[GitHub] rdhabalia commented on a change in pull request #577: CPP add receiveAsync API

[gi...@git.apache.org]

rdhabalia commented on a change in pull request #577: CPP add receiveAsync API
URL: https://github.com/apache/incubator-pulsar/pull/577#discussion_r128063623
 
 

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 File path: pulsar-client-cpp/lib/PartitionedConsumerImpl.h
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 @@ -79,6 +80,7 @@ namespace pulsar {
         typedef std::vector<ConsumerImplPtr> ConsumerList;
         ConsumerList consumers_;
         boost::mutex mutex_;
+        boost::mutex pendingReceiveMutex_;
 
 Review comment:
   `pendingReceiveMutex_` is a mutex which requires to sync `pendingReceives-queue` and `incomingMessages-queue` together to make sure message-queue is empty while adding into pending-queue.
   `mutex_` will not work here for example:
   -  [receive()](https://github.com/apache/incubator-pulsar/blob/master/pulsar-client-cpp/lib/PartitionedConsumerImpl.cc#L67) is a blocking call which takes locks on `mutext_` until message is received
   - now, if we use the same `mutex_` on [message-received](https://github.com/rdhabalia/pulsar/blob/12dec47295d9a2b896c4b46bb5e7cb37ddd8fbf3/pulsar-client-cpp/lib/PartitionedConsumerImpl.cc#L338) then it will create a deadlock. 
   
 
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