Memory leak when QoS > 1

[alanxz]

Memory leak when QoS > 1

[alanxz]

This is definitely a bug. I can reproduce the effects on my machine with the above code.

I believe the reason behind this is the way rabbitmq-c handles memory. rabbitmq-c allocates all incoming frames in a common memory pool, and it can only recycle this pool once all of the frames that have been allocated have been dealt with. When the QoS is set to be > 1, there is always a backlog of frames, so the memory pool is never allowed to recycle, thus the unbounded memory growth. Its also possible there is a frame on another channel hanging around somewhere, which would have the same effect, though not seeing the behavior when QoS == 1 makes me think its not another frame on a different channel.

This is what alanxz/rabbitmq-c#5 is supposed to solve (for a variety of reasons I don't think I will end up merging that PR). I think in this case however, I don't think even that will help, as this is all happening in one channel.

I think the 'solution' is: internally when reading frames we need to try hard to immediately use all of the frames that rabbitmq-c generates so that the memory pool can be recycled.

[RafalGoslawski]

The problem exists when there is only one channel. If I use seperate channels for consume/ack and publish memory pool is recycled just fine. But that's just a workaround not a solution.

[alanxz]

Interesting. Given what I think the problem is - I would not have expected separating out publish and consumer to their own Channel objects would've alleviated the memory issue. But I'm glad you found a workaround for the moment.

[chenyujian]

#30