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https://issues.apache.org/jira/browse/HBASE-3896?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13463995#comment-13463995
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Jesse Yates commented on HBASE-3896:
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I don't think that abstracting out the serverManger and catalogtracker has any
real value, at the moment. I don't think there are other implementations of
those classes, so pulling out an interface only makes things more complicated,
not less. If there were other implementations, for different use cases, then it
would make sense to put it all behind an interface to swap them out easily.
I'm +1 on stack's original comment though that mocking out the classes passes
into the AssignmentManager (which is already pretty well setup for testing
since it can take in all its dependencies) it enough to make the assignment
manager easy to test.
However, I do think there is value in making the serverManger more composition
based. Cody mentioned (offline) functions like stop that could be more cleanly
abstracted not only here, but around the codebase (I'm thinking you have a
StopBuilder that takes in a bunch of things to stop and then builds your
'stopper' so you can close everything out easily). I'm all for adding a couple
new classes to help break out the functions of the SM some more, but that
shouldn't happen to just hide functionality from certain parts of the code
(e.g. hmaster shouldn't know about function X, so we make another interface
that doesn't include that.... leads to a really complex inheritance heirarchy
that is hard to reason about and makes the concrete classes even harder to
read).
TL;DR anything to make the SM smaller (break out functionality) and composition
based would be great, but the root of this ticket should be solvable via
mocking. Maybe, at the very least if we still end up doing this, rename the
ticket?
> Make AssignmentManager standalone testable by having its constructor take
> Interfaces rather than a CatalogTracker and a ServerManager
> -------------------------------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-3896
> URL: https://issues.apache.org/jira/browse/HBASE-3896
> Project: HBase
> Issue Type: Task
> Reporter: stack
> Assignee: Cody Marcel
>
> If we could stand up an instance of AssignmentManager, a core fat class that
> has a bunch of critical logic managing state transitions, then it'd be easier
> writing unit tests around its logic. Currently its hard because it takes a
> ServerManager and a CatalogTracker, but a little bit of work could turn these
> into Interfaces. SM looks easy to do. Changing CT into an Interface instead
> might ripple a little through the code base but it'd probably be well worth
> it.
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