Intervention Command Pipeline

[mxgrey]

Feature request

Add an intervention command pipeline that is parallel to the task request pipeline.

Description

The Full Control Fleet Adapter implementation currently allows users to place task requests, and the fleet adapters will automatically dispatch and queue a task that satisfies the request. This is great for dealing with the ordinary use case of task requests being issued by end users. However, this system does not accommodate use cases where a developer or operator wants a specific command to be issued to a specific robot.

To accommodate both end users and expert operators, we should introduce an intervention command feature. Intervention commands are issued to specific robots. When a robot receives an intervention command, it will pause any task it is currently performing and immediately begin executing the intervention command. When it is finished executing the command, it will return to its last task. If it did not originally have a task before starting the command then it will return to an idle state or begin its next task.

Only one intervention command will be followed at a time. If a new intervention command arrives, the robot will immediately cancel any intervention command that it was already following. Intervention commands will not be queued up, although we could consider allowing a single intervention to contain a sequence of commands.