EDIT2: My issue here was caused by an insufficient understanding of how transport connectors work in ActiveMQ. TL;DR is that ActiveMQ will implicitly "transform" or "relay" messages between your transport connector configurations defined in activemq.xml.
EDIT: Additional info, the STOMP messages received by the Angular application are used for debugging and demo purposes. Hence, simply converting the OpenWire message to a blob of readable text is sufficient.
I'm creating an Angular application (preferably website, avoiding native applications), which objective is to "tap in" by web sockets on an ActiveMQ server and subscribe to OpenWire messages. How do I let ActiveMQ transform OpenWire messages to STOMP messages and send these to any clients (i.e. my Angular application) connected to the ActiveMQ WebSocket connector?
In addtiion, it would be nice-to-have if I could transform STOMP to OpenWire as well.
It must be Angular
Avoiding the use of native applications on the client-side is preferable although not a deal-breaker.
Adding extra processing stress on the ActiveMQ server must be done with caution.
To the best of my knowledge, it is only possible to let Angular "talk directly" with the ActiveMQ server by STOMP messages send by web socket, if I am to avoid using native applications.
I already have an Angular application capable of STOMP communication by web sockets (e.g. something like https://github.com/stomp-js/ng2-stompjs-angular7).
I am missing information on how to configure the ActiveMQ server to transform OpenWire-->STOMP through its transport connectors.
In my understanding, what I am trying to do should be possible. It is noted by other users but not how. E.g. users hint that what I want is possible in ActiveMQ but not Apollo: ActiveMQ to Apollo transition, Openwire to Stomp protocol configuration.
I expect (preferably) the need to use something like an ActiveMQ transformer (e.g. adding transformer to the connector configuration: AMQP & Openwire - Activemq broker and 2 different consumers) or maybe writing an ActiveMQ plugin (http://activemq.apache.org/developing-plugins.html). On ActiveMQ's website, an existing transformer is mentioned (http://activemq.apache.org/stomp.html Message Transformations section):
Currently, ActiveMQ comes with a transformer that can transform XML/JSON text to Java objects
... but no mention of how to use this and I am unsure if I can benefit from this and if this means that there are no transformers for OpenWire-->STOMP or vice versa.
I expect I might have misunderstood some of the concepts, and a "you're going in a wrong direction, do this instead" can work out as a good answer for me. At the time of writing, I expect I will have to create an ActiveMQ plugin using their Message Transformer interface (http://activemq.apache.org/message-transformation.html) although their sub links are 404. I hope to achieve a more simple solution, e.g. an existing OpenWire-->STOMP transformer:
<transportConnector name="openwire" uri="{some-openwire-uri}?transport.transformer=stomp"/>
ActiveMQ will "transform" any Openwire message into a STOMP message and vice versa as needed based on client connections. I an Openwire based JMS client connects and places a message onto a queue and a STOMP based client comes along and subscribes to that queue the message will be converted into a STOMP message to send to that client.
Without knowing more about what issue you are having it is hard to provide more insight than that though. There are some cases where the transformation from Openwire to STOMP might not yield exactly the right thing for you such as a MapMessage or StreamMessage and definitely an ObjectMessage so some care needs to be taken about cross protocol messaging.
You do of course need to add a transport connector for each of the protocols you want to support, Openwire, STOMP, AMQP etc. The clients need something to connect to, then once they connect the broker manages the message transformations amongst subscriptions on Topics and Queues.
Related
I'm building a spring-websocket application that currently uses RabbitMQ as a message broker via the STOMP protocol. The rest of our organization mostly uses IBM Websphere MQ as a message broker, so we'd like to convert it away from RabbitMQ. However Websphere MQ doesn't support the STOMP protocol, which is spring-websocket's default. MQTT seems like the easiest supported protocol to use instead. Ideally our front-end web clients will continue to use STOMP, but I'm also OK with migrating them to MQTT if needed.
What classes do I need to overwrite to make spring-websocket interface with the broker via MQTT instead of STOMP? This article provides some general guidance that I should extend AbstractMessageBrokerConfiguration, but I'm unclear where to begin.
Currently I'm using the standard configuration methods: registry.enableStompBrokerRelay and registerStompEndpoints in AbstractWebSocketMessageBrokerConfigurer
Ryan has some good pointers.
