Command 

<node>/command/<code>[/<component>]

Examples:

45fe/command/tlc.plan.set              # set signal plan (for main component) on node 45fe
45fe/command/traffic.17/sg/1           # hypothetical M0017 set detector threshold for signal group 1 on node 45fe

All devices subscribe to a command topic that includes their id, which the supervisor can publish to.

Device subscribe to <node>/command/<code>[/<component>]

node: the id of the device itself (incl. hierarchy) code: the command code (flattened)

The payload contains the parameters in JSON format.

For example, a traffic light with id 45fe might subscribe to all commands for all components using: 45fe/command/#

Now the supervisor can send commands to this particular traffic light and component by publishing to 45fe/command/...

Suppose the traffic light has these components:

  • main: the main controller, handles, eg. signal program changes
  • sg1: signal group 1
  • sg2: signal group 2
  • dl1: detector logic 1
  • dl2: detector logic 2

And let’s suppose the traffic light supports these modules:

  • tlc: traffic light controller commands
  • detector: traffic detectors used for local traffic control

Change signal plan

45fe/command/tlc.plan.set

We send the command to the main component (by omitting the component part). We use plan.set command in the tlc module (code tlc.plan.set).

The payload would include the arguments, like what plan to switch to.

Set detector sensibility

45fe/command/detector.sensibility/dl1

We send the command to the dl1 component. We use sensibility command in the detector module (code detector.sensibility).

The payload would include the arguments, like the sensibility value.

Sending to many devices

A traffic light with id 45fe could subscribe to a topic with the id ‘all’ (if supported by project governance): all/command/#

The supervisor can publish to this topic to e.g. change the signal plan on all traffic lights at the same: all/command/tlc.plan.set

Result

How would command results be handled? We would use the request-result pattern, which is based on Result Topics. When you send a command, you pass a topic that would want to result to be published to. A supervisor sending a command could pass the result topic: <supervisor_id>/result/<code>[/<component>].

When a supervisor with id 22ba changing plan with 45fe/command/tlc.plan.set, the response would be send to 22ba/result/tlc.plan.set.

All supervisor can receive result if the just subscribe to +/result/tlc.plan.set.

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