For a Spring Framework app working with ActiveMQ and with/without WebSocket
The requirement is prior to send any message to a Topic a check should be done about Number Of Consumers, if it returns 1 the message can be sent safely. If it returns 0, the message can't be sent.
The clients could be come from websocket and consider there is no durable subscription. Thus if a message is sent, and there are no clients, the message arrives to the Topic and practically is lost (never consumed) and Messages Enqueued increments +1
I already did a research and I have read the following:
JMSTemplate check if topic exists and get subscriber count
Notify ActiveMQ producer if consumer on the destination is down
ActiveMQ get number of consumers listening to a topic from java
Detect change in Consumers of an ActiveMQ topic
Practically all is based on Advisory Message. I already have read:
Advisory Message
Handling Advisory Messages
Apache ActiveMQ Advisory Example
I understand that if exists a Topic named abc.xyz then ActiveMQ creates ActiveMQ.Advisory.Consumer.Topic.abc.xyz, until here I am ok with this pattern. I can confirm this approach through ActiveMQ Web Console
What is confuse for me is that practically all the examples available from the previous links works around creating a Session and uses mostly the onMessage method. For the latter I know it works how a listener.
Question 01: Thus who is expected to call that ActiveMQ.Advisory.Consumer.Topic.abc.xyz? It to trigger that onMessage method? That is my confusion.
What I need is work with the Spring Framework API (The app is already working and running with a CachingConnectionFactory, thus a Connection can be retrieved and other #Beans about infrastructure about ActiveMQ) and get access to that ActiveMQ.Advisory.Consumer.Topic.abc.xyz destination and retrieve the Number Of Consumers value.
Note: even when exists ActiveMQTopic declared with #Bean and is possible to retrieve that Destination for some #Component, sadly the API does not offer a method such getConsumers().
Question 02: How can be accomplished this?
I am assuming the JMS API for 2.0.x could help perhaps in someway.
Related
I am developing an application in which I have jms message queue.
There is a producer which enqueue message to the queue and a consumer to dequeue the message.
There might be cases when consumer is not running. If a message is not consumed by the consumer within a certain amount of time I need to catch that from producer.
I want to use JMX to monitor message queue's message whether it is expired.
Any suggestion or sample code how to this.....
It depends on the JMX implementer... Some servers provide JMX implementations to monitor its resources. If its not provided, then you will need to write the JMX implementation that uses the API provided by the MQ implementer.
An easier way to solve this problem is to use the request-response pattern with expiry. The consumer needs to respond in a specified internal of time. If it can't then the message on the queue can expire. If the response is not received the producer can take further action. JMS selector with correlation ID can be used to relate the responses with the request.
This is not totally on JMS Queue handler test. So, continue reading.
We have an architecture where spring channel listens to a queue from ActiveMQ. The listener of this queue will receive messages and has a static list of sub-listeners (identified by unique subjects). All the messages will have some parameters including the subject to which this message has to be delivered.
SMSService will drop its messages to the activemq with a subject SEND_SMS. It will be listened either by some HTTP Service or SMPP Service. You can even design your own Listener and wire that as a spring component with the required "subject".
Problem:
There is a better chance that this internal subject might change. This doesn't even throw an explicit Runtime Exception when there are no listeners. Is there a way to test this message being actually received by the intended listener?
`
As tim Bish siad, your problem statement is much too vague.
Have you tried to create your own ActivemMQ interceptor (I do not know if it could be usefull for your problem)
I read the hornetQ documentation, confused a lot. Can someone give an exact example to create a JMS topic in hornetQ. I mean the xml configurations in hornetq-jms.xml and hornetq-configuration.xml. assume we have a topic named top and 2 subscribers named: sub1, sub2. what I get is that we should define two queues(one for each subscribers) and bind them to an address which is the topic name actually, but how the subscriber would know they should connect to which one?(They only know the topic name)
I think you are confused by the way HornetQ handles topics internaly in contrast to the way the JMS specification describes topics.
Let's start with the JMS specification. Here you have one topic, where n subscribers can listen to the messages, that will be published by a client. In JMS we talk only about the destination in singular, eg. we'll send a message to the topic, or the queue respectively.
HornetQ is a JMS Provider - a server that implements the JMS specification, so Java-clients can connect to it, and use the JMS-API. The JMS Provider might change, but the code should still work when using another JMS provider.
However, HornetQ does not distinguish internally the destinations (topic or queue), since it tries to be a generic messaging middleware. In HornetQ all topics or queues are implemented as "addresses" and "queues". When you use the HornetQ API (CoreAPI) instead of the JMS-API, you have to deal with such things. You should read the Address section in the HornetQ documentation:
In core, there is no concept of a Topic, Topic is a JMS only term.
Instead, in core, we just deal with addresses and queues.
For example, a JMS topic would be implemented by a single address to
which many queues are bound. Each queue represents a subscription of
the topic. A JMS Queue would be implemented as a single address to
which one queue is bound - that queue represents the JMS queue.
For an example how to use a topic with JMS via HornetQ, I stongly recommend the examples that come with HornetQ itself. After donwloading and extracting the hornetq archive, just go to the examples/jms/topic directory and see the readme.html for a brief overview how to implement and how to execute the example (mvn verify).
How to configure cluster of Consumers in ActiveMQ?
I created a simple embedded ActiveMQ application with two consumers of one Queue, consumers are working in separate threads. But when I send a message to the Queue, JMS delivers it to first consumer no matter how long it sleeps after receiving.
I think you're trying to explain that the first consumer is receiving all the messages. There is a FAQ entry for this type of problem available here:
http://activemq.apache.org/i-do-not-receive-messages-in-my-second-consumer.html
Bruce
I'm connecting to an IBM Websphere MQ and currently reading one message at a time using the method receive() from the object:
javax.jms.Message;
Is there a way to retrieve multiple messages from the queue in one go?
Many thanks,
G.
Depends on whether you make a distinction between "read" and "retrieve".
From a JMS perspective, no. The API will return one message per method call.
From the WMQ perspective, yes - provided the client and queue manager are both at v7 and the messages are non-persistent or being browsed. In this case you can enable read-ahead in the managed object definition or dynamically at run time. The queue manager will stream several messages off of the queue and deliver them to the application before the first one is acknowledged. For more information on this, see Using read ahead with WebSphere MQ classes for JMS.