# Addressing Model

Apache ActiveMQ Artemis has a unique addressing model that is both powerful and
flexible and that offers great performance. The addressing model comprises
three main concepts: **addresses**, **queues**, and **routing types**.

### Address

An address represents a messaging endpoint. Within the configuration, a typical
address is given a unique name, 0 or more queues, and a routing type.

### Queue

A queue is associated with an address. There can be multiple queues per
address. Once an incoming message is matched to an address, the message will be
sent on to one or more of its queues, depending on the routing type configured.
Queues can be configured to be automatically created and deleted.

### Routing Types

A routing type determines how messages are sent to the queues associated with
an address. An Apache ActiveMQ Artemis address can be configured with two
different routing types.

Table 1. Routing Types

If you want your messages routed to...|Use this routing type...
---|---
A single queue within the matching address, in a point-to-point manner.|Anycast
Every queue within the matching address, in a publish-subscribe manner.|Multicast


**Note:** It is possible to define more than one routing type per address, but
this typically results in an anti-pattern and is therefore not recommended.  If
an address does use both routing types, however, and the client does not show a
preference for either one, the broker typically defaults to the anycast routing
type.

The one exception is when the client uses the MQTT protocol. In that case, the
default routing type is multicast.

For additional details about these concepts refer to [the core](core.md) chapter.

## Basic Address Configuration

The following examples show how to configure basic point to point and publish
subscribe addresses.

### Point-to-Point Messaging

Point-to-point messaging is a common scenario in which a message sent by a
producer has only one consumer. AMQP and JMS message producers and consumers
can make use of point-to-point messaging queues, for example. Define an anycast
routing type for an address so that its queues receive messages in a
point-to-point manner.

When a message is received on an address using anycast, Apache ActiveMQ Artemis
locates the queue associated with the address and routes the message to it.
When consumers request to consume from the address, the broker locates the
relevant queue and associates this queue with the appropriate consumers. If
multiple consumers are connected to the same queue, messages are distributed
amongst each consumer equally, providing the consumers are equally able to
handle them.

![Point to Point](images/addressing-model-p2p.png)
Figure 1. Point to Point Messaging

#### Using the Anycast Routing Type

Open the file `<broker-instance>/etc/broker.xml` for editing.

Add an address configuration element and its associated queue if they do not
exist already.

**Note:** For normal Point to Point semantics, the queue name **MUST** match the
address name.

```xml
<addresses>
   <address name="orders">
      <anycast>
         <queue name="orders"/>
      </anycast>
   </address>
</addresses>
```

### Publish-Subscribe Messaging

In a publish-subscribe scenario, messages are sent to every consumer subscribed
to an address. JMS topics and MQTT subscriptions are two examples of
publish-subscribe messaging.

To configure an address with publish-subscribe semantics, create an address
with the multicast routing type.

![Publish Subscribe](images/addressing-model-pubsub.png)
Figure 2. Publish-Subscribe

#### Using the Multicast Routing Type

Open the file `<broker-instance>/etc/broker.xml` for editing.

Add an address configuration element with multicast routing type.

```xml
<addresses>
   <address name="pubsub.foo">
      <multicast/>
   </address>
</addresses>
```

When clients connect to an address with the multicast element, a subscription
queue for the client will be automatically created for the client. It is also
possible to pre-configure subscription queues and connect to them directly
using the queue's [Fully Qualified Queue names](#fully-qualified-queue-names).

Optionally add one or more queue elements to the address and wrap the multicast
element around them. This step is typically not needed since the broker will
automatically create a queue for each subscription requested by a client.

```xml
<addresses>
   <address name="pubsub.foo">
      <multicast>
         <queue name="client123.pubsub.foo"/>
         <queue name="client456.pubsub.foo"/>
      </multicast>
   </address>
</addresses>
```

Figure 3. Point-to-Point with Two Queues

### Point-to-Point Address multiple Queues

It is actually possible to define more than one queue on an address with an
anycast routing type. When messages are received on such an address, they are
firstly distributed evenly across all the defined queues. Using [Fully
Qualified Queue names](#fully-qualified-queue-names), clients are able to
select the queue that they would like to subscribe to. Should more than one
consumer connect directly to a single queue, Apache ActiveMQ Artemis will take
care of distributing messages between them, as in the example above.

![Point to Point](images/addressing-model-p2p2.png)
Figure 3. Point-to-Point with Two Queues

**Note:** This is how Apache ActiveMQ Artemis handles load balancing of queues
across multiple nodes in a cluster.  Configuring a Point-to-Point Address with
two queues, open the file `<broker-instance>/etc/broker.xml` for editing.

