# Management

Apache ActiveMQ Artemis has an extensive *management API* that allows a user to
modify a server configuration, create new resources (e.g. addresses and
queues), 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). Apache
ActiveMQ Artemis also allows clients to subscribe to management notifications.

There are four ways to access Apache ActiveMQ Artemis management API:

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

- Using Jolokia -- Jolokia exposes the JMX API of an application through a
  *REST interface*

- Using the Core Client -- management operations are sent to Apache ActiveMQ
  Artemis server using *Core Client messages*

- Using any JMS Client -- management operations are sent to Apache ActiveMQ 
  Artemis server using *JMS Client messages*

Although there are four 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.

Besides these four management interfaces, a [Web Console](management-console.md) 
and a Command Line *management utility* are also available to administrators of 
ActiveMQ Artemis.

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

> **Note:**
>
> In version 2 of Apache ActiveMQ Artemis the syntax used for MBean Object
> names has changed significantly due to changes in the addressing scheme. See
> the documentation for each individual resource for details on the new syntax.

## 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
operations can be invoked for this type of resource.

To learn about available *management operations*, see the Javadoc for these
interfaces. They are located in the
`org.apache.activemq.artemis.api.core.management` package and they are named
with the word `Control` at the end.

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

### Management API

For full details of the API please consult the Javadoc. In summary:

#### Server Management

The `ActiveMQServerControl` interface is the entry point for broker management.

- Listing, creating, deploying and destroying queues

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

  Queues can be created or destroyed using the management operations
  `createQueue()` or `deployQueue()` or `destroyQueue()`.

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

- 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()`).

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

  To do this use the `forceFailover()` operation. 

  > **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.

#### Address Management

Individual addresses can be managed using the `AddressControl` interface.

- 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

#### Queue Management

The bulk of the management API deals with queues. The `QueueControl` interface
defines the queue management operations.

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.)

> **Note:**
>
> Passing `null` or an empty string in the `filter` parameter means that the
> management operation will be performed on *all messages* in a 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). The
  message counters can also be reset for a single queue using the
  `resetMessageCounter()` method.

- Retrieving the queue attributes

  The `QueueControl` exposes 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 resumed,
  it'll begin delivering the queued messages, if any.

#### Other 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` interface. The acceptors parameters can be retrieved using
  the `AcceptorControl` attributes (see [Understanding
  Acceptors](configuring-transports.md))

- Diverts

  They can be started or stopped using the `start()` or `stop()` method on the
  `DivertControl` interface. Diverts parameters can be retrieved using the
  `DivertControl` attributes (see [Diverting and Splitting Message
  Flows)](diverts.md))

- Bridges

  They can be started or stopped using the `start()` (resp. `stop()`) method on
  the `BridgeControl` interface. Bridges parameters can be retrieved using the
  `BridgeControl` attributes (see [Core bridges](core-bridges.md))

- Broadcast groups

  They can be started or stopped using the `start()` or `stop()` method on the
  `BroadcastGroupControl` interface. Broadcast groups parameters can be retrieved
  using the `BroadcastGroupControl` attributes (see [Clusters](clusters.md))

- Cluster connections

  They can be started or stopped using the `start()` or `stop()` method on the
  `ClusterConnectionControl` interface. Cluster connections parameters can be
  retrieved using the `ClusterConnectionControl` attributes (see
  [Clusters](clusters.md))

## Using Management Via JMX

Apache ActiveMQ Artemis can be managed using
[JMX](http://www.oracle.com/technetwork/java/javase/tech/javamanagement-140525.html).

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

For example, the `ObjectName` to manage the anycast queue `exampleQueue` on the
address `exampleAddress` is:

```
org.apache.activemq.artemis:broker=<brokerName>,component=addresses,address="exampleAddress",subcomponent=queues,routing-type="anycast",queue="exampleQueue"
```

and the MBean is:

```
org.apache.activemq.artemis.api.core.management.QueueControl
```

The MBean `ObjectName`'s 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 MBean you want to manage.

Example usage of the `ObjectNameBuilder` to obtain `ActiveMQServerControl`'s name:

``` java
brokerName = "0.0.0.0";  // configured e.g. in broker.xml <broker-name> element
objectNameBuilder = ObjectNameBuilder.create(ArtemisResolver.DEFAULT_DOMAIN, brokerName, true);
serverObjectName = objectNameBuilder.getActiveMQServerObjectName()
```

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`:

```xml
<!-- false to disable JMX management for Apache ActiveMQ Artemis -->
<jmx-management-enabled>false</jmx-management-enabled>
```
  
#### Role Based Authorisation for JMX

Although by default Artemis uses the Java Virtual Machine's `Platform
MBeanServer` this is guarded using role based authentication that leverages
Artemis's JAAS plugin support.  This is configured via the `authorisation`
element in the `management.xml` configuration file and can be used to restrict
access to attributes and methods on mbeans.

