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From Josh Elser <josh.el...@gmail.com>
Subject Re: [VOTE] ACCUMULO-3176
Date Tue, 25 Nov 2014 20:50:57 GMT
Thanks, Sean. This was very helpful.

Sean Busbey wrote:
>> altering the public API (as a standalone change)
>
> I am very conservative about changes to our public API. I have had to write
> code that works across Accumulo versions and even when only working with
> the public API is it painful on almost every release. I have also seen
> plenty of cases where deployments of Accumulo lag behind version changes
> because of this same issue.
>
> I fully support that major version changes are there for us to break APIs.
> That doesn't mean that such breakage doesn't have a high cost that needs to
> be weighed carefully.
>
> In general, for me to be positive on an API change there needs to be a
> compelling improvement or a correctness issue. For me, that correctness
> issue is the race condition on property updates you mention.
>
> While I acknowledge that a per-table configured load balancer can't be set
> prior to the initial tablet assignment without this change, I don't think
> that out weighs having to update all table creation code. (this will be the
> case even if we go through a deprecation cycle. the cycle just draws it
> out.) Granted, I have never had cause to use a per-table load balancer that
> was hampered by where the initial tablet was assigned. So I might just not
> know the level of pain that fix would address.
>
>>   implementing a partial fix for the larger problem
>
> This fix leaves those who need a consistent view of some set of properties
> with only options that involve table creation, either in this changed API
> or via Keith's clone table work around on an offline table. That means if
> you need to alter a constraint or an iterator (that needs to be used
> universally), you have the same negative consequence as some of the
> proposed solutions while also having to change the underlying table id. More
> importantly, I think it leaves people prone to not realizing that their
> change to these things won't be uniformly enforced during
> the propagation period.
>
> We could mitigate some of the gotchas around when property updates need to
> be strongly consistent with better docs, but that only helps when people
> are at the point of reading docs. I'd rather stop them from self inflicted
> pain directly because people often don't have the time to read docs. I see
> stopping this correctness problem as worth the behavior change something
> like "only update properties when tables are offline" would necessitate.  But
> this vote isn't about the merits of that particular alternative.
>
> I'm willing to consider other options for solving the consistent property
> issue and have tried to work through them in the comments around
> ACCUMULO-3176. I just don't believe the one meets my standard for
> inflicting API pain.
>
> On Tue, Nov 25, 2014 at 1:16 PM, Josh Elser<josh.elser@gmail.com>  wrote:
>
>> Can I pick your brain some more? (also, I'm sorry if this is already
>> addressed in the JIRA comments somewhere. I'm being lazy)
>>
>> As we know, there is a larger problem of ensuring consistent configuration
>> across all servers in the cluster. I don't think there is any contention
>> here. There are ways we can do this, but no one has done it yet. That's the
>> general problem, and, I believe, what you mean by the "underlying issue".
>>
>> A subset of that problem is configuration updates for a table which is
>> newly created. In my experience, this is often how I get bitten by this
>> race condition -- I create a table, I updated some property (typically set
>> an iterator/combiner/constraint), and then did some insert/scan before the
>> tabletserver I communicated with got my property update.
>>
>> I see this taking what is a technically difficult problem (assumption,
>> since no one has done it yet) and making the problem partially better. In
>> practice for me, this also means that how I often encountered this race
>> condition is addressed.
>>
>> I also don't see the changes that Jenna wrote as a blocker to implementing
>> a "proper" blocking configuration update.
>>
>> Can you clarify your level of concern with this change in: altering the
>> public API (as a standalone change), implementing a partial fix for the
>> larger problem, and the combination of the previous two points? It would be
>> much appreciated.
>>
>>
>>
>> Sean Busbey wrote:
>>
>>> -1
>>>
>>> This change alters our public API while not solving the underlying issue
>>> of
>>> race conditions in property updates.
>>>
>>> On Tue, Nov 25, 2014 at 11:14 AM, Christopher<ctubbsii@apache.org>
>>> wrote:
>>>
>>>   Committers, this is a consensus vote on whether or not to include Jenna's
>>>> patch for ACCUMULO-3176 to the 1.7.0-SNAPSHOT (master) branch.
>>>>
>>>> This patch improves the table creation API with the introduction of a
>>>> NewTableConfiguration object (similar to the pattern for
>>>> BatchWriterConfig), which allows us to be flexible on improving table
>>>> creation options in the future without creating many overloaded methods
>>>> (as
>>>> the table creation API has been plagued by in the past). The main goal of
>>>> the patch is to allow table properties to be set on a table at the time
>>>> of
>>>> creation, before any tablets are assigned, but it also lays the
>>>> foundation
>>>> for future table creation improvements. Creating initial table properties
>>>> was already present in the RPC calls, but not exposed in the API. This
>>>> can
>>>> support a number of use cases.
>>>>
>>>> Since an objection was raised by Sean Busbey (and a veto expected), I've
>>>> initiated this vote in lieu of applying the patch under lazy consensus so
>>>> that any veto votes can be justified and addressed here.
>>>>
>>>> Note: there are a few bugs in the Mock implementation of this that I've
>>>> fixed, as well as some minor deprecation warnings and javadoc
>>>> improvements
>>>> I'm adding, please apply your vote under the assumption that those will
>>>> be
>>>> fixed before it will be applied.
>>>>
>>>> Please vote in accordance with the bylaws for consensus voting.
>>>> My vote is +1.
>>>>
>>>> Thanks.
>>>>
>>>> --
>>>> Christopher L Tubbs II
>>>> http://gravatar.com/ctubbsii
>>>>
>>>>
>>>
>>>
>
>

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