> My understanding is that the only interface that is expected to be stable for
> external consumers is the secondary index API
I may be wrong here, but the CEP directly calls out making this api public for
people who wish to replace the SSTable format ("Cassandra developers who want
to develop and publish different file format implementations."), so if we need
to support 2i API, why would we not support SSTable API as well?
> All of the other mentioned APIs are in my opinion for internal usage only
This gets back to my point; it is currently tribal knowledge what needs to work
and what doesn’t, and without the broader set of committers knowing this then
the likely hood any new API will break in a minor is high.
> On Nov 9, 2021, at 12:13 PM, bened...@apache.org wrote:
>
> I agree that we don’t need to block the CEP on this, and that we should have
> that discussion. But it’s worth noting that the CEP should not anticipate or
> depend on any specific outcome of that discussion.
>
> Since it is somewhat relevant for this discussion, my view is that no
> interface should be assumed to be stable without the prior explicit agreement
> of the community.
>
> My understanding is that the only interface that is expected to be stable for
> external consumers is the secondary index API. Perhaps also snitches? But
> also perhaps not, as the difficulty of upgrading these at the same time is
> pretty low for custom snitches. All of the other mentioned APIs are in my
> opinion for internal usage only, so users should not assume compile time
> compatibility across any release, and I am certain we have never tried to
> maintained this. This still facilitates forks of course, by localising the
> compatibility work.
>
>
> From: Jeremiah D Jordan <jeremiah.jor...@gmail.com>
> Date: Tuesday, 9 November 2021 at 19:43
> To: Cassandra DEV <dev@cassandra.apache.org>
> Subject: Re: [DISCUSS] CEP-17: SSTable format API (CASSANDRA-17056)
> I would love to have this discussion and setup annotations or similar to
> formalize things. I just do not think we need to hold any up CEPs to do so.
> That discussion should possibly be a CEP of its own proposing how we want to
> formalize interfaces? I would be happy to go through and try to put together
> something for that or since you feel so strongly about it maybe you want to
> David? At the very least it should get its own DISCUSS thread and then be
> written up in the wiki.
>
> -Jeremiah
>
>> On Nov 9, 2021, at 1:06 PM, Joshua McKenzie <jmcken...@apache.org> wrote:
>>
>>>
>>> trunk -> anything goes, not trunk -> try not to change these interfaces
>>
>> Have we ever clarified what "these interfaces" are? Was just talking to
>> David and I realized I didn't even JavaDoc CommitLogReadHandler as _being
>> designed_ for external usage. /sigh
>>
>> I think it'd be valuable for us to go through the codebase and annotate
>> interfaces as intended to be exposed to 3rd parties; this has bothered me
>> for years. Especially as we come up on a large number of new cleanups,
>> refactorings, and potentially genericizing some subsystems into API's
>> (CEP-18 descendents).
>>
>>
>> On Tue, Nov 9, 2021 at 2:01 PM David Capwell <dcapw...@apple.com.invalid>
>> wrote:
>>
>>>> We already have many interfaces similar to these for Compaction
>>> Strategy, Indexing, Query Handler.
>>>
>>> Today-I-Learned QueryHandler is not allowed to be touched in a minor… good
>>> to know…
>>>
>>>> not trunk -> try not to change these interfaces
>>>
>>> Outside of MBeans, I honestly do not know what interfaces fall into this
>>> group; and for MBeans we have tests which block breaking changes. The
>>> point I am making is that not everyone is aware of the rules, so having
>>> something in place to help enforce such rules should be thought about; if
>>> we want to add pluggable hooks with the intent that external parties can
>>> leverage such hooks, we should also add to the scope the maintenance of
>>> these interfaces (we should not assume “tribal knowledge” will work).
>>>
>>> I am not trying to ask for something large or something requiring a ton of
>>> work, I am just asking that this gets thought about during the project so
>>> it doesn’t get neglected. This could be as simple as an annotation like
>>> @ExposedTo3rdParties (Hadoop does this to show an interface is exposed and
>>> must be maintained), or it could be something like split directories
>>> (src/java = private, src/java-exposed = public); I am trying not to dictate
>>> an implementation, only trying to make sure we are setup to support the CEP
>>> after the work is done.
