- Introduction
- 1. Legal Notice
- 2. Preface
- 3. Project Info
- 4. Messaging Concepts
- 5. Architecture
- 6. Using the Server
- 7. Using JMS
- 8. Using Core
- 9. Mapping JMS Concepts to the Core API
- 10. The Client Classpath
- 11. Examples
- 12. Routing Messages With Wild Cards
- 13. Understanding the Apache ActiveMQ Artemis Wildcard Syntax
- 14. Filter Expressions
- 15. Persistence
- 16. Configuring Transports
- 17. Detecting Dead Connections
- 18. Detecting Slow Consumers
- 19. Resource Manager Configuration
- 20. Flow Control
- 21. Guarantees of sends and commits
- 22. Message Redelivery and Undelivered Messages
- 23. Message Expiry
- 24. Large Messages
- 25. Paging
- 26. Queue Attributes
- 27. Scheduled Messages
- 28. Last-Value Queues
- 29. Message Grouping
- 30. Extra Acknowledge Modes
- 31. Management
- 32. Security
- 33. Resource Limits
- 34. The JMS Bridge
- 35. Client Reconnection and Session Reattachment
- 36. Diverting and Splitting Message Flows
- 37. Core Bridges
- 38. Duplicate Message Detection
- 39. Clusters
- 40. High Availability and Failover
- 41. Graceful Server Shutdown
- 42. Libaio Native Libraries
- 43. Thread management
- 44. Logging
- 45. REST Interface
- 46. Embedding Apache ActiveMQ Artemis
- 47. Spring Integration
- 48. AeroGear Integration
- 49. VertX Integration
- 50. Intercepting Operations
- 51. Protocols and Interoperability
- 52. Tools
- 53. Maven Plugin
- 54. Troubleshooting and Performance Tuning
- 55. Configuration Reference
- Published with GitBook

# ActiveMQ Artemis Documentation

# Management

Apache ActiveMQ Artemis has an extensive management API that allows a user to modify a server configuration, create new resources (e.g. JMS queues and topics), inspect these resources (e.g. how many messages are currently held in a queue) and interact with it (e.g. to remove messages from a queue). All the operations allows a client to manage Apache ActiveMQ Artemis. It also allows clients to subscribe to management notifications.

There are 3 ways to manage Apache ActiveMQ Artemis:

- Using JMX -- JMX is the standard way to manage Java applications

- Using the core API -- management operations are sent to Apache ActiveMQ Artemis server using core messages

- Using the JMS API -- management operations are sent to Apache ActiveMQ Artemis server using JMS messages

Although there are 3 different ways to manage Apache ActiveMQ Artemis each API supports the same functionality. If it is possible to manage a resource using JMX it is also possible to achieve the same result using Core messages or JMS messages.

This choice depends on your requirements, your application settings and your environment to decide which way suits you best.

## The Management API

Regardless of the way you invoke management operations, the management API is the same.

For each managed resource, there exists a Java interface describing what can be invoked for this type of resource.

Apache ActiveMQ Artemis exposes its managed resources in 2 packages:

- Core resources are located in the `org.apache.activemq.artemis.api.core.management` package

- JMS resources are located in the `org.apache.activemq.artemis.api.jms.management` package

The way to invoke a management operations depends whether JMX, core messages, or JMS messages are used.

> Note

> A few management operations requires a `filter` parameter to chose which messages are involved by the operation. Passing `null` or an empty string means that the management operation will be performed on all messages.

### Core Management API

Apache ActiveMQ Artemis defines a core management API to manage core resources. For full details of the API please consult the javadoc. In summary:

#### Core Server Management

- Listing, creating, deploying and destroying queues

  A list of deployed core queues can be retrieved using the `getQueueNames()` method.

  Core queues can be created or destroyed using the management operations `createQueue()` or `deployQueue()` or `destroyQueue()`)on the `ActiveMQServerControl` (with the ObjectName `org.apache.activemq.artemis:module=Core,type=Server` or the resource name `core.server`)

  `createQueue` will fail if the queue already exists while `deployQueue` will do nothing.

- Pausing and resuming Queues

  The `QueueControl` can pause and resume the underlying queue. When a queue is paused, it will receive messages but will not deliver them. When it's resumed, it'll begin delivering the queued messages, if any.