Add an address configuration with Anycast routing type element and its
associated queues.

```xml
<addresses>
   <address name="address.foo">
      <anycast>
         <queue name="q1"/>
         <queue name="q2"/>
      </anycast>
   </address>
</addresses>
```

### Point-to-Point and Publish-Subscribe Addresses

It is possible to define an address with both point-to-point and
publish-subscribe semantics enabled. While not typically recommend, this can be
useful when you want, for example, a JMS Queue say orders and a JMS Topic named
orders.  The different routing types make the addresses appear to be distinct.

Using an example of JMS Clients, the messages sent by a JMS message producer
will be routed using the anycast routing type. Messages sent by a JMS topic
producer will use the multicast routing type. In addition when a JMS topic
consumer attaches, it will be attached to it’s own subscription queue. JMS
queue consumer will be attached to the anycast queue.

![Point to Point](images/addressing-model-p2p-pubsub.png)
Figure 4. Point-to-Point and Publish-Subscribe

**Note:** The behavior in this scenario is dependent on the protocol being
used. For JMS there is a clear distinction between topic and queue producers
and consumers, which make the logic straight forward. Other protocols like AMQP
do not make this distinction. A message being sent via AMQP will be routed by
both anycast and multicast and consumers will default to anycast. For more
information, please check the behavior of each protocol in the sections on
protocols.

The XML snippet below is an example of what the configuration for an address
using both anycast and multicast would look like in
`<broker-instance>/etc/broker.xml`. Note that subscription queues are typically
created on demand, so there is no need to list specific queue elements inside
the multicast routing type.

```xml
<addresses>
   <address name="foo.orders">
      <anycast>
         <queue name="orders"/>
      </anycast>
      <multicast/>
   </address>
</addresses>
```

## How to filter messages

Apache ActiveMQ Artemis supports the ability to filter messages using Apache
Artemis [Filter Expressions](filter-expressions.md).

Filters can be applied in two places, on a queue and on a consumer.

### Queue Filter

When a filter is applied to a queue, messages are filtered before they are sent to
the queue.  To add a queue filter use the filter element when configuring a
queue.  Open up `<broker-instance>/etc/broker.xml` and add an address with a
queue, using the filter element to configure a filter on this queue.

```xml
<addresses>
   <address name="filter">
      <queue name="filter">
         <filter string="color='red'"/>
      </queue>
   </address>
</addresses>
```

The filter defined above ensures that only messages with an attribute
`"color='red'"` is sent to this queue.

### Consumer Filters

Consumer filters are applied after messages have reached a queue and are
defined using the appropriate client APIs. The following JMS example shows how
consumer filters work.

1. Define an address with a single queue, with no filter applied.

```xml
<addresses>
   <address name="filter">
      <queue name="filter"/>
   </address>
</addresses>
```

```java
...
// Send some messages
for (int i = 0; i < 3; i ++) {
  TextMessage redMessage = senderSession.createTextMessage("Red");
  redMessage.setStringProperty("color", "red");
  producer.send(redMessage)

  TextMessage greenMessage = senderSession.createTextMessage("Green");
  greenMessage.setStringProperty("color", "green");
  producer.send(greenMessage)
}
```

At this point the queue would have 6 messages: red,green,red,green,red,green
         
```java
MessageConsumer redConsumer = redSession.createConsumer(queue, "color='red'");
```

The redConsumer has a filter that only matches "red" messages.  The redConsumer
will receive 3 messages.

```
red, red, red
```

The resulting queue would now be

```
green, green, green
```

## Automatic Address/Queue Management

You can configure Apache ActiveMQ Artemis to automatically create addresses and
queues, and then delete them when they are no longer in use. This saves you
from having to preconfigure each address and queue before a client can connect
to it. Automatic creation and deletion is configured on a per address basis and
is controlled by following:

Parameter|Description
---|---
`auto-create-addresses`|When set to true, the broker will create the address requested by the client if it does not exist already. The default is `true`.
`auto-delete-addresses`|When set to true, the broker will be delete any **auto-created** address once all of it’s queues have been deleted. The default is `true`
`default-address-routing-type`|The routing type to use if the client does not specify one. Possible values are `MULTICAST` and `ANYCAST`. See earlier in this chapter for more information about routing types. The default value is `MULTICAST`.

### Auto Address Creation

- Edit the file `<broker-instance>/etc/broker.xml` and add the
  `auto-create-addresses` element to the `address-setting` you want the broker
  to automatically create.

- (Optional) Add the `address-setting` if it does not exist. Use the match
  parameter and the [wildcard syntax](wildcard-syntax.md) to match more than
  one specific address.

