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.
Related
I've got a Java application that uses RabbitMQ. This application creates a TOPIC exchange and pushes messages to the TOPIC with its own routing key. From this way if I want the data from any application I create a queue binding with the exchange TOPIC and the routing key I want to.
I want to do the same thing by using a Java application with Qpid JMS as the client and ActiveMQ as the server. The information says it's possible, but I don't know how. I cannot found a specific example seems to RabbitMQ. I can create queues but I don't know how to create the exchange and the binding. What steps should I follow to achieve it?
You might consider using ActiveMQ Artemis instead of ActiveMQ 5.x as the address model of Artemis is much more similar to RabbitMQ's than 5.x's address model (which is more JMS-centric).
As far as JMS goes I think what you need is:
A topic. This is analogous to the "exchange" from RabbitMQ. Any message sent to a JMS topic is delivered to every subscriber. It's basic publish/subscribe semantics.
A topic subscriber with a selector. As noted in #1, every subscriber on a topic will get any message sent to that topic, but a JMS "selector" can be used to filter messages similar to the routing key in RabbitMQ.
An agreed-upon key for a message property. In order to create a viable selector for the topic subscriber the producer and the subscriber must agree upon the property key to filter on.
If each subscription is going to have lots of messages and those messages need to be shared among multiple subscribers/consumers (e.g. for load-balancing/distribution) then you will need to use a JMS "shared subscription." However, shared subscriptions are only part of JMS 2 and only ActiveMQ Artemis implements JMS 2. You can't use ActiveMQ 5.x with JMS shared subscriptions as it only supports JMS 1.1.
Both ActiveMQ 5.x and ActiveMQ Artemis create server-side resources (e.g. topics, queues, etc.) on-demand by default so all you need to do is write your JMS application.
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.
I understand that every messaging platform (rabbitmq, activemq) provides some mechanism that guarantees message delivery between the server (rabbitmq) and the consumers, so if a consumer is down, the message will still be in a queue and redelivered. But what happens in case the messaging platform is down and the client (producer of the message) could not deliver the message to the platform (Rabbitmq)? In that case, a retry method to redeliver the message is needed, but I'm not sure if I have to implement it myself, or clients libraries have this option , is it declared as a parameter in the connection/channel creation? is it platform specific? Also, protocols like AMQP specifies this? I heard also from Spring Retry as a option.
A spring-retry RetryTemplate can be wired directly into Spring AMQP's RabbitTemplate.
Kafka has retry capability built into the Producer (see the retries property).
For JMS, you can wrap the JmsTemplate into a RetryTemplate.execute() method.
The retry policy, back-off etc is all configurable.
I was fiddling with MQTT brokers and created channels and subscribed to them. Today I log into my RabbitMq interface and I find two queues titled
mqtt-subscription-1qos1 and mqtt-subscription-2qos1. I was very confused because I don't know how the two relate to each other.
Is MQTT built on top of AMQP so thats why it creates queues?
To answer the question in the subject, No MQTT is it's own independent protocol and has nothing to do with AMQP.
RabbitMQ's implementation of MQTT may make use of queues for clients subscribing to topics at QOS 1/2 in order to ensure those messages are delivered when the client is offline and also to ensure the messages are delivered in order.
I am using RabbitMQ as a Stomp broker for Spring Websocket application. The client uses SockJS library to connect to the websocket interface.
Every queue created on the RabbitMQ by the Spring is durable while topics are non durable. Is there any way to make the queues non durable as well?
I do not think I can configure on the application side. I played a bit with RabbitMQ configuration but could not set it up either.
Example destination on RabbitMQ used for SUBSCRIBE and SEND:
services-user-_385b304f-7a8f-4cf4-a0f1-d6ceed6b8c92
It will be possible to specify properties for endpoints as of RabbitMQ 3.6.0 according to comment in RabbitMQ issues - https://github.com/rabbitmq/rabbitmq-stomp/issues/24#issuecomment-137896165:
as of 3.6.0, it will be possible to explicitly define properties for endpoints such as /topic/ and /queue using subscription headers: durable, auto-delete, and exclusive, respectively.
As a workaround you can try to create queues by your own using AMQP protocol and then refer to that queues from STOMP protocol.