- Listing and closing remote connections

  Client's remote addresses can be retrieved using `listRemoteAddresses()`. It is also possible to close the connections associated with a remote address using the `closeConnectionsForAddress()` method.

  Alternatively, connection IDs can be listed using `listConnectionIDs()` and all the sessions for a given connection ID can be listed using `listSessions()`.

- Transaction heuristic operations

  In case of a server crash, when the server restarts, it it possible that some transaction requires manual intervention. The `listPreparedTransactions()` method lists the transactions which are in the prepared states (the transactions are represented as opaque Base64 Strings.) To commit or rollback a given prepared transaction, the `commitPreparedTransaction()` or `rollbackPreparedTransaction()` method can be used to resolve heuristic transactions. Heuristically completed transactions can be listed using the `listHeuristicCommittedTransactions()` and `listHeuristicRolledBackTransactions` methods.

- Enabling and resetting Message counters

  Message counters can be enabled or disabled using the `enableMessageCounters()` or `disableMessageCounters()` method. To reset message counters, it is possible to invoke `resetAllMessageCounters()` and `resetAllMessageCounterHistories()` methods.

- Retrieving the server configuration and attributes

  The `ActiveMQServerControl` exposes Apache ActiveMQ Artemis server configuration through all its attributes (e.g. `getVersion()` method to retrieve the server's version, etc.)

- Listing, creating and destroying Core bridges and diverts

  A list of deployed core bridges (resp. diverts) can be retrieved using the `getBridgeNames()` (resp. `getDivertNames()`) method.

  Core bridges (resp. diverts) can be created or destroyed using the management operations `createBridge()` and `destroyBridge()` (resp. `createDivert()` and `destroyDivert()`) on the `ActiveMQServerControl` (with the ObjectName `org.apache.activemq.artemis:module=Core,type=Server` or the resource name `core.server`).

- It is possible to stop the server and force failover to occur with any currently attached clients.

  to do this use the `forceFailover()` on the `ActiveMQServerControl` (with the ObjectName `org.apache.activemq.artemis:module=Core,type=Server` or the resource name `core.server`)

  > Note

  > Since this method actually stops the server you will probably receive some sort of error depending on which management service you use to call it.

#### Core Address Management

Core addresses can be managed using the `AddressControl` class (with the ObjectName `org.apache.activemq.artemis:module=Core,type=Address,name="<the address name>"` or the resource name `core.address.<the address name>`).

- Modifying roles and permissions for an address

  You can add or remove roles associated to a queue using the `addRole()` or `removeRole()` methods. You can list all the roles associated to the queue with the `getRoles()` method

#### Core Queue Management

The bulk of the core management API deals with core queues. The `QueueControl` class defines the Core queue management operations (with the ObjectName `org.apache.activemq.artemis:module=Core,type=Queue,address="<the bound address>",name="<the queue name>"` or the resource name `core.queue.<the queue name>`).

Most of the management operations on queues take either a single message ID (e.g. to remove a single message) or a filter (e.g. to expire all messages with a given property.)

- Expiring, sending to a dead letter address and moving messages

  Messages can be expired from a queue by using the `expireMessages()` method. If an expiry address is defined, messages will be sent to it, otherwise they are discarded. The queue's expiry address can be set with the `setExpiryAddress()` method.

  Messages can also be sent to a dead letter address with the `sendMessagesToDeadLetterAddress()` method. It returns the number of messages which are sent to the dead letter address. If a dead letter address is not defined, message are removed from the queue and discarded. The queue's dead letter address can be set with the `setDeadLetterAddress()` method.

  Messages can also be moved from a queue to another queue by using the `moveMessages()` method.

- Listing and removing messages

  Messages can be listed from a queue by using the `listMessages()` method which returns an array of `Map`, one `Map` for each message.

  Messages can also be removed from the queue by using the `removeMessages()` method which returns a `boolean` for the single message ID variant or the number of removed messages for the filter variant. The `removeMessages()` method takes a `filter` argument to remove only filtered messages. Setting the filter to an empty string will in effect remove all messages.

- Counting messages

  The number of messages in a queue is returned by the `getMessageCount()` method. Alternatively, the `countMessages()` will return the number of messages in the queue which match a given filter

- Changing message priority

  The message priority can be changed by using the `changeMessagesPriority()` method which returns a `boolean` for the single message ID variant or the number of updated messages for the filter variant.

