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From Alexander Denissov <adenis...@pivotal.io>
Subject question on [STACK]/[SERVICE]/metainfo.xml inheritance rules
Date Fri, 05 Sep 2014 00:02:05 GMT
I am trying to understand the inheritance rules that govern services
metainfo.xml file contents. I looked at
https://issues.apache.org/jira/browse/AMBARI-2819 but it didn't answer the
following:

1. If a component exists in the parent stack and is defined again in the
child stack with just a few attributes, are these values just to override
the parent's values or the whole component definition is replaced.

Example: HDP-2.1 YARN/metainfo.xml contains definition of RESOURCEMANAGER
with just 4 attributes, out of which only the value for "cardinality" is
different one in HDP-2.0.6 definition. But 2.0.6 definition also has a lot
more attributes (such as custom commands) that are not mentioned in 2.1.
Will these "missing" attributes be inherited by 2.1 stack ? If yes, why
other attributes (category and configuration-dependencies) are defined
again with the same values instead of being inherited ?

2. If a component is missing in the new definition but is present in the
parent, does it get inherited ?

3. Configuration dependencies for the service -- are they overwritten or
merged ?

Example: HDP-2.1 YARN/metainfo.xml contains <configuration-dependencies>
element with 4 <config-type>, where as in HDP-2.0.6 the same element has
5 <config-type> (extra line is mapred-site). So will <config-type>mapred
-site</config-type> be inherited and present in 2.1 definition or was this
the way to get rid of this specific line for the new stack ?

4. What about other elements in metainfo.xml -- which rules apply ?

--
Thanks,
Alex.

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