[GitHub] [pulsar] massakam opened a new pull request #4064: [client] Set actual topic name to partitioned consumer

[GitBox]

massakam opened a new pull request #4064: [client] Set actual topic name to 
partitioned consumer
URL: https://github.com/apache/pulsar/pull/4064
 
 
   ### Motivation
   
   When I got "proxy stats" from our WebSocket proxy, it contained a large 
number of entries as follows:
   
   ```sh
   $ curl -s 
http://dev-websocket20.pulsar.xxx.yahoo.co.jp:4080/admin/v2/proxy-stats/stats | 
jq .
   
   {
     "TopicsConsumerFakeTopicNamec7f8a": {
       "producerStats": [],
       "consumerStats": []
     },
     "TopicsConsumerFakeTopicName68c2f": {
       "producerStats": [],
       "consumerStats": []
     },
     "TopicsConsumerFakeTopicName4401e": {
       "producerStats": [],
       "consumerStats": []
     },
     "TopicsConsumerFakeTopicName0fedd": {
       "producerStats": [],
       "consumerStats": []
     },
     "TopicsConsumerFakeTopicName1c581": {
       "producerStats": [],
       "consumerStats": []
     },
     ...
   ```
   
   `TopicsConsumerFakeTopicName*` is a dummy topic name that is set when an 
instance of `MultiTopicsConsumerImpl` is created.
   
https://github.com/apache/pulsar/blob/bdfc09867325a271dc40a3aa87dcefb905769f06/pulsar-client/src/main/java/org/apache/pulsar/client/impl/MultiTopicsConsumerImpl.java#L97-L100
   
   This topic name changes every time a new consumer is created, even if the 
consumer is for the same topic. This means that the memory usage of WebSocket 
proxy will increase endlessly.
   
   ### Modifications
   
   `MultiTopicsConsumerImpl` is used in the following three cases:
   
   - (A) When subscribing to a partitioned topic
   - (B) When subscribing to multiple topics by specifying a list
   - (C) When subscribing to multiple topics by specifying a pattern
   
   Of these, the cause of memory leak in WebSocket proxy is (A). So, only in 
the case of (A), set the actual topic name to `MultiTopicsConsumerImpl`.
   
   ### Verifying this change
   
   - [ ] Make sure that the change passes the CI checks.

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