AspnetcoreExample.cs

#pragma warning disable IL2026
using FastCache;
using Markdig;
using Microsoft.AspNetCore.Mvc;
using NonBlocking;

var builder = WebApplication.CreateBuilder();
builder.Services.AddHttpClient();

var app = builder.Build();
var stampedeGuard = new ConcurrentDictionary<string, SemaphoreSlim>();

app.MapGet("weather", async (
    [FromQuery] string city,
    [FromServices] HttpClient http) =>
{
    Begin:
    if (Cached<IResult>.TryGet("/weather", city, out var cached))
    {
        return cached.Value;
    }

    var queryLock = stampedeGuard.GetOrAdd(city, static _ => new SemaphoreSlim(1, 1));
    if (!queryLock.Wait(0))
    {
        // Wait for the first in-flight request to complete then retry
        await queryLock.WaitAsync();
        queryLock.Release();

        goto Begin;
    }

    var query = $"https://wttr.in/{city}";
    var weather = await http.GetStringAsync(query);
    var result = cached
        .Save(Results.Content(weather, "text/html"), TimeSpan.FromMinutes(10), limit: 1000);

    queryLock.Release();
    return result;
});

app.MapGet("/posts/{postName}", static async (
    [FromRoute] string postName) =>
{
    if (Cached<IResult>.TryGet("posts", postName, out var cached))
    {
        return cached.Value;
    }

    var text = await File.ReadAllTextAsync($"posts/{postName}.md");
    var html = Markdown.ToHtml(text);
    var result = Results.Content(html, "text/html");

    return cached.Save(result, TimeSpan.FromMinutes(30), limit: 100);
});

await app.RunAsync();