+++
title = "Use the hit counter"
weight = 400
+++

## Add a hit counter to our stack

Okay, our hit counter is ready. Let's use it in our app. Open `src/CdkWorkshop/CdkWorkshopStack.cs` and add
the following highlighted code:

{{<highlight csharp "hl_lines=20-23 28">}}
using Amazon.CDK;
using Amazon.CDK.AWS.APIGateway;
using Amazon.CDK.AWS.Lambda;
using Constructs;

namespace CdkWorkshop
{
    public class CdkWorkshopStack : Stack
    {
        public CdkWorkshopStack(Construct scope, string id, IStackProps props = null) : base(scope, id, props)
        {
            // Defines a new lambda resource
            var hello = new Function(this, "HelloHandler", new FunctionProps
            {
                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"
            });

            var helloWithCounter = new HitCounter(this, "HelloHitCounter", new HitCounterProps
            {
                Downstream = hello
            });

            // defines an API Gateway REST API resource backed by our "hello" function.
            new LambdaRestApi(this, "Endpoint", new LambdaRestApiProps
            {
                Handler = helloWithCounter.Handler
            });
        }
    }
}

{{</highlight>}}

Notice that we changed our API Gateway handler to `helloWithCounter.handler`
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

```
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.