The main work is going to be creating a replacement for StompBrokerRelayMessageHandler with an MqttBrokerMessageHandler that not only talks to an MQTT broker but also adapts client STOMP frames to MQTT and vice versa. The protocols are similar enough that it may be possible to find common ground but you won't know until you try.
Note that we did have plans for for MQTT support https://jira.spring.io/browse/SPR-12581 but the key issue was that SockJS which is required over the Web for fallback support does not support binary messages.
Here's my stab at this after reviewing the spring-websocket source code:
Change WebSocketConfig:
Remove #EnableWebSocketMessageBroker
Add new annotation: #EnableMqttWebSocketMessageBroker
Create MqttBrokerMessageHandler that extends AbstractBrokerMessageHandler -- suggest we copy and edit StompBrokerRelayMessageHandler
Create a new class that EnableMqttWebSocketMessageBroker imports: DelegatingMqttWebSocketMessageBrokerConfiguration
DelegatingMqttWebSocketMessageBrokerConfiguration extends AbstractMessageBrokerConfiguration directly and routes to MqttBrokerMessageHandler
Add this to server.xml on WebSphere Liberty:
<feature>websocket-1.1</feature>
we are using ActiveMQ for message Queuing with openwire transport.In this context there will be one producer and one consumer with a message listener registered. We heard about MQTT protocol and its support in activeMQ. But i saw examples only for Publisher/subscriber semantics , where subscriber need to call receive method explicitly to get the published message. Can I use mqtt with Producer/Consumer envirnment. Please give a sample..
The MQTT protocol is based a publish / subscribe based model, it has no queuing semantics built into the protocol. If you need Queue's then you need to stick to openwire clients or use a STOMP based client which supports both Topics and Queues.
RabbitMQ supports multiple protocols, AMQP, MQTT, STOMP, ....
When using PHP for example, it's easier to publish using the STOMP library since the PHP AMQP libraries requires compiled C code and is somewhat of a mission to setup if you don't have to.
On the JAVA side, apache camel with AMQP on spring is pretty straight forward.
Is it possible to setup a queue, publish to it via STOMP and then consume via AMQP and then again publish via AMQP and consume via STOMP if the message broker is RabbitMQ?
Yes, this should work, given that you have installed RabbitMQ's STOMP plugin on your RabbitMQ node(s).
The protocol only defines the communication between client and server and has no impact on a message itself.
You should note that using protocols other than AMQP will most likely come along with limitations and/or worse performance.
There also exist native PHP libraries for RabbitMQ that don't require compiling C code. Unfortunately, I cannot tell you which one is the best, because I am a Java guy ;-).
I'm currently in the middle of developing a webapplication which needs a websocket connection to receive notifications of events from the server.
The clients are separated in groups and all the clients in a group must receive the same event notifications.
I thought that ActiveMQ could probably support this model, using different queues for each group of clients. It would also be relatively easy to push events to ActiveMQ using stomp, and then use stomp-over-websockets for the clients.
The problem I see is that messages should not be consumed by only one client, but distributed to all the clients connected to the queue.
Also the queue should not be stored. If a client is not connected when the event is generated, then it will never receive it.
I don't know ActiveMQ that much, so I'm not sure if this is possible or if there is another easy solution that could be used instead of writing my own message server.
Thanks
ActiveMQ 5.4.1 supports WebSockets natively (just like Stomp, JMS, etc.).
There is the concept of queues (you mentioned these), but also of topics.
In a queue, a single message will be received by exactly one consumer, in a topic
it goes to all the subscribers. See: http://activemq.apache.org/how-does-a-queue-compare-to-a-topic.html
There are some Stomp-WebSocket JS libraries floating around. Kaazing has a bundle that includes ActiveMQ and supports JMS API/Stomp protocol over WebSockets with support for older browsers, different client technologies, and Cross-Site security.
Look at Pusher, otherwise you'll need something that supports topic based pub/sub. You could look at Redis or RabbitMQ
I'm developing a STOMP binding for Ada, which is working fine utilizing TCP/IP as the transport between the client and an ActiveMQ server configured as a STOMP broker. I thought to support UDP as well (i.e. STOMP over UDP), however, the lack of pertinent information in the ActiveMQ documentation or in web searches suggests to me that this isn't possible, and perhaps it doesn't even make any sense :-)
Confirmation one way or the other (and an ActiveMQ configuration excerpt if this is possible) would be appreciated.
this is not implemented in ActiveMQ at the moment as Stomp transport uses TCP only. It is possible to implement, so if you have a time to do it, give it a try.