Reuse image for functions with same build metadata

Description:

It looks like if you have 2 functions using PackageType: Image using the same Dockerfile, sam build does not correctly add ImageUri to all functions.

I have traced through the code that all functions are added to the same build_definition but the build results are not copied to all functions. There is an explicit if condition to only do this to ZIP, is there a reason for this or it’s just a feature not supported yet?

https://github.com/aws/aws-sam-cli/blob/12efe15b682926b006ce2a846d7cc6c71f5f2d74/samcli/lib/build/build_strategy.py#L117

Steps to reproduce:

Example template:

AWSTemplateFormatVersion: "2010-09-09"
Transform: AWS::Serverless-2016-10-31

Parameters:
  Tag:
    Type: String
    Default: latest
    Description: Docker tag to build and deploy.

Globals:
  Function:
    Timeout: 5

Resources:
  FooFunction:
    Type: AWS::Serverless::Function
    Properties:
      PackageType: Image
      ImageConfig:
        Command:
          - foo
    Metadata:
      DockerTag: !Ref Tag
      DockerContext: .

  BarFunction:
    Type: AWS::Serverless::Function
    Properties:
      PackageType: Image
      ImageConfig:
        Command:
          - bar
    Metadata:
      DockerTag: !Ref Tag
      DockerContext: .

Observed result:

The “built” template only has ImageUri on the BarFunction:

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Parameters:
  Tag:
    Type: String
    Default: latest
    Description: Docker tag to build and deploy.
Globals:
  Function:
    Timeout: 5
Resources:
  BarFunction:
    Type: AWS::Serverless::Function
    Properties:
      PackageType: Image
      ImageConfig:
        Command:
        - bar
      ImageUri: barfunction:latest
    Metadata:
      DockerTag:
        Ref: Tag
      DockerContext: .
  FooFunction:
    Type: AWS::Serverless::Function
    Properties:
      PackageType: Image
      ImageConfig:
        Command:
        - foo
    Metadata:
      DockerTag:
        Ref: Tag
      DockerContext: .

Expected result:

Expect to re-use the same image for multiple functions.

I can however see an issue because the image name includes the first function name.

Additional environment details (Ex: Windows, Mac, Amazon Linux etc)

1. OS: mac
2. sam --version: 1.13.2

[KylePeterDavies]

Commenting for support, I would also like to be able to reuse the same image for multiple lambdas.

[jasonmk]

FYI, I found another bug, though I believe this one is much deeper than SAM (or at least the part that runs locally). It appears that if you specify a Command in the template it will lose track of the EntryPoint. I found that I had to specify both Command and Entrypoint (‘/lambda-entrypoint.sh’) in order to be able to successfully override the command. If you run into issues about missing entry points then give that a shot.