Abstract

The previous tutorial showed how to create abstract compositions, and how to select what should run (at the point where you are using the ‘add’ statements).

This tutorial describes a typical development workflow when using Rock’s system management layer:

• how to restart the deployments when developing the task contexts
• how to define multiple subsystems and manage them at runtime
• how to inspect a running system

Starting and restarting processes

When developing components, one wants the specific processes to be restarted so that the changes get picked up. In Rock’s system management layer, it is done by using the rock-roby shell.

In a terminal, run the script

rock-roby run scripts/rockRoby2.rb

In another terminal, start the shell

rock-roby shell

Let’s now assume that you changed some code in the rock_tutorial::RockTutorialControl task and would like to restart the deployment. You would have to compile and install your changed task, for instance by doing

amake tutorials/orogen/rock_tutorial

Then, in the rock-roby shell we just created, type

orocos.restart_deployments RockTutorial::RockTutorialControl

To restart all deployments, don’t provide any argument

orocos.restart_deployments

And, finally, CTRL+C the “rock-roby run” script. No need to stop the shell.

Defining modalities

Right now, we have two ways (so-called modalities) to control our rock:

• by using a random motion generator
• by using a joystick

(Note if you don’t have a joystick: you can do most of the tutorials without one !)

Let’s reflect that by defining, i.e. by giving a name to both the ways. Copy the scripts/rockRoby2.rb to scripts/rockRoby3.rb and edit the latter: (1) remove the ‘add’ line at the bottom and (2) add the following lines:

define('joystick', Cmp::RockControl).use(Controldev::JoystickTask)
define('random', Cmp::RockControl).use(TutBrownian::Task)

Using ‘define’ allows you to map a composition to a name and reference it lateron using this name lateron. It is then possible to use the name instead of the complete definition in the ‘add’ lines, or in other definition’s ‘use()’ statements. However, using ‘add’ or ‘use’ is not what we’re going to do right now. Instead, we are going to use the shell to start these modalities and switch between them.

Start the rock-roby controller:

rock-roby run scripts/rockRoby3.rb

If you did not already do it, start a rock-roby shell in a separate terminal:

rock-roby shell

In this shell, type:

joystick!

It requests that the supervision starts the joystick-based control, as you can see in the log or in the live display (if you start that in parallel):

localhost:48902 > joystick!
=> #<service Roby::Task:0x7fedaea11a00{}[]>
localhost:48902 >
[1] joystick! started to plan
[1] joystick!: Roby::Task:0x7fedaea11a00{}[] has been replaced by Orocos::RobyPlugin::Compositions::RockControl:0x7fedae9f08f0{}[]
[1] joystick!: Orocos::RobyPlugin::Compositions::RockControl:0x7fedae9f08f0{}[] has been replaced by Orocos::RobyPlugin::Compositions::RockControl:0x7fedaead30b0{conf => [default]}[] 
[1] joystick!: task Orocos::RobyPlugin::Compositions::RockControl:0x7fedaead30b0{conf => [default]}[] started

To inspect the set of running jobs, just do:

jobs

localhost:48902> jobs 1 joystick! #<DRb::DRbObject:0x7f35780b5fe0 @uri=”druby://127.0.1.1:48902”, @ref=70329407281240> =>

The joystick-based control can now be stopped with

localhost:48902> kill_job 1
[1] joystick!: task Orocos::RobyPlugin::Compositions::RockControl:0x7fedaead30b0{conf => [default]}[] failed
= fatal exception 1: mission failed: Orocos::RobyPlugin::Compositions::RockControl:0x7fedaead30b0{conf => [default]}[]
| [09:45:47.355 @7] Orocos::RobyPlugin::Compositions::RockControl:0x7fedaead30b0{conf => [default]}[]/failed
| The following tasks have been killed:
| #<Compositions::RockControl < Composition < Transformer::CompositionExtension>:0x7fedaead30b0
[1] joystick!: task Orocos::RobyPlugin::Compositions::RockControl:0x7fedaead30b0{conf => [default]}[] has been removed

Alternatively, one can get the task object and stop it:

job(1).stop!

Or

t = joystick!
t.stop!

OK, now, let’s try to start both the joystick and random control at the same time.

random!
joystick!

Ouch, a lot of criptic information there: happened:

The error message tells you that there is no deployment of type RockTutorial::RockTutorialControl available for the composition ‘Cmp::RockControl’. Well, in the current setup, we have a deployment defined and said to use it - it is ‘rock_tutorial’:

use_deployment ‘rock_tutorial’

But this is only one deployment and is being used for the composition ‘Cmp::RockControl’ which has been started first by ‘random!’. Since the deployment cannot be used for more than one composition at the same time and error is generated.

Stop the controller with CTRL+C and the shell with “exit”, and pass on to the next tutorial.

Summary

In this tutorial you learned:

• how to define some ready-to-deploy networks, and how to use the shell to start them
• how to manage the tasks started through the shell, in particular to support development of components
• what happens if you try to deploy multiple tasks that can’t be deployed at the same time

The next tutorial will introduce you to the configuration file management.