defenseunicorns / maru-runner

The Unicorn Task Runner

maru-runner

Maru is a task runner that enables developers to automate builds and perform common shell tasks and shares a syntax similar to zarf.yaml actions. Many Zarf Actions features are also available in the runner.

Table of Contents

• Runner
  • Quickstart
  • Key Concepts
    • Tasks
    • Actions
      • Task
      • Cmd
    • Variables
    • Wait
    • Includes
    • Task Inputs and Reusable Tasks

Quickstart

Create a file called tasks.yaml

variables:
  - name: FOO
    default: foo

tasks:
  - name: default
    actions:
      - cmd: echo "run default task"

  - name: example
    actions:
      - task: set-variable
      - task: echo-variable

  - name: set-variable
    actions:
      - cmd: echo "bar"
        setVariables:
          - name: FOO

  - name: echo-variable
    actions:
      - cmd: echo ${FOO}

From the same directory as the tasks.yaml, run the example task using:

run example

This will run the example tasks which in turn runs the set-variable and echo-variable. In this example, the text " bar" should be printed to the screen twice.

Optionally, you can specify the location and name of your tasks.yaml using the --file or -f flag:

run example -f tmp/tasks.yaml

You can also view the tasks that are available to run in your current task file using the list flag, or you can view all tasks including tasks from external files that are being included in your task file by using the list-all flag:

run -f tmp/tasks.yaml --list

run -f tmp/tasks.yaml --list-all

Key Concepts

Tasks

Tasks are the fundamental building blocks of the runner and they define operations to be performed. The tasks key at the root of tasks.yaml define a list of tasks to be run. This underlying operations performed by a task are defined under the actions key:

tasks:
  - name: all-the-tasks
    actions:
      - task: make-build-dir
      - task: install-deps

In this example, the name of the task is "all-the-tasks", and it is composed of multiple sub-tasks to run. These sub-tasks would also be defined in the list of tasks:

tasks:
  - name: default
    actions:
      - cmd: echo "run default task"

  - name: all-the-tasks
    actions:
      - task: make-build-dir
      - task: install-deps

  - name: make-build-dir
    actions:
      - cmd: mkdir -p build

  - name: install-deps
    actions:
      - cmd: go mod tidy

These tasks can be run individually:

run all-the-tasks   # runs all-the-tasks, which calls make-build-dir and install-deps
run make-build-dir  # only runs make-build-dir

Default Tasks

In the above example, there is also a default task, which is special, optional, task that can be used for the most common entrypoint for your tasks. When trying to run the default task, you can omit the task name from the run command:

run

Actions

Actions are the underlying operations that a task will perform. Each action under the actions key has a unique syntax.

Task

A task can reference a task, thus making tasks composable.

tasks:
  - name: foo
    actions:
      - task: bar
  - name: bar
    actions:
      - task: baz
  - name: baz
    actions:
      - cmd: "echo task foo is composed of task bar which is composed of task baz!"

In this example, the task foo calls a task called bar which calls a task baz which prints some output to the console.

Cmd

Actions can run arbitrary bash commands including in-line scripts, and the output of a command can be placed in a variable using the setVariables key

tasks:
  - name: foo
    actions:
      - cmd: echo -n 'dHdvIHdlZWtzIG5vIHByb2JsZW0=' | base64 -d
        setVariables:
          - name: FOO

This task will decode the base64 string and set the value as a variable named FOO that can be used in other tasks.

Command blocks can have several other properties including:

• description: description of the command

  • mute: boolean value to mute the output of a command

  • dir: the directory to run the command in

  • env: list of environment variables to run for this cmd block only

    tasks:
      - name: foo
        actions:
          - cmd: echo ${BAR}
            env:
              - BAR=bar

  • maxRetries: number of times to retry the command

  • maxTotalSeconds: max number of seconds the command can run until it is killed; takes precedence over maxRetries

Variables

Variables can be defined in several ways:

1. At the top of the tasks.yaml

   variables:
     - name: FOO
       default: foo
   
   tasks: ...

2. As the output of a cmd

   variables:
     - name: FOO
       default: foo
   tasks:
     - name: foo
       actions:
         - cmd: uname -m
           mute: true
           setVariables:
             - name: FOO
         - cmd: echo ${FOO}

3. As an environment variable prefixed with MARU_. In the example above, if you create an env var MARU_FOO=bar, then theFOO variable would be set to bar.

4. Using the --set flag in the CLI : run foo --set FOO=bar

To use a variable, reference it using ${VAR_NAME}

Note that variables also have the following attributes when setting them with YAML:

• sensitive: boolean value indicating if a variable should be visible in output
• default: default value of a variable
  • In the example above, if FOO did not have a default, and you have an environment variable MARU_FOO=bar, the default would get set to bar.

