Sean Busbey created HADOOP-11656:
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Summary: Classpath isolation for downstream clients
Key: HADOOP-11656
URL: https://issues.apache.org/jira/browse/HADOOP-11656
Project: Hadoop Common
Issue Type: New Feature
Reporter: Sean Busbey
Assignee: Sean Busbey
Currently, Hadoop exposes downstream clients to a variety of third party
libraries. As our code base grows and matures we increase the set of libraries
we rely on. At the same time, as our user base grows we increase the likelihood
that some downstream project will run into a conflict while attempting to use a
different version of some library we depend on. This has already happened with
i.e. Guava several times for HBase, Accumulo, and Spark (and I'm sure others).
While YARN-286 and MAPREDUCE-1700 provided an initial effort, they default to
off and they don't do anything to help dependency conflicts on the driver side
or for folks talking to HDFS directly. This should serve as an umbrella for
changes needed to do things thoroughly on the next major version.
We should ensure that downstream clients
1) can depend on a client artifact for each of HDFS, YARN, and MapReduce that
doesn't pull in any third party dependencies
2) only see our public API classes (or as close to this as feasible) when
executing user provided code, whether client side in a launcher/driver or on
the cluster in a container or within MR.
This provides us with a double benefit: users get less grief when they want to
run substantially ahead or behind the versions we need and the project is freer
to change our own dependency versions because they'll no longer be in our
compatibility promises.
Project specific task jiras to follow after I get some justifying use cases
written in the comments.
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