Allow Java client to create consumer with receiverQueueSize(0) when receiving with timeout

Currently, consumer with receiverQueueSize == 0 cannot be user when using receive with timeout (see sample code below).

Suggested solution

Remove this constraint (i.e. allow receiverQueueSize == 0 when using receive with timeout) to facilitate usage cases of shared subscriptions with long term processing of the message.

Sample code

package sample;

import org.apache.pulsar.client.api.*;
import java.util.concurrent.TimeUnit;

public class App {
    public static void main(String[] args) {

        try (PulsarClient client = PulsarClient.builder().serviceUrl("pulsar://localhost:6650").build()) {
            try (Consumer consumer = client.newConsumer().topic("sample").subscriptionName("try")
                    .subscriptionType(SubscriptionType.Shared)
                    .subscriptionInitialPosition(SubscriptionInitialPosition.Earliest)
                    .receiverQueueSize(0)
                    .subscribe()) {
                Message msg;
                while ((msg = consumer.receive(10, TimeUnit.SECONDS)) != null) {
                    var data = msg.getValue();
                    System.out.println("Received: " + data.toString());
                    consumer.acknowledge(msg);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Error message

org.apache.pulsar.client.api.PulsarClientException$InvalidConfigurationException: Can't use receive with timeout, if the queue size is 0
        at org.apache.pulsar.client.impl.ConsumerBase.receive(ConsumerBase.java:175)
        at sample.App.main(App.java:16)

[eolivelli]

when can implement some dummy loop that pools for a message for the given time, every X ms we call “receive”…

the user can do it by himself, but providing it out-of-the-box may be a good idea in order to provide user (developer) experience

[bry00]

2.7.1

Ok i will follow up the problem

Super, thx.