you > want to generate events for client-side actions, I suppose you could just > implement a dynamic proxy class over the metastore client class which does > whatever you need it to. Similar technique could work in the server side - > I believe there is already a RetryingMetaStoreClient proxy class in place. > > > On Wed, May 27, 2015 at 7:32 AM, Ashutosh Chauhan <hashut...@apache.org> > wrote: > > > Are you running pre-0.12 or with hive.metastore.try.direct.sql = false; > > > > Work done on https://issues.apache.org/jira/browse/HIVE-4051 should > > alleviate some of your problems. > > > > > > On Mon, May 25, 2015 at 8:19 PM, Sivaramakrishnan Narayanan < > > tarb...@gmail.com> wrote: > > > > > Apologies if this has been discussed in the past - my searches did not > > pull > > > up any relevant threads. If there are better solutions available out of > > the > > > box, please let me know! > > > > > > Problem statement > > > -------------------------- > > > > > > We have a setup where a single metastoredb is used by Hive, Presto and > > > SparkSQL. In addition, there are 1000s of hive queries submitted in > batch > > > form from multiple machines. Oftentimes, the metastoredb ends up being > > > remote (in a different region in AWS etc) and round-trip latency is > high. > > > We've seen single thrift calls getting translated into lots of small > SQL > > > calls by datanucleus and the roundtrip latency ends up killing > > performance. > > > Furthermore, any of these systems may create / modify a hive table and > > this > > > should be reflected in the other system. Example, I may create a table > in > > > hive and query it using Presto or vice versa. In our setup, there may > be > > > multiple thrift metastore servers pointing to the same metastore db. > > > > > > Investigation > > > ------------------- > > > > > > Basically, we've been looking at caching to solve this problem (will > come > > > to invalidation in a bit). I looked briefly at DN's support for > caching - > > > these two parameters seem to be switched off by default. > > > > > > METASTORE_CACHE_LEVEL2("datanucleus.cache.level2", false), > > > METASTORE_CACHE_LEVEL2_TYPE("datanucleus.cache.level2.type", > "none"), > > > > > > Furthermore, my reading of > > > http://www.datanucleus.org/products/datanucleus/jdo/cache.html > suggests > > > that there is no sophistication in invalidation - seems like only > > > time-based invalidation is supported and it can't work across multiple > > PMFs > > > (therefore, multiple thrift metastore servers) > > > > > > Solution Outline > > > ----------------------- > > > > > > - Every table / partition will have an additional property called > > > 'version' > > > - Any call that modifies table or partition will bump up version of > > the > > > table / partition > > > - Guava based cache of thrift objects that come from metastore calls > > > - We fire a single SQL matching versions before returning from cache > > > - It is conceivable to have a mode wherein invalidation based on > > version > > > happens in a background thread (for higher performance, lower > > fidelity) > > > - Not proposing any locking (not shooting for world peace here :) ) > > > - We could extend HiveMetaStore class or create a new server > > altogether > > > > > > Is this something that would be interesting to the community? Is this > > > problem already solved and should I spend my time watching GoT instead? > > > > > > Thanks > > > Siva > > > > > >