- Set `auto-create-addresses` to `true`

- (Optional) Assign `MULTICAST` or `ANYCAST` as the default routing type for
  the address.

The example below configures an `address-setting` to be automatically created
by the broker. The default routing type to be used if not specified by the
client is MULTICAST. Note that wildcard syntax is used. Any address starting
with `/news/politics/` will be automatically created by the broker.

```xml
<address-setting match="/news/politics/#">
  <auto-create-addresses>true</auto-create-addresses>
  <default-address-routing-type>MULTICAST</default-address-routing-type>
</address-setting>
```

### Auto Address Deletion

- Edit the file `<broker-instance>/etc/broker.xml` and add the
  `auto-delete-addresses` element to the `address-setting` you want the broker to
  automatically create.

- (Optional) Add the `address-setting` if it does not exist. Use the match
  parameter and the [wildcard syntax](wildcard-syntax.md) to match more than one
  specific address.

- Set `auto-delete-addresses` to `true`

The example below configures an `address-setting` to be automatically deleted
by the broker. Note that wildcard syntax is used. Any address request by the
client that starts with `/news/politics/` is configured to be automatically
deleted by the broker.

```xml
<address-setting match="/news/politics/#">
  <auto-delete-addresses>true</auto-delete-addresses>
  <default-address-routing-type>MULTICAST</default-address-routing-type>
</address-setting>
```

## "Fully Qualified" Queue Names

Internally the broker maps a client’s request for an address to specific
queues. The broker decides on behalf of the client which queues to send
messages to or from which queue to receive messages. However, more advanced use
cases might require that the client specify a queue directly. In these
situations the client uses a fully qualified queue name, by specifying both
the address name and the queue name, separated by a ::.

Currently Artemis supports fully qualified queue names on Core, AMQP, JMS,
OpenWire, MQTT and STOMP protocols for receiving messages only.

### Specifying a Fully Qualified Queue Name

In this example, the address foo is configured with two queues q1, q2 as shown
in the configuration below.

```xml
<addresses>
   <address name="foo">
      <anycast>
         <queue name="q1" />
         <queue name="q2" />
      </anycast>
   </address>
</addresses>
```

In the client code, use both the address name and the queue name when
requesting a connection from the broker. Remember to use two colons, `::`, to
separate the names, as in the example Java code below.

```java
String FQQN = "foo::q1";
Queue q1 session.createQueue(FQQN);
MessageConsumer consumer = session.createConsumer(q1);
```

## Using Prefixes to Determine Routing Type

Normally, if the broker receives a message sent to a particular address, that
has both `ANYCAST` and `MULTICAST` routing types enable, it will route a copy
of the message to **one** of the `ANYCAST` queues and to **all** of the
`MULTICAST` queues.

However, clients can specify a special prefix when connecting to an address to
indicate which kind of routing type to use. The prefixes are custom values that
are designated using the anycastPrefix and multicastPrefix parameters within
the URL of an acceptor. When multiple values are needed, these can be separated by a comma.

### Configuring an Anycast Prefix

In `<broker-instance>/etc/broker.xml`, add the `anycastPrefix` to the URL of
the desired acceptor. In the example below, the acceptor is configured to use
`anycast://` for the `anycastPrefix`. Client code can specify `anycast://foo/`
if the client needs to send a message to only one of the `ANYCAST` queues.

```xml
<acceptor name="artemis">tcp://0.0.0.0:61616?protocols=AMQP;anycastPrefix=anycast://</acceptor>
```

### Configuring a Multicast Prefix

In `<broker-instance>/etc/broker.xml`, add the `multicastPrefix` to the URL of
the desired acceptor. In the example below, the acceptor is configured to use
`multicast://` for the `multicastPrefix`. Client code can specify
`multicast://foo/` if the client needs to send a message to only one of the
`MULTICAST` queues.

```xml
<acceptor name="artemis">tcp://0.0.0.0:61616?protocols=AMQP;multicastPrefix=multicast://</acceptor>
```

## Advanced Address Configuration

### Static Subscription Queues

In most cases it’s not necessary to statically configure subscription queues.
The relevant protocol managers take care of dynamically creating subscription
queues when clients request to subscribe to an address.  The type of
subscription queue created depends on what properties the client request.  For
example, durable, non-shared, shared etc.  Protocol managers use special queue
naming conventions to identify which queues belong to which consumers and users
need not worry about the details.

