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AI-Article API ASP.NET Core C# FetchExtension MarkDig Markdown Nuget

Een remote Markdown Fetcher bouwen voor Markdig

Friday, 07 November 2025

Inleiding

Een van de uitdagingen die ik geconfronteerd tijdens het bouwen van deze blog was hoe efficiënt externe markdown inhoud zonder handmatig kopiëren en plakken overal.

Ik wilde README-bestanden uit mijn GitHub repositories ophalen, documentatie van andere projecten opnemen en alles automatisch synchroniseren.Mostlylucid.Markdig.FetchExtensionDe oplossing?

Een aangepaste Markdig extensie die remote markdown ophaalt op het moment van weergeven en het intelligent caches.

In deze post, zal ik u door hoe ik gebouwd

**- een complete oplossing voor het ophalen en cachen van remote markdown content met ondersteuning voor meerdere opslag backends, automatische polling, en een oud-while-revalidate caching patroon.**OPMERKING: Dit is nog steeds prerelease, maar ik wilde het naar buiten krijgen.disable="true"Veel plezier, maar het werkt misschien nog niet.

**Dit artikel is AI gegenereerd - met behulp van claude code die ook hielp me bouwen van de functie.**UPDAAT[TOC]: Toegevoegd

parameter zodat we nu de tags goed kunnen demograferen zonder dat ze verwerkt wordenUPDATE (nov 7, 2025).

: Toegevoegd Inhoudsopgave (TOC) generatie functie! Gebruik

in uw markdown om automatisch een klikbare inhoudsopgave uit documentkoppen te genereren.

Zie de bron ervoor hier

  1. op de GitHub voor deze siteNuGet
  2. NuGetWaarom dit bouwen?
  3. **Voordat ik in de technische details duik, leg ik het probleem uit.**Ik heb verschillende scenario's waarin ik externe markdown content moet opnemen:
  4. README's van het pakket: Wanneer ik schrijf over een NuGet pakket dat ik heb gepubliceerd, wil ik de README direct van GitHub

API-documentatie

  • : Externe API-docs die vaak moeten blijven synchroniseren
  • Gedeelde inhoud
  • : Documentatie die in één repository leeft maar op meerdere plaatsen moet verschijnen
  • Prestaties

: Ik wil deze inhoud niet ophalen op elke pagina lading - dat zou langzaam en verspillend zijn

De naïeve benadering zou zijn om een HTTP client te gebruiken om markdown op te halen wanneer je het nodig hebt.

Maar dat is problematisch:

graph TD
    A[Markdown with fetch tags] --> B[MarkdownFetchPreprocessor]
    B --> C{Check Cache}
    C -->|Fresh| D[Return Cached Content]
    C -->|Stale/Missing| E[Fetch from Remote URL]
    E -->|Success| F[Update Cache]
    E -->|Failure| G{Has Cached?}
    G -->|Yes| H[Return Stale Cache]
    G -->|No| I[Return Error Comment]
    F --> J[Replace fetch with Content]
    D --> J
    H --> J
    I --> J
    J --> K[Processed Markdown]
    K --> L[Your Markdig Pipeline]
    L --> M[Final HTML]

Elk verzoek raakt de externe serverNetwerk latency impact pagina laadtijdenGeen offline ondersteuning

  1. Geen behandeling van voorbijgaande storingen<fetch>Ik had iets slimmer nodig: één keer ophalen, intelligent cachen, automatisch opfrissen en fouten op een elegante manier afhandelen.
  2. Overzicht architectuur
  3. De uitbreiding volgt eerder een voorbewerkingsaanpak dan deel uit te maken van de Markdig-ontleedpijplijn.
  4. Dit is cruciaal omdat het betekent opgehaalde inhoud stroomt door uw hele Markdig pijplijn, het krijgen van al uw aangepaste extensies, syntax highlighting, en styling.

