[GitHub] [pulsar] merlimat opened a new pull request #3764: Fixed Reader.HasNext() in Go client

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

merlimat opened a new pull request #3764: Fixed Reader.HasNext() in Go client
URL: https://github.com/apache/pulsar/pull/3764
 
 
   ### Motivation
   
   In Go client, the `Reader.HasNext()` is currently broken because it returns "true" when there are no more messages to read. 
   
   The issue is in the C++ `Consumer::hasMessageAvailable()`, combined with the use of message listener. The `lastDequedMessage` is being updated only after the listener is triggered, therefore an app checking `hasMessageAvailable()` from the listener thread will always be 1 message behind.
   
   Since Go client wrapper, uses the listener internally, it is affected by this problem and it looks like a race condition with the `lastDequedMessage` being updated in a background thread.

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