Camel ZeroMQ Component
Available as of Camel 2.11
The camel-zeromq component is provided by the Camel Extra project which hosts *GPL related components for Camel.
The camel-zeromq component allows you to consumer or produce messages using ZeroMQ. Zeromq requires a bit of work to get setup, especially on windows. Refer to the documentation. Note: This component works with the stable 2.2 branch and not the pre-release 3.2.
This component uses Akka for it's Zeromq "driver" but does not use Scala Actors. This means the component does not require the JZMQ libraries to be built and present, just the native ZeroMQ library that is installed when you build ZeroMQ on your system. There is some discussion as to the speed of the Akka driver, and so it is possible to switch to using the JZMQ driver if you wish. Simply remove the Akka Zeromq dependancy and replace it with the JZMQ jar and ensure the zmq.lib is present on your system. For more information see here.
Maven users will need to add the following dependency to their
pom.xml for this component:
Where hostname is the hostname or ip where the server will run.
Choose from PULL, SUBSCRIBE for consumers, or PUSH, PUBLISH for producers
Sets the consumer to be async.
Applicable for subscribers and publishers only. Determines which topics to subscribe or publish to. If not specified then the subscriber will subscribe to all messages. If not specified by a publisher then no topic will be prefixed to the message. Specify multiple topics by a comma separated list
If enabled then camel-zeromq will add a unique UUID to each message as it is received
The message convertor that is used to turn an exchange into a byte array for dispatch through zeromq. See later section.
By default, zeromq will keep messages in an in-memory buffer while waiting for clients to receive. The high water mark is the max number of messages to hold before throwing an exception. -1 sets to the zeromq default, 0 disables, and any positive value sets to that value.
By default, zeromq will wait for sending messages to be received before shutting down. Linger is the number of seconds to wait before force closing the socket. -1 sets to the zeromq default, 0 disables, and any positive value sets to that value.
The follwing headers are set on exchanges during message transport.
A type 4 UUID that is added to received messages
The timestamp when the message was received
The socket address where the message was received from or pushed to
The type of zeromq that the message was received from or pushed to
ZeroMQ sends its messages as a byte stream and so incoming messages have the body set as a byte array. When sending to a producer, the messageConvertor is invoked, and passed the Exchange. The DefaultMessageConvertor will return the body as is, if it is a byte array, otherwise it will call toString().getBytes(). You can provide custom conversion strategies by specifying a class to the messageConvertor option on the endpoint.
To receive all messages from a publisher, and then print those to a logger:
To broadcast a message every second on three topics: