[GitHub] [pulsar] Technoboy- commented on pull request #13960: [improve][client] Close consumer when topic terminates.

[GitBox <gi...@apache.org>]

Technoboy- commented on PR #13960:
URL: https://github.com/apache/pulsar/pull/13960#issuecomment-1121003868

   > In addition, this also makes consumer not able to seek to an older position after topic terminates.
   > 
   > ```java
   >         try (PulsarClient client = PulsarClient.builder().serviceUrl("pulsar://localhost:6650").build()) {
   >             CountDownLatch latch = new CountDownLatch(1);
   >             Consumer<byte[]> consumer = client.newConsumer()
   >                     .topic("my-topic")
   >                     .subscriptionName("sub")
   >                     .subscriptionInitialPosition(SubscriptionInitialPosition.Earliest)
   >                     .messageListener(new MessageListener<byte[]>() {
   >                         @Override
   >                         public void received(Consumer<byte[]> consumer, Message<byte[]> msg) {
   >                             System.out.println("Received " + new String(msg.getValue()));
   >                             consumer.acknowledgeAsync(msg);
   >                         }
   > 
   >                         @Override
   >                         public void reachedEndOfTopic(Consumer<byte[]> consumer) {
   >                             System.out.println("consumer closed");
   >                             latch.countDown();
   >                         }
   >                     })
   >                     .subscribe();
   >             latch.await();
   >             try {
   >                 consumer.seek(MessageId.earliest);
   >                 System.out.println("seek done");
   >             } catch (PulsarClientException e) {
   >                 e.printStackTrace();
   >             }
   > ```
   > 
   > Run the application above, the run following commands.
   > 
   > ```shell
   > ./bin/pulsar-client produce -m hello my-topic
   > ./bin/pulsar-admin topics terminate my-topic 
   > ```
   > 
   > Before this patch, the output will be:
   > 
   > ```
   > Received hello
   > consumer closed
   > seek done
   > ```
   > 
   > After this patch, the output will be:
   > 
   > ```
   > Received hello
   > consumer closed
   > org.apache.pulsar.client.api.PulsarClientException$AlreadyClosedException: The consumer d9dc7 was already closed when seeking the subscription sub of the topic persistent://public/default/my-topic to the message -1:-1:-1
   > ```
   > 
   > It's only a case for `seek`. I'm not sure whether the methods added in future could still fail automatically by this behavior change. Whatever, it will make users confused.
   
   yes, right. this is a case.  even if the topic is terminated, the subscription can be created. 
   So I decide to close this patch.


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