Potential Incorrect Reuse of NDEATH Payload in Java Code

[joshwheeler-ggrx]

In EdgeClient::connectToTargetServer, we have the following block of code that is making the connection to the server:

// Connect to the MQTT Server
options.setAutomaticReconnect(true);
options.setCleanSession(true);
options.setConnectionTimeout(30);
options.setKeepAliveInterval(30);
options.setUserName(username);
options.setPassword(password.toCharArray());
options.setWill(NAMESPACE + "/" + groupId + "/NDEATH/" + edgeNode, deathBytes, 0, false);
client = new MqttClient(serverUrl, clientId);
client.setTimeToWait(2000); 
client.setCallback(this);                   // short timeout on failure to connect

The deathBytes come from MetricHandler.getDeathPayloadBytes(). The issue is that by reusing the death payload, the nodes on the network cannot distinguish between an unexpected network disconnect, or a graceful shutdown.

The cleanest fix would most likely be to add a MetricHandler.getLWTPayloadBytes() (Last Will and Testament). The dirty hack would be to have everyone interested on the network check for a metric akin to GracefulShutdown, which I don't recommend.