- Message counters

  Message counters can be listed for a queue with the `listMessageCounter()` and `listMessageCounterHistory()` methods (see Message Counters section). The message counters can also be reset for a single queue using the `resetMessageCounter()` method.

- Retrieving the queue attributes

  The `QueueControl` exposes Core queue settings through its attributes (e.g. `getFilter()` to retrieve the queue's filter if it was created with one, `isDurable()` to know whether the queue is durable or not, etc.)

- Pausing and resuming Queues

  The `QueueControl` can pause and resume the underlying queue. When a queue is paused, it will receive messages but will not deliver them. When it's resume, it'll begin delivering the queued messages, if any.

#### Other Core Resources Management

Apache ActiveMQ Artemis allows to start and stop its remote resources (acceptors, diverts, bridges, etc.) so that a server can be taken off line for a given period of time without stopping it completely (e.g. if other management operations must be performed such as resolving heuristic transactions). These resources are:

- Acceptors

  They can be started or stopped using the `start()` or. `stop()` method on the `AcceptorControl` class (with the ObjectName `org.apache.activemq.artemis:module=Core,type=Acceptor,name="<the acceptor name>"` or the resource name `core.acceptor.<the address name>`). The acceptors parameters can be retrieved using the `AcceptorControl` attributes (see Understanding Acceptors)

- Diverts

  They can be started or stopped using the `start()` or `stop()` method on the `DivertControl` class (with the ObjectName `org.apache.activemq.artemis:module=Core,type=Divert,name=<the divert name>` or the resource name `core.divert.<the divert name>`). Diverts parameters can be retrieved using the `DivertControl` attributes (see Diverting and Splitting Message Flows))

- Bridges

  They can be started or stopped using the `start()` (resp. `stop()`) method on the `BridgeControl` class (with the ObjectName `org.apache.activemq.artemis:module=Core,type=Bridge,name="<the bridge name>"` or the resource name `core.bridge.<the bridge name>`). Bridges parameters can be retrieved using the `BridgeControl` attributes (see Core bridges)

- Broadcast groups

  They can be started or stopped using the `start()` or `stop()` method on the `BroadcastGroupControl` class (with the ObjectName `org.apache.activemq.artemis:module=Core,type=BroadcastGroup,name="<the broadcast group name>"` or the resource name `core.broadcastgroup.<the broadcast group name>`). Broadcast groups parameters can be retrieved using the `BroadcastGroupControl` attributes (see Clusters)

- Discovery groups

  They can be started or stopped using the `start()` or `stop()` method on the `DiscoveryGroupControl` class (with the ObjectName `org.apache.activemq.artemis:module=Core,type=DiscoveryGroup,name="<the discovery group name>"` or the resource name `core.discovery.<the discovery group name>`). Discovery groups parameters can be retrieved using the `DiscoveryGroupControl` attributes (see Clusters)

- Cluster connections

  They can be started or stopped using the `start()` or `stop()` method on the `ClusterConnectionControl` class (with the ObjectName `org.apache.activemq.artemis:module=Core,type=ClusterConnection,name="<the cluster connection name>"` or the resource name `core.clusterconnection.<the cluster connection name>`). Cluster connections parameters can be retrieved using the `ClusterConnectionControl` attributes (see Clusters)

### JMS Management API

Apache ActiveMQ Artemis defines a JMS Management API to manage JMS administrated objects (i.e. JMS queues, topics and connection factories).

#### JMS Server Management

JMS Resources (connection factories and destinations) can be created using the `JMSServerControl` class (with the ObjectName `org.apache.activemq.artemis:module=JMS,type=Server` or the resource name `jms.server`).

- Listing, creating, destroying connection factories

  Names of the deployed connection factories can be retrieved by the `getConnectionFactoryNames()` method.

