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From Chris Douglas <cdoug...@apache.org>
Subject Re: When are incompatible changes acceptable (HDFS-12990)
Date Tue, 09 Jan 2018 19:21:17 GMT
Particularly since 9820 isn't in the contiguous range of ports in
HDFS-9427, is there any value in this change?

Let's change it back to prevent the disruption to users, but
downstream projects should treat this as a bug in their tests. Please
open JIRAs in affected projects. -C

On Tue, Jan 9, 2018 at 5:18 AM, larry mccay <lmccay@apache.org> wrote:
> On Mon, Jan 8, 2018 at 11:28 PM, Aaron T. Myers <atm@apache.org> wrote:
>> Thanks a lot for the response, Larry. Comments inline.
>> On Mon, Jan 8, 2018 at 6:44 PM, larry mccay <lmccay@apache.org> wrote:
>>> Question...
>>> Can this be addressed in some way during or before upgrade that allows it
>>> to only affect new installs?
>>> Even a config based workaround prior to upgrade might make this a change
>>> less disruptive.
>>> If part of the upgrade process includes a step (maybe even a script) to
>>> set the NN RPC port explicitly beforehand then it would allow existing
>>> deployments and related clients to remain whole - otherwise it will uptake
>>> the new default port.
>> Perhaps something like this could be done, but I think there are downsides
>> to anything like this. For example, I'm sure there are plenty of
>> applications written on top of Hadoop that have tests which hard-code the
>> port number. Nothing we do in a setup script will help here. If we don't
>> change the default port back to what it was, these tests will likely all
>> have to be updated.
> I may not have made my point clear enough.
> What I meant to say is to fix the default port but direct folks to
> explicitly set the port they are using in a deployment (the current
> default) so that it doesn't change out from under them - unless they are
> fine with it changing.
>>> Meta note: we shouldn't be so pedantic about policy that we can't back
>>> out something that is considered a bug or even mistake.
>> This is my bigger point. Rigidly adhering to the compat guidelines in this
>> instance helps almost no one, while hurting many folks.
>> We basically made a mistake when we decided to change the default NN port
>> with little upside, even between major versions. We discovered this very
>> quickly, and we have an opportunity to fix it now and in so doing likely
>> disrupt very, very few users and downstream applications. If we don't
>> change it, we'll be causing difficulty for our users, downstream
>> developers, and ourselves, potentially for years.
> Agreed.
>> Best,
>> Aaron

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