ActiveMQ supports advisory messages which allows you to watch the system using regular JMS messages. Currently we have advisory messages that support:
- consumers, producers and connections starting and stopping
- temporary destinations being created and destroyed
- messages expiring on topics and queues
- brokers sending messages to destinations with no consumers.
- connections starting and stopping
Advisory messages can be thought as some kind of administrative channel where you receive information regarding what is happening on your JMS provider along with what's happening with producers, consumers and destinations. When you look at a broker via JMX you will see the advisory topics prefixed with ActiveMQ.Advisory..
Every Advisory has the message type 'Advisory' and some predefined message properties:
Property | Type | Description | Version |
|---|
originBrokerId
| StringProperty
| The id of the broker where the advisory originated. | 5.x |
originBrokerName
| StringProperty
| The name of the broker where the advisory originated. | 5.x |
originBrokerURL
| StringProperty
| The first URL of the broker where the advisory originated. | 5.2 |
In addition, some messages carry a Command object, which carries additional information about the nature of the advisory, e.g., a subscription to each of the destination returns an ActiveMQMessage. Specific DataStructure objects, e.g.,. ConsumerInfo, ProducerInfo, ConnectionInfo can be retrieved using ActiveMQMessage.getDataStructure().
For example:
Destination advisoryDestination = AdvisorySupport.getProducerAdvisoryTopic(destination)
MessageConsumer consumer = session.createConsumer(advisoryDestination);
consumer.setMessageListener(this);
public void onMessage(Message msg){
if(msg instanceof ActiveMQMessage) {
try {
ActiveMQMessage aMsg = (ActiveMQMessage)msg;
ProducerInfo prod = (ProducerInfo) aMsg.getDataStructure();
}
catch(JMSException e) {
log.error("Failed to process message: " + msg);
}
}
}
The following advisory topics are supported
Client based advisories
Advisory Topics | Description | Properties | Data Structure |
|---|
ActiveMQ.Advisory.Connection
| Connection start & stop messages. | | ConnectionInfo, RemoveInfo
|
ActiveMQ.Advisory.Producer.Queue
| Producer start & stop messages on a Queue. | String='producerCount' - the number of producers
| ProducerInfo
|
ActiveMQ.Advisory.Producer.Topic
| Producer start & stop messages on a Topic. | String='producerCount' - the number of producers
| ProducerInfo
|
ActiveMQ.Advisory.Consumer.Queue
| Consumer start & stop messages on a Queue. | String='consumerCount' - the number of Consumers
| ConnectionInfo, RemoveInfo
|
ActiveMQ.Advisory.Consumer.Topic
| Consumer start & stop messages on a Topic. | String='consumerCount' - the number of Consumers
| ConnectionInfo, RemoveInfo
|
Note that the consumer start/stop advisory messages also have a consumerCount header to indicate the number of active consumers on the destination when the advisory message was sent. This means you can use the following selector to be notified when there are no active consumers on a given destination:
Destination and Message based advisories
Advisory Topics | Description | Properties | Data Structure | Default | PolicyEntry Property |
|---|
ActiveMQ.Advisory.Queue
| Queue create & destroy. | null
| DestinationInfo
| true
| none
|
ActiveMQ.Advisory.Topic
| Topic create & destroy. | null
| DestinationInfo
| true
| none
|
ActiveMQ.Advisory.TempQueue
| Temporary Queue create & destroy. | null
| DestinationInfo
| true
| none
|
ActiveMQ.Advisory.TempTopic
| Temporary Topic create & destroy. | null
| DestinationInfo
| true
| none
|
ActiveMQ.Advisory.Expired.Queue
| Expired messages on a Queue. | String='orignalMessageId' - the expired id
| Message
| true
| none
|
ActiveMQ.Advisory.Expired.Topic
| Expired messages on a Topic. | String='orignalMessageId' - the expired id
| Message
| true
| none
|
ActiveMQ.Advisory.NoConsumer.Queue
| No consumer is available to process messages being sent on a Queue. | null
| Message
| false
| sendAdvisoryIfNoConsumers
|
ActiveMQ.Advisory.NoConsumer.Topic
| No consumer is available to process messages being sent on a Topic. | null
| Message
| false
| sendAdvisoryIfNoConsumers
|
New advisories in version 5.2
Advisory Topics | Description | Properties | Data Structure | Default | PolicyEntry Property |
|---|
ActiveMQ.Advisory.SlowConsumer.Queue
| Slow Queue Consumer. | String='consumerId' - the consumer id
| ConsumerInfo
| false
| advisoryForSlowConsumers
|
ActiveMQ.Advisory.SlowConsumer.Topic
| Slow Topic Consumer. | String='consumerId' - the consumer id
| ConsumerInfo
| false
| advisoryForSlowConsumers
|
ActiveMQ.Advisory.FastProducer.Queue
| Fast Queue producer. | String='producerId' - the producer id
| ProducerInfo
| false
| advisdoryForFastProducers
|
ActiveMQ.Advisory. FastProducer.Topic
| Fast Topic producer. | String='consumerId'' - the producer id
| ProducerInfo
| false
| advisdoryForFastProducers
|
ActiveMQ.Advisory.MessageDiscarded.Queue
| Message discarded. | String='orignalMessageId' - the discarded id
| Message
| false
| advisoryForDiscardingMessages
|
