The resiliency features of .NET are built upon the Polly project and made available through Microsoft.Extensions. You can add a standard resilience strategy that uses sensible defaults by adding a single line of code to your app.
Add resilience to your app
To add resilience to an app built using a microservices architecture, using HTTP requests between individual services, take these steps:
- Add the
Microsoft.Extensions.Http.Resiliencepackage to your project. - Add a resilience handler to your HttpClient service calls.
- Configure the resilience strategy.
Add the NuGet package to your project
Run the following command to add the resiliency NuGet package:
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dotnet add package Microsoft.Extensions.Http.Resilience
Running this command from the terminal in the apps project folder will add the package reference to the project file.
Then add the following using statement in your application’s startup class :
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using Microsoft.Extensions.Http.Resilience;
Add a resilience strategy
You can now add a standard resilience strategy to your HttpClient service. .NET provides this out-of-the-box configuration combining a number of strategies.
The request handler goes through each of these strategies in order form left to right:
- Total request timeout strategy: This sets a total amount of time that the request can take. You can think of this as setting the upper time limit for all the other strategies.
- Retry strategy: This strategy controls the options on number of retries, backoff, and jitter. These options can’t exceed the total timeout set in the previous strategy.
- Circuit breaker strategy: This strategy opens the circuit if the failure ratio exceeds the threshold.
- Attempt timeout strategy: This strategy sets a timeout for each individual request. If the request takes longer than this time, then an exception is thrown.
You can add this standard strategy, with all the default values by adding this extension method:
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.AddStandardResilienceHandler();
For example if you have declared a WebApplication, and you want to add a resilience strategy to the HttpClient service use this code:
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builder.Services.AddHttpClient<ServiceBeingCalled>(httpClient =>
{
httpClient.BaseAddress = new Uri("https://service.endpoint/");
}).AddStandardResilienceHandler();
The first line of the preceding code adds a standard resilience handler to the HTTPClient. This will use all the default settings for the retry and circuit breaker strategies.
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