Minimal container lambda example

1. Minimal SAM template image function definition

    AWSTemplateFormatVersion: '2010-09-09'
    Transform: AWS::Serverless-2016-10-31
    Description: Minimal lambda containers example
   
    Parameters:
        Namespace:
            Type: String
            Default: ''
        
    Resources:
        ContainerFunction:
            Type: AWS::Serverless::Function
            Metadata:
                Dockerfile: Dockerfile
                DockerContext: ./lambda
            Properties:
                FunctionName: !Sub "ContainerFunction${Namespace}"
                PackageType: Image
                Timeout: 900
                MemorySize: 10240

2. Dockerfile in the folder defined by Metadata

   .
   ├── Makefile
   ├── README.md
   ├── lambda
   │   ├── Dockerfile
   │   ├── index.js
   │   └── package.json
   └── template.yaml
   

   • can be in a different directory also

3. Dockerfile

   FROM public.ecr.aws/lambda/nodejs:12
   RUN yum install ImageMagick-devel -y
   COPY ./* ./
   RUN npm install
   CMD [ "./index.lambdaHandler"]

   • the dockerfile will reference an aws lambda container FROM public.ecr.aws/lambda/nodejs:12 and extend it with own dependencies
   • CMD [ "./index.lambdaHandler"] runs the executable on lambda invoke

4. Build and Deploy

   1. make create_repository - run only once
   2. make deploy - builds and deploys

---

The Makefile

1. make create_repository

   account=$(aws sts get-caller-identity | jq --raw-output .Account)
   aws ecr create-repository --repository-name container-lambda --image-scanning-configuration scanOnPush=true

   • makes sure the ecr image repository exists in account
   • the --repository-name parameter set to the ecr repo you want to create, in this case container-lambda, you will use the repo url in the package and deploy SAM commands

2. make build

   sam build
   

   • sam handles building the container with docker for you

3. make package

   sam package --s3-bucket $$BUCKET --image-repository $$ACCOUNT.dkr.ecr.us-east-1.amazonaws.com/container-lambda
   

   • runs package the built files and stage in ecr and s3

4. make deploy

   sam deploy \
    	--s3-bucket $$BUCKET \
    	--image-repository $$ACCOUNT.dkr.ecr.us-east-1.amazonaws.com/container-lambda \
    	--stack-name LambdaContainers-mike \
    	--capabilities CAPABILITY_NAMED_IAM \
    	--no-fail-on-empty-changeset --tags logical_name=LambdaContainers-mike

   • runs sam deploy which launches the stack
   • the --image-repository is required for functions with PackageType: Image
   • the --s3-bucket is required for large templates (not in this case but leaving it in for extending in the future)
   • the --tags parameter with the logical_name tag tags the stack resources for cost explorer and is our convention

5. make test

   aws lambda invoke --function-name "ContainerFunction" --payload '{}' out.json && cat out.json && rm out.json
   

   • invokes lambda function and prints the response