activemq-artemis/docs/user-manual/en/management.md

# 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 the Core JMS Client -- management operations are sent to Apache ActiveMQ Artemis
    server using *Core 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 the programmatic management interfaces, a *Web Console* 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 Core JMS messages are used.

### Apache ActiveMQ Artemis Management API

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

#### Apache ActiveMQ Artemis 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`:

    <!-- false to disable JMX management for Apache ActiveMQ Artemis -->
    <jmx-management-enabled>false</jmx-management-enabled>
    
#### Role Based Authentication with 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](http://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`:

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

### Example

See the [Examples](examples.md) 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://www.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](http://www.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 Via Apache ActiveMQ Artemis API

The management 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](http://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`:

    <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:

    <!-- 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 [Examples](examples.md) 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 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`:

    <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 [Examples](examples.md) 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 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`:

    <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`:

    <!-- 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 [Examples](examples.md) chapter for an example which shows how to use message counters to retrieve information on a queue.