Het belangrijkste inzicht hier is

voorbewerking

# My Documentation

<!-- Failed to fetch content from https://raw.githubusercontent.com/user/repo/main/README.md: HTTP 404: Not Found -->

Voordat je de Markdig-pijpleiding raakt, zijn we:

  • Scannen op
  • tags
  • De inhoud op te lossen (van cache of remote)
  • De tags vervangen door echte markdown

Laat Markdig dan alles samen verwerken.

Dit zorgt voor consistentie - alle markdown krijgt dezelfde behandeling ongeacht de bron.De basissyntaxisHet gebruik van de extensie is eenvoudig.

graph LR
    A[IMarkdownFetchService Interface] --> B[InMemoryMarkdownFetchService]
    A --> C[FileBasedMarkdownFetchService]
    A --> D[PostgresMarkdownFetchService]
    A --> E[SqliteMarkdownFetchService]
    A --> F[SqlServerMarkdownFetchService]
    A --> G[YourCustomService]

    B --> H[ConcurrentDictionary]
    C --> I[File System + SemaphoreSlim]
    D --> J[PostgreSQL Database]
    E --> K[SQLite Database]
    F --> L[SQL Server Database]
    G --> M[Your Storage Backend]

In je afdruk:

Dat is het!IMarkdownFetchService:

public interface IMarkdownFetchService
{
    Task<MarkdownFetchResult> FetchMarkdownAsync(
        string url,
        int pollFrequencyHours,
        int blogPostId = 0);

    Task<bool> RemoveCachedMarkdownAsync(
        string url,
        int blogPostId = 0);
}

De uitbreiding zal:

Haal de README van GitHub

Cache het voor 24 uurConcurrentDictionary:

public class InMemoryMarkdownFetchService : IMarkdownFetchService
{
    private readonly ConcurrentDictionary<string, CacheEntry> _cache = new();
    private readonly IHttpClientFactory _httpClientFactory;
    private readonly ILogger<InMemoryMarkdownFetchService> _logger;

    public async Task<MarkdownFetchResult> FetchMarkdownAsync(
        string url,
        int pollFrequencyHours,
        int blogPostId)
    {
        var cacheKey = GetCacheKey(url, blogPostId);

        // Check cache
        if (_cache.TryGetValue(cacheKey, out var cached))
        {
            var age = DateTimeOffset.UtcNow - cached.FetchedAt;
            if (age.TotalHours < pollFrequencyHours)
            {
                _logger.LogDebug("Returning cached content for {Url}", url);
                return new MarkdownFetchResult
                {
                    Success = true,
                    Content = cached.Content
                };
            }
        }

        // Fetch fresh content
        var fetchResult = await FetchFromUrlAsync(url);

        if (fetchResult.Success)
        {
            _cache[cacheKey] = new CacheEntry
            {
                Content = fetchResult.Content,
                FetchedAt = DateTimeOffset.UtcNow
            };
        }
        else if (cached != null)
        {
            // Fetch failed, return stale cache
            _logger.LogWarning("Fetch failed, returning stale cache for {Url}", url);
            return new MarkdownFetchResult
            {
                Success = true,
                Content = cached.Content
            };
        }

        return fetchResult;
    }

    private static string GetCacheKey(string url, int blogPostId)
        => $"{url}_{blogPostId}";
}

Teruggeven van gecachede inhoud op volgende verzoeken

  1. Automatisch vernieuwen wanneer de cache verloopt
  2. Architectuur van de opslagprovider
  3. Een van de ontwerpprincipes die ik volgde was
  4. flexibiliteit
  5. Verschillende toepassingen hebben verschillende behoeften.
  6. Een kleine demo app heeft PostgreSQL niet nodig, maar een multi-server productie implementatie wel.

Dus bouwde ik een pluggable opslag architectuur:De kerninterfaceAlles implementeert

Eenvoudig en schoon.