There are 3 elements within the `authorisation` element, `whitelist`,
`default-access` and `role-access`, Lets discuss each in turn.

Whitelist contains a list of mBeans that will by pass the authentication, this
is typically used for any mbeans that are needed by the console to run etc. The
default configuration is:

```xml
<whitelist>
   <entry domain="hawtio"/>
</whitelist>
```
This means that any mbean with the domain `hawtio` will be allowed access
without authorisation. for instance `hawtio:plugin=artemis`. You can also use
wildcards for the mBean properties so the following would also match.

```xml
<whitelist>
   <entry domain="hawtio" key="type=*"/>
</whitelist>
```

The `role-access`defines how roles are mapped to particular mBeans and its
attributes and methods, the default configuration looks like:

```xml 
<role-access>
  <match domain="org.apache.activemq.artemis">
     <access method="list*" roles="view,update,amq"/>
     <access method="get*" roles="view,update,amq"/>
     <access method="is*" roles="view,update,amq"/>
     <access method="set*" roles="update,amq"/>
     <access method="*" roles="amq"/>
  </match>
</role-access>
```
This contains 1 match and will be applied to any mBean that has the domain
`org.apache.activemq.artemis`.  Any access to any mBeans that have this domain
are controlled by the `access` elements which contain a method and a set of
roles. The method being invoked will be used to pick the closest matching
method and the roles for this will be applied for access. For instance if you
try the invoke a method called `listMessages` on an mBean with the
`org.apache.activemq.artemis` domain then this would match the `access` with
the method of `list*`.  You could also explicitly configure this by using the
full method name, like so:

```xml
<access method="listMessages" roles="view,update,amq"/>
```
You can also match specific mBeans within a domain by adding a key attribute
that is used to match one of the properties on the mBean, like:

```xml
<match domain="org.apache.activemq.artemis" key="subcomponent=queues">
   <access method="list*" roles="view,update,amq"/>
   <access method="get*" roles="view,update,amq"/>
   <access method="is*" roles="view,update,amq"/>
   <access method="set*" roles="update,amq"/>
   <access method="*" roles="amq"/>
</match>
```
You could also match a specific queue for instance:

```
org.apache.activemq.artemis:broker=<brokerName>,component=addresses,address="exampleAddress",subcomponent=queues,routing-type="anycast",queue="exampleQueue"
```

by configuring:

```xml
<match domain="org.apache.activemq.artemis" key="queue=exampleQueue">
   <access method="list*" roles="view,update,amq"/>
   <access method="get*" roles="view,update,amq"/>
   <access method="is*" roles="view,update,amq"/>
   <access method="set*" roles="update,amq"/>
   <access method="*" roles="amq"/>
</match>
```

Access to JMX mBean attributes are converted to method calls so these are
controlled via the `set*`, `get*` and `is*`.  The `*` access is the catch all
for everything other method that isn't specifically matched.

The `default-access` element is basically the catch all for every method call
that isn't handled via the `role-access` configuration.  This has teh same
semantics as a `match` element.

> **Note:**
>
> If JMX is enabled, Apache ActiveMQ Artemis can *not* be managed locally using
> `jconsole` when connecting as a local process, this is because jconsole does
> not using any authentication when connecting this way. If you want to use
> jconsole you will either have to disable authentication, by removing the
> `authentication` element or enable remote access.
 
#### Configuring remote JMX Access

By default remote JMX access to Artemis is disabled for security reasons.

Artemis has a JMX agent which allows access to JMX mBeans remotely. This is
configured via the `connector` element in the `management.xml` configuration
file. To enable this you simply add the following xml:

```xml
<connector connector-port="1099"/>
```

This exposes the agent remotely on the port 1099. If you were connecting via
jconsole you would connect as a remote process using the service url
`service:jmx:rmi:///jndi/rmi://localhost:1099/jmxrmi` and an appropriate user
name and password.

You can also configure the connector using the following:

- `connector-host`
   
  The host to expose the agent on.
  
- `connector-port`
   
  The port to expose the agent on.
   
- `jmx-realm`
   
  The jmx realm to use for authentication, defaults to `activemq` to match the
  JAAS configuration.
  
- `object-name`
   
  The object name to expose the remote connector on; default is
  `connector:name=rmi`.
  
- `secured`
   
  Whether the connector is secured using SSL.
  