Environment Variable Files

To include a file containing environment variables that you'd like to load into a task, use the envPath key in the task. This will load all of the environment variables in the file into the task being called and its child tasks.

tasks:
  - name: env
    actions:
      - cmd: echo $FOO
      - cmd: echo $MARU_ARCH
      - task: echo-env
  - name: echo-env
    envPath: ./path/to/.env
    actions:
      - cmd: echo different task $FOO

Automatic Environment Variables

The following Environment Variables are set automatically by maru-runner and are available to any action being performed:

• MARU - Set to 'true' to indicate the action was executed by maru-runner.
• MARU_ARCH - Set to the current architecture. e.g. 'amd64'

Example:

• tasks.yaml

    - name: print-common-env
      actions:
        - cmd: echo MARU_ARCH=[$MARU_ARCH]
        - cmd: echo MARU=[$MARU]

• maru run print-common-env output:

      MARU_ARCH=[amd64]
    ✔  Completed "echo MARU_ARCH=[$MARU_ARCH]"
      MARU=[true]
    ✔  Completed "echo MARU=[$MARU]"
  

Variable Precedence

Variable precedence is as follows, from least to most specific:

• Variable defaults set in YAML
• Environment variables prefixed with MARU_
• Variables set with the --set flag in the CLI

That is to say, variables set via the --set flag take precedence over all other variables.

There are a couple of exceptions to this precedence order:

• When a variable is modified using setVariable, which will change the value of the variable during runtime.
• When another application is vendoring in maru, it can use config.AddExtraEnv to add extra environment variables. Any variables set by an application in this way take precedence over everything else.

Wait

The waitkey is used to block execution while waiting for a resource, including network responses and K8s operations

tasks:
  - name: network-response
    wait:
      network:
        protocol: https
        address: 1.1.1.1
        code: 200
  - name: configmap-creation
    wait:
      cluster:
        kind: configmap
        name: simple-configmap
        namespace: foo

Includes

The includes key is used to import tasks from either local or remote task files. This is useful for sharing common tasks across multiple task files. When importing a task from a local task file, the path is relative to the file you are currently in. When running a task, the tasks in the task file as well as the includes get processed to ensure there are no infinite loop references.

includes:
  - local: ./path/to/tasks-to-import.yaml
  - remote: https://raw.githubusercontent.com/defenseunicorns/maru-runner/main/src/test/tasks/remote-import-tasks.yaml

tasks:
  - name: import-local
    actions:
      - task: local:some-local-task
  - name: import-remote
    actions:
      - task: remote:echo-var

Note that included task files can also include other task files, with the following restriction:

• If a task file includes a remote task file, the included remote task file cannot include any local task files

Tasks from an included file can also be run individually, by using the includes reference name followed by a colon and the name of the task, like in the example below. Both of these commands run the same task.

run import-local

run local:some-local-task

Task Inputs and Reusable Tasks

Although all tasks should be reusable, sometimes you may want to create a task that can be reused with different inputs. To create a reusable task that requires inputs, add an inputs key with a map of inputs to the task:

tasks:
  - name: echo-var
    inputs:
      hello-input:
        default: hello world
        description: This is an input to the echo-var task
      deprecated-input:
        default: foo
        description: this is a input from a previous version of this task
        deprecatedMessage: this input is deprecated, use hello-input instead
    actions:
      # to use the input, reference it using INPUT_<INPUT_NAME> in all caps
      - cmd: echo $INPUT_HELLO_INPUT

  - name: use-echo-var
    actions:
      - task: echo-var
        with:
          # hello-input is the name of the input in the echo-var task, hello-unicorn is the value we want to pass in
          hello-input: hello unicorn

In this example, the echo-var task takes an input called hello-input and prints it to the console; notice that the input can have a default value. The use-echo-var task calls echo-var with a different input value using the with key. In this case "hello unicorn" is passed to the hello-input input.

Note that the deprecated-input input has a deprecatedMessage attribute. This is used to indicate that the input is deprecated and should not be used. If a task is run with a deprecated input, a warning will be printed to the console.

Templates

When creating a task with inputs you can use Go templates in that task's actions. For example:

tasks:
  - name: length-of-inputs
    inputs:
      hello-input:
        default: hello world
        description: This is an input to the echo-var task
      another-input:
        default: another world
    actions:
      # index and len are go template functions, while .inputs is map representing the inputs to the task
      - cmd: echo ${{ index .inputs "hello-input" | len }}
      - cmd: echo ${{ index .inputs "another-input" | len }}

  - name: len
    actions:
      - task: length-of-inputs
        with:
          hello-input: hello unicorn

Running run len will print the length of the inputs to hello-input and another-input to the console.