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Interoperability

Stomp

Stomp is a text-orientated wire protocol that allows Stomp clients to communicate with Stomp Brokers. ActiveMQ now supports Stomp 1.0, 1.1 and 1.2.

Stomp clients are available for several languages and platforms making it a good choice for interoperability.

Native Stomp support

ActiveMQ provides native support for Stomp. To be able to send and receive Stomp messages, you must configure a NettyAcceptor with a protocols parameter set to have stomp:

<acceptor name="stomp-acceptor">
   <factory-class>org.apache.activemq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class>
   <param key="protocols"  value="STOMP"/>
   <param key="port"  value="61613"/>
</acceptor>

With this configuration, ActiveMQ will accept Stomp connections on the port 61613 (which is the default port of the Stomp brokers).

See the stomp example which shows how to configure a ActiveMQ server with Stomp.

Limitations

Message acknowledgements are not transactional. The ACK frame can not be part of a transaction (it will be ignored if its transaction header is set).

Stomp 1.1/1.2 Notes

Virtual Hosting

ActiveMQ currently doesn't support virtual hosting, which means the 'host' header in CONNECT fram will be ignored.

Heart-beating

ActiveMQ specifies a minimum value for both client and server heart-beat intervals. The minimum interval for both client and server heartbeats is 500 milliseconds. That means if a client sends a CONNECT frame with heartbeat values lower than 500, the server will defaults the value to 500 milliseconds regardless the values of the 'heart-beat' header in the frame.

Mapping Stomp destinations to ActiveMQ addresses and queues

Stomp clients deals with destinations when sending messages and subscribing. Destination names are simply strings which are mapped to some form of destination on the server - how the server translates these is left to the server implementation.

In ActiveMQ, these destinations are mapped to addresses and queues. When a Stomp client sends a message (using a SEND frame), the specified destination is mapped to an address. When a Stomp client subscribes (or unsubscribes) for a destination (using a SUBSCRIBE or UNSUBSCRIBE frame), the destination is mapped to a ActiveMQ queue.

STOMP and connection-ttl

Well behaved STOMP clients will always send a DISCONNECT frame before closing their connections. In this case the server will clear up any server side resources such as sessions and consumers synchronously. However if STOMP clients exit without sending a DISCONNECT frame or if they crash the server will have no way of knowing immediately whether the client is still alive or not. STOMP connections therefore default to a connection-ttl value of 1 minute (see chapter on connection-ttl for more information. This value can be overridden using connection-ttl-override.

If you need a specific connection-ttl for your stomp connections without affecting the connection-ttl-override setting, you can configure your stomp acceptor with the "connection-ttl" property, which is used to set the ttl for connections that are created from that acceptor. For example:

<acceptor name="stomp-acceptor">
   <factory-class>org.apache.activemq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class>
   <param key="protocols"  value="STOMP"/>
   <param key="port"  value="61613"/>
   <param key="connection-ttl"  value="20000"/>
</acceptor>

The above configuration will make sure that any stomp connection that is created from that acceptor will have its connection-ttl set to 20 seconds.

Note

Please note that the STOMP protocol version 1.0 does not contain any heartbeat frame. It is therefore the user's responsibility to make sure data is sent within connection-ttl or the server will assume the client is dead and clean up server side resources. With Stomp 1.1 users can use heart-beats to maintain the life cycle of stomp connections.

Stomp and JMS interoperability

Using JMS destinations

As explained in Mapping JMS Concepts to the Core API, JMS destinations are also mapped to ActiveMQ addresses and queues. If you want to use Stomp to send messages to JMS destinations, the Stomp destinations must follow the same convention:

send or subscribe to a JMS Queue by prepending the queue name by jms.queue..

For example, to send a message to the orders JMS Queue, the Stomp client must send the frame:
```
SEND
destination:jms.queue.orders

hello queue orders
^@
```
send or subscribe to a JMS Topic by prepending the topic name by jms.topic..

For example to subscribe to the stocks JMS Topic, the Stomp client must send the frame:
```
SUBSCRIBE
destination:jms.topic.stocks

^@
```

Sending and consuming Stomp message from JMS or ActiveMQ Core API

Stomp is mainly a text-orientated protocol. To make it simpler to interoperate with JMS and ActiveMQ Core API, our Stomp implementation checks for presence of the content-length header to decide how to map a Stomp message to a JMS Message or a Core message.

If the Stomp message does not have a content-length header, it will be mapped to a JMS TextMessage or a Core message with a single nullable SimpleString in the body buffer.

Alternatively, if the Stomp message has a content-length header, it will be mapped to a JMS BytesMessage or a Core message with a byte[] in the body buffer.

The same logic applies when mapping a JMS message or a Core message to Stomp. A Stomp client can check the presence of the content-length header to determine the type of the message body (String or bytes).

Message IDs for Stomp messages

When receiving Stomp messages via a JMS consumer or a QueueBrowser, the messages have no properties like JMSMessageID by default. However this may bring some inconvenience to clients who wants an ID for their purpose. ActiveMQ Stomp provides a parameter to enable message ID on each incoming Stomp message. If you want each Stomp message to have a unique ID, just set the stomp-enable-message-id to true. For example:

<acceptor name="stomp-acceptor">
   <factory-class>org.apache.activemq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class>
   <param key="protocols" value="STOMP"/>
   <param key="port" value="61613"/>
   <param key="stomp-enable-message-id" value="true"/>
</acceptor>

When the server starts with the above setting, each stomp message sent through this acceptor will have an extra property added. The property key is hq-message-id and the value is a String representation of a long type internal message id prefixed with "STOMP", like:

hq-message-id : STOMP12345

If stomp-enable-message-id is not specified in the configuration, default is false.

