There have been various discussions on various JIRAs where upstream projects
such as YARN apps ( Tez, Slider, etc ) are called out for using the above
so-called Private APIs. A lot of YARN applications that have been built out
have picked up various bits and pieces of implementation from MapReduce and
DistributedShell to get things to work.
A recent example is a backward incompatible change introduced ( where the API
is not even directly invoked ) in the Credentials class related to the ability
to read tokens/credentials from a file. This functionality is required by
pretty much everyone as YARN provides the credentials to the app by writing the
credentials/tokens to a local file which is read in when
UserGroupInformation.getCurrentUser() is invoked. This change breaks rolling
upgrades for yarn applications from 2.x to 3.x (whether we end up supporting
rolling upgrades across 2.x to 3.x is a separate discussion )
I would like to change our compatibility docs to state that any API that is
marked as LimitedPrivate{Mapreduce} implies LimitedPrivate{YARN Applications}.
Comments/concerns?
thanks
— Hitesh
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