Elke implementatie behandelt opslag op zijn eigen manier, maar de interface blijft consistent.

public class FileBasedMarkdownFetchService : IMarkdownFetchService
{
    private readonly string _cacheDirectory;
    private readonly IHttpClientFactory _httpClientFactory;
    private readonly ILogger<FileBasedMarkdownFetchService> _logger;
    private readonly SemaphoreSlim _fileLock = new(1, 1);

    public async Task<MarkdownFetchResult> FetchMarkdownAsync(
        string url,
        int pollFrequencyHours,
        int blogPostId)
    {
        var cacheKey = ComputeCacheKey(url, blogPostId);
        var cacheFile = GetCacheFilePath(cacheKey);

        await _fileLock.WaitAsync();
        try
        {
            // Check if file exists and is fresh
            if (File.Exists(cacheFile))
            {
                var fileInfo = new FileInfo(cacheFile);
                var age = DateTimeOffset.UtcNow - fileInfo.LastWriteTimeUtc;

                if (age.TotalHours < pollFrequencyHours)
                {
                    var cached = await File.ReadAllTextAsync(cacheFile);
                    return new MarkdownFetchResult
                    {
                        Success = true,
                        Content = cached
                    };
                }
            }

            // Fetch fresh
            var fetchResult = await FetchFromUrlAsync(url);

            if (fetchResult.Success)
            {
                await File.WriteAllTextAsync(cacheFile, fetchResult.Content);
            }
            else if (File.Exists(cacheFile))
            {
                // Return stale on fetch failure
                var stale = await File.ReadAllTextAsync(cacheFile);
                return new MarkdownFetchResult
                {
                    Success = true,
                    Content = stale
                };
            }

            return fetchResult;
        }
        finally
        {
            _fileLock.Release();
        }
    }

    private string GetCacheFilePath(string cacheKey)
        => Path.Combine(_cacheDirectory, $"{cacheKey}.md");

    private static string ComputeCacheKey(string url, int blogPostId)
    {
        var combined = $"{url}_{blogPostId}";
        using var sha256 = SHA256.Create();
        var bytes = Encoding.UTF8.GetBytes(combined);
        var hash = sha256.ComputeHash(bytes);
        return Convert.ToHexString(hash);
    }
}

In-Geheugen opslag: Perfect voor demo's

  1. De eenvoudigste implementatie maakt gebruik vanSemaphoreSlimZoals je kunt zien doet dit het volgende:
  2. Maakt een cache sleutel van de URL en blog post ID
  3. Controleer of we gecached inhoud hebben en of het vers is
  4. Als cache vers is, geeft deze onmiddellijk terug
  5. Als oud, probeert om verse inhoud op te halen

Bij succes, update de cache

Bij fout met gecachede inhoud, geeft oude cache terug (stale-while-revalidate!)

public class PostgresMarkdownFetchService : IMarkdownFetchService
{
    private readonly MarkdownCacheDbContext _dbContext;
    private readonly IHttpClientFactory _httpClientFactory;
    private readonly ILogger<PostgresMarkdownFetchService> _logger;

    public async Task<MarkdownFetchResult> FetchMarkdownAsync(
        string url,
        int pollFrequencyHours,
        int blogPostId)
    {
        var cacheKey = GetCacheKey(url, blogPostId);

        // Query cache
        var cached = await _dbContext.MarkdownCache
            .FirstOrDefaultAsync(c => c.CacheKey == cacheKey);

        if (cached != null)
        {
            var age = DateTimeOffset.UtcNow - cached.LastFetchedAt;
            if (age.TotalHours < pollFrequencyHours)
            {
                return new MarkdownFetchResult
                {
                    Success = true,
                    Content = cached.Content
                };
            }
        }

