I am using ActiveMQ messaging broker and I have a requirement where the producer application would want to know if the consumer application consuming on the particular destination is up or not?
How can I achieve this?
Thanks!
You should checkout Advisory messages. It's a topic you can subscribe to if you want updates on such events.
Specifically the topic: ActiveMQ.Advisory.NoConsumer.Queue should be of interest. You need to enable it broker side though using the destination policy property: sendAdvisoryIfNoConsumers.
You can do that by using java code as follows:
Destination class has a method getConsumers() which will return List of Subscriptions to that destination,and it will in turn give you consumer information, by this you can check whether your required consumer is active or not.
Good luck!
Related
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.
I am trying to use a queue in activemq to dequeue messages from a virtual topic. I tried sending some messages and it is showing up in the topic under "message enqueued" but it is not able to be consumed.
The virtual topic name that i created was VirtualTopic.AA and the consumer is called Consumer.client1.VirtualTopic.AA.
In the consumer.client1.VirtualTopic.AA, i can see that there is a consumer but it is just not able to dequeue messages from the virtual topic.
Anyone knows why this is happening ? Do i need to change some settings in the configuration in the xml file ?
When you publish to a virtual topic using Spring's JmsTemplate, you need to configure it for a topic by setting the pubSubDomain property to "true".
From the JmsTemplate documentation:
If you want to use dynamic destination creation, you must specify the type of JMS destination to create, using the "pubSubDomain" property. For other operations, this is not necessary. Point-to-Point (Queues) is the default domain.
And in JmsDestinationAccessor#setPubSubDomain:
pubSubDomain - "true" for the Publish/Subscribe domain (Topics), "false" for the Point-to-Point domain (Queues)
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.
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.
Can anybody point out a reference on how to implement
a single consumer multiple producer in activemq? Or could give a very simple implementation.
This will be very helpful.
Thanks
Matt Raible's AppFuse project is a good skeleton project which is implemented using different libraries. You can pick the one which uses Spring and introduce ActiveMQ as Bharati Raja has explained in his blog post jms with appfuse1x.
There is no special implementation required for this. This is the core business of MessageBrokers. The only thing you need to make sure of:
If you decide to give an ID to your producers, make sure they are different from each other.. You cannot have multiple producers with the same ID. Same goes for consumers.
If you need to guarantee that a message can be consumed by only one consumer, then this is the point-to-point communication model which can be implemented using a JMS Queue in ActiveMQ.
Many producers can send messages to the same queue. Only one active consumer will receive a message from the queue.