Skip to main content

Quickstart: Create your first application with LoadShedding

In this guide, you will use C# and the .NET CLI to create a WebApi that will have LoadShedding with the default configurations.

By the end of the guide, you will know how to use LoadShedding on your application.

Prerequisites​

  • One of the following .NET versions:
    • .NET Core 2.0 or above.

Overview​

You will create a WebApi using LoadShedding.

Steps​

1. Create a folder for your applications​

Create a new folder with the name LoadSheddingQuickstart.

2. Create WebApi Project​

Run the following command to create a WebApi Project named LoadSheddingQuickstart:

dotnet new webapi -controllers -n LoadSheddingQuickstart

3. Install LoadShedding package​

Inside the LoadSheddingQuickstart project directory, run the following command to install the required package:

dotnet add package Farfetch.LoadShedding.AspNetCore

4 Add Metrics​

Inside the LoadSheddingQuickstart project directory, run the following command to install Prometheus:

dotnet add package prometheus-net.AspNetCore
dotnet add package Farfetch.LoadShedding.Prometheus
info

This step is optional. With this you will be able to confirm that LoadShedding is configured on the Run! step.

5. Add LoadShedding on the WebApi​

Add the LoadShedding services by calling the AddLoadShedding extension:

services.AddLoadShedding();

Optionally you can configure SubscribeEvents() and you will be able to confirm that LoadShedding is configured on the Run! step:

services.AddLoadShedding((provider, options) =>
{
    options.SubscribeEvents(events =>
    {
        events.ItemEnqueued.Subscribe(args => Console.WriteLine($"QueueLimit: {args.QueueLimit}, QueueCount: {args.QueueCount}"));
        events.ItemDequeued.Subscribe(args => Console.WriteLine($"QueueLimit: {args.QueueLimit}, QueueCount: {args.QueueCount}"));
        events.ItemProcessing.Subscribe(args => Console.WriteLine($"ConcurrencyLimit: {args.ConcurrencyLimit}, ConcurrencyItems: {args.ConcurrencyCount}"));
        events.ItemProcessed.Subscribe(args => Console.WriteLine($"ConcurrencyLimit: {args.ConcurrencyLimit}, ConcurrencyItems: {args.ConcurrencyCount}"));
        events.Rejected.Subscribe(args => Console.Error.WriteLine($"Item rejected with Priority: {args.Priority}"));
    });
});
note

For more information about de default configurations and possible customizations see here.

6. Use LoadShedding on the WebApi​

Use the UseLoadShedding extension method by extending the IApplicationBuilder interface:

app.UseLoadShedding();

7. Run!​

From the LoadSheddingQuickstart directory run the project:

dotnet run --project LoadSheddingQuickstart/LoadSheddingQuickstart.csproj

And you should be able to call the available endpoint with Swagger Web Interface: https://localhost:7231/swagger/index.html

Now, you can confirm that LoadShedding is correctly configured on your WebApi by calling the following endpoint: https://localhost:7231/metrics

You should see the LoadShedding metrics referenced here.

Additionally, you can also confirm if LoadShedding is correctly configured by checking the following console output:

ConcurrencyLimit: 5, ConcurrencyItems: 1
ConcurrencyLimit: 5, ConcurrencyItems: 0