However, there are scenarios where a user may want to use broker side
configuration to statically configure a subscription and later connect to that
queue directly using a [Fully Qualified Queue
name](#fully-qualified-queue-names).  The examples below show how to use broker
side configuration to statically configure a queue with publish subscribe
behavior for shared, non-shared, durable and non-durable subscription behavior.

#### Shared, Durable Subscription Queue using max-consumers

The default behavior for queues is to not limit the number connected queue
consumers.  The **max-consumers** parameter of the queue element can be used to
limit the number of connected consumers allowed at any one time.

Open the file `<broker-instance>/etc/broker.xml` for editing.

```xml
<addresses>
   <address name="durable.foo">
      <multicast>
         <!-- pre-configured shared durable subscription queue -->
         <queue name="q1" max-consumers="10">
            <durable>true</durable>
         </queue>
      </multicast>
   </address>
</addresses>
```

#### Non-shared, Durable Subscription Queue

The broker can be configured to prevent more than one consumer from connecting
to a queue at any one time. The subscriptions to queues configured this way are
therefore "non-shared".  To do this simply set the **max-consumers** parameter
to `1`:

```xml
<addresses>
   <address name="durable.foo">
      <multicast>
         <!-- pre-configured non shared durable subscription queue -->
         <queue name="q1" max-consumers="1">
            <durable>true</durable>
         </queue>
      </multicast>
   </address>
</addresses>
```

#### Non-durable Subscription Queue

Non-durable subscriptions are again usually managed by the relevant protocol
manager, by creating and deleting temporary queues.

If a user requires to pre-create a queue that behaves like a non-durable
subscription queue the **purge-on-no-consumers** flag can be enabled on the
queue.  When **purge-on-no-consumers** is set to **true**.  The queue will not
start receiving messages until a consumer is attached.  When the last consumer
is detached from the queue.  The queue is purged (its messages are removed)
and will not receive any more messages until a new consumer is attached.

Open the file `<broker-instance>/etc/broker.xml` for editing.

```xml
<addresses>
   <address name="non.shared.durable.foo">
      <multicast>
         <queue name="orders1" purge-on-no-consumers="true"/>
      </multicast>
   </address>
</addresses>
```

#### Exclusive Consumer Queue

If a user requires to statically configure a queue that routes exclusively to
one active consumer the **exclusive** flag can be enabled on the queue.
  
When **exclusive** is set to **true** the queue will route messages to a
single active consumer.  When the active consumer that is being routed to is
detached from the queue, if another active consumer exist, one will be chosen
and routing will now be exclusive to it.

See [Exclusive Queue](exclusive-queues.md) for further information.

Open the file `<broker-instance>/etc/broker.xml` for editing.

```xml
<addresses>
   <address name="foo.bar">
      <multicast>
         <queue name="orders1" exclusive="true"/>
      </multicast>
   </address>
</addresses>
```

#### Disabled Queue

If a user requires to statically configure a queue and disable routing to it,
for example where a queue needs to be defined so a consumer can bind, 
but you want to disable message routing to it for the time being.

Or you need to stop message flow to the queue to allow investigation keeping the consumer bound, 
but don't wish to have further messages routed to the queue to avoid message build up.
  
When **enabled** is set to **true**  the queue will have messages routed to it. (default)

When **enabled** is set to **false**  the queue will NOT have messages routed to it.

Open the file `<broker-instance>/etc/broker.xml` for editing.

```xml
<addresses>
   <address name="foo.bar">
      <multicast>
         <queue name="orders1" enabled="false"/>
      </multicast>
   </address>
</addresses>
```

Warning: Disabling all the queues on an address means that any message sent to that address will be silently dropped.

### Temporary Queues

For some protocols and APIs which only support monolithic "destinations"
without the address/queue separation (e.g. AMQP, JMS, etc.) temporary queues
are created by the broker using a UUID (i.e universally unique identifier) as
the name for both the address and the queue. Because the name is a UUID it is
impossible to create an `address-setting` for it whose `match` is anything but
`#`.

To solve this problem one can specify the `temporary-queue-namespace` in
`broker.xml` and then create an `address-setting` whose `match` value
corresponds to the configured `temporary-queue-namespace`. When the
`temporary-queue-namespace` is set and a temporary queue is created then the
broker will prepend the `temporary-queue-namespace` value along with the
`delimiter` value configured in `wildcard-addresses` (defaults to `.`) to the
address name and use that to lookup the associated `address-setting` values.

Here's a simple example configuration:

```xml
<temporary-queue-namespace>temp</temporary-queue-namespace>

<address-settings>
   <address-setting match="temp.#">
      <enable-metrics>false</enable-metrics>
   </address-setting>
</address-settings>
```

Using this configuration any temporary queue will have metrics disabled.

