7.2.5. Avoiding a Blocked Asynchronous Send

An asynchronous send call will place the message into the send buffer and return to execution immediately. However, if the send buffer is full the call will block until space is available.
If you need to ensure that an asynchronous send call does not block on a full buffer, you should query the buffer state before making the call. For example, in C++:
C++
  if (sender.getAvailable() > 0)
      sender.send(message, false)
   // else drop the message
Python
if sender.available() > 0:
  sender.send(message, sync=False)
else:
  # drop the message
You can also increase the size of the sender's replay buffer to reduce the chances of it filling up:
C++
sender.setCapacity(SOME_LARGE_NUMBER)
Python
sender.capacity = SOME_LARGE_NUMBER
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