Handling of Large Messages with Stomp

Stomp clients may send very large bodys of frames which can exceed the size of ActiveMQ server's internal buffer, causing unexpected errors. To prevent this situation from happening, ActiveMQ provides a stomp configuration attribute stomp-min-large-message-size. This attribute can be configured inside a stomp acceptor, as a parameter. For example:

   <acceptor name="stomp-acceptor">
   <factory-class>org.apache.activemq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class>
   <param key="protocols" value="STOMP"/>
   <param key="port" value="61613"/>
   <param key="stomp-min-large-message-size" value="10240"/>
</acceptor>

The type of this attribute is integer. When this attributed is configured, ActiveMQ server will check the size of the body of each Stomp frame arrived from connections established with this acceptor. If the size of the body is equal or greater than the value of stomp-min-large-message, the message will be persisted as a large message. When a large message is delievered to a stomp consumer, the HorentQ server will automatically handle the conversion from a large message to a normal message, before sending it to the client.

If a large message is compressed, the server will uncompressed it before sending it to stomp clients. The default value of stomp-min-large-message-size is the same as the default value of min-large-message-size.

Stomp Over Web Sockets

ActiveMQ also support Stomp over Web Sockets. Modern web browser which support Web Sockets can send and receive Stomp messages from ActiveMQ.

To enable Stomp over Web Sockets, you must configure a NettyAcceptor with a protocol parameter set to stomp_ws:

<acceptor name="stomp-ws-acceptor">
   <factory-class>org.apache.activemq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class>
   <param key="protocols" value="STOMP_WS"/>
   <param key="port" value="61614"/>
</acceptor>

With this configuration, ActiveMQ will accept Stomp connections over Web Sockets on the port 61614 with the URL path /stomp. Web browser can then connect to ws://<server>:61614/stomp using a Web Socket to send and receive Stomp messages.

A companion JavaScript library to ease client-side development is available from GitHub (please see its documentation for a complete description).

The stomp-websockets example shows how to configure ActiveMQ server to have web browsers and Java applications exchanges messages on a JMS topic.

StompConnect

StompConnect is a server that can act as a Stomp broker and proxy the Stomp protocol to the standard JMS API. Consequently, using StompConnect it is possible to turn ActiveMQ into a Stomp Broker and use any of the available stomp clients. These include clients written in C, C++, c# and .net etc.

To run StompConnect first start the ActiveMQ server and make sure that it is using JNDI.

Stomp requires the file jndi.properties to be available on the classpath. This should look something like:

java.naming.factory.initial=org.apache.activemq.jndi.ActiveMQInitialContextFactory

Configure any required JNDI resources in this file according to the documentation.

Make sure this file is in the classpath along with the StompConnect jar and the ActiveMQ jars and simply run java org.codehaus.stomp.jms.Main.

REST

Please see Rest Interface

AMQP

ActiveMQ supports the AMQP 1.0 specification. To enable AMQP you must configure a Netty Acceptor to receive AMQP clients, like so:

<acceptor name="stomp-acceptor">
<factory-class>org.apache.activemq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class>
<param key="protocols"  value="AMQP"/>
<param key="port"  value="5672"/>
</acceptor>

ActiveMQ will then accept AMQP 1.0 clients on port 5672 which is the default AMQP port.

There are 2 Stomp examples available see proton-j and proton-ruby which use the qpid Java and Ruby clients respectively

AMQP and security

The ActiveMQ Server accepts AMQP SASL Authentication and will use this to map onto the underlying session created for the connection so you can use the normal ActiveMQ security configuration.

AMQP Links

An AMQP Link is a uni directional transport for messages between a source and a target, i.e. a client and the ActiveMQ Broker. A link will have an endpoint of which there are 2 kinds, a Sender and A Receiver. At the Broker a Sender will have its messages converted into a ActiveMQ Message and forwarded to its destination or target. A Receiver will map onto a ActiveMQ Server Consumer and convert ActiveMQ messages back into AMQP messages before being delivered.

AMQP and destinations

If an AMQP Link is dynamic then a temporary queue will be created and either the remote source or remote target address will be set to the name of the temporary queue. If the Link is not dynamic then the the address of the remote target or source will used for the queue. If this does not exist then an exception will be sent

Note

For the next version we will add a flag to aut create durable queue but for now you will have to add them via the configuration

AMQP and Coordinations - Handling Transactions

An AMQP links target can also be a Coordinator, the Coordinator is used to handle transactions. If a coordinator is used the the underlying HormetQ Server session will be transacted and will be either rolled back or committed via the coordinator.

Note

AMQP allows the use of multiple transactions per session, amqp:multi-txns-per-ssn, however in this version ActiveMQ will only support single transactions per session

OpenWire

ActiveMQ now supports the OpenWire protocol so that an ActiveMQ JMS client can talk directly to a ActiveMQ server. To enable OpenWire support you must configure a Netty Acceptor, like so:

<acceptor name="openwire-acceptor">
<factory-class>org.apache.activemq.core.remoting.impl.netty.NettyAcceptorFactory</factory-class>
<param key="protocols"  value="OPENWIRE"/>
<param key="port"  value="61616"/>
</acceptor>

The ActiveMQ server will then listens on port 61616 for incoming openwire commands. Please note the "protocols" is not mandatory here. The openwire configuration conforms to ActiveMQ's "Single Port" feature. Please refer to Configuring Single Port for details.

Please refer to the openwire example for more coding details.

Currently we support ActiveMQ clients that using standard JMS APIs. In the future we will get more supports for some advanced, ActiveMQ specific features into ActiveMQ.

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