[GitHub] [pulsar] liketic commented on issue #3733: support Pattern subscribe in kafka compat client

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liketic commented on issue #3733: support Pattern subscribe in kafka compat client
URL: https://github.com/apache/pulsar/issues/3733#issuecomment-471170264
 
 
   Thank you @jiazhai @sijie . The method ```subscribe``` https://github.com/apache/pulsar/blob/41b286dc0cc7b6ca3aa24acfccd53dfed547c0c5/pulsar-client-kafka-compat/pulsar-client-kafka/src/main/java/org/apache/kafka/clients/consumer/PulsarKafkaConsumer.java#L215 
   
   lists all partitions for each topic and create a ```TopicPartition``` instance for each pair of them, and update the member variables ```consumers``` and ```unpolledPartitions``` for later use.
   What I mean is if we need to do the same things, try to get all topics matched the pattern and then get all partitions for each topic...  , which means we need a method to list all topics based on a regex in client.
   
   Otherwise, what I can think of is something like:
   ```
       @Override
       public void subscribe(Pattern pattern, ConsumerRebalanceListener callback) {
           ConsumerBuilder<byte[]> consumerBuilder = PulsarConsumerKafkaConfig.getConsumerBuilder(client, properties);
           consumerBuilder.subscriptionType(SubscriptionType.Failover);
           consumerBuilder.messageListener(this);
           consumerBuilder.subscriptionName(groupId);
           consumerBuilder.topicsPattern(pattern);
           try {
               consumerBuilder.subscribe();
           } catch (Exception ex) {
               throw new RuntimeException(ex);
           }
       }
   ```
   

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