  JMS connection factories can be created or destroyed using the `createConnectionFactory()` methods or `destroyConnectionFactory()` methods. These connection factories are bound to JNDI so that JMS clients can look them up. If a graphical console is used to create the connection factories, the transport parameters are specified in the text field input as a comma-separated list of key=value (e.g. `key1=10, key2="value", key3=false`). If there are multiple transports defined, you need to enclose the key/value pairs between curly braces. For example `{key=10}, {key=20}`. In that case, the first `key` will be associated to the first transport configuration and the second `key` will be associated to the second transport configuration (see Configuring Transports for a list of the transport parameters)

- Listing, creating, destroying queues

  Names of the deployed JMS queues can be retrieved by the `getQueueNames()` method.

  JMS queues can be created or destroyed using the `createQueue()` methods or `destroyQueue()` methods. These queues are bound to JNDI so that JMS clients can look them up

- Listing, creating/destroying topics

  Names of the deployed topics can be retrieved by the `getTopicNames()` method.

  JMS topics can be created or destroyed using the `createTopic()` or `destroyTopic()` methods. These topics are bound to JNDI so that JMS clients can look them up

- Listing and closing remote connections

  JMS Clients remote addresses can be retrieved using `listRemoteAddresses()`. It is also possible to close the connections associated with a remote address using the `closeConnectionsForAddress()` method.

  Alternatively, connection IDs can be listed using `listConnectionIDs()` and all the sessions for a given connection ID can be listed using `listSessions()`.

#### JMS ConnectionFactory Management

JMS Connection Factories can be managed using the `ConnectionFactoryControl` class (with the ObjectName `org.apache.activemq.artemis:module=JMS,type=ConnectionFactory,name="<the connection factory name>"` or the resource name `jms.connectionfactory.<the connection factory name>`).

- Retrieving connection factory attributes

  The `ConnectionFactoryControl` exposes JMS ConnectionFactory configuration through its attributes (e.g. `getConsumerWindowSize()` to retrieve the consumer window size for flow control, `isBlockOnNonDurableSend()` to know whether the producers created from the connection factory will block or not when sending non-durable messages, etc.)

#### JMS Queue Management

JMS queues can be managed using the `JMSQueueControl` class (with the ObjectName `org.apache.activemq.artemis:module=JMS,type=Queue,name="<the queue name>"` or the resource name `jms.queue.<the queue name>`).

The management operations on a JMS queue are very similar to the operations on a core queue.

- Expiring, sending to a dead letter address and moving messages

  Messages can be expired from a queue by using the `expireMessages()` method. If an expiry address is defined, messages will be sent to it, otherwise they are discarded. The queue's expiry address can be set with the `setExpiryAddress()` method.

  Messages can also be sent to a dead letter address with the `sendMessagesToDeadLetterAddress()` method. It returns the number of messages which are sent to the dead letter address. If a dead letter address is not defined, message are removed from the queue and discarded. The queue's dead letter address can be set with the `setDeadLetterAddress()` method.

  Messages can also be moved from a queue to another queue by using the `moveMessages()` method.

- Listing and removing messages

  Messages can be listed from a queue by using the `listMessages()` method which returns an array of `Map`, one `Map` for each message.

  Messages can also be removed from the queue by using the `removeMessages()` method which returns a `boolean` for the single message ID variant or the number of removed messages for the filter variant. The `removeMessages()` method takes a `filter` argument to remove only filtered messages. Setting the filter to an empty string will in effect remove all messages.

- Counting messages

  The number of messages in a queue is returned by the `getMessageCount()` method. Alternatively, the `countMessages()` will return the number of messages in the queue which match a given filter

- Changing message priority

  The message priority can be changed by using the `changeMessagesPriority()` method which returns a `boolean` for the single message ID variant or the number of updated messages for the filter variant.

- Message counters

  Message counters can be listed for a queue with the `listMessageCounter()` and `listMessageCounterHistory()` methods (see Message Counters section)

- Retrieving the queue attributes

  The `JMSQueueControl` exposes JMS queue settings through its attributes (e.g. `isTemporary()` to know whether the queue is temporary or not, `isDurable()` to know whether the queue is durable or not, etc.)

- Pausing and resuming queues

  The `JMSQueueControl` can pause and resume the underlying queue. When the queue is paused it will continue to receive messages but will not deliver them. When resumed again it will deliver the enqueued messages, if any.

#### JMS Topic Management

JMS Topics can be managed using the `TopicControl` class (with the ObjectName `org.apache.activemq.artemis:module=JMS,type=Topic,name="<the topic name>"` or the resource name `jms.topic.<the topic name>`).

