ActuatorValueRequest

ActuatorAgent Interaction

Once an Task has been scheduled and the time slot for one or more of the devices has started an agent may interact with the device using the get and set topics.

Both get and set are responded to the same way. See [#ActuatorReply Actuator Reply] below.

Getting values

While the sMap driver for a device should always be setup to periodically broadcast the state of a device you may want an up to the moment value for an actuation point on a device.

To request a value publish a message to the following topic:

#python
'devices/actuators/get/<full device path>/<actuation point>'

Setting Values

Value are set in a similar manner:

To set a value publish a message to the following topic:

#python
'devices/actuators/set/<full device path>/<actuation point>'

With this header:

#python
{
    'requesterID': <Agent ID>
}

And the message contents being the new value of the actuator.

The actuator agent expects all messages to be JSON and will parse them accordingly. Use publish_json to send messages where possible. This is significant for Boolean values especially.

Actuator Reply

#ActuatorReply The ActuatorAgent will reply to both get and set' on the value topic for an actuator:

#python
'devices/actuators/value/<full device path>/<actuation point>'

With this header:

#python
{
    'requesterID': <Agent ID>
}

With the message containing the value encoded in JSON.

Actuator Error Reply

If something goes wrong the ActuatorAgent will reply to both get and set' on the error topic for an actuator:

#python
'devices/actuators/error/<full device path>/<actuation point>'

With this header:

#python
{
    'requesterID': <Agent ID>
}

The message will be in the following form:

#python
{
    'type': <Error Type or name of the exception raised by the request>
    'value': <Specific info about the error>
}

Common Error Types

LockError:: Returned when a request is made when we do not have permission to use a device. (Forgot to schedule, preempted and we did not handle the preemption message correctly, ran out of time in time slot, etc...) ValueError:: Message missing or could not be parsed as JSON.

Other error types involve problem with communication between the ActuatorAgent and sMap.