        // Fetch fresh
        var fetchResult = await FetchFromUrlAsync(url);

        if (fetchResult.Success)
        {
            if (cached == null)
            {
                cached = new MarkdownCacheEntry
                {
                    CacheKey = cacheKey,
                    Url = url,
                    BlogPostId = blogPostId
                };
                _dbContext.MarkdownCache.Add(cached);
            }

            cached.Content = fetchResult.Content;
            cached.LastFetchedAt = DateTimeOffset.UtcNow;
            await _dbContext.SaveChangesAsync();
        }
        else if (cached != null)
        {
            // Return stale
            return new MarkdownFetchResult
            {
                Success = true,
                Content = cached.Content
            };
        }

        return fetchResult;
    }
}

Bij fout zonder cache, geeft fout terug

CREATE TABLE markdown_cache (
    id SERIAL PRIMARY KEY,
    cache_key VARCHAR(128) NOT NULL UNIQUE,
    url VARCHAR(2048) NOT NULL,
    blog_post_id INTEGER NOT NULL,
    content TEXT NOT NULL,
    last_fetched_at TIMESTAMP WITH TIME ZONE NOT NULL,
    CONSTRAINT ix_markdown_cache_cache_key UNIQUE (cache_key)
);

CREATE INDEX ix_markdown_cache_url_blog_post_id
    ON markdown_cache(url, blog_post_id);

Dit patroon -

graph TB
    subgraph "Load Balancer"
        LB[Load Balancer]
    end

    subgraph "Application Servers"
        A1[App Server 1<br/>FetchExtension]
        A2[App Server 2<br/>FetchExtension]
        A3[App Server 3<br/>FetchExtension]
    end

    subgraph "Shared Cache"
        PG[(PostgreSQL<br/>markdown_cache table)]
    end

    subgraph "External Content"
        R1[Remote URL 1]
        R2[Remote URL 2]
        R3[Remote URL 3]
    end

    LB --> A1
    LB --> A2
    LB --> A3

    A1 <-->|Read/Write Cache| PG
    A2 <-->|Read/Write Cache| PG
    A3 <-->|Read/Write Cache| PG

    A1 -.->|Fetch if cache miss| R1
    A2 -.->|Fetch if cache miss| R2
    A3 -.->|Fetch if cache miss| R3

oud-while-revalidate

- is cruciaal voor betrouwbaarheid.

Zelfs als GitHub is neer, uw site blijft werken met gecached inhoud.

dotnet add package mostlylucid.Markdig.FetchExtension

Bestandsgestuurde opslag: Eenvoudige Persistentie

# For in-memory (demos/testing)
# Already included in base package

# For file-based storage
# Already included in base package

# For PostgreSQL
dotnet add package mostlylucid.Markdig.FetchExtension.Postgres

# For SQLite
dotnet add package mostlylucid.Markdig.FetchExtension.Sqlite

# For SQL Server
dotnet add package mostlylucid.Markdig.FetchExtension.SqlServer

Voor single-server implementaties, file-based storage werkt geweldig:

Belangrijkste punten:Program.cs:

using Mostlylucid.Markdig.FetchExtension;

var builder = WebApplication.CreateBuilder(args);

// Option 1: In-Memory (simplest)
builder.Services.AddInMemoryMarkdownFetch();

// Option 2: File-Based (persists across restarts)
builder.Services.AddFileBasedMarkdownFetch("./markdown-cache");

// Option 3: PostgreSQL (multi-server)
builder.Services.AddPostgresMarkdownFetch(
    builder.Configuration.GetConnectionString("MarkdownCache"));

// Option 4: SQLite (single server with DB)
builder.Services.AddSqliteMarkdownFetch("Data Source=markdown-cache.db");

// Option 5: SQL Server (enterprise)
builder.Services.AddSqlServerMarkdownFetch(
    builder.Configuration.GetConnectionString("MarkdownCache"));

var app = builder.Build();

// If using database storage, ensure schema exists
if (app.Environment.IsDevelopment())
{
    app.Services.EnsureMarkdownCacheDatabase();
}

// Configure the extension with your service provider
FetchMarkdownExtension.ConfigureServiceProvider(app.Services);

app.Run();