- Listing subscriptions and messages

  JMS topics subscriptions can be listed using the `listAllSubscriptions()`, `listDurableSubscriptions()`, `listNonDurableSubscriptions()` methods. These methods return arrays of `Object` representing the subscriptions information (subscription name, client ID, durability, message count, etc.). It is also possible to list the JMS messages for a given subscription with the `listMessagesForSubscription()` method.

- Dropping subscriptions

  Durable subscriptions can be dropped from the topic using the `dropDurableSubscription()` method.

- Counting subscriptions messages

  The `countMessagesForSubscription()` method can be used to know the number of messages held for a given subscription (with an optional message selector to know the number of messages matching the selector)

## Using Management Via JMX

Apache ActiveMQ Artemis can be managed using JMX.

The management API is exposed by Apache ActiveMQ Artemis using MBeans interfaces. Apache ActiveMQ Artemis registers its resources with the domain `org.apache.activemq`.

For example, the `ObjectName` to manage a JMS Queue `exampleQueue` is:

    org.apache.activemq.artemis:module=JMS,type=Queue,name="exampleQueue"

and the MBean is:

    org.apache.activemq.artemis.api.jms.management.JMSQueueControl

The MBean's `ObjectName` are built using the helper class `org.apache.activemq.artemis.api.core.management.ObjectNameBuilder`. You can also use `jconsole` to find the `ObjectName` of the MBeans you want to manage.

Managing Apache ActiveMQ Artemis using JMX is identical to management of any Java Applications using JMX. It can be done by reflection or by creating proxies of the MBeans.

### Configuring JMX

By default, JMX is enabled to manage Apache ActiveMQ Artemis. It can be disabled by setting `jmx-management-enabled` to `false` in `broker.xml`:

    <!-- false to disable JMX management for Apache ActiveMQ Artemis -->
    <jmx-management-enabled>false</jmx-management-enabled>

If JMX is enabled, Apache ActiveMQ Artemis can be managed locally using `jconsole`.

> Note

> Remote connections to JMX are not enabled by default for security reasons. Please refer to Java Management guide to configure the server for remote management (system properties must be set in `run.sh` or `run.bat` scripts).

By default, Apache ActiveMQ Artemis server uses the JMX domain "org.apache.activemq.artemis". To manage several Apache ActiveMQ Artemis servers from the same MBeanServer, the JMX domain can be configured for each individual Apache ActiveMQ Artemis server by setting `jmx-domain` in `broker.xml`:

    <!-- use a specific JMX domain for ActiveMQ Artemis MBeans -->
    <jmx-domain>my.org.apache.activemq</jmx-domain>

#### MBeanServer configuration

When Apache ActiveMQ Artemis is run in standalone, it uses the Java Virtual Machine's `Platform MBeanServer` to register its MBeans. By default Jolokia is also deployed to allow access to the mbean server via rest.

### Example

See the chapters chapter for an example which shows how to use a remote connection to JMX and MBean proxies to manage Apache ActiveMQ Artemis.

### Exposing JMX using Jolokia

The default Broker configuration ships with the Jolokia http agent deployed as a Web Application. Jolokia is a remote JMX over HTTP bridge that exposed mBeans, for a full guids as to how to use refer to Jolokia Documentation, however a simple example to query thebrokers version would be to use a brower and go to the URL http://localhost:8161/jolokia/read/org.apache.activemq.artemis:module=Core,type=Server/Version.

This would give you back something like the following:

    {"timestamp":1422019706,"status":200,"request":{"mbean":"org.apache.activemq.artemis:module=Core,type=Server","attribute":"Version","type":"read"},"value":"1.0.0.SNAPSHOT (Active Hornet, 126)"}

## Using Management Via Core API

The core management API in ActiveMQ Artemis is called by sending Core messages to a special address, the management address.

Management messages are regular Core messages with well-known properties that the server needs to understand to interact with the management API:

- The name of the managed resource

- The name of the management operation

- The parameters of the management operation

When such a management message is sent to the management address, Apache ActiveMQ Artemis server will handle it, extract the information, invoke the operation on the managed resources and send a management reply to the management message's reply-to address (specified by `ClientMessageImpl.REPLYTO_HEADER_NAME`).

