Custom Metrics to AWS CloudWatch from ASP.NET Core

CloudWatch Custom Metrics

I was playing around with AWS CloudWatch and was curious to send custom metrics from ASP.NET Core. Specifically the execution time of an HTTP request.


I created a simple middleware that starts a StopWatch before calling the next middleware in the pipeline. When it returns, stop the StopWatch and send the data to CloudWatch.

First is to add the relevant NuGet packages.


If you’ve never used the AWS SDK/Packages, I recommend checking out my post on Configuring AWS SDK in ASP.NET Core. It goes over creating a named profile to store your AWS credentials and using appSettings or Environment variables to pass them through to ASP.NET Core.


Next is to create a simple middleware using the SDK. The middleware is having the IAmazonCloudwatch injected into the constructor. In the Startup’s ConfigureServices is where this is configured.

We’re simply calling the PutMetricDataAsync with a list of one MetricDatum. It contains the metric name, value, unit, timestamp, and dimensions.


As mentioned, in order to use the AWS SDK and the IAmazonCloudWatch in the middleware, you can use the AddDefaultAWSOptions and AddAWSService<IAmazonCloudWatch> to ConfigureServices to register the appropriate types.


If you look in CloudWatch, you can now see the new custom metrics we’ve published.


Before you start using this in a production environment, there are a couple of glaring issues.

First, sending the metrics to AWS, although incredibly fast should be handled outside of the actual HTTP request. this can be done completely asynchronously from the actual request. There is no point in delaying the HTTP response to the client. To solve this, we’ll add a queue and do it in a background service.

Secondly, some of the cost associated with CloudWatch is based on the number of API calls. This is why there is a List<MetricDatum> in the PutMetricDataRequest. It allows you to send/batch multiple metrics together to limit the number of API calls.

This is a better solution is to collect PutMetricDataRequest separately and send them in batch in a background service.

More on that coming soon.

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Using AWS Parameter Store for .NET Core Configuration

Parameter Store for .NET Core

One of the aspects I love about .NET Core is the new configuration and options pattern. In a continuation from my last post on using AWS Parameter Store for Data Protection keys, you can imagine it is possible to use Parameter Store for .NET Core Configuration.


There is a package by AWS that facilitates making using Parameter Store incredibly easy. Simply add the Amazon.Extensions.Configuration.SystemsManager package to your project and use the AddSystemsManager extension method on IConfigurationBuilder

The argument you pass to AddSystemsManager will be the prefix to your configuration hierarchy within Parameter Store. In my example, I’m using /Demo as my prefix, as you will also see below.

If you look at the first two entries, I can now create classes that match this hierarchy.


Next step is to add this configuration via the IServiceCollection using the Configure<T> method. Where T is our configuration type DemoConfig

This will add registration for the type IOptions<DemoConfig> so we can inject it in our Controllers or anywhere else the ServiceProvider is used.

This results in our config variable being set to the values from Parameter Store.

Parameter Store for .NET Core

If you have any questions or comments, please let me know on twitter as I will focus my posts on those questions and comments.

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Configuring AWS SDK in ASP.NET Core

Configuring AWS SDK in ASP.NET Core

If you’re using any AWS Services, you’re likely going to be using the AWS SDK via NuGet packages. You don’t need to configure anything to start using the SDK, but there are a few things that can make your life a lot easier. Follow along for a how-to on configuring AWS SDK in ASP.NET Core.

AWS CLI Named Profiles

The AWS Command Line Interface (CLI) is the first thing you’re going to want to have. Beyond controlling AWS services it allows you to configure credential profiles.

Once you have the CLI installed, to configure the default profile simply run and follow the prompt to enter your access key, secret and region.

> aws configure

For the rest of this example, I’m going to be using the default profile that I’ve configured that contains my access key and secret.


The AWS SDK will look for an AWS key in your appsettings.json file. It will use this section for configuration. In this section, you can define which Profile to use as well as many other options including as Region.

Environment Variables

You can also use Environment Variables to define these same settings. Be sure to use colon as hierarchy.


The AWSSDK.Extensions.NETCore.Setup NuGet package that adds extension methods to IConfiguration and IServiceCollection that makes it simple to retrieve AWS configuration and types.

Now if you inject the IAmazonS3 from a Controller or even if you resolve it from context.RequestServices.GetService<IAmazonS3>() you will get out an instance that is auto-configured with the access key and secret from your Default profile as well as the Region defined in your appsetting or Environment Variable.


That’s the quick start way of being able to use the AWS SDK without having to specify any of your credentials in your source as well as being able to use dependency injection to have the AWS SDK types resolve pre-configured.

If you have any questions or comments, please let me know on twitter as I will focus my posts on those questions and comments.

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