Fabric3 supports low-latency, high performance communications between clients and services and producers and consumers (Pub/Sub) via a binding built on the ZeroMQ Library. The following messaging patterns are supported:
- Non-blocking (asynchronous) queue-based messaging
- Non-blocking (asynchronous) queue-based messaging with callbacks
- Request-reply messaging
It is generally recommended to use non-blocking message patterns for better performance.
Configuring a Service and Reference Binding
Wiring a reference to a service using the ZeroMQ is done as follows in Java:
public class Client ...{
@ZeroMQ(target="ZMQService")
protected Service service;
public void invoke(){
service.invoke("message");
}
}
@ZeroMQ(service="ZMQService")
public class ServiceImpl implements Service {
public void invoke(String message){
//....
}
}
Or in XML as follows:
<component name="Client">
<implementation.java class="org.fabric3.binding.zeromq.client.Client"/>
<reference name="service">
<f3:binding.zeromq target="ZMQService"/>
</reference>
</component>
<component name="ZMQService">
<implementation.java class="org.fabric3.binding.zeromq.service.ServiceImpl"/>
<service name="ZMQService">
<f3:binding.zeromq/>
</service>
</component>
In the above example, if Service uses non-blocking operations (i.e. uses operations annotated with @OneWay), a ZeroMQ PUSH/PULL socket will be established between the reference and service. If the operations are blocking, XREQ/XREP will be used instead.
Cluster Operation
Note that the binding configuration in the previous figure did not specify an IP address and port combination to connect/bind to. If one is not specified, Fabric3 will allocate a port from the block reserved for each runtime. Addressing information will then be propagated by Fabric3 to required runtimes in the domain. For example, if Client is hosted on a different machine than Service, Fabric3 will transparently propagate the latter's address so that Client can connect to the service.
Further, if TestService is deployed to a clustered zone, all endpoint addresses will be propagated to Client, which in turn will round-robin requests to cluster instances.
Port Allocation
The ZeroMQ binding attempts to acquire ports for sockets from the block configured for a particular runtime or zone. For information on how to configure a port block, see Port Allocation.
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