A `ClientConsumer` can be used to consume the management reply and retrieve the result of the operation (if any) stored in the reply's body. For portability, results are returned as a JSON String rather than Java Serialization (the `org.apache.activemq.artemis.api.core.management.ManagementHelper` can be used to convert the JSON string to Java objects).

These steps can be simplified to make it easier to invoke management operations using Core messages:

1. Create a `ClientRequestor` to send messages to the management address and receive replies

2. Create a `ClientMessage`

3. Use the helper class `org.apache.activemq.artemis.api.core.management.ManagementHelper` to fill the message with the management properties

4. Send the message using the `ClientRequestor`

5. Use the helper class `org.apache.activemq.artemis.api.core.management.ManagementHelper` to retrieve the operation result from the management reply

For example, to find out the number of messages in the core queue `exampleQueue`:

    ClientSession session = ...
    ClientRequestor requestor = new ClientRequestor(session, "jms.queue.activemq.management");
    ClientMessage message = session.createMessage(false);
    ManagementHelper.putAttribute(message, "core.queue.exampleQueue", "messageCount");
    session.start();
    ClientMessage reply = requestor.request(m);
    int count = (Integer) ManagementHelper.getResult(reply);
    System.out.println("There are " + count + " messages in exampleQueue");

Management operation name and parameters must conform to the Java interfaces defined in the `management` packages.

Names of the resources are built using the helper class `org.apache.activemq.artemis.api.core.management.ResourceNames` and are straightforward (`core.queue.exampleQueue` for the Core Queue `exampleQueue`, `jms.topic.exampleTopic` for the JMS Topic `exampleTopic`, etc.).

### Configuring Core Management

The management address to send management messages is configured in `broker.xml`:

    <management-address>jms.queue.activemq.management</management-address>

By default, the address is `jms.queue.activemq.management` (it is prepended by "jms.queue" so that JMS clients can also send management messages).

The management address requires a special user permission `manage` to be able to receive and handle management messages. This is also configured in broker.xml:

    <!-- users with the admin role will be allowed to manage -->
    <!-- Apache ActiveMQ Artemis using management messages        -->
    <security-setting match="jms.queue.activemq.management">
       <permission type="manage" roles="admin" />
    </security-setting>

## Using Management Via JMS

Using JMS messages to manage ActiveMQ Artemis is very similar to using core API.

An important difference is that JMS requires a JMS queue to send the messages to (instead of an address for the core API).

The management queue is a special queue and needs to be instantiated directly by the client:

    Queue managementQueue = ActiveMQJMSClient.createQueue("activemq.management");

All the other steps are the same than for the Core API but they use JMS API instead:

1. create a `QueueRequestor` to send messages to the management address and receive replies

2. create a `Message`

3. use the helper class `org.apache.activemq.artemis.api.jms.management.JMSManagementHelper` to fill the message with the management properties

4. send the message using the `QueueRequestor`

5. use the helper class `org.apache.activemq.artemis.api.jms.management.JMSManagementHelper` to retrieve the operation result from the management reply

For example, to know the number of messages in the JMS queue `exampleQueue`:

    Queue managementQueue = ActiveMQJMSClient.createQueue("activemq.management");

    QueueSession session = ...
    QueueRequestor requestor = new QueueRequestor(session, managementQueue);
    connection.start();
    Message message = session.createMessage();
    JMSManagementHelper.putAttribute(message, "jms.queue.exampleQueue", "messageCount");
    Message reply = requestor.request(message);
    int count = (Integer)JMSManagementHelper.getResult(reply);
    System.out.println("There are " + count + " messages in exampleQueue");

### Configuring JMS Management

Whether JMS or the core API is used for management, the configuration steps are the same (see Configuring Core Management section).

### Example

See the examples chapter for an example which shows how to use JMS messages to manage the Apache ActiveMQ Artemis server.

## Management Notifications

Apache ActiveMQ Artemis emits notifications to inform listeners of potentially interesting events (creation of new resources, security violation, etc.).