> **Note:**
>
> This setting does *not* change the actual name of the temporary queue. It
> only changes the name used to *lookup* the address-settings.

## Protocol Managers

A "protocol manager" maps protocol-specific concepts down to the core
addressing model (using addresses, queues and routing types). For example, when
a client sends a MQTT subscription packet with the addresses: 

```
/house/room1/lights
/house/room2/lights
```

The MQTT protocol manager understands that the two addresses require
`MULTICAST` semantics. The protocol manager will therefore first look to ensure
that `MULTICAST` is enabled for both addresses. If not, it will attempt to
dynamically create them. If successful, the protocol manager will then create
special subscription queues with special names, for each subscription requested
by the client.

The special name allows the protocol manager to quickly identify the required
client subscription queues should the client disconnect and reconnect at a
later date.  If the subscription is temporary the protocol manager will delete
the queue once the client disconnects.

When a client requests to subscribe to a point to point address.  The protocol
manager will look up the queue associated with the point to point address.
This queue should have the same name as the address.

**Note:** If the queue is auto created, it will be auto deleted once there are
no consumers and no messages in it.  For more information on auto create see
the next section [Configuring Addresses and Queues via Address
Settings](#configuring-addresses-and-queues-via-address-settings)

## Configuring Addresses and Queues via Address Settings

There are some attributes that are defined against an address wildcard rather
than a specific address/queue. Here an example of an `address-setting` entry
that would be found in the `broker.xml` file.

```xml
<address-settings>
   <address-setting match="order.foo">
      <dead-letter-address>DLA</dead-letter-address>
      <auto-create-dead-letter-resources>false</auto-create-dead-letter-resources>
      <dead-letter-queue-prefix>DLQ.</dead-letter-queue-prefix>
      <dead-letter-queue-suffix></dead-letter-queue-suffix>
      <expiry-address>ExpiryQueue</expiry-address>
      <auto-create-expiry-resources>false</auto-create-expiry-resources>
      <expiry-queue-prefix>EXP.</expiry-queue-prefix>
      <expiry-queue-suffix></expiry-queue-suffix>
      <expiry-delay>123</expiry-delay>
      <redelivery-delay>5000</redelivery-delay>
      <redelivery-delay-multiplier>1.0</redelivery-delay-multiplier>
      <redelivery-collision-avoidance-factor>0.0</redelivery-collision-avoidance-factor>
      <max-redelivery-delay>10000</max-redelivery-delay>
      <max-delivery-attempts>3</max-delivery-attempts>
      <max-size-bytes>100000</max-size-bytes>
      <max-size-bytes-reject-threshold>-1</max-size-bytes-reject-threshold>
      <page-size-bytes>20000</page-size-bytes>
      <page-max-cache-size></page-max-cache-size>
      <address-full-policy>PAGE</address-full-policy>
      <message-counter-history-day-limit></message-counter-history-day-limit>
      <last-value-queue>true</last-value-queue> <!-- deprecated! see default-last-value-queue -->
      <default-last-value-queue>false</default-last-value-queue>
      <default-non-destructive>false</default-non-destructive>
      <default-exclusive-queue>false</default-exclusive-queue>
      <default-consumers-before-dispatch>0</default-consumers-before-dispatch>
      <default-delay-before-dispatch>-1</default-delay-before-dispatch>
      <redistribution-delay>0</redistribution-delay>
      <send-to-dla-on-no-route>true</send-to-dla-on-no-route>
      <slow-consumer-threshold>-1</slow-consumer-threshold>
      <slow-consumer-policy>NOTIFY</slow-consumer-policy>
      <slow-consumer-check-period>5</slow-consumer-check-period>
      <auto-create-jms-queues>true</auto-create-jms-queues> <!-- deprecated! see auto-create-queues -->
      <auto-delete-jms-queues>true</auto-delete-jms-queues> <!-- deprecated! see auto-delete-queues -->
      <auto-create-jms-topics>true</auto-create-jms-topics> <!-- deprecated! see auto-create-addresses -->
      <auto-delete-jms-topics>true</auto-delete-jms-topics> <!-- deprecated! see auto-delete-addresses -->
      <auto-create-queues>true</auto-create-queues>
      <auto-delete-queues>true</auto-delete-queues>
      <auto-delete-created-queues>false</auto-delete-created-queues>
      <auto-delete-queues-delay>0</auto-delete-queues-delay>
      <auto-delete-queues-message-count>0</auto-delete-queues-message-count>
      <config-delete-queues>OFF</config-delete-queues>
      <config-delete-diverts>OFF</config-delete-diverts>
      <auto-create-addresses>true</auto-create-addresses>
      <auto-delete-addresses>true</auto-delete-addresses>
      <auto-delete-addresses-delay>0</auto-delete-addresses-delay>
      <config-delete-addresses>OFF</config-delete-addresses>
      <management-browse-page-size>200</management-browse-page-size>
      <default-purge-on-no-consumers>false</default-purge-on-no-consumers>
      <default-max-consumers>-1</default-max-consumers>
      <default-queue-routing-type></default-queue-routing-type>
      <default-address-routing-type></default-address-routing-type>
      <default-ring-size>-1</default-ring-size>
      <retroactive-message-count>0</retroactive-message-count>
      <enable-metrics>true</enable-metrics>
   </address-setting>
</address-settings>
```

