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README.md

AWS Lambda Container Images

This project contains the source needed to build the Docker image used in Lambda to run image-based developments.

For .NET developments, the Docker image used to deploy those developments in Lambda is a based on an Amazon Linux base image. Lambda requires the images used to have the following folder structure:

  • /var/lang
    • This folder should contain the .Net binaries
  • /var/runtime
    • This folder should contain the Amazon Lambda Runtime Support libary which enables the end-user binaries to be detected and executed in Lambda
  • /var/task
    • This folder should contain the end-user binaries, which is the code to be executed in Lambda

Base Image

Structure

The dockerfile(s) included in this project are used to build the image(s) used in Lambda based on the abovementioned structure. We are using a multi-stage dockerfile to install the .NET binaries, build and publish the Amazon Lambda Runtime Support libary and define an entrypoint to the end-user assemblies.

The 1st stage of the dockerfile uses a lambda/provided:al2 image to install needed dependencies which will be copied into the /rootfs folder of the base image.

The 2nd stage of the dockerfile uses a lambda/provided:al2 image to install the .NET binaries which will be copied into the /var/lang/bin folder.

The 3rd stage of the dockerfile uses a mcr.microsoft.com/dotnet/sdk image to build the Amazon Lambda Runtime Support library and its dependencies. The Amazon Lambda Runtime Support library is responsible for locating and loading the user-code assemblies into context. The library takes in a Function Handler string which is used to locate the user's lambda function and allows the user-code to be invoked by the Lambda service. The project is built as an executable which the dotnet process will execute in order to locate the end-user binaries. The project is then published and copied to the /var/runtime folder of the base image.

The entrypoint of the image is a shell script that is used to find the end-user's .deps.json and .runtimeconfig.json files in the /var/task folder. The script then calls the dotnet process to execute the Amazon Lambda Runtime Library and pass the .deps.json and .runtimeconfig.json files that enables the detection of the end-user binaries in Lambda.

This file structure is based on https://github.com/dotnet/dotnet-docker

Building

Run .\build.ps1 to generate the specific aws-lambda-dotnet:local docker image.

Using the Base Image

In order for you to deploy your Lambda function as an Image, you need to create a dockerfile and build on top of the aws-lambda-dotnet:local base image. The main purpose of this dockerfile is to put your project's assemblies inside the /var/task folder of the base image.

We have included a sample project in the directory that contains a basic docker file. Essentially, the dockerfile is referencing the aws-lambda-dotnet:local as the base image.Then building the end-user's lambda project inside a mcr.microsoft.com/dotnet/sdk image and publishing the assemblies to the /var/task folder.