These notifications can be received by 3 different ways:

- JMX notifications

- Core messages

- JMS messages

### JMX Notifications

If JMX is enabled (see Configuring JMX section), JMX notifications can be received by subscribing to 2 MBeans:

- `org.apache.activemq.artemis:module=Core,type=Server` for notifications on Core resources

- `org.apache.activemq.artemis:module=JMS,type=Server` for notifications on JMS resources

### Core Messages Notifications

Apache ActiveMQ Artemis defines a special management notification address. Core queues can be bound to this address so that clients will receive management notifications as Core messages

A Core client which wants to receive management notifications must create a core queue bound to the management notification address. It can then receive the notifications from its queue.

Notifications messages are regular core messages with additional properties corresponding to the notification (its type, when it occurred, the resources which were concerned, etc.).

Since notifications are regular core messages, it is possible to use message selectors to filter out notifications and receives only a subset of all the notifications emitted by the server.

#### Configuring The Core Management Notification Address

The management notification address to receive management notifications is configured in `broker.xml`:

    <management-notification-address>activemq.notifications</management-notification-address>

By default, the address is `activemq.notifications`.

### JMS Messages Notifications

Apache ActiveMQ Artemis's notifications can also be received using JMS messages.

It is similar to receiving notifications using Core API but an important difference is that JMS requires a JMS Destination to receive the messages (preferably a Topic).

To use a JMS Destination to receive management notifications, you must change the server's management notification address to start with `jms.queue` if it is a JMS Queue or `jms.topic` if it is a JMS Topic:

    <!-- notifications will be consumed from "notificationsTopic" JMS Topic -->
    <management-notification-address>jms.topic.notificationsTopic</management-notification-address>

Once the notification topic is created, you can receive messages from it or set a `MessageListener`:

    Topic notificationsTopic = ActiveMQJMSClient.createTopic("notificationsTopic");

    Session session = ...
    MessageConsumer notificationConsumer = session.createConsumer(notificationsTopic);
    notificationConsumer.setMessageListener(new MessageListener()
    {
       public void onMessage(Message notif)
       {
          System.out.println("------------------------");
          System.out.println("Received notification:");
          try
          {
             Enumeration propertyNames = notif.getPropertyNames();
             while (propertyNames.hasMoreElements())
             {
                String propertyName = (String)propertyNames.nextElement();
                System.out.format("  %s: %s\n", propertyName, notif.getObjectProperty(propertyName));
             }
          }
          catch (JMSException e)
          {
          }
          System.out.println("------------------------");
       }
    });

### Example

See the examples chapter for an example which shows how to use a JMS `MessageListener` to receive management notifications from ActiveMQ Artemis server.

### Notification Types and Headers

Below is a list of all the different kinds of notifications as well as which headers are on the messages. Every notification has a `_AMQ_NotifType` (value noted in parentheses) and `_AMQ_NotifTimestamp` header. The timestamp is the un-formatted result of a call to `java.lang.System.currentTimeMillis()`.

- `BINDING_ADDED` (0)

  `_AMQ_Binding_Type`, `_AMQ_Address`, `_AMQ_ClusterName`, `_AMQ_RoutingName`, `_AMQ_Binding_ID`, `_AMQ_Distance`, `_AMQ_FilterString`

- `BINDING_REMOVED` (1)

  `_AMQ_Address`, `_AMQ_ClusterName`, `_AMQ_RoutingName`, `_AMQ_Binding_ID`, `_AMQ_Distance`, `_AMQ_FilterString`

- `CONSUMER_CREATED` (2)

  `_AMQ_Address`, `_AMQ_ClusterName`, `_AMQ_RoutingName`, `_AMQ_Distance`, `_AMQ_ConsumerCount`, `_AMQ_User`, `_AMQ_RemoteAddress`, `_AMQ_SessionName`, `_AMQ_FilterString`

- `CONSUMER_CLOSED` (3)

  `_AMQ_Address`, `_AMQ_ClusterName`, `_AMQ_RoutingName`, `_AMQ_Distance`, `_AMQ_ConsumerCount`, `_AMQ_User`, `_AMQ_RemoteAddress`, `_AMQ_SessionName`, `_AMQ_FilterString`

- `SECURITY_AUTHENTICATION_VIOLATION` (6)

  `_AMQ_User`

- `SECURITY_PERMISSION_VIOLATION` (7)

  `_AMQ_Address`, `_AMQ_CheckType`, `_AMQ_User`

- `DISCOVERY_GROUP_STARTED` (8)

