Re: [DISCUSSION] PIP-108: Add method to help user judge if consumer queue has message

[ZhangJian He]

3. Our solution implements the distributed flow control ability at client
side, so we don't use the listener way.
2. Per customer per consumer in different tenants and namespace, and the
`flow-control` need(Some of our customer's machines can't work on high
traffic), So `Multi-topic` can't use.
1. We want to use this api to judge if there's messages to receive, like
that pseudo code
if (consumer.hasMessage()) {
   .submit(() -> {
      consumer.pollMessagesAccordingToTheDistributedFlowControl()
   })
}

Matteo Merli <matteo.me...@gmail.com> 于2021年10月26日周二 下午12:15写道：

> I'm a bit hesitant about this because I think there are already at
> least 3 different ways to handle similar scenarios.
>
>  1. Using listener and avoid calling receive directly
>  2. Use multi-topic consumer, so there's a single `Consumer` instance
> exposed
>  3. Use `consumer.receive(0, TimeUnit.SECONDS)` to probe for message
>
>
> --
> Matteo Merli
> <matteo.me...@gmail.com>
>
> On Mon, Oct 25, 2021 at 7:34 PM ZhangJian He <shoot...@gmail.com> wrote:
> >
> > I think it's better to add the method to Consumer interface instead of
> let
> > user casting it to `ConsumerBase`.
> > `peek` is most complexly,  for the reason, I can use the `peek` object to
> > ack、negative ack, but when to remove from the `BlockingQueue`?
> > IMHO, people use this api are just to judge if has the message,
> otherwise,
> > they can just use `receive(0,TimeUnit)
> >
> > JiangHaiting <jianghait...@foxmail.com> 于2021年10月26日周二 上午10:19写道：
> >
> > > Can this method
> > > "org.apache.pulsar.client.impl.ConsumerBase#getTotalIncomingMessages"
> do
> > > the trick? Though you have to change the type to ConsumerBase.
> > >
> > >
> > > And maybe `peek` is more suitable and useful to add to the Consumer
> > > interface？
> > >
> > >
> > >
> > >
> > >
> > >
> > > ------------------&nbsp;Original&nbsp;------------------
> > > From:
> > >                                                   "dev"
> > >                                                                 <
> > > shoot...@gmail.com&gt;;
> > > Date:&nbsp;Mon, Oct 25, 2021 07:24 PM
> > > To:&nbsp;"dev"<dev@pulsar.apache.org&gt;;
> > >
> > > Subject:&nbsp;[DISCUSSION] PIP-108: Add method to help user judge if
> > > consumer queue has message
> > >
> > >
> > >
> > > https://github.com/apache/pulsar/issues/12479
> > >
> > > --- Pasted here for quoting convenience ---
> > >
> > > ## Motivation
> > > Currently, I have an application that manages ten thousand of
> consumers,
> > > and a logic to schedule consumers's receive. It would be helpful to
> know if
> > > one of the consumers have message to recive.
> > >
> > > ## Goal
> > > To make `Consumer` can judge if there are unreceiving messages
> > >
> > > ## API Changes
> > >
> > > Add `hasMessageInReceiverQueue` on the `Consumer` interface.
> > >
> > > ## Implementation
> > >
> > > For `ZeroQueueConsumerImpl` return false, Others, judge the
> > > `receiveQueueSize` greater than zero.
> > >
> > >
> > > ## Reject Alternatives
> > >
> > > No alternatives yet.
> > >
> > >
> > >
> > >
> > > ---
> > > Thanks,
> > > Haiting Jiang (Github: Jason918)
>