The idea with address settings, is you can provide a block of settings which
will be applied against any addresses that match the string in the `match`
attribute. In the above example the settings would only be applied to the
address "order.foo" address but you can also use
[wildcards](wildcard-syntax.md) to apply settings.

For example, if you used the `match` string `queue.#` the settings would be
applied to all addresses which start with `queue.`

The meaning of the specific settings are explained fully throughout the user
manual, however here is a brief description with a link to the appropriate
chapter if available.

`dead-letter-address` is the address to which messages are sent when they
exceed `max-delivery-attempts`. If no address is defined here then such
messages will simply be discarded. Read more about [undelivered
messages](undelivered-messages.md#configuring-dead-letter-addresses).

`auto-create-dead-letter-resources` determines whether or not the broker will
automatically create the defined `dead-letter-address` and a corresponding
dead-letter queue when a message is undeliverable. Read more in the chapter
about [undelivered messages](undelivered-messages.md).

`dead-letter-queue-prefix` defines the prefix used for automatically created
dead-letter queues. Read more in the chapter about
[undelivered messages](undelivered-messages.md).

`dead-letter-queue-suffix` defines the suffix used for automatically created
dead-letter queues. Read more in the chapter about
[undelivered messages](undelivered-messages.md).

`expiry-address` defines where to send a message that has expired. If no
address is defined here then such messages will simply be discarded. Read more
about [message expiry](message-expiry.md#configuring-expiry-addresses).

`auto-create-expiry-resources` determines whether or not the broker will
automatically create the defined `expiry-address` and a corresponding expiry
queue when a message expired. Read more in the chapter about
[undelivered messages](undelivered-messages.md).

`expiry-queue-prefix` defines the prefix used for automatically created expiry
queues. Read more in the chapter about [message expiry](message-expiry.md).

`expiry-queue-suffix` defines the suffix used for automatically created expiry
queues. Read more in the chapter about [message expiry](message-expiry.md).

`expiry-delay` defines the expiration time that will be used for messages which
are using the default expiration time (i.e. 0). For example, if `expiry-delay`
is set to "10" and a message which is using the default expiration time (i.e.
0) arrives then its expiration time of "0" will be changed to "10." However, if
a message which is using an expiration time of "20" arrives then its expiration
time will remain unchanged. Setting `expiry-delay` to "-1" will disable this
feature. The default is "-1". Read more about [message
expiry](message-expiry.md#configuring-expiry-addresses).

`max-delivery-attempts` defines how many time a cancelled message can be
redelivered before sending to the `dead-letter-address`. Read more about
[undelivered
messages](undelivered-messages.md#configuring-dead-letter-addresses).

`redelivery-delay` defines how long to wait before attempting redelivery of a
cancelled message. Default is `0`. Read more about [undelivered
messages](undelivered-messages.md#configuring-delayed-redelivery).

`redelivery-delay-multiplier` defines the number by which the
`redelivery-delay` will be multiplied on each subsequent redelivery attempt.
Default is `1.0`. Read more about [undelivered
messages](undelivered-messages.md#configuring-delayed-redelivery).

`redelivery-collision-avoidance-factor` defines an additional factor used to
calculate an adjustment to the `redelivery-delay` (up or down). Default is
`0.0`. Valid values are between 0.0 and 1.0. Read more about [undelivered
messages](undelivered-messages.md#configuring-delayed-redelivery).

`max-size-bytes`, `page-size-bytes`, & `page-max-cache-size` are used to
configure paging on an address. This is explained
[here](paging.md#configuration).

`max-size-bytes-reject-threshold` is used with the address full `BLOCK` policy,
the maximum size (in bytes) an address can reach before messages start getting
rejected. Works in combination with `max-size-bytes` **for AMQP clients only**.
Default is `-1` (i.e. no limit).