  `name`

- `DISCOVERY_GROUP_STOPPED` (9)

  `name`

- `BROADCAST_GROUP_STARTED` (10)

  `name`

- `BROADCAST_GROUP_STOPPED` (11)

  `name`

- `BRIDGE_STARTED` (12)

  `name`

- `BRIDGE_STOPPED` (13)

  `name`

- `CLUSTER_CONNECTION_STARTED` (14)

  `name`

- `CLUSTER_CONNECTION_STOPPED` (15)

  `name`

- `ACCEPTOR_STARTED` (16)

  `factory`, `id`

- `ACCEPTOR_STOPPED` (17)

  `factory`, `id`

- `PROPOSAL` (18)

  `_JBM_ProposalGroupId`, `_JBM_ProposalValue`, `_AMQ_Binding_Type`, `_AMQ_Address`, `_AMQ_Distance`

- `PROPOSAL_RESPONSE` (19)

  `_JBM_ProposalGroupId`, `_JBM_ProposalValue`, `_JBM_ProposalAltValue`, `_AMQ_Binding_Type`, `_AMQ_Address`, `_AMQ_Distance`

- `CONSUMER_SLOW` (21)

  `_AMQ_Address`, `_AMQ_ConsumerCount`, `_AMQ_RemoteAddress`, `_AMQ_ConnectionName`, `_AMQ_ConsumerName`, `_AMQ_SessionName`

## Message Counters

Message counters can be used to obtain information on queues over time as Apache ActiveMQ Artemis keeps a history on queue metrics.

They can be used to show trends on queues. For example, using the management API, it would be possible to query the number of messages in a queue at regular interval. However, this would not be enough to know if the queue is used: the number of messages can remain constant because nobody is sending or receiving messages from the queue or because there are as many messages sent to the queue than messages consumed from it. The number of messages in the queue remains the same in both cases but its use is widely different.

Message counters gives additional information about the queues:

- `count`

  The total number of messages added to the queue since the server was started

- `countDelta`

  the number of messages added to the queue since the last message counter update

- `messageCount`

  The current number of messages in the queue

- `messageCountDelta`

  The overall number of messages added/removed from the queue since the last message counter update. For example, if `messageCountDelta` is equal to `-10` this means that overall 10 messages have been removed from the queue (e.g. 2 messages were added and 12 were removed)

- `lastAddTimestamp`

  The timestamp of the last time a message was added to the queue

- `udpateTimestamp`

  The timestamp of the last message counter update

These attributes can be used to determine other meaningful data as well. For example, to know specifically how many messages were consumed from the queue since the last update simply subtract the `messageCountDelta` from `countDelta`.

### Configuring Message Counters

By default, message counters are disabled as it might have a small negative effect on memory.

To enable message counters, you can set it to `true` in `broker.xml`:

    <message-counter-enabled>true</message-counter-enabled>

Message counters keeps a history of the queue metrics (10 days by default) and samples all the queues at regular interval (10 seconds by default). If message counters are enabled, these values should be configured to suit your messaging use case in `broker.xml`:

    <!-- keep history for a week -->
    <message-counter-max-day-history>7</message-counter-max-day-history>
    <!-- sample the queues every minute (60000ms) -->
    <message-counter-sample-period>60000</message-counter-sample-period>

Message counters can be retrieved using the Management API. For example, to retrieve message counters on a JMS Queue using JMX:

    // retrieve a connection to Apache ActiveMQ Artemis's MBeanServer
    MBeanServerConnection mbsc = ...
    JMSQueueControlMBean queueControl = (JMSQueueControl)MBeanServerInvocationHandler.newProxyInstance(mbsc,
       on,
       JMSQueueControl.class,
       false);
    // message counters are retrieved as a JSON String
    String counters = queueControl.listMessageCounter();
    // use the MessageCounterInfo helper class to manipulate message counters more easily
    MessageCounterInfo messageCounter = MessageCounterInfo.fromJSON(counters);
    System.out.format("%s message(s) in the queue (since last sample: %s)\n",
    messageCounter.getMessageCount(),
    messageCounter.getMessageCountDelta());

### Example

See the examples chapter for an example which shows how to use message counters to retrieve information on a JMS `Queue`.