I think this model is more confusing than it needs to be. We end up with 4 prefixes despite only have 3 types of consumers. We have prefixes for: "base", "main", "global", and "restore". However, we only instantiate consumers of type "main", "global", and "restore".
Until now, we've only had two types of configs mapping to two types of consumers, despite internally having some common shared configs as a baseline to bootstrap the two "public" ones (see StreamsConfig.getCommonConsumerConfigs). Do we want to complicate this to 4 levels of "public" configs when there are only 3 types of concrete configs we instantiate? More generally, I worry that we're optimizing too much to avoid copy/paste in less common cases to the point that we would confuse users with yet more concepts before they can even write their configuration. What if we took an (perhaps modified) all or nothing approach to inheriting from the the "main" consumer properties? In that mode if you override *anything*, you should specify *everything*. But if it was just, e.g. group.id, client.id, and offset.reset that needed adjustment for a restoreConsumer, that would be the default and everything else is inherited. Same deal for a clearly specified set of configs for global consumers that required override. I feel like I'm also concurrently seeing the opposite side of this problem in Connect where we namespaced and didn't proactively implement inheritance; and while people find the config duplication annoying (and confusing!), we inevitably find cases where they need it. I think inheritance in these configuration setups needs to be approached very carefully. Admittedly, some of the challenges in Connect don't appear here (e.g. conflicts in producer/consumer config naming, since this is a Consumer-only KIP), but similar problems arise. -Ewen On Wed, Apr 4, 2018 at 10:56 PM, Boyang Chen <bche...@outlook.com> wrote: > Thanks Guozhang! I already updated the pull request and KIP to deprecate > getConsumerConfigs() function. Do you think we could move to a voting stage > now? > > > ________________________________ > From: Guozhang Wang <wangg...@gmail.com> > Sent: Thursday, April 5, 2018 9:52 AM > To: dev@kafka.apache.org > Subject: Re: [DISCUSS] KIP-276: Add StreamsConfig prefix for different > consumers > > I agree that renaming the method in this case may not worth it. Let's keep > the existing function names. > > On Wed, Apr 4, 2018 at 6:06 PM, Matthias J. Sax <matth...@confluent.io> > wrote: > > > Thanks for updating the KIP. > > > > One more comment. Even if we don't expect users to call > > `StreamsConfig#getConsumerConfigs()` it is still public API. Thus, we > > cannot just rename the method. > > > > I think we have two options: either we keep the current name or we > > deprecate the method and introduce `getMainConsumerConfigs()` in > > parallel. The deprecated method would just call the new method. > > > > I am not sure if we gain a lot renaming the method, thus I have a slight > > preference in just keeping the method name as is. (But I am also ok to > > rename it, if people prefer this) > > > > -Matthias > > > > > > On 4/3/18 1:59 PM, Bill Bejeck wrote: > > > Boyang, > > > > > > Thanks for making changes to the KIP, I'm +1 on the updated version. > > > > > > -Bill > > > > > > On Tue, Apr 3, 2018 at 1:14 AM, Boyang Chen <bche...@outlook.com> > wrote: > > > > > >> Hey friends, > > >> > > >> > > >> both KIP<https://cwiki.apache.org/confluence/display/KAFKA/KIP- > > >> 276+Add+StreamsConfig+prefix+for+different+consumers> and pull > request< > > >> https://github.com/apache/kafka/pull/4805> are updated. Feel free to > > take > > >> another look. > > >> > > >> > > >> > > >> Thanks for your valuable feedback! > > >> > > >> > > >> Best, > > >> > > >> Boyang > > >> > > >> ________________________________ > > >> From: Boyang Chen <bche...