`address-full-policy`. This attribute can have one of the following values:
`PAGE`, `DROP`, `FAIL` or `BLOCK` and determines what happens when an address
where `max-size-bytes` is specified becomes full. The default value is `PAGE`.
If the value is `PAGE` then further messages will be paged to disk. If the
value is `DROP` then further messages will be silently dropped. If the value is
`FAIL` then further messages will be dropped and an exception will be thrown on
the client-side. If the value is `BLOCK` then client message producers will
block when they try and send further messages.  See the [Flow
Control](flow-control.md) and [Paging](paging.md) chapters for more info.

`message-counter-history-day-limit` is the number of days to keep message
counter history for this address assuming that `message-counter-enabled` is
`true`. Default is `0`.

`last-value-queue` is **deprecated**. See `default-last-value-queue`. It
defines whether a queue only uses last values or not. Default is `false`. Read
more about [last value queues](last-value-queues.md).

`default-last-value-queue` defines whether a queue only uses last values or
not. Default is `false`. This value can be overridden at the queue level using
the `last-value` boolean. Read more about [last value
queues](last-value-queues.md).

`default-exclusive-queue` defines whether a queue will serve only a single
consumer. Default is `false`. This value can be overridden at the queue level
using the `exclusive` boolean. Read more about [exclusive
queues](exclusive-queues.md).

`default-consumers-before-dispatch` defines the number of consumers needed on a
queue bound to the matching address before messages will be dispatched to those
consumers. Default is `0`. This value can be overridden at the queue level using
the `consumers-before-dispatch` boolean. This behavior can be tuned using
`delay-before-dispatch` on the queue itself or by using the
`default-delay-before-dispatch` address-setting.

`default-delay-before-dispatch` defines the number of milliseconds the broker
will wait for the configured number of consumers to connect to the matching queue
before it will begin to dispatch messages. Default is `-1` (wait forever).

`redistribution-delay` defines how long to wait when the last consumer is
closed on a queue before redistributing any messages. Read more about
[clusters](clusters.md#message-redistribution).

`send-to-dla-on-no-route`. If a message is sent to an address, but the server
does not route it to any queues (e.g. there might be no queues bound to that
address, or none of the queues have filters that match) then normally that
message would be discarded. However, if this parameter is `true` then such a
message will instead be sent to the `dead-letter-address` (DLA) for that
address, if it exists.

`slow-consumer-threshold`. The minimum rate of message consumption allowed
before a consumer is considered "slow." Measured in messages-per-second.
Default is `-1` (i.e. disabled); any other valid value must be greater than 0.
Read more about [slow consumers](slow-consumers.md).

`slow-consumer-policy`. What should happen when a slow consumer is detected.
`KILL` will kill the consumer's connection (which will obviously impact any
other client threads using that same connection). `NOTIFY` will send a
CONSUMER\_SLOW management notification which an application could receive and
take action with. Read more about [slow consumers](slow-consumers.md).

`slow-consumer-check-period`. How often to check for slow consumers on a
particular queue. Measured in *seconds*. Default is `5`. Read more about [slow
consumers](slow-consumers.md).

`auto-create-jms-queues` is **deprecated**. See `auto-create-queues`. Whether
or not the broker should automatically create a JMS queue when a JMS message is
sent to a queue whose name fits the address `match` (remember, a JMS queue is
just a core queue which has the same address and queue name) or a JMS consumer
tries to connect to a queue whose name fits the address `match`. Queues which
are auto-created are durable, non-temporary, and non-transient. Default is
`true`.

`auto-delete-jms-queues` is **deprecated**. See `auto-delete-queues`. Whether
or not the broker should automatically delete auto-created JMS queues when they
have both 0 consumers and 0 messages. Default is `true`.

`auto-create-jms-topics` is **deprecated**. See `auto-create-addresses`.
Whether or not the broker should automatically create a JMS topic when a JMS
message is sent to a topic whose name fits the address `match` (remember, a JMS
topic is just a core address which has one or more core queues mapped to it) or
a JMS consumer tries to subscribe to a topic whose name fits the address
`match`. Default is `true`.

`auto-delete-jms-topics` is **deprecated**. See `auto-delete-addresses`.
Whether or not the broker should automatically delete auto-created JMS topics
once the last subscription on the topic has been closed. Default is `true`.

`auto-create-queues`. Whether or not the broker should automatically create a
queue when a message is sent or a consumer tries to connect to a queue whose
name fits the address `match`. Queues which are auto-created are durable,
non-temporary, and non-transient. Default is `true`. **Note:** automatic queue
creation does *not* work for the core client. The core API is a low-level API
and is not meant to have such automation.

