The result of this tutorial can be found in bundles/tutorials_scripts if you followed the instructions at the bottom of this page

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 Syskit, it is done by using the roby shell.

In a terminal, run scripts/02_services.rb

syskit run scripts/02_services.rb

Then, in another terminal, start the shell

syskit 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 Syskit shell we just created, type

syskit.restart_deployments RockTutorial::RockTutorialControl

To restart all deployments, don’t provide any argument

syskit.restart_deployments

And, finally, CTRL+C the syskit 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 ways. Copy scripts/02_services.rb to scripts/03_defines.rb and edit the latter by: (1) removing the ‘add_mission’ line at the bottom and (2) adding the following lines:

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

Using ‘define’ allows you to map a composition to a name and reference it later on using this name. 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 application:

syskit run scripts/03_defines.rb

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

syskit shell

The definitions are available as actions in the shell. Run the following command and look at the top of the output

localhost:48902 > help
Available Actions
=================

Name          | Description
----------------------------------------------
joystick_def! | definition from profile Script
random_def!   | definition from profile Script

Then run the joystick definition:

localhost:48902 > joystick_def!

It requests that Syskit starts the joystick-based control, as you can see in the log or in the live display (if you started it):

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[1] joystick_def!: Tutorials::RockControl:0x7fedae9f08f0{}[] has been replaced by Tutorials::RockControl:0x7fedaead30b0{conf =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

To inspect the set of running actions, just do:

localhost:48902> jobs
1 joystick_def! Tutorials::RockControl:0x54b4a60{conf => [default]}[]
=>

The joystick-based control can now be stopped with

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

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

random_def!
joystick_def!

Ouch, a lot of cryptic information there. The most interesting bit is at the top:

= planning joystick_def failed with
| cannot deploy the following tasks
| RockTutorial::RockTutorialControl:0x4714400{conf => [default]}[]
|   child rock of Tutorials::RockControl:0x46f7120{conf => [default]}[]
| RockTutorial::RockTutorialControl:0x4714400{conf => [default]}[]: some deployments exist, but they are already used in this network
|   task rock_tutorial from deployment Deployments::RockTutorial on localhost
|     already used by RockTutorial::RockTutorialControl:0x334ba68{orocos_name => rock_tutorial, conf => [default]}[]: child rock of Tutorials::RockControl:0x47432f0{conf => [default]}[]

The other error messages are just consequences of this one. This error message tells you that there actually are some deployments declared for RockTutorial::RockTutorialControl, but that they are already used.

Indeed, both the random and joystick definitions need a RockTutorial::RockTutorialControl component. Since they use it in a different way (the command port gets its data from different sources), Syskit requires more than one deployment and it fails.

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.