How to start a component with greengrasscoreipc client?

[drodriguez-dlc]

Hello, I've been able to successfully stop a component using the below function

async function change_component_state(component_name, state){
  const states = {
    'stop': 'stopComponent',
    'pause': 'pauseComponent',
    'restart': 'restartComponent',
    'resume': 'resumeComponent'
  }

  try {
    const component_request = {
      componentName: component_name
    };
    console.log(states[state], component_request)
    const result = await CLIENT[states[state]](component_request);
    console.log(`Component ${state} successfully:`, result);
  } catch (error) {
    console.error(`Failed to ${state} component:`, error);
  }
}

Has anyone been able to start a component using the ipc client? Id also add stopComponent is the only function that works, all others throw unauthorized errors.

[MikeDombo]

Hi, all APIs are documented in the AWS documentation:
https://docs.aws.amazon.com/greengrass/v2/developerguide/interprocess-communication.html

There is no API to start a component. Components are always supposed to be running automatically.

[drodriguez-dlc]

Thanks for the reply. Can you help me understand the difference between the link you posted and the sdk documentation(https://aws.github.io/aws-iot-device-sdk-js-v2/node/classes/greengrasscoreipc.Client-1.html#restartComponent)?

Based on your link, I'm only seeing the Pause and Resume capabilities, but the SDK exposes stop/resume/pause/restart methods. I can successfully stop a generic component using

await client.stopComponent("Component_Name")

[MikeDombo]

The difference? There is no difference, but the AWS documentation has more details including the access control settings that you must enable. https://docs.aws.amazon.com/greengrass/v2/developerguide/ipc-local-deployments-components.html#ipc-operation-restartcomponent

Why do you want to start/stop/pause/resume components? That is not a typical use case for Greengrass. Components are expected to just run forever. When configuration changes, the component will automatically restart if the configuration is used as part of the component lifecycle definition in the recipe.

[drodriguez-dlc]

Ok that makes more sense, I didn't see they broke the documentation into the lifecycle and local components. Thank you.

My IoT devices are part of a fleet that is installed in 30 motorsports vehicles. One component I have is for video streaming. Commands are received over MQTT, and then executed by the IPC client to Pause or Resume the stream. The IP that the video is streamed to can change, so maybe updating the configuration will be better suited for this task.

[MikeDombo]

Pausing and resuming a stream sounds like something that your application logic should handle, rather than actually stopping the component on the device.

[drodriguez-dlc]

Agreed.

I was trying to get away with having a component manage my other components, but it does makes more sense to have each component subscribe to a topic and manage itself without messing with the component states.

I appreciate the feedback and clarity on the documentation!

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.