[BUG] Dynamic API endpoint creation with dynamic url is slow

[LuukVerhagen]

Describe the bug I use Refit with different host URLs, which come dynamically from the database. To accomplish this, I have created a factory service, which creates the Refit Endpoints dynamically based on the URL of the database. The problem which I encountered, is that the first API call with this newly created endpoint object is really slow (more than 40 seconds). If I debug the same code with a literal string URL instead of an URL from the database, I don't encounter this slowness.

//Slow
Project project = await projectService.GetSelectedProject();
var endpointWithDynamicUrl = Refit.RestService.For<TApiEndpoint>(project.Url, new Refit.RefitSettings()
{
    AuthorizationHeaderValueGetter = this.apiAuthService.GetToken
});

//Fast
var endpointWithLiteralUrl = Refit.RestService.For<TApiEndpoint>("https://example.com/", new Refit.RefitSettings()
{
    AuthorizationHeaderValueGetter = this.apiAuthService.GetToken
});

Steps To Reproduce

Expected behavior

That dynamically created API endpoint objects with a dynamic URL source doesn't cause a slow endpoint call.

Screenshots

Environment

• OS: Windows
• Device: Lenovo thinkpad p1
• Version:
• Working Version:

Additional context

If the URL in the database is a local URL, the first call is much faster.

[codeex]

Any suggestions for improvement? It doesn't look like a bug!

[LuukVerhagen]

I finally found the problem. The underlying HttpClient wasn't able to resolve my IPv6 address (which was wrongly configured in my DNS). It takes more than half a minute for the HttpClient to figure out IPv6 won't work and to switch to IPv4. To conclude the problem wasn't in Refit.

[0xced]

I just hit this same issue, also thinking that Refit might be the culprit. For me it did not take half a minute, just a few seconds (but very noticeable at application startup).

What I ended up doing is disabling IPv6 by adding the following runtime configuration option in my application csproj:

<ItemGroup>
  <RuntimeHostConfigurationOption Include="System.Net.DisableIPv6" Value="true" />
</ItemGroup>

After disabling IPv6, startup time went from ~2.5 seconds to ~0.2 seconds.

See also Forcing HttpClient to use IPv4 or IPv6 addresses by @meziantou and .NET 6 Networking Improvements (An option to globally disable IPv6).

Addendum: Turns out the server was listening on http://127.0.0.1:5000 and the client was connecting to http://localhost:5000 so by changing the server configuration to listen on localhost the slowness issue disappeared without having to disable IPv6.

Same conclusion as Luuk: no problem in Refit!

[github-actions[bot]]

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