Hello World example

Hello World introduces the main CRADLE concepts through two Ubuntu instances, one network, one external object, and one event in each lifecycle phase.

The example below follows the structure of the current CRADLE source scenario. Its artifact repository uses a public-safe placeholder; replace that value with an authorized repository before deployment.

What the scenario contains

Component	Name	Purpose
Scenario	HelloWorld	Names the environment and its generated outputs.
Application instance	HelloWorld	Runs the example object and requests monitoring configurations.
Router instance	router	Connects the environment and requests router and monitoring configurations.
Network	lan_0	Connects both instances through DHCP.
Object	HelloWorld	Locates the external HelloWorld.sh artifact.
Events	1, 2, and 3	Run the object in the pre, main, and post phases.

Scenario definition

instances() >
    instance("HelloWorld"),
    instance("router").

instance("HelloWorld") >
    os("ubuntu", "20.04"),
    config("linux-tcpdump"),
    config("ubuntu-focal-auditd"),
    config("linux-sysdig"),
    object("HelloWorld").

instance("router") >
    os("ubuntu", "20.04"),
    config("linux-tcpdump"),
    config("ubuntu-focal-auditd"),
    config("linux-router").

networks() >
    network("lan_0").

network("lan_0") >
    endpoint("HelloWorld", "DHCP"),
    endpoint("router", "DHCP").

metadata() >
    name("HelloWorld"),
    eventType("sequence"),
    repositoryRemote("https://artifacts.example.org"),
    object("HelloWorld").

events() >
    preEvent(),
    mainEvent(),
    postEvent().

preEvent() >
    event("1").

event("1") >
    instance("HelloWorld"),
    needRoot("false"),
    subject("bash", ""),
    runObject("HelloWorld", ""),
    pauseBeforeRun("0"),
    pauseAfterRun("0"),
    waitfor("false"),
    scheduleExecution("2018-11-13T20:20:39+00:00"),
    description("HelloWorld pre-event").

mainEvent() >
    event("2").

event("2") >
    instance("HelloWorld"),
    needRoot("false"),
    subject("bash", ""),
    runObject("HelloWorld", ""),
    pauseBeforeRun("0"),
    pauseAfterRun("0"),
    waitfor("false"),
    scheduleExecution("2018-11-13T20:20:39+00:00"),
    description("HelloWorld main event").

postEvent() >
    event("3").

event("3") >
    instance("HelloWorld"),
    needRoot("false"),
    subject("bash", ""),
    runObject("HelloWorld", ""),
    pauseBeforeRun("0"),
    pauseAfterRun("0"),
    waitfor("false"),
    scheduleExecution("2018-11-13T20:20:39+00:00"),
    description("HelloWorld post-event").

object("HelloWorld") >
    location("${uriRemote}/HelloWorld/object/HelloWorld.sh").

Read the scenario

Instances

instances() declares HelloWorld and router. Their named blocks define the operating system and requested configurations. The application instance also associates itself with the HelloWorld object.

Configuration availability depends on the selected CRADLE distribution and deployment provider.

Network

networks() declares lan_0. Its definition connects both instances using DHCP. This source scenario does not specify a subnet, so the provider-specific generation path supplies or resolves the network details.

Metadata and object

metadata() names the scenario, selects sequential event handling, identifies the artifact repository, and declares the object. The object definition uses ${uriRemote} to build the complete artifact location.

The placeholder repository in this public example does not host the artifact. Use the repository supplied for your authorized CRADLE environment.

Event phases

The scenario defines one event in each phase:

1. event 1 runs during preEvent;
2. event 2 runs during mainEvent; and
3. event 3 runs during postEvent.

All three events run the same object through bash on the HelloWorld instance without requesting root privileges.

Follow the references

Names connect the scenario:

1. metadata declares the HelloWorld object;
2. the application instance associates itself with that object;
3. each event selects the HelloWorld instance;
4. each event selects the HelloWorld object through runObject; and
5. the object definition supplies the artifact path.

A spelling or capitalization mismatch can leave a reference unresolved.

Generate or deploy the example

Follow the Quick start to generate and optionally deploy the example. Use the CRADLE language structure for property-level details, or Write a scenario to create your own.

For structured-output and compiler integration details, see the developer schema reference.