Srimanth Gunturi created AMBARI-5628:
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Summary: Explicitly disabling datanucleus l2 cache for hive
Key: AMBARI-5628
URL: https://issues.apache.org/jira/browse/AMBARI-5628
Project: Ambari
Issue Type: Bug
Components: client
Affects Versions: 1.5.1
Reporter: Srimanth Gunturi
Assignee: Srimanth Gunturi
Fix For: 1.6.1
Ambari installations of hive currently do not set any datanucleus related
properties. There is such a thing as a datanucleus l2 cache, that is pretty bad
for hive in a distributed environment if it is set. (If there is a lone
embedded hive instance, with no other codepaths to the db, then it's fine, but
that never happens in a distributed environment.)
By default, if no setting is present, datanucleus defaults the l2 cache to
being on, so hive ups the ante by defaulting to turning it off by default if
no other setting is configured.
Now, in a war of "defaults", the hive default should win, but this is an area
where we have had recurring support issues from clients that turn it on
expecting improved performance. Thus, I'd like ambari installed hive-site.xml
to explicitly have this config parameter turned off, with a comment asking
users to not switch it on as it impacts hive negatively.
The parameter in question is "datanucleus.cache.level2.type" , and it's value
should be "none". (Note that I've seen some older configs that seem to do
things like turning datanucleus.cache.level2 = false and stuff like that, that
is bogus config and does nothing and should not be assumed to be a catch-all
enabler.)
As a comment, I'd like the following comment "Disables datanucleus l2 cache.
This must be set to 'none' for hive to work properly" or something to that
effect.
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