ActiveMQ.Advisory.MessageDiscarded.Topic
| Message discarded. | String='orignalMessageId' - the discarded id
| Message
| false
| advisoryForDiscardingMessages
|
ActiveMQ.Advisory.MessageDelivered.Queue
| Message delivered to the broker. | String='orignalMessageId' - the delivered id
| Message
| false
| advisoryForDelivery
|
ActiveMQ.Advisory.MessageDelivered.Topic
| Message delivered to the broker. | String='orignalMessageId' - the delivered id
| Message
| false
| advisoryForDelivery
|
ActiveMQ.Advisory.MessageConsumed.Queue
| Message consumed by a client. | String='orignalMessageId' - the delivered id
| Message
| false
| advisoryForConsumed
|
ActiveMQ.Advisory.MessageConsumed.Topic
| Message consumed by a client. | String='orignalMessageId' - the delivered id
| Message
| false
| advisoryForConsumed
|
ActiveMQ.Advisory.FULL
| A Usage resource is at its limit. | String='usageName' - the name of Usage resource
| null
| false
| advisoryWhenFull
|
ActiveMQ.Advisory.MasterBroker
| A broker is now the master in a master/slave configuration. | null
| null
| true
| none
|
New Advisories in 5.4
Advisory Topics | Description | Properties | Data Structure | Default | PolicyEntry Property |
|---|
ActiveMQ.Advisory.MessageDLQd.Queue
| Message sent to DLQ. | String='orignalMessageId' - the delivered id
| Message
| Always on | advisoryForConsumed
|
ActiveMQ.Advisory.MessageDLQd.Topic
| Message sent to DLQ. | String='orignalMessageId' - the delivered id
| Message
| Always on | advisoryForConsumed
|
Network bridge advisories
Starting with ActiveMQ version 5.5 you can watch advisory topics for events related to the status of network bridges. You can get advisory messages when the network bridge is started or stopped.
Advisory Topics | Description | Properties | Data Structure | Default |
|---|
ActiveMQ.Advisory.NetworkBridge
| Network bridge being stopped or started. | Boolean="started" - true if bridge is started, false if it is stopped.
Boolean="createdByDuplex" - true if the bridge is created by remote network connector.
| BrokerInfo - provides data of the remote broker
| Always on |
Enabling Advisories Disabled by Default
The advisories that are not turned on by default (see the last column) can be enabled on a PolicyEntry in the ActiveMQ Broker Configuration, e.g., to enable a message consumed advisory you can configure the following:
<destinationPolicy>
<policyMap>
<policyEntries>
<policyEntry topic=">" advisoryForConsumed="true"/>
</policyEntries>
</policyMap>
</destinationPolicy>
Disabling Advisory Messages
The use of advisory messages incurs a small overhead in terms of memory and connection resources that is related to the number of destinations in your system. In some cases it can make sense to disable all advisories.
Advisories need to be disabled both on the Broker, via XML Configuration
<broker advisorySupport="false">
or from java code:
BrokerService broker = new BrokerService();
broker.setAdvisorySupport(false);
// ...
broker.start();
and on your ActiveMQConnectionFactory (because a subscription to an advisory topic will auto create it) via the brokerUrl:
tcp://localhost:61616?jms.watchTopicAdvisories=false
or via java code using the watchTopicAdvisories attribute on the ActiveMQConnectionFactory.
ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory();
factory.setWatchTopicAdvisories(false);
Using the Destinations
All of the above destinations are really prefixes which are appended with important information (like the actual topic or queue, the client ID, producer ID, consumer ID etc). This allows you to reuse the power of publish/subscribe, Wildcards and Selectors to filter the advisory messages as you see fit.
For example if you want to subscribe to expired messages on a topic FOO.BAR you could subscribe to ActiveMQ.Advisory.Expired.Topic.FOO.BAR. To subscribe to all messages of a certain kind of advisory just append .> to the topic, e.g., to subscribe to all the consumers starting and stopping to topics and queues subscribe to ActiveMQ.Advisory.Consumer..>.
Helper Methods
Methods to get the advisory destination objects are available in AdvisorySupport through the following methods.
AdvisorySupport.getConsumerAdvisoryTopic()
AdvisorySupport.getProducerAdvisoryTopic()
AdvisorySupport.getExpiredTopicMessageAdvisoryTopic()
AdvisorySupport.getExpiredQueueMessageAdvisoryTopic()
AdvisorySupport.getNoTopicConsumersAdvisoryTopic()
AdvisorySupport.getNoQueueConsumersAdvisoryTopic()
AdvisorySupport.getDestinationAdvisoryTopic()
AdvisorySupport.getExpiredQueueMessageAdvisoryTopic()
AdvisorySupport.getExpiredTopicMessageAdvisoryTopic()
AdvisorySupport.getNoQueueConsumersAdvisoryTopic()
AdvisorySupport.getNoTopicConsumersAdvisoryTopic()
// Version 5.2 on:
AdvisorySupport.getSlowConsumerAdvisoryTopic()
AdvisorySupport.getFastProducerAdvisoryTopic()
AdvisorySupport.getMessageDiscardedAdvisoryTopic()
AdvisorySupport.getMessageDeliveredAdvisoryTopic()
AdvisorySupport.getMessageConsumedAdvisoryTopic()
AdvisorySupport.getMasterBrokerAdvisoryTopic()
AdvisorySupport.getFullAdvisoryTopic()
Some helper classes to deal with advisory messages are available in the advisories package.