[Lambda] [request]: ECS-"like" Private Registry Support for Lambda Docker Images

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**Tell us about your request**
Add ECS-"like" Private Registry Auth / Interop support to AWS Lambda Service, for Lambda Functions built, deployed, and run as Docker Images / Containers...

**Which service(s) is this request for?**
Lambda

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**

For AWS Lambda Functions Built and Deployed as Docker Images / "Containerized" - seems at current the only supported option for image "hosting" is to push custom Lambda Docker Image build artifact versions in to an AWS ECR registry / repository, and then configure target Lambda Functions to pull those image build artifacts from AWS ECR at runtime.

For companies like my own - we are constrained by corporate standards / policy to push our custom Docker Image build artifacts into our Private JFrog Artifactory Instance and the Repositories we create therein as the last step in our CI / CD pipeline workflow automation. This means ALL custom Docker Images we build MUST exist in our Private JFA Instance, regardless of their respective use cases - always...

The AWS ECS Service currently supports Private Registry Auth / Interop - for Images hosted externally to AWS:
- https://docs.aws.amazon.com/AmazonECS/latest/developerguide/private-auth.html

This supported functionality has been a VERY nice option for us, allowing us to reference and obtain at runtime our custom Docker Image build artifact versions from one central location (our Private JFA) - and eliminating the need for duplication of those image build artifacts (by pushing to and hosting from BOTH our Private JFA AND AWS ECR) - saving us the additional storage, hosting, usage costs, etc. whilst reducing CI / CD pipeline workflow automation complexity / dependencies, and eliminating any possibility of disparity between image artifacts stored in multiple locations...

I know in our case it would be VERY nice to have the same Private Registry support in the case of "Dockerized" Lambda functions, allowing us to push custom Lambda Docker Image build artifact versions in to our Private JFA registry / repository (they would have to be pushed here anyway, per corp. policy...), and then configure target Lambda Functions to pull those image build artifacts from our Private JFA at runtime.

At current, while evaluating whether a new Lambda Function that I required to build for integration with a larger Terraform deployment task - the requirement for use of and explicit dependency on AWS ECR ultimately made the final decision for me to go the traditional file-based "lambda_payload" route.

If this Private Registry Auth feature were available for AWS Lambda - We would definitely begin adopting the "Lambda as Docker" development and deployment strategy to take advantage of the additional features and benefits it provides, whilst simultaneously aligning our Lambda Function development and deployment operations more closely with how we handle our larger CI / CD pipeline workflows...

I am willing to bet there are lots of other customers who would benefit from this very same feature, and it would be yet another incentive to migrate to (or start from) the new "containerized" Lambda Functions for anyone...

Cheers,

Chris Bishop

**Are you currently working around this issue?**
Not "working around" per se, rather choosing NOT to migrate to / adopt other recently released features and functionality - opting for Building, Deploying, Running Lambda Functions "the old fashioned way"...

Start with the issue's linked AWS ECS private-auth documentation and compare that capability with Lambda container-image deployment and AWS ECR requirements. No repository files or tests are mentioned; done would mean Lambda can authenticate to and pull the requested images from a private external registry without requiring an ECR copy.

Written by the indexing model from the issue text.