`auto-delete-queues`. Whether or not the broker should automatically delete
auto-created queues when they have both 0 consumers and the message count is 
less than or equal to `auto-delete-queues-message-count`. Default is
`true`.

`auto-delete-created-queues`. Whether or not the broker should automatically delete
created queues when they have both 0 consumers and the message count is 
less than or equal to `auto-delete-queues-message-count`. Default is
`false`.

`auto-delete-queues-delay`. How long to wait (in milliseconds) before deleting
auto-created queues after the queue has 0 consumers and the message count is 
less than or equal to `auto-delete-queues-message-count`. 
Default is `0` (delete immediately). The broker's `address-queue-scan-period` controls
how often (in milliseconds) queues are scanned for potential deletion. Use `-1`
to disable scanning. The default scan value is `30000`.

`auto-delete-queues-message-count`. The message count that the queue must be 
less than or equal to before deleting auto-created queues. 
To disable message count check `-1` can be set.
Default is `0` (empty queue).

**Note:** the above auto-delete address settings can also be configured 
individually at the queue level when a client auto creates the queue.
 
For Core API it is exposed in createQueue methods. 

For Core JMS you can set it using the destination queue attributes
`my.destination?auto-delete=true&auto-delete-delay=120000&auto-delete-message-count=-1`

`config-delete-queues`. How the broker should handle queues deleted on config
reload, by delete policy: `OFF` or `FORCE`.  Default is `OFF`. Read more about
[configuration reload](config-reload.md).

`config-delete-diverts`. How the broker should handle diverts deleted on config
reload, by delete policy: `OFF` or `FORCE`.  Default is `OFF`. Read more about
[configuration reload](config-reload.md).
`auto-create-addresses`. Whether or not the broker should automatically create
an address when a message is sent to or a consumer tries to consume from a
queue which is mapped to an address whose name fits the address `match`.
Default is `true`. **Note:** automatic address creation does *not* work for the
core client. The core API is a low-level API and is not meant to have such
automation.

`auto-delete-addresses`. Whether or not the broker should automatically delete
auto-created addresses once the address no longer has any queues. Default is
`true`.

`auto-delete-addresses-delay`. How long to wait (in milliseconds) before
deleting auto-created addresses after they no longer have any queues. Default
is `0` (delete immediately). The broker's `address-queue-scan-period` controls
how often (in milliseconds) addresses are scanned for potential deletion. Use
`-1` to disable scanning. The default scan value is `30000`.

`config-delete-addresses`. How the broker should handle addresses deleted on
config reload, by delete policy: `OFF` or `FORCE`. Default is `OFF`. Read more
about [configuration reload](config-reload.md).

`management-browse-page-size` is the number of messages a management resource
can browse. This is relevant for the `browse, list and count-with-filter` management
methods exposed on the queue control. Default is `200`.

`default-purge-on-no-consumers` defines a queue's default
`purge-on-no-consumers` setting if none is provided on the queue itself.
Default is `false`. This value can be overridden at the queue level using the
`purge-on-no-consumers` boolean. Read more about [this
functionality](#non-durable-subscription-queue).

`default-max-consumers` defines a queue's default `max-consumers` setting if
none is provided on the  queue itself.  Default is `-1` (i.e. no limit). This
value can be overridden at the queue level using the `max-consumers` boolean.
Read more about [this
functionality](#shared-durable-subscription-queue-using-max-consumers).

`default-queue-routing-type` defines the routing-type for an auto-created queue
if the broker is unable to determine the routing-type based on the client
and/or protocol semantics. Default is `MULTICAST`. Read more about [routing
types](#routing-type).

`default-address-routing-type` defines the routing-type for an auto-created
address if the broker is unable to determine the routing-type based on the
client and/or protocol semantics. Default is `MULTICAST`. Read more about
[routing types](#routing-type).

`default-consumer-window-size` defines the default `consumerWindowSize` value 
for a `CORE` protocol consumer, if not defined the default will be set to 
1 MiB (1024 * 1024 bytes). The consumer will use this value as the window size
if the value is not set on the client. Read more about
[flow control](flow-control.md).

`default-ring-size` defines the default `ring-size` value for any matching queue
which doesn't have `ring-size` explicitly defined. If not defined the default will
be set to -1. Read more about [ring queues](ring-queues.md).

`retroactive-message-count` defines the number of messages to preserve for future
queues created on the matching address. Defaults to 0. Read more about
[retroactive addresses](retroactive-addresses.md).

`enable-metrics` determines whether or not metrics will be published to any
configured metrics plugin for the matching address. Default is `true`. Read more
about [metrics](metrics.md).