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I want to use the HttpClientFactory that is available in .NET Core 2.1 but I also want to use the HttpClientHandler to utilize the AutomaticDecompression property when creating HttpClients.
I am struggling because the .AddHttpMessageHandler<> takes a DelegatingHandler not a HttpClientHandler.
Does anyone know how to get this to work?
Thanks, Jim
885
In general, HttpClientHandler can be used to configure a specific configuration like custom policy, headers, or security mechanism, compression, certificates, etc. We shall cover the below aspects in this article, Configure HttpClientHandler for Authentication Example: Bearer or Basic.
Not only that HttpClientFactory can create and manage new HttpClient instances but also, it works with underlying handlers. Basically, when creating new HttpClient instances, it doesn't recreate a new message handler but it takes one from a pool. Then, it uses that message handler to send the requests to the API.
It has a method CreateClient which returns the HttpClient Object. But in reality, HttpClient is just a wrapper, for HttpMessageHandler. HttpClientFactory manages the lifetime of HttpMessageHandelr, which is actually a HttpClientHandler who does the real work under the hood.
HttpClient is a mutable object but as long as you are not mutating it, it is actually thread safe and can be shared.
More properly to define primary HttpMessageHandler via ConfigurePrimaryHttpMessageHandler() method of HttpClientBuilder. See example below to configure typed client how.
services.AddHttpClient<TypedClient>() .ConfigureHttpClient((sp, httpClient) => { var options = sp.GetRequiredService<IOptions<SomeOptions>>().Value; httpClient.BaseAddress = options.Url; httpClient.Timeout = options.RequestTimeout; }) .SetHandlerLifetime(TimeSpan.FromMinutes(5)) .ConfigurePrimaryHttpMessageHandler(x => new HttpClientHandler() { AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate; }) .AddHttpMessageHandler(sp => sp.GetService<SomeCustomHandler>().CreateAuthHandler()) .AddPolicyHandlerFromRegistry(PollyPolicyName.HttpRetry) .AddPolicyHandlerFromRegistry(PollyPolicyName.HttpCircuitBreaker); Also you can define error handling policy via usage of special builders methods of Polly library. In this example policy should be predefined and stored into policy registry service.
public static IServiceCollection AddPollyPolicies( this IServiceCollection services, Action<PollyPoliciesOptions> setupAction = null) { var policyOptions = new PollyPoliciesOptions(); setupAction?.Invoke(policyOptions); var policyRegistry = services.AddPolicyRegistry(); policyRegistry.Add( PollyPolicyName.HttpRetry, HttpPolicyExtensions .HandleTransientHttpError() .WaitAndRetryAsync( policyOptions.HttpRetry.Count, retryAttempt => TimeSpan.FromSeconds(Math.Pow(policyOptions.HttpRetry.BackoffPower, retryAttempt)))); policyRegistry.Add( PollyPolicyName.HttpCircuitBreaker, HttpPolicyExtensions .HandleTransientHttpError() .CircuitBreakerAsync( handledEventsAllowedBeforeBreaking: policyOptions.HttpCircuitBreaker.ExceptionsAllowedBeforeBreaking, durationOfBreak: policyOptions.HttpCircuitBreaker.DurationOfBreak)); return services; } Actually I'm not using automatic decompression but the way to achieve this is to properly register http client
services.AddHttpClient<MyCustomHttpClient>() .ConfigureHttpMessageHandlerBuilder((c) => new HttpClientHandler() { AutomaticDecompression = System.Net.DecompressionMethods.GZip } ) .AddHttpMessageHandler((s) => s.GetService<MyCustomDelegatingHandler>()) If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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