- `key-store-path`
   
  The location of the keystore.
   
- `key-store-password`
   
  The keystore password.
   
- `key-store-provider`

  The provider; `JKS` by default.
  
- `trust-store-path`
   
  The location of the truststore.
   
- `trust-store-password`
   
  The trustore password.
   
- `trust-store-provider`
   
  The provider; `JKS` by default.

> **Note:**
>
> It is important to note that the rmi registry will pick an ip address to bind
> to, If you have a multi IP addresses/NICs  present on the system then you can
> choose the ip address to use by adding the following to artemis.profile
> `-Djava.rmi.server.hostname=localhost`

> **Note:**
>
> Remote connections using the default JVM Agent not enabled by default as
> Artemis exposes the mBean Server via its own configuration.  This is so
> Artemis can leverage the JAAS authentication layer via JMX. If you want to
> expose this then you will need to disable both the connector and the
> authorisation by removing them from the `management.xml` configuration.
> Please refer to [Java Management
> guide](https://docs.oracle.com/javase/8/docs/technotes/guides/management/agent.html)
> to configure the server for remote management (system properties must be set
> in `artemis.profile`).

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`:

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

### Example

See the [JMX Management Example](examples.md#jmx-management) 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](https://jolokia.org)
HTTP agent deployed as a web application. Jolokia is a remote JMX-over-HTTP
bridge that exposes MBeans. For a full guide as to how to use it refer to
[Jolokia Documentation](https://jolokia.org/documentation.html), however a
simple example to query the broker's version would be to use a browser and go
to the URL
[http://username:password@localhost:8161/console/jolokia/read/org.apache.activemq.artemis:broker="0.0.0.0"/Version]().

This would give you back something like the following:

```
{"request":{"mbean":"org.apache.activemq.artemis:broker=\"0.0.0.0\"","attribute":"Version","type":"read"},"value":"2.0.0-SNAPSHOT","timestamp":1487017918,"status":200}
```

### JMX and the Console

The console that ships with Artemis uses Jolokia under the covers which in turn
uses JMX. This will use the authentication configuration in the
`management.xml` file as described in the previous section. This means that
when mBeans are accessed via the console the credentials used to log into the
console and the roles associated with them. By default access to the console is
only allow via users with the amq role. This is configured in the
`artemis.profile` via the system property `-Dhawtio.role=amq`.  You can
configure multiple roles by changing this to `-Dhawtio.roles=amq,view,update`.

If a user doesn't have the correct role to invoke a specific operation then
this will display an authorisation exception in the console. 

## Using Management Message API

The management message API in ActiveMQ Artemis is accessed by sending Core
Client messages to a special address, the *management address*.

*Management messages* are regular Core Client 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](https://json.org) 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 queue `exampleQueue`:

```java
ClientSession session = ...
ClientRequestor requestor = new ClientRequestor(session, "activemq.management");
ClientMessage message = session.createMessage(false);
ManagementHelper.putAttribute(message, "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 (e.g. `queue.exampleQueue` for `QueueControl` of the Queue
`exampleQueue`, or `broker` for the `ActiveMQServerControl`).

> **Note:**
>
> The `ManagementHelper` class can be used only with Core JMS messages.  When
> called with a message from a different JMS library, an exception will be
> thrown.

### Configuring Management

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

```xml
<management-address>activemq.management</management-address>
```

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

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:

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

### Example

See the [Management Example](examples.md#management) 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 two different ways:

- JMX notifications

- Notification messages

### JMX Notifications

If JMX is enabled (see Configuring JMX section), JMX notifications can be
received by subscribing to
`org.apache.activemq.artemis:type=Broker,brokerName=<broker
name>,module=Core,serviceType=Server` for notifications on resources.

### Notification Messages

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

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

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

Since notifications are regular 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 Management Notification Address

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

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

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

#### Receiving Notification Messages

Apache ActiveMQ Artemis's Core JMS Client can be used to receive notifications:

```java
Topic notificationsTopic = ActiveMQJMSClient.createTopic("activemq.notifications");

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 [Management Notification Example](examples.md#management-notification)
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 give 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`:

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

Message counters keep a history of the queue metrics (10 days by default) and
sample 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`:

```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 queue using JMX:

```java
// retrieve a connection to Apache ActiveMQ Artemis's MBeanServer
MBeanServerConnection mbsc = ...
QueueControlMBean queueControl = (QueueControl)MBeanServerInvocationHandler.newProxyInstance(mbsc,
   on,
   QueueControl.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 [Message Counter Example](examples.md#message-counter) which shows how
to use message counters to retrieve information on a queue.
