Use the hit counter

Add a hit counter to our stack #

Okay, our hit counter is ready. Let’s use it in our app. Open ~/CdkWorkshopStack.java and add the following highlighted code:

package com.myorg;

import software.constructs.Construct;
import software.amazon.awscdk.Stack;
import software.amazon.awscdk.StackProps;

import software.amazon.awscdk.services.apigateway.LambdaRestApi;
import software.amazon.awscdk.services.lambda.Code;
import software.amazon.awscdk.services.lambda.Function;
import software.amazon.awscdk.services.lambda.Runtime;

public class CdkWorkshopStack extends Stack {
    public CdkWorkshopStack(final Construct parent, final String id) {
        this(parent, id, null);
    }

    public CdkWorkshopStack(final Construct parent, final String id, final StackProps props) {
        super(parent, id, props);

        // Defines a new lambda resource
        final Function hello = Function.Builder.create(this, "HelloHandler")
            .runtime(Runtime.NODEJS_14_X)    // execution environment
            .code(Code.fromAsset("lambda"))  // code loaded from the "lambda" directory
            .handler("hello.handler")        // file is "hello", function is "handler"
            .build();

        // Defines our hitcounter resource
        final HitCounter helloWithCounter = new HitCounter(this, "HelloHitCounter", HitCounterProps.builder()
            .downstream(hello)
            .build());

        // Defines an API Gateway REST API resource backed by our "hello" function
        LambdaRestApi.Builder.create(this, "Endpoint")
            .handler(helloWithCounter.getHandler())
            .build();
    }
}

Notice that we changed our API Gateway handler to helloWithCounter.getHandler() instead of hello. This basically means that whenever our endpoint is hit, API Gateway will route the request to our hit counter handler, which will log the hit and relay it over to the hello function. Then, the responses will be relayed back in the reverse order all the way to the user.

Deploy #

mvn package
cdk deploy

It might take a little while.

And the output:

CdkWorkshopStack.Endpoint8024A810 = https://xxxxxxxxxx.execute-api.us-east-1.amazonaws.com/prod/

Test #

Okay, ready to give this a go? (you should, again, see the URL of your API in the output of the “deploy” command).

Use curl or your web browser to hit your endpoint (we use -i to show HTTP response fields and status code):

curl -i https://xxxxxxxxxx.execute-api.us-east-1.amazonaws.com/prod/

Oh no… seems like something went wrong:

HTTP/1.1 502 Bad Gateway
...

{"message": "Internal server error"}

Let’s see how to find out what happened and fix it.