Sean Busbey wrote:
On Tue, Apr 11, 2017 at 11:43 PM Nick Dimiduk<[email protected]> wrote:
This effort is about our internals. We have a mess of other components
all
up inside us such as HDFS, etc., each with their own sets of dependencies
many of which we have in common. This project t is about making it so we
can upgrade at a rate independent of when our upstreamers choose to
change.
Pardon as I try to get a handle on the intention behind this thread.
If the above quote is true, then I think what we want is a set of shaded
Hadoop client libs that we can depend on so as to not get all the
transitive deps. Hadoop doesn't provide it, but we could do so ourselves
with (yet another) module in our project. Assuming, that is, the upstream
client interfaces are well defined and don't leak stuff we care about. It
also creates a terrible nightmare for anyone downstream of us who
repackages HBase. The whole thing is extremely error-prone, because there's
not very good tooling for this. Realistically, we end up with a combination
of the enforcer plugin and maybe our own custom plugin to ensure clean
transitive dependencies...
Hadoop does provide a shaded client as of the 3.0.0* release line. We could
push as a community for a version of that for Hadoop's branch-2.
Unfortunately, that shaded client won't help where we're reaching into the
guts of Hadoop (like our reliance on their web stuff).
Well put, Nick.
With Sean's point about the Hadoop shaded client, it seems to me that we
have things which could be pursued in parallel:
1) Roadmap to Hadoop3 (and shaded hdfs client).
2) Identify components which we use from Hadoop, for each component:
2a) Work with Hadoop to isolate that component from other cruft (best
example is the Configuration class -- you get something like 8MB of
"jar" just to parse an xml file).
2b) Pull the implementation into HBase, removing dependency from
Hadoop entirely.
I think that both of these can/should be done in parallel to the
isolation of the dependencies which HBase requires (isolating ourselves
from upstream, and isolating downstream from us).
