ALB Lambda Target Support

[dbettin]

I am perhaps missing something, but I don't see support for Lambdas as an ALB target.

Please let me know if it is currently supported.

[sam-goodwin]

IFunction needs to be updated to implement IApplicationGroupTarget

Good discussion in SAM: aws/serverless-application-model#721

[slipdexic]

New to the project, I would like to work on this.

[eladb]

@slipdexic yey! Feel free. No one is actively working on this.

[slipdexic]

Cool, I will start working on this.

[bweigel]

@slipdexic are you still working on this?

Also at anyone → What is the sensible way to do here, concerning the target group:

• add a new LambdaTargetGroup (introducing some duplication), or
• implement the expected behavior inside ApplicationTargetGroup? (it is after all still an [overloaded] application load balancer target in cloudformation...)

Also, since now vpc should be optional (or rather conditional) in BaseTargetGroupProps and TargetGroupBase how would you suggest going about the linting-error that enforces all optional property-Props needing to be optional themselves? Should that be solved with some kind of type-system trickery?

constructor(scope: Construct, id: string, props: ApplicationTargetGroupProps) → constructor(scope: Construct, id: string, props?: ApplicationTargetGroupProps)

[mitchlloyd]

Was looking at this today. Here are the issues I found:

1. As other noted, the value 'lambda' missing from enum type. Easy to work around with a type assertion.
2. Using loadbalancerListener.addTargets doesn't work because adding the target without a protocol or port will fail CDK validation with "Supply at least one of protocol and port". However adding a protocol or port fails Cfn validation with "Port cannot be specified for target groups with target type 'lambda'".

Here's the code I was using up to the point where I got stuck.

import cdk = require("@aws-cdk/core");
import lambda = require("@aws-cdk/aws-lambda");
import elbv2 = require("@aws-cdk/aws-elasticloadbalancingv2");
import ec2 = require("@aws-cdk/aws-ec2");

export class TheStack extends cdk.Stack {
  constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const vpc = new ec2.Vpc(this, "Main");

    const fn = new lambda.Function(this, "API", {
      handler: "index",
      runtime: lambda.Runtime.NODEJS_10_X,
      code: new lambda.AssetCode("dist"),
      vpc
    });

    const fnAlias = new lambda.Alias(this, "Live", {
      version: fn.addVersion("1"),
      aliasName: "Live"
    });

    const lb = new elbv2.ApplicationLoadBalancer(this, "LoadBalancer", {
      vpc,
      internetFacing: false
    });

    const listener = lb.addListener("Listener", {
      port: 80,
    });
    listener.addTargets('Targets', {
      targets: [new LambdaALBTarget(fnAlias)]
    });
  }
}

class LambdaALBTarget implements elbv2.IApplicationLoadBalancerTarget {
  private fn: lambda.IFunction;

  constructor(fn: lambda.IFunction) {
    this.fn = fn;
  }

  attachToApplicationTargetGroup(
    targetGroup: elbv2.ApplicationTargetGroup
  ): elbv2.LoadBalancerTargetProps {
    return {
      targetType: "lambda" as elbv2.TargetType,
      targetJson: {
        id: this.fn.functionArn
      }
    };
  }
}

[hleb-albau]

Also, it is not possible to enable health-check (no such property, and it is disabled by default for lambda).