Re: [libvirt] [PATCH v3 06/13] Add support for non-blocking calls in client RPC

When a client wants to send a keepalive message it needs to do so in a non-blocking way to avoid blocking its event loop. This patch adds dontBlock flag which says that the call should be processed without blocking. Such calls do not have a thread waiting for the result associated with them. This means, that sending such call fails if no thread is dispatching and writing to the socket would block. In case there is a thread waiting for its (normal) call to finish, sending non-blocking call just pushes it into the queue and lets the dispatching thread send it. The thread which has the buck tries to send all non-blocking calls in the queue in a best effort way---if sending them would block or there's an error on the socket, non-blocking calls are simply removed from the queue and discarded.