DotNet minimal lambdas

References

• Minimal guide: https://pikedev.com/net-6-minimal-api-on-aws-lambda/
• Another minimal start: https://dotnetcoretutorials.com/2021/07/16/building-minimal-apis-in-net-6/
• With Swagger (see ASP.NET Core minimal APIs): https://aws.amazon.com/blogs/compute/introducing-the-net-6-runtime-for-aws-lambda/
• MS Docs: https://docs.microsoft.com/en-us/aspnet/core/tutorials/min-web-api?view=aspnetcore-6.0&tabs=visual-studio
• With JWT Auth: https://dotnetthoughts.net/minimal-api-in-aspnet-core-mvc6-part2/
• Another JWT Example: https://dev.to/moe23/net-6-minimal-api-authentication-jwt-with-swagger-and-open-api-2chh
• Using Cognito auth in ASP.NET: https://medium.com/onebyte-llc/authentication-and-authorization-using-cognito-in-asp-net-7bdedf176f8c
• AWS Guide to Cognito Auth: https://docs.aws.amazon.com/sdk-for-net/v3/developer-guide/cognito-apis-intro.html
• Cognito Auth Extensions: https://docs.aws.amazon.com/sdk-for-net/v3/developer-guide/cognito-authentication-extension.html

Create

• dotnet new web -o . -n dotnet-minimal-lambda
• Install libraries for Swagger
  • dotnet add package Swashbuckle.AspNetCore
• Add Swagger including UI in Program.cs after initial .Build()

app.UseSwagger();
app.UseSwaggerUI();

• Add Swagger build config in Program.cs (before .Build()):

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

• Install libraries for AWS Lambda wrapper
  • dotnet add package Amazon.Lambda.AspNetCoreServer.Hosting
• Modify Program.cs to add Lambda wrapper to builder:

// Register Lambda to replace Kestrel as the web server for the ASP.NET Core application.
// If the application is not running in Lambda then this method will do nothing. 
builder.Services.AddAWSLambdaHosting(LambdaEventSource.HttpApi);

• Add ports and tasks for certs, restore, build and watch-run task to .gitpod.yml

tasks:
  - name: Create dev certificate for HTTPS
    init: dotnet dev-certs https # NB: Could add `gp sync-done create-cert`
  - name: Build and watch-run aspnet application/API
    init: | # Could add `gp sync-await create-cert`
      dotnet restore
      dotnet build
    command: dotnet watch run

ports:
  - port: 5113 # HTTP
    onOpen: open-browser

• When you restart now the app should build and watch-run then open the browser.
• Swagger is available on /swagger, and the JSON is at /swagger/v1/swagger.json
• Now you can simply update functions in the Program.cs file.
  • NB: Detection runs at startup so if you add a new function you will need to stop the watch-run and restart with dotnet watch run
• NB: At the time of writing the latest tooling is dotnet7 but dotnet6 is the latest on lambda, so change this in the .csproj if you get a framework load error when deployed.
• Add a serverless template with a handler using Path /{proxy+}, ensure you match the Handler name, and add any addition permissions and/or resources e.g.

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Transform": "AWS::Serverless-2016-10-31",
  "Description": "An Minimal AWS Serverless Application.",
  "Resources": {
    "AspNetCoreFunction": {
      "Type": "AWS::Serverless::Function",
      "Properties": {
        "Handler": "dotnet-minimal-lambda",
        "Runtime": "dotnet6",
        "MemorySize": 256,
        "Timeout": 35,
        "Role": null,
        "Policies": [
          "AWSLambda_FullAccess",
          "AmazonS3ReadOnlyAccess"
        ],
        "Events": {
          "ProxyResource": {
            "Type": "HttpApi",
            "Properties": {
              "Path": "/{proxy+}",
              "Method": "ANY"
            }
          },
          "RootResource": {
            "Type": "HttpApi",
            "Properties": {
              "Path": "/",
              "Method": "ANY"
            }
          }
        },
      }
    }
  },
  "Outputs": {
    "ApiURL": {
      "Description": "API endpoint URL for Prod environment",
      "Value": {
        "Fn::Sub": "https://${ServerlessHttpApi}.execute-api.${AWS::Region}.amazonaws.com/"
      }
    }
  }
}

• If required for your environment, add a Tags map, in the function's Properties section such as

      "Properties": {
        // ...
        "Tags": {
          "Name": "APM Badges",
          "Environment": "prod",
          "OwnerName": "Central Infrastructure",
          "OwnerEmail": "central-db@trilogy.com",
        },
        // ...
   },

• Generate the CloudFormation template with sam build
• Use SAM guided mode to configure for deployment with sam deploy --guided
• For a single stage, Bootstrap a deployment pipeline sam pipeline bootstrap
  • Enter stage name e.g. prod
  • Select AWS credentials source e.g. 2 - default (named profile)
  • Select pipline IAM and build resources if previously created (or enter nothing to create)
  • Defaults are generally fine for the remaining options, but review to requirement
  • Check summary and confirm, then confirm creation of resources
  • Then init pipeline sam pipeline init
• Otherwise, apply both together for guide multi-stage:
  • sam pipeline init --bootstrap
  • Note the generated pipeline user access key and secret
  • Add these to github as variables AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY NB: Go to repo -> Settings -> Secrets
  • Confirm the variable names in pipeline config
• Need to tidy up smooth path, but to resolve deployment failures (listed in GitHub actions) I followed through creating a Role with Sts:AssumeRole for the relevant deployment + Modifying the role to allow the GitHub pipeline IAM user permissions to assume the role.

TODO

• Add Blue/Green deployment configuration and basic health monitor alarm to check correct operation