Before this change, the StompProtocolHandler always responded to
clients with a CONNECTED frame, while the STOMP broker relay
independantly forwarded the client CONNECT to the broker and waited
for the CONNECTED frame back. That meant the relay had to buffer
client messages until it received the CONNECTED response from
the message broker.
This change ensures that clients wait for a CONNECTED frame from
the message broker. The broker relay forwards the CONNECT frame to
the broker. The broker responds with a CONNECTED frame, which the
relay then forwards to the client. As a result, a (well-written)
client will not send any messages to the relay until the connection
to the broker is fully established.
The StompProtcolHandler can now be configured whether to send CONNECTED
frame back. By default that is off. So when using the simple broker,
the StompProtocolHandler can still respond with CONNECTED frames.
The relay's handling of a connection being dropped has also been
improved. When a connection for a client relay session is dropped
an ERROR frame will be sent back to the client. If a connection is
closed as part of a DISCONNECT frame being sent, no ERROR frame
is sent back to the client. When the connection for the system relay
session is dropped, an event is published indicating that the broker
is unavailable. Reactor's TcpClient will then attempt to re-restablish
the connection.
8d2a376b0f