Gebruik

voor thread-veilige bestandstoegang

public class MarkdownRenderingService
{
    private readonly IServiceProvider _serviceProvider;
    private readonly MarkdownFetchPreprocessor _preprocessor;
    private readonly MarkdownPipeline _pipeline;

    public MarkdownRenderingService(IServiceProvider serviceProvider)
    {
        _serviceProvider = serviceProvider;
        _preprocessor = new MarkdownFetchPreprocessor(serviceProvider);

        _pipeline = new MarkdownPipelineBuilder()
            .UseAdvancedExtensions()
            .UseSyntaxHighlighting()
            .UseToc()  // Add TOC support for [TOC] markers
            .UseYourCustomExtensions()
            .Build();
    }

    public string RenderMarkdown(string markdown)
    {
        // Step 1: Preprocess to handle fetch tags
        var processed = _preprocessor.Preprocess(markdown);

        // Step 2: Run through your normal Markdig pipeline
        return Markdown.ToHtml(processed, _pipeline);
    }
}

Hashes de URL + blog post ID om veilige bestandsnamen te maken

  1. Gebruikt bestandsmodificatie tijd om versheid te bepalen<fetch>Persistent over toepassing herstarten
  2. Zelfde oud-while-revalidate patroon
  3. Database-opslag: Productie-klaar
  4. Voor productie-implementaties, met name multi-server opstellingen, wilt u een gedeelde cache.

Dat is waar de database providers komen in:

Het databaseschema is eenvoudig:

In een multi-server implementatie, dit geeft je cache consistentie over alle instanties:**Alle servers delen dezelfde cache.**Wanneer Server 1 een README haalt, profiteren Servers 2 en 3 onmiddellijk van die gecachede inhoud.

De extensie instellen

Aan de slag gaan is eenvoudig.[TOC]Installeer eerst het basispakket:

# My Document

[TOC]

# Introduction
Content here...

# Getting Started
More content...

## Installation
Details...

Kies vervolgens uw opslagprovider:

<nav class="ml_toc" aria-label="Table of Contents">
  <ul>
    <li><a href="#introduction">Introduction</a></li>
    <li><a href="#getting-started">Getting Started</a>
      <ul>
        <li><a href="#installation">Installation</a></li>
      </ul>
    </li>
  </ul>
</nav>

Configuratie in ASP.NET Core

In uw

[TOC cssclass="my-custom-toc"]

Integratie met uw Markdown Rendering

<nav class="my-custom-toc" aria-label="Table of Contents">
  <!-- TOC content -->
</nav>

De sleutel is de voorbewerkingsstap.

  1. **Zo integreer ik het in mijn blog:**De stroom is:

  2. Uw markdown bevattags

    • Preprocessor lost ze op tot werkelijke markdownid="getting-started"
    • De gecombineerde afwaardering gaat via Markdigid="api-reference"
  3. **Alles krijgt uw aangepaste extensies, styling, enz.**Geavanceerde functiesul/liInhoudsopgave

Het pakket bevat nu een

apart

var pipeline = new MarkdownPipelineBuilder()
    .UseAdvancedExtensions()
    .UseToc()  // Add TOC support - position in pipeline doesn't matter!
    .Use<YourOtherExtensions>()
    .Build();

**Inhoudsopgave (TOC) uitbreiding!**Terwijl het is verpakt naast de fetch extensie, het is volledig onafhankelijk en kan worden gebruikt op zijn eigen.**U kunt automatisch een klikbare inhoudsopgave genereren uit de rubrieken van uw document.**Basisgebruik:

  • Simpelweg toevoegen
  • overal in uw markdown:

Dit genereert een geneste lijst van alle rubrieken met ankerverbindingen:.UseToc()Aangepaste CSS-klassen:

**U kunt een aangepaste CSS-klasse opgeven voor styling:**Dit rendert met uw aangepaste klasse:

  • Hoe het werkt:
  • Autodetectie
  • : De TOC detecteert automatisch het minimale koersniveau in uw document en past dienovereenkomstig aan.

