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From "Mike Rhodes" <couc...@dx13.co.uk>
Subject Re: Batch mode options for CouchDB 4.0
Date Tue, 29 Oct 2019 10:24:17 GMT
There are a two things I'd like to break down here:

1. The non-functional behaviour of the API is changing. What was hopefully a short request
could now block for much longer as the client must wait for a write to happen. Among other
things, this affects UI latency, as well as the power consumption of low-power devices. Silently
changing this behaviour is very hard to debug client side. This is an example where the new
behaviour may not be better for some use-cases.
2. The request is documented as returning 202 only. We are proposing changing that API contract.

IMO, the HTTP response code is a fundamental part of any HTTP API, and it's reasonable for
clients to listen on the 202 that is documented as the only possible response code in this
scenario. For example, the client might want to be sure CouchDB is interpreting the argument
they are sending correctly.

On the question of accepting any 2XX response being desirable, I would agree that perhaps
it is better to be liberal in what you accept, but we need to therefore be strict in what
we send. CouchDB isn't great at returning 400 when there are mutually exclusive parameters
supplied in a request, for example.

If the only reason for retaining this setting is to maintain backwards API compatibility,
and we are not worried about API purity, returning 202 seems the appropriate approach to me;
it may not be "correct" but it is seemingly the way of achieving the stated goal of silently
dropping the param in a safe(ish) manner.

-- 
Mike.

On Wed, 23 Oct 2019, at 13:32, Jan Lehnardt wrote:
> 
> 
> > On 23. Oct 2019, at 14:26, Arturo GARCIA-VARGAS <arturo@ficuslabs.com> wrote:
> > 
> > I guess the way I see it (and where I may be wrong) is that batch=ok will become
a deprecated use of the API.  And if we are to support a deprecated behaviour:
> > 
> > 1. Behave as before because you are nice, via an explicit config enable; or
> 
> The point is, we would be behaving “better than before”
> 
> > 2. Stop doing it because it is well..., deprecated.  Update your client.
> 
> …and we don’t want to break client software, when we don’t have to.
> 
> Best
> Jan
> —
> > 
> > -A.
> > 
> > Again my opinion :-)
> > 
> > On 23/10/2019 13:19, Jan Lehnardt wrote:
> >>> On 23. Oct 2019, at 13:56, Arturo GARCIA-VARGAS <arturo@ficuslabs.com>
wrote:
> >>> 
> >>> Maybe my point is not coming across correctly.
> >>> 
> >>> By reading the docs, a consumer would match *explicitly* to a 202 response,
to acknowledge success.
> >>> 
> >>> We better be consistent and either hard-break this behaviour, or behave
as before, but not silently switch the behaviour, even more if the operation behind is a no-op.
> >> I think I do understand your point, however, the nature of this API allows us
to argue for the best of both worlds: batch=ok today says that the client is fine with letting
CouchDB decide when to fully commit data. Depending on the circumstances, that decision could
be “immediately”, or it could be “some time later”. The proposal here now suggests
that we switch this to be always “immediately”, but regardless of batch=ok being present
or not, the client doesn’t really care about that. So I don’t think there is a good reason
for suggesting a hard break.
> >> Best
> >> Jan
> >> —
> >>> 
> >>> Well, my opinion.
> >>> 
> >>> On 23/10/2019 12:50, Jan Lehnardt wrote:
> >>>>> On 23. Oct 2019, at 13:32, Arturo GARCIA-VARGAS <arturo@ficuslabs.com>
wrote:
> >>>>> 
> >>>>> Well, a consumer would be explicitly waiting the the accept response
code like responseCode === '202' as a sign of "success".  We have silently broken the consumer.
> >>>>> 
> >>>>> Granted a consumer should cater for a '201' response, but the docs
explicitly say you do not get a 201 when using batch=ok.
> >>>> A consumer that can’t deal with different HTTP response codes already
isn’t doing HTTP correctly. They could already equally receive a 400, 401, 500 or any other
variety or responses, so I think we’re fine here.
> >>>>> 
> >>>>> On 23/10/2019 12:29, Jan Lehnardt wrote:
> >>>>>>> On 23. Oct 2019, at 13:25, Arturo GARCIA-VARGAS <arturo@ficuslabs.com>
wrote:
> >>>>>>> 
> >>>>>>> My opinion....
> >>>>>>> 
> >>>>>>> On 23/10/2019 12:15, Jan Lehnardt wrote:
> >>>>>>>> 
> >>>>>>>>> On 23. Oct 2019, at 12:40, Robert Samuel Newson
<rnewson@apache.org> wrote:
> >>>>>>>>> 
> >>>>>>>>> Hi,
> >>>>>>>>> 
> >>>>>>>>> Just confirming my position on this. We should treat
a request with batch=ok as if the setting was not there. That is, make the same durable commit
as normal. We should therefore send a 201 Created response code. We should continue to validate
the batch setting (it can be absent or it can be "ok" but every other value is a 400 Bad Request).
> >>>>>>>> 
> >>>>>>> -1 from me, we should:
> >>>>>>> 1. Drop it and be consistent with the API.  Maybe warning
of deprecation in couchdb-3?
> >>>>>>> 2. Enable same behaviour as before (accepted) with a no-op
and config file parameter.
> >>>>>>> 
> >>>>>>> But not modify the behaviour of the API
> >>>>>> Can you explain why?
> >>>>>> The proposed behaviour is no worse than what the option enables,
and it ensures that existing software continues to work without (much) change.
> >>>>>> API purity for the sake of it is not really a goal here.
> >>>>>> Best
> >>>>>> Jan
> 
> -- 
> Professional Support for Apache CouchDB:
> https://neighbourhood.ie/couchdb-support/
> 
>

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