@outlook.com> > > >> Sent: Tuesday, April 3, 2018 11:39 AM > > >> To: dev@kafka.apache.org > > >> Subject: Re: [DISCUSS] KIP-276: Add StreamsConfig prefix for different > > >> consumers > > >> > > >> Thanks Matthias, Ted and Guozhang for the inputs. I shall address them > > in > > >> next round. > > >> > > >> > > >> ________________________________ > > >> From: Matthias J. Sax <matth...@confluent.io> > > >> Sent: Tuesday, April 3, 2018 4:43 AM > > >> To: dev@kafka.apache.org > > >> Subject: Re: [DISCUSS] KIP-276: Add StreamsConfig prefix for different > > >> consumers > > >> > > >> Yes, your examples make sense to me. That was the idea behind the > > proposal. > > >> > > >> > > >> -Matthias > > >> > > >> On 4/2/18 11:25 AM, Guozhang Wang wrote: > > >>> @Matthias > > >>> > > >>> That's a good question: I think adding another config for the main > > >> consumer > > >>> makes good tradeoffs between compatibility and new user convenience. > > Just > > >>> to clarify, from user's pov on upgrade: > > >>> > > >>> 1) I'm already overriding some consumer configs, and now I want to > > >> override > > >>> these values differently for restore consumers, I'd add one new line > > for > > >>> the restore consumer prefix. > > >>> > > >>> 2) I'm already overriding some consumer configs, and now I want to > NOT > > >>> overriding them for restore consumers, I'd change my override from > > >>> `consumer.X` to `main.consumer.X`. > > >>> > > >>> 3) I'm new and have not any consumer overrides, and now if I want to > > >>> override some, I'd use `main.consumer`, `restore.consumer` for > specific > > >>> consumer types, and ONLY consider `consumer` for the ones that I want > > to > > >>> apply universally. > > >>> > > >>> 4) I'm already overriding some consumer configs and I'm happy with > > what I > > >>> get, I do not change anything. > > >>> > > >>> > > >>> Guozhang > > >>> > > >>> On Mon, Apr 2, 2018 at 11:10 AM, Ted Yu <yuzhih...@gmail.com> wrote: > > >>> > > >>>> bq. to introduce one more prefix `main.consumer.` > > >>>> > > >>>> Makes sense. > > >>>> > > >>>> On Mon, Apr 2, 2018 at 11:06 AM, Matthias J. Sax < > > matth...@confluent.io > > >>> > > >>>> wrote: > > >>>> > > >>>>> Boyang, > > >>>>> > > >>>>> thanks a lot for the KIP. > > >>>>> > > >>>>> Couple of questions: > > >>>>> > > >>>>>> (MODIFIED) public Map<String, Object> getRestoreConsumerConfigs( > > final > > >>>>> String clientId); > > >>>>> > > >>>>> You mean that the implementation/semantics of this method changes, > > but > > >>>>> not the API itself? Might be good to add this as "comment style" > > >> instead > > >>>>> of "(MODIFIED)" prefix. > > >>>>> > > >>>>>> By rewriting the getRestoreConsumerConfigs() function and adding > the > > >>>>> getGlobalConsumerConfigs() function, if one user uses > > >>>>> restoreConsumerPrefix() or globalConsumerPrefix() when adding new > > >>>>> configurations, the configs shall overwrite base consumer config. > If > > >> not > > >>>>> specified, restore consumer and global consumer shall share the > same > > >>>> config > > >>>>> with base consumer. > > >>>>> > > >>>>> While this does make sense for backward compatibility, I am wonder > if > > >> it > > >>>>> makes the config "inheritance logic" (ie, hierarchy) too complex? > We > > >>>>> basically introduce a second level of overwrites. It might be > simpler > > >> to > > >>>>> not introduce this hierarchy with the cost to break backward > > >>>> compatibility. > > >>>>> > > >>>>> For example, config `request.timeout.ms`: > > >>>>> > > >>>>> User sets `request.timeout.ms=<user-value>` > > >>>>> To change it for the main consumer, user also sets > > >>>>> `consumer.request.timeout.ms=<consumer-value>` > > >>>>> > > >>>>> If user only wants to change the config for main consumer, but not > > for > > >>>>> global or restore consumer, user needs to add two more configs: > > >>>>> > > >>>>> `restore.consumer.request.timeout.ms=<user-value>` > > >>>>> and > > >>>>> `global.consumer.request.timeout.ms=<user-value>` > > >>>>> > > >>>>> to reset both back to the default config. IMHO, this is not an > > optimal > > >>>>> user experience. Thus, it might be worth to change the semantics > for > > >>>>> `consumer.