**Als uw document begint met H2, behandelt de TOC H2 als het hoogste niveau.**ID-generatie[TOC]: Headings worden automatisch ID's gegeven voor het verankeren van:.UseToc()"Aan de slag" →

"API-referentie" →

Geneste structuur

<!-- Failed to fetch content from https://raw.githubusercontent.com/user/repo/main/docs/README.md: HTTP 404: Not Found -->

: De renderer bouwt een goed geneste

  • ./CONTRIBUTING.mdhttps://github.com/user/repo/blob/main/docs/CONTRIBUTING.md
  • ../images/logo.pnghttps://github.com/user/repo/blob/main/images/logo.png
  • structuur die uw documenthiërarchie weerspiegelt.

TOC-ondersteuning inschakelen:

public class MarkdownLinkRewriter
{
    public static string RewriteLinks(string markdown, string sourceUrl)
    {
        var document = Markdown.Parse(markdown);
        var baseUri = GetBaseUri(sourceUrl);

        foreach (var link in document.Descendants<LinkInline>())
        {
            if (IsRelativeLink(link.Url))
            {
                link.Url = ResolveRelativeLink(baseUri, link.Url);
            }
        }

        using var writer = new StringWriter();
        var renderer = new NormalizeRenderer(writer);
        renderer.Render(document);
        return writer.ToString();
    }

    private static bool IsRelativeLink(string url)
    {
        if (string.IsNullOrEmpty(url)) return false;
        if (url.StartsWith("http://") || url.StartsWith("https://")) return false;
        if (url.StartsWith("#")) return false;  // Anchor
        if (url.StartsWith("mailto:")) return false;
        return true;
    }
}

Voeg bij het configureren van uw Markdig-pijpleiding de TOC-extensie toe:

Pijplijnpositie:

<!-- Failed to fetch content from https://api.example.com/status.md: HTTP request failed: Name or service not known (api.example.com:443) -->

In tegenstelling tot sommige Markdig extensies, de TOC extensie

maakt het niet uit waar je het toevoegtin de pijplijn.De extensie automatisch:

Voegt zijn parser toe aan het begin van de parserlijst (positie 0)

<!-- Failed to fetch content from https://example.com/docs.md: HTTP 404: Not Found -->

Renders nadat alle ontleden is voltooid, het verzamelen van rubrieken uit het hele document

Dus je kunt toevoegen

overal - begin, midden, of einde van uw pijpleiding configuratie.

  • {retrieved:format}Belangrijk:
  • {age}De TOC extensie is volledig onafhankelijk van de fetch extensie.
  • {url}Ze zijn gewoon samen verpakt voor het gemak.
  • {nextrefresh:format}U kunt:
  • {pollfrequency}TOC gebruiken zonder ophalen
  • {status}Ophalen zonder TOC gebruiken

Gebruik beide samen

Opmerking:disable="true"De TOC-markering werkt zowel in uw belangrijkste markdown-bestanden als in opgehaalde inhoud op afstand.

<!-- This will be processed and fetch content -->
<!-- Failed to fetch content from https://example.com/README.md: HTTP 404: Not Found -->

<!-- This will NOT be processed - useful for documentation -->
<!-- Failed to fetch content from https://example.com/README.md: HTTP 404: Not Found -->

Als u een README van GitHub die bevat ophalen

  • , het zal automatisch een inhoudsopgave genereren uit de rubrieken van dat document (aangenomen dat u hebt toegevoegd
  • naar uw pijpleiding).
  • Transformatie koppelen

Bij het ophalen van remote markdown (vooral van GitHub), relatieve links breken.<fetch>De extensie kan ze automatisch herschrijven:<fetch-summary>Dit transformeert:

<!-- No fetch data available for https://example.com/api/status.md -->

Bewaart absolute URL's en ankers

De implementatie maakt gebruik van de Markdig AST om links te herschrijven:

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddPostgresMarkdownFetch(connectionString);

        var sp = services.BuildServiceProvider();
        var eventPublisher = sp.GetRequiredService<IMarkdownFetchEventPublisher>();

