Scheduling a Mission Application’s Execution¶

The Kubos scheduler service is responsible for scheduling applications for execution.

This tutorial walks the user through:

Creating a new schedule mode

Creating a task list specifying the application execution details

Importing the task list into the scheduler for execution

Activating the schedule mode to begin execution

This tutorial is written to be run entirely within your local development environment, however, you may also interact with the scheduler service on your OBC by setting up its ethernet connection.

Setup¶

This tutorial will build on the application registration tutorial. It assumes the application, monitor, and telemetry services are running. It also assumes the example mission application exists and is registered with the application service.

This tutorial will use the following example directories:

/home/user/kubos - Cloned copy of the kubos responsible

/home/user/kubos/schedules - Directory used by the schedules service to store schedule information

Navigate to /home/user/kubos (or your preferred copy of the kubos repo).
Run the following command to start the scheduler service in the background (the service may need to be built first, which will take several minutes to complete):
```
$ cargo run -p scheduler-service -- -c tools/local_config.toml &
```

GraphiQL¶

All Kubos services which provide an HTTP interface have a special endpoint which can be used to send and receive GraphQL data via an in-browser graphical interface, GraphiQL.

To access this endpoint for the scheduler service, make sure the service has started, then open a web browser and navigate to http://127.0.0.1:8010/graphiql. This URL assumes that the stock version of local_config.toml is in use.

Creating a Mode¶

Modes are the highest level of schedule organization. They are made up of lists of tasks which are loaded into the scheduler for future execution. Each mode is represented by a directory in the file system which can hold any number of task lists.

To create a new scheduler mode, we use the service’s createMode mutation. It has the following schema:

mutation {
    createMode(name: String!) {
        success: Boolean,
        errors: String
    }
}

The name input specifies the name of the mode to be created.

The creation action will create an empty, inactive mode that the scheduler may interact with.

Our creation mutation should look like this:

mutation {
    createMode(name: "nominal") {
        success
        errors
    }
}

The response should look like this:

{
    "data": {
        "createMode": {
            "success": true,
            "errors": ""
        }
    }
}

Creating and Importing a Task List¶

Task lists are the individual files stored in modes which contain the actual schedule specification. Each task list contains a list of one or more tasks to be scheduled and executed.

We’ll go ahead and create a new task list which schedules my-mission-app to execute every 10 seconds, after an initial 10 second delay.

Create a new file called my-mission.json with the following contents:

{
    "tasks": [
        {
            "description": "Execute mission logic",
            "delay": "10s",
            "period": "10s",
            "app": {
                "name": "my-mission-app"
            }
        }
    ]
}

The tasks list is required in each task list and holds all task specifications. Each task requires a description, one of either delay, period, or time to specify execution time, and app to specify the details of the app execution. More details on the task list specification can be found here.

To import a task list, we use the service’s importTaskList mutation. It has the following schema:

mutation {
    importTaskList(path: String!, name: String!, mode:String!): {
        success: Boolean,
        errors: String
    }
}

Our import mutation should look like this:

mutation {
    importTaskList(name: "my-mission", path: "/home/user/kubos/my-mission.json", mode: "nominal") {
        success
        errors
    }
}

The response should look like this:

{
    "data": {
        "importTaskList": {
            "success": true,
            "errors": ""
        }
    }
}

Activating the Schedule¶

The scheduler may only have one active mode at a time. The active mode is the one whose tasks are loaded into the scheduler for future execution. New modes are inactive by default. In order to load up our new task list and execute our example mission app, we must activate the newly created mode.

To activate a mode, we use the service’s activateMode mutation. It has the following schema:

mutation {
    activateMode(name: String!): {
        success: Boolean,
        errors: String
    }
}

Our activation mutation should look like this:

mutation {
    activateMode(name: "nominal") {
        success
        errors
    }
}

The response should look like this:

{
    "data": {
        "activateMode": {
            "success": true,
            "errors": ""
        }
    }
}

At this point our mode and task list have been loaded into the scheduler and will begin execution. The console where you started the app service should show the app’s execution messages after 10 seconds and then every 10 seconds after that:

Successfully pinged monitor service