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Bus Descriptor Format

A loopback message bus can be configured via a descriptor string as follows which uses the address to indicate the loopback bus instance to which to connect followed by a list of provider properties. 

loopback://<busname>&prop1=val1&propN=valN

An example bus descriptor for solace would like like:

loopback://<busname>&topic_starts_with_channel=false&set_bus_and_channel_on_receipt=true

DDL

In a DDL config file a solace bus can equivalently be configured in one of two ways

<buses>
  <bus name="my-bus">
    <provider>loopback</provider>
    <address>my-bus</address>
    <properties>
	   <topic_starts_with_channel>false<topic_starts_with_channel>
       <set_bus_and_channel_on_receipt>true<set_bus_and_channel_on_receipt>
    </properties>
    <channels>
      ...
    </channels>
  </bus>
</buses>

The descriptor form is useful in cases where the descriptor name may be supplied as an external configuration property that is substituted at runtime, but defaults to loopback for testing:

<buses>
  <bus name="my-bus" descriptor="${myBusDescriptor::solace://somehost:55555&amp;topic_starts_with_channel=false">
    <channels>
      ...
    </channels>
  </bus>
</buses>

Working with Loopback Buses

Loopback Bus Naming

When working with loopback buses it is sometimes useful to be able to look up a loopback by name. Loopback buses are named using their address (and optionally their port). If you have configured a loopback bus via loopback://my-bus, you can look up the bus as follows:

LoopbackBus bus = LoopbackBus.getInstance("my-bus");
StringBuilder dump = new StringBuilder();
bus.dumpPendingAck(dump);
System.out.println(dump.toString());

Loopback Bus Topic Format

Loopback bus topics can be specified hierarchically with each level in the topic separated by a '/' character. A valid loopback topic may start with a '/', but it is not required. 

Wildcard Topics

The loopback bus supports 2 wildcard character sequences that can be used in Channel Filters to match multiple sending topics. Wildcard characters are not applied to sent topics and are treated as character literals. The loopback binding implementation is sensitive to the following wildcards when nv.sma.cleanchannelfilter=true and will preserve these characters rather than replace them with an '_':