        // Subscribe to events
        eventPublisher.FetchBeginning += (sender, args) =>
        {
            Console.WriteLine($"Fetching {args.Url}...");
        };

        eventPublisher.FetchCompleted += (sender, args) =>
        {
            var source = args.WasCached ? "cache" : "remote";
            Console.WriteLine($"Fetched {args.Url} from {source} in {args.Duration.TotalMilliseconds}ms");
        };

        eventPublisher.FetchFailed += (sender, args) =>
        {
            Console.WriteLine($"Failed to fetch {args.Url}: {args.ErrorMessage}");
        };
    }
}

Overzicht van metadata ophalen

sequenceDiagram
    participant MD as Markdown Processor
    participant EP as Event Publisher
    participant FS as Fetch Service
    participant ST as Storage Backend
    participant L as Your Listeners

    MD->>EP: FetchBeginning
    EP->>L: Notify FetchBeginning
    EP->>FS: FetchMarkdownAsync(url)
    FS->>ST: Check Cache
    alt Cache Fresh
        ST-->>FS: Cached Content
        FS->>EP: FetchCompleted (cached=true)
    else Cache Stale/Missing
        FS->>FS: HTTP GET
        alt Success
            FS->>ST: Update Cache
            ST-->>FS: OK
            FS->>EP: FetchCompleted (cached=false)
        else Failure
            FS->>EP: FetchFailed
            EP->>L: Notify FetchFailed
        end
    end
    EP->>L: Notify FetchCompleted
    EP->>L: Notify ContentUpdated
    FS-->>MD: MarkdownFetchResult

    Note over L: Listeners can be: Logging, Metrics, Telemetry, Webhooks

U kunt de lezers tonen wanneer de inhoud voor het laatst is opgehaald:

Dit rendert met een voettekst:

stateDiagram-v2
    [*] --> CheckCache: Fetch Request

    CheckCache --> Fresh: Cache exists & age < pollFrequency
    CheckCache --> Stale: Cache exists & age >= pollFrequency
    CheckCache --> Missing: No cache entry

    Fresh --> ReturnCached: Return cached content
    ReturnCached --> [*]

    Stale --> FetchRemote: Attempt HTTP GET
    Missing --> FetchRemote: Attempt HTTP GET

    FetchRemote --> UpdateCache: Success
    FetchRemote --> HasStale: Failure

    UpdateCache --> ReturnFresh: Return new content
    ReturnFresh --> [*]

    HasStale --> ReturnStale: Return stale cache
    HasStale --> ReturnError: No cache available

    ReturnStale --> [*]
    ReturnError --> [*]

    note right of Fresh
        pollFrequency = 0
        means always stale
    end note

    note right of HasStale
        Stale-while-revalidate
        pattern ensures uptime
    end note

Inhoud opgehaald van

  1. **https://api.example.com/status.md**op 06 jan 2025 (2 uur geleden)
  2. **Of pas het sjabloon aan:**Uitvoer:~~~~
  3. Laatst bijgewerkt: 06 januari 2025 14:30Beschikbare plaatshouders:
  4. - Laatste ophalen datum/tijd- Menselijk leesbare tijd sinds het halen
  • Bron URL- Wanneer de inhoud wordt ververst- Cache duur in uren

- Cachestatus (vers/gecached/verhaal)

Verwerking voor documentatie uitschakelen

public class MarkdownController : Controller
{
    private readonly IMarkdownFetchService _fetchService;

    public async Task<IActionResult> InvalidateCache(string url)
    {
        var removed = await _fetchService.RemoveCachedMarkdownAsync(url);

        if (removed)
        {
            return Ok(new { message = "Cache invalidated" });
        }

        return NotFound(new { message = "No cache entry found" });
    }
}

Bij het schrijven van documentatie over de fetch extensie (zoals dit artikel!), heb je een manier nodig om de tags te tonen zonder dat ze worden verwerkt.

