How I can change configuration of HttpMessageHandler from Polly retry?

问题

I have the following issue. I have a proxy set. If a request via proxy very slow or has crashed I would like to try again without proxy.

For setting proxy I have the following code in the Startup.cs file:

services.AddHttpClient<ICheckPackagesService, CheckPackagesService>(x =>
{
    x.Timeout = TimeSpan.FromSeconds(10);
}).ConfigurePrimaryHttpMessageHandler(() => new SocketsHttpHandler
{
    Proxy = new WebProxy(IpService.GetIp())
});

But I can't imagine what I have to do for sending new one request without proxy (if the previous one has crashed of course!). A fast research in the official documentation gives me nothing.

Please, share your experience for this case. Thank you!

P.S. I use .NET Core 2.2.401.

回答1:

You cannot change the any of the properties of HttpClientHandler or assign a new version of HttpClientHandler to an existing HttpClient after it is instantiated.

Therefore you cannot use a Polly retry policy configured via HttpClientFactory to call via a new proxy (Polly policies configured via HttpClientFactory are applied as a DelegatingHandler within HttpClient).

As stated in the first link, use named clients defined on IHttpClientFactory instead, and define a named client for each proxy endpoint.

来源：https://stackoverflow.com/questions/58708315/how-i-can-change-configuration-of-httpmessagehandler-from-polly-retry