>>>
>>>
>>>> On Nov 9, 2021, at 9:52 AM, Jeremiah D Jordan <jeremiah.jor...@gmail.com>
>>> wrote:
>>>>
>>>> We already have many interfaces similar to these for Compaction
>>> Strategy, Indexing, Query Handler. I would hope that commiters are already
>>> following a policy along the lines of trunk -> anything goes, not trunk ->
>>> try not to change these interfaces. I would expect that to be the same
>>> policy for any new internal interfaces that are added. But given we
>>> already have many such interfaces, I see no reason to block adding more of
>>> them while change policies are discussed.
>>>>
>>>> -Jeremiah
>>>>
>>>>> On Nov 9, 2021, at 10:44 AM, David Capwell <dcapw...@apple.com.INVALID>
>>> wrote:
>>>>>
>>>>> I still have one outstanding comment, but this is a comment for several
>>> of the CEPs being worked on
>>>>>
>>>>>> And last comment, which I have also done in the other modularity
>>> thread… backwards compatibility and maintenance. It is not clear right now
>>> what java interfaces may not break and how we can maintain and extend such
>>> interfaces in the future. If the goal is to allow 3rd parties to plugin
>>> and offer new SSTable formats, are we as a project ok with having a minor
>>> release do a binary or source non-compatible change? If not how do we
>>> detect this? Until this problem is solved, I do not think we should add
>>> any such interfaces.
>>>>>
>>>>> I would love some clarity on this. Specifically, if we assume a patch
>>> author/reviewers are not familiar with the impact of changes these
>>> interfaces, what happens? Do we have tools to block this? Do we require
>>> 3rd party authors to create massive shims to deal with every patch level
>>> version out there? I would love more clarity on how we maintain these new
>>> pluggable interfaces.
>>>>>
>>>>>> On Nov 9, 2021, at 4:45 AM, Branimir Lambov <blam...@apache.org>
>>> wrote:
>>>>>>
>>>>>> Does anyone have any further comments or questions on the proposal, or
>>> are
>>>>>> we ready to move forward to a vote?
>>>>>>
>>>>>> Regards,
>>>>>> Branimir
>>>>>>
>>>>>> On Tue, Nov 2, 2021 at 7:15 PM David Capwell
>>> <dcapw...@apple.com.invalid>
>>>>>> wrote:
>>>>>>
>>>>>>>> I apologize I did not mention those things explicitly. All the places
>>>>>>> where
>>>>>>>> sstable files are accessed directly would have to be refactored.
>>>>>>>
>>>>>>> Works for me
>>>>>>>
>>>>>>>> Speaking about the implementation, one idea I was thinking about was
>>> that
>>>>>>>> the factories for formats are registered using Java's native service
>>>>>>>> loader.
>>>>>>>
>>>>>>> I am a fan of ServiceLoader as a means of plugging in.
>>>>>>>
>>>>>>>> I hope this explains a bit
>>>>>>>
>>>>>>> Yep; thanks!
>>>>>>>
>>>>>>>> On Nov 2, 2021, at 1:46 AM, Jacek Lewandowski <
>>>>>>> lewandowski.ja...@gmail.com> wrote:
>>>>>>>>
>>>>>>>> David,
>>>>>>>>
>>>>>>>> I apologize I did not mention those things explicitly. All the places
>>>>>>> where
>>>>>>>> sstable files are accessed directly would have to be refactored.
>>>>>>>>
>>>>>>>> Regarding TableMetrics - currently it includes many metrics, some of
>>> them
>>>>>>>> are unrelated to sstables at all, but there are metrics which are
>>>>>>> specific
>>>>>>>> to the current sstable format, like metrics related to index
>>> summaries or
>>>>>>>> bloom filters. The created gauges query certain methods on sstable
>>>>>>> reader -
>>>>>>>> I think the only common metrics for sstables we can leave in
>>> TableMetrics
>>>>>>>> are those for which there are query methods in generic sstable
>>> interface.
>>>>>>>> Other metrics, specific to the certain sstable format should be
>>>>>>> registered
>>>>>>>> by the implementation itself.
>>>>>>>>
>>>>>>>> Speaking about the implementation, one idea I was thinking about was
>>> that
>>>>>>>> the factories for formats are registered using Java's native service
>>>>>>>> loader. This way we could get the list of all the factories on the
>>>>>>>> classpath and call some method, like `registerMetrics` during system
>>>>>>>> initialization. That could be also implemented in static initializer
>>> in
>>>>>>> the
>>>>>>>> factory but it would make it less obvious for the implementors where
>>> such
>>>>>>>> initialization should be done.
>>>>>>>>
>>>>>>>> I hope this explains a bit
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Jacek
>>>>>>>
>>>>>>>
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>>>>>
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