AWS.Lambda.Powertools.Metrics.AspNetCore 0.1.0

AWS Lambda Powertools Metrics for ASP.NET Core

This library provides utilities for capturing and publishing custom metrics from your AWS Lambda functions using ASP.NET Core.

Getting Started

This library provides utilities for capturing and publishing custom metrics from your AWS Lambda functions using ASP.NET Core.

Installation

You can install the package via the NuGet package manager just search for AWS.Lambda.Powertools.Metrics.AspNetCore.

You can also install via powershell using the following command.

dotnet add package AWS.Lambda.Powertools.Metrics.AspNetCore

using AWS.Lambda.Powertools.Metrics;
using AWS.Lambda.Powertools.Metrics.AspNetCore.Http;

var builder = WebApplication.CreateBuilder(args);

// Configure metrics
builder.Services.AddSingleton<IMetrics>(_ => new MetricsBuilder()
    .WithNamespace("MyApi") // Namespace for the metrics
    .WithService("WeatherService") // Service name for the metrics
    .WithCaptureColdStart(true) // Capture cold start metrics
    .WithDefaultDimensions(new Dictionary<string, string> // Default dimensions for the metrics
    {
        {"Environment", "Prod"},
        {"Another", "One"}
    })
    .Build()); // Build the metrics

// Add AWS Lambda support. When the application is run in Lambda, Kestrel is swapped out as the web server with Amazon.Lambda.AspNetCoreServer. This
// package will act as the web server translating requests and responses between the Lambda event source and ASP.NET Core.
builder.Services.AddAWSLambdaHosting(LambdaEventSource.RestApi);

var app = builder.Build();

app.MapGet("/powertools", (IMetrics metrics) => 
    {
        // add custom metrics
        metrics.AddMetric("MyCustomMetric", 1, MetricUnit.Count);
        // flush metrics - this is required to ensure metrics are sent to CloudWatch
        metrics.Flush();
    })
    .WithMetrics();

app.Run();

WithMetrics() filter

The WithMetrics method is an extension method for the RouteHandlerBuilder class.

It adds a metrics filter to the specified route handler builder, which captures cold start metrics (if enabled) and flushes metrics on function exit.

Here is the highlighted WithMetrics method:

/// <summary>
/// Adds a metrics filter to the specified route handler builder.
/// This will capture cold start (if CaptureColdStart is enabled) metrics and flush metrics on function exit.
/// </summary>
/// <param name="builder">The route handler builder to add the metrics filter to.</param>
/// <returns>The route handler builder with the metrics filter added.</returns>
public static RouteHandlerBuilder WithMetrics(this RouteHandlerBuilder builder)
{
    builder.AddEndpointFilter<MetricsFilter>();
    return builder;
}

Explanation:

• The method is defined as an extension method for the RouteHandlerBuilder class.
• It adds a MetricsFilter to the route handler builder using the AddEndpointFilter method.
• The MetricsFilter captures and records metrics for HTTP endpoints, including cold start metrics if the CaptureColdStart option is enabled.
• The method returns the modified RouteHandlerBuilder instance with the metrics filter added.

UseMetrics() Middleware

The UseMetrics middleware is an extension method for the IApplicationBuilder interface.

It adds a metrics middleware to the specified application builder, which captures cold start metrics (if enabled) and flushes metrics on function exit.

Example

    
using AWS.Lambda.Powertools.Metrics.AspNetCore.Http;

var builder = WebApplication.CreateBuilder(args);

// Configure metrics
builder.Services.AddSingleton<IMetrics>(_ => new MetricsBuilder()
    .WithNamespace("MyApi") // Namespace for the metrics
    .WithService("WeatherService") // Service name for the metrics
    .WithCaptureColdStart(true) // Capture cold start metrics
    .WithDefaultDimensions(new Dictionary<string, string> // Default dimensions for the metrics
    {
        {"Environment", "Prod"},
        {"Another", "One"}
    })
    .Build()); // Build the metrics

builder.Services.AddAWSLambdaHosting(LambdaEventSource.RestApi);

var app = builder.Build();

app.UseMetrics(); // Add the metrics middleware

app.MapGet("/powertools", (IMetrics metrics) => 
    {
        // add custom metrics
        metrics.AddMetric("MyCustomMetric", 1, MetricUnit.Count);
        // flush metrics - this is required to ensure metrics are sent to CloudWatch
        metrics.Flush();
    });
    
app.Run();

Here is the highlighted UseMetrics method:

/// <summary>
/// Adds a metrics middleware to the specified application builder.
/// This will capture cold start (if CaptureColdStart is enabled) metrics and flush metrics on function exit.
/// </summary>
/// <param name="app">The application builder to add the metrics middleware to.</param>
/// <returns>The application builder with the metrics middleware added.</returns>
public static IApplicationBuilder UseMetrics(this IApplicationBuilder app)
{
    app.UseMiddleware<MetricsMiddleware>();
    return app;
}

Explanation:

• The method is defined as an extension method for the IApplicationBuilder interface.
• It adds a MetricsMiddleware to the application builder using the UseMiddleware method.
• The MetricsMiddleware captures and records metrics for HTTP requests, including cold start metrics if the CaptureColdStart option is enabled.