` prefix to only apply those configs to the main > consumer. > > >>>>> > > >>>>> > > >>>>> Not sure what other think what the better solution is (I am not > sure > > by > > >>>>> myself to be honest---just wanted to point it out and discuss the > > >>>>> pros/cons for both). > > >>>>> > > >>>>> > > >>>>> Another though would be, to introduce one more prefix > > `main.consumer.` > > >>>>> -- using this, the existing `consumer.` prefix would apply to all > > >>>>> consumers (keeping it's current semantics) while we have overwrites > > for > > >>>>> all three consumers -- this allow to directly set `main.consumer` > > >>>>> instead of `consumer` avoiding the weird pattern from my example > > above > > >>>>> and preserves backward compatibility. Ie, if we introduce an > > hierarchy > > >>>>> of overwrite, a "full" hierarchy might be better than a "partial" > > >>>>> hierarchy. > > >>>>> > > >>>>> > > >>>>> Looking forward to your thoughts. > > >>>>> > > >>>>> > > >>>>> -Matthias > > >>>>> > > >>>>> > > >>>>> On 4/1/18 5:55 PM, Guozhang Wang wrote: > > >>>>>> Thanks for the KIP Boyang, the KIP looks good to me. > > >>>>>> > > >>>>>> For config values, we use underscore for keeping a single word; > for > > >>>>> config > > >>>>>> keys, though, we do not use underscores or dashes. I'd suggest > using > > >>>> dots > > >>>>>> to be consistent with others. > > >>>>>> > > >>>>>> > > >>>>>> Otherwise I'm +1 on the KIP. > > >>>>>> > > >>>>>> > > >>>>>> Guozhang > > >>>>>> > > >>>>>> > > >>>>>> On Sun, Apr 1, 2018 at 10:56 AM, Ted Yu <yuzhih...@gmail.com> > > wrote: > > >>>>>> > > >>>>>>> Looks good overall. > > >>>>>>> > > >>>>>>> public static final String RESTORE_CONSUMER_PREFIX = > > >>>>> "restore-consumer."; > > >>>>>>> > > >>>>>>> For other constants in StreamsConfig, underscore is used instead > of > > >>>>> dash. > > >>>>>>> > > >>>>>>> Cheers > > >>>>>>> > > >>>>>>> On Sun, Apr 1, 2018 at 9:38 AM, Boyang Chen <bche...@outlook.com > > > > >>>>> wrote: > > >>>>>>> > > >>>>>>>> Hey friends, > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> I would like to start a discussion thread for KIP 276: > > >>>>>>>> > > >>>>>>>> https://cwiki.apache.org/confluence/display/KAFKA/KIP- > > >>>>>>>> 276+Add+StreamsConfig+prefix+for+different+consumers > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> And pull request is here: > > >>>>>>>> > > >>>>>>>> https://github.com/apache/kafka/pull/4805 > > >>>>>>>> > > >>>>>>>> [https://avatars3.githubusercontent.com/u/5845561?s=400&v=4 > > >>>> ]<https:// > > >>>>>>>> github.com/apache/kafka/pull/4805> > > >>>>>>>> > > >>>>>>>> KAFKA-6657: Add StreamsConfig prefix for different consumers by > > >>>>> abbccdda > > >>>>>>> · > > >>>>>>>> Pull Request #4805 · apache/kafka<https://github. > > >>>>>>>> com/apache/kafka/pull/4805> > > >>>>>>>> github.com > > >>>>>>>> This pull request is for jira 6657. The KIP proposal is here > Added > > >>>> unit > > >>>>>>>> tests for new getGlobalConsumerConfigs API and make sure > existing > > >>>>> restore > > >>>>>>>> consumer tests are passing. > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> > > >>>>>>>> Thanks, > > >>>>>>>> > > >>>>>>>> Boyang > > >>>>>>>> > > >>>>>>> > > >>>>>> > > >>>>>> > > >>>>>> > > >>>>> > > >>>>> > > >>>> > > >>> > > >>> > > >>> > > >> > > >> > > > > > > > > > > -- > -- Guozhang >
