hive-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Ashutosh Chauhan <hashut...@apache.org>
Subject Re: Caching metastore objects
Date Wed, 27 May 2015 05:25:22 GMT
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 <
tarball@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 <hashutosh@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 <
> > tarball@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
> > >
> >
>

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message