This post is an attempt to define a naming convention for MQTT topic that combines physical and location information.

1
2
3
4

topic : '/' class '/' id '/' direction '/' command '/' declaringClass '/' feature (qualifiedName)?;
direction : 'in' | 'out';
command : 'get' | 'set' | 'unset' | 'val' | 'op';
qualifiedName : ( '/' STRING )+;

Where

• class: the class of the device
• id: the unique id of the device
• direction indicates the direction of the message
  • 'in': the message goes to the device
  • 'out': the message goes from the device
• command: the command to execute
  • 'get': get the value of the feature
  • 'set': set the value of the feature
  • 'unset': unset the value of the feature
  • 'val': send the value of the feature
  • 'op': execute an operation on the device
• declaringClass: the class in which the feature is declared
• feature: the feature (property or operation)
• qualifiedName: the fully qualified name of the device

Examples

Machine case

• A Machine has a property freeMemory
• A JavaVirtualMachine is a Machine
• A JavaVirtualMachine has an operation called gc which runs the garbage collecor

• There is an instance of a JavaVirtualMachine with

  • id is 42
  • is deployed on a host called myhost
  • is running a web app called mywebapp
  • qualifiedName is /myhost/mywebapp

• The JavaVirtualMachine 42 would publish its free memory on topic /JavaVirtualMachine/42/out/val/Machine/freeMemory/myhost/mywebapp

• In order to receive operation call, the JavaVirtualMachine 42 would subscibe to topics
  • /JavaVirtualMachine/42/in/op/#; if id is kind of UUID, it could only subscribe to /+/42/in/#
  • and to /+/+/in/op/+/+/myhost/mywebapp
• An application would subscribe to
  • /+/+/out/val/Machine/freeMemory/# to receive freeMemory values from any instance of Machine
  • /JavaVirtualMachine/+/out/val/Machine/freeMemory/# to receive freeMemory values from any instance of JavaVirtualMachine
  • /+/+/out/val/Machine/freeMemory/myhost/# to receive freeMemory values from any instance deployed on myhost
• An application would publish to /JavaVirtualMachine/42/in/op/JavaVirtualMachine/gc to run the gc on JVM 42

Not tested but it should work …