[Issue 8311][pulsar-client-go] Fix memory leak in cgo golang client (a…

…pache#8325)

* [Issue 8311] Fixes memory leak in cgo golang client

In the C/C++ glue code, file c_Producer.cc function handle_producer_send(),
a new pulsar_message_id_t is created. This needs to be freed at some point.

Because of issues with legacy C clients, it is not possible to call delete
from inside c_Producer.cc. Instead, the client must call pulsar_message_id_free().

Previously, the cgo interface was not freeing this message ID, which caused a
memory leak on every message sent.

* The explicit free inside pulsarProducerSendCallbackProxyWithMsgID() is not required, because the getMessageId() call attaches a finalizer which will take care of things.

pulsar-client-go/pulsar/c_go_pulsar.h

@@ -61,7 +61,7 @@ static inline void _pulsar_producer_close_async(pulsar_producer_t *producer, voi
     pulsar_producer_close_async(producer, pulsarProducerCloseCallbackProxy, ctx);
 }
 
-void pulsarProducerSendCallbackProxy(pulsar_result result, pulsar_message_id_t *message, void *ctx);
+void pulsarProducerSendCallbackProxy(pulsar_result result, pulsar_message_id_t *messageId, void *ctx);
 
 void pulsarProducerSendCallbackProxyWithMsgID(pulsar_result result, pulsar_message_id_t *messageId, void *ctx);
 

pulsar-client-go/pulsar/c_producer.go

@@ -268,7 +268,6 @@ func (p *producer) SendAndGetMsgID(ctx context.Context, msg ProducerMessage) (Me
 	}
 }
 
-
 type sendCallback struct {
 	message  ProducerMessage
 	callback func(ProducerMessage, error)
@@ -287,6 +286,7 @@ func pulsarProducerSendCallbackProxy(res C.pulsar_result, messageId *C.pulsar_me
 		sendCallback.callback(sendCallback.message, newError(res, "Failed to send message"))
 	} else {
 		sendCallback.callback(sendCallback.message, nil)
+		C.pulsar_message_id_free(messageId)
 	}
 }