TokenExchangeService: Add documentation how to use GreengrassTokenExchangeRole permissions in the ECS Service

[AntonBy]

Feature description
The last version of documentation contains short descrption how TES works. And it really works with using DefaultAWSCredentialsProviderChain(AWS SDK Java). It works as native application, as Docker application, but it doesn't work as ECS Service. Because ECS Service TaskRole credentials will overlap GreengrassTockenExchangeRole credentials from TES.
It would be great to have a short comment about this in TES documentation.

Use Case
To avoid wasting time on issue

Proposed Solution
Upgrade documentation OR/AND suggest solution

Other

• 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change

[junfuchen99]

Hello,

Thanks for reporting this issue. We will look into updating the relevant documentation and let you know once it's updated. We will also check if there is a way for ECS to prefer TES creds

[jcosentino11]

@AntonBy, just curious, what's your use case here? ECS is already an orchestration service, why add Greengrass on top of that?

[AntonBy]

@jcosentino11 It's a part of our pipeline. We want to have a virtual "gg-device" for integration tests

[jcosentino11]

Ah okay. To make this work in the meantime, you can write your own CredentialsProvider by copying the above, and either switch the order or simply remove the ECS credentials part so that it only attempts to resolve TES. Then pass in your custom provider

https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/credentials-specify.html

[AntonBy]

Thank you for answer.
I used this approach with the custom provider, all worked properly.

All I wanted to offer - is to add a short note in https://docs.aws.amazon.com/greengrass/v2/developerguide/token-exchange-service-component.html with information about a potential conflict between TES credential env-variables and ECS env-variables(+ the link on the custom credentials provider page)

This task was created after 6 hours were spent investigating the access issue.
BUT "Greengrass from ECS" could be a quite rare case, so I'm not certain it's worth the effort