@Override
    public void deliverMessage(Message msg, String session) {
        MessageHandler msgHandler = sessions.get(session);
        if (msgHandler == null) {
            deliverError(msg, ErrorCode.UNKNOWN_SESSION, "Session '" + session + "' does not exist.");
        } else if (!checkPending(msg)) {
            deliverError(msg, ErrorCode.SESSION_BUSY, "Session '" + net.net().getConnectionSpec() + "/" + session +
                                                      "' is busy, try again later.");
        } else {
            msn.deliverMessage(msg, msgHandler);
        }
    }
<p>This method handles choking input data so that message bus does not
blindly accept everything. This prevents an application running
out-of-memory in case it fail to choke input data itself. If this method
returns false, it means that it should be rejected.</p>

@param msg The message to count.
@return True if the message was accepted.
messagebus/src/main/java/com/yahoo/messagebus/MessageBus.java