onlyMIT commented on a change in pull request #2528: ARTEMIS-2226 last consumer
connection should close the previous consu…
URL: https://github.com/apache/activemq-artemis/pull/2528#discussion_r252914292
##########
File path:
artemis-protocols/artemis-mqtt-protocol/src/main/java/org/apache/activemq/artemis/core/protocol/mqtt/MQTTProtocolManager.java
##########
@@ -62,11 +73,44 @@
List<BaseInterceptor> outgoingInterceptors) {
this.server = server;
this.updateInterceptors(incomingInterceptors, outgoingInterceptors);
+ server.getManagementService().addNotificationListener(this);
}
@Override
public void onNotification(Notification notification) {
- // TODO handle notifications
+ if (!(notification.getType() instanceof CoreNotificationType))
+ return;
+
+ CoreNotificationType type = (CoreNotificationType)
notification.getType();
+ if (type != CONSUMER_CREATED)
+ return;
+
+ TypedProperties props = notification.getProperties();
+
+ SimpleString protocolName =
props.getSimpleStringProperty(ManagementHelper.HDR_PROTOCOL_NAME);
+
+ if (protocolName == null ||
!protocolName.toString().equals(MQTTProtocolManagerFactory.MQTT_PROTOCOL_NAME))
+ return;
+
+ int distance = props.getIntProperty(ManagementHelper.HDR_DISTANCE);
+
+ if (distance > 0) {
+ SimpleString queueName =
props.getSimpleStringProperty(ManagementHelper.HDR_ROUTING_NAME);
+
+ Binding binding = server.getPostOffice().getBinding(queueName);
+ if (binding != null) {
+ Queue queue = (Queue) binding.getBindable();
+ String clientId =
props.getSimpleStringProperty(ManagementHelper.HDR_CLIENT_ID).toString();
+ //If the client ID represents a client already connected to the
server then the server MUST disconnect the existing client.
+ //Avoid consumers with the same client ID in the cluster appearing
at different nodes at the same time
+ Collection<Consumer> consumersSet = queue.getConsumers();
+ for (Consumer consumer : consumersSet) {
+ ServerConsumerImpl serverConsumer = (ServerConsumerImpl)
consumer;
+ if (clientId.equals(serverConsumer.getConnectionClientID()))
+ serverConsumer.getRemotingConnection().destroy();
Review comment:
Our goal is to avoid simultaneous occurrence of multiple MQTT connections
with the same clientId, not to prevent MQTT consumers with the same clientId to
subscribe the same topic.
described in the [two
solutions](https://github.com/apache/activemq-artemis/pull/2528#issue-248449219)
. Adding a new cluster notification when the client’s connections connect to
Artemis,
it is the best way to address the MQTT agreement, but the cost is too great.
So it put the logic in CREATE_CONSUMER cluster-notification.
The following code description, before each processing of the mqtt
connection request in artemis, check whether there is a connection with the
same clientId in the node, and if so, close it.
Similarly, in the cluster, we also want to avoid the connection of the same
clientId. Executing this logic only in CREATE_CONSUMER is just that I think it
can reduce resource consumption and avoid problems, although this is not the
way to match the MQTT specification.
```
private String validateClientId(String clientId, boolean cleanSession) {
if (clientId == null || clientId.isEmpty()) {
// [MQTT-3.1.3-7] [MQTT-3.1.3-6] If client does not specify a
client ID and clean session is set to 1 create it.
if (cleanSession) {
clientId = UUID.randomUUID().toString();
} else {
// [MQTT-3.1.3-8] Return ID rejected and disconnect if clean
session = false and client id is null
return null;
}
} else {
MQTTConnection connection =
session.getProtocolManager().addConnectedClient(clientId,
session.getConnection());
if (connection != null) {
// [MQTT-3.1.4-2] If the client ID represents a client already
connected to the server then the server MUST disconnect the existing client
connection.disconnect(false);
}
}
return clientId;
}
```
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