InvalidEntrypoint for AWS Lambda with python docker container

Question

I've built an image for Lambda using public.ecr.aws/lambda/python:3.8 but always get this error.

Tried changing up the function and file names, but not getting any more details for debugging.

Also I've run the function locally and the entrypoint/cmd works.

START RequestId: cb4ba88c-c347-4e7d-b1ca-031a2e02fde4 Version: $LATEST
IMAGE   Launch error: fork/exec /lambda-entrypoint.sh: exec format error    Entrypoint: [/lambda-entrypoint.sh] Cmd: [index.lambda_handler] WorkingDir: [/var/task]IMAGE    Launch error: fork/exec /lambda-entrypoint.sh: exec format error    Entrypoint: [/lambda-entrypoint.sh] Cmd: [index.lambda_handler] WorkingDir: [/var/task]END RequestId: cb4ba88c-c347-4e7d-b1ca-031a2e02fde4
REPORT RequestId: cb4ba88c-c347-4e7d-b1ca-031a2e02fde4  Duration: 12.86 ms  Billed Duration: 13 ms  Memory Size: 128 MB Max Memory Used: 3 MB   
RequestId: cb4ba88c-c347-4e7d-b1ca-031a2e02fde4 Error: fork/exec /lambda-entrypoint.sh: exec format error
Runtime.InvalidEntrypoint

Answer 1

Turned out to be an architecture compatibility issue -

Needed to make sure the arch matched between the lambda function, and the docker image.

Locally I was building on an M1 with arm64 but the function is configured by default to use amd64

I changed my build command to
docker buildx build --platform linux/amd64 -t <image_name>:<image_tag>

Although I could have also updated the arch type for the lambda function to use arm64

Answer 2

For those weary travellers using Serverless framework and experiencing similar issues...

I had the same for nodejs and docker on Mac M1 using the standard aws-nodejs-docker-demo.

To Jeremy's point above, yes you can also simply add architecture: arm64 to serverless.yml to change the lambda architecture. Arm should be sightly cheaper too.

provider:
  name: aws
  region: ap-southeast-2
  architecture: arm64
  ecr:
uploaded to ECR
    images:
      appimage:
        path: ./

You should then see the function version switch architecture from x86_64 to arm64