// GitHub webhook notifies of README update
app.MapPost("/webhooks/github", async (
    GitHubWebhookPayload payload,
    IMarkdownFetchService fetchService) =>
{
    if (payload.Repository?.FullName == "user/repo" &&
        payload.Commits?.Any(c => c.Modified?.Contains("README.md") == true) == true)
    {
        var url = "https://raw.githubusercontent.com/user/repo/main/README.md";
        await fetchService.RemoveCachedMarkdownAsync(url);

        return Results.Ok(new { message = "Cache invalidated" });
    }

    return Results.Ok(new { message = "No action needed" });
});

Gebruik de

attribuut:

public class MarkdownFetchServiceTests
{
    [Fact]
    public async Task FetchMarkdownAsync_CachesContent()
    {
        // Arrange
        var services = new ServiceCollection();
        services.AddLogging();
        services.AddInMemoryMarkdownFetch();
        var sp = services.BuildServiceProvider();

        var fetchService = sp.GetRequiredService<IMarkdownFetchService>();
        var url = "https://raw.githubusercontent.com/user/repo/main/README.md";

        // Act - First fetch (from network)
        var result1 = await fetchService.FetchMarkdownAsync(url, 24, 0);

        // Act - Second fetch (from cache)
        var result2 = await fetchService.FetchMarkdownAsync(url, 24, 0);

        // Assert
        Assert.True(result1.Success);
        Assert.True(result2.Success);
        Assert.Equal(result1.Content, result2.Content);
    }

    [Fact]
    public async Task FetchMarkdownAsync_ReturnsStaleOnFailure()
    {
        // Arrange
        var services = new ServiceCollection();
        services.AddLogging();
        services.AddInMemoryMarkdownFetch();
        var sp = services.BuildServiceProvider();

        var fetchService = sp.GetRequiredService<IMarkdownFetchService>();
        var url = "https://httpstat.us/200?sleep=100";

        // Act - First fetch succeeds
        var result1 = await fetchService.FetchMarkdownAsync(url, 0, 0);

        // Change URL to fail
        var badUrl = "https://httpstat.us/500";

        // Act - Second fetch fails, should return stale
        var result2 = await fetchService.FetchMarkdownAsync(badUrl, 0, 0);

        // Assert
        Assert.True(result1.Success);
        // Even though fetch failed, we return success with stale content
        Assert.True(result2.Success);
    }
}

De uitgeschakelde tag blijft in de markdown as-is, perfect voor:

Documenten schrijven over de extensie zelf

  1. Voorbeelden maken in tutorialsSyntaxis van tag tonen zonder ophalen te activerenConcurrentDictionaryDit werkt voor beide
  2. entags:
  3. Gebeurtenissysteem voor monitoringDe extensie publiceert evenementen voor alle ophalen operaties:
  4. **Dit maakt het eenvoudig om te integreren met Application Insights, Prometheus, of uw logging infrastructuur:**Caching Strategie in detailIHttpClientFactoryHet caching gedrag volgt een state machine patroon:
  5. **De belangrijkste inzichten hier:**Verse cache
  • Return onmiddelijk, geen netwerk hit

  • Stamcache

    • Probeer fris te halen, maar val terug naar oud als apporteren mislukt
  • Ontbrekende cache

    • Moet een foutmelding ophalen of retourneren

Nul Pollfrequentie

  • Altijd vers ophalen (handig voor het testen)
name: Publish Markdig.FetchExtension

on:
  push:
    tags:
      - 'fetchextension-v*.*.*'

permissions:
  id-token: write
  contents: read

jobs:
  build-and-publish:
    runs-on: ubuntu-latest

    steps:
    - name: Checkout code
      uses: actions/checkout@v4

    - name: Setup .NET
      uses: actions/setup-dotnet@v4
      with:
        dotnet-version: '9.0.x'

    - name: Extract version from tag
      id: get_version
      run: |
        TAG=${GITHUB_REF#refs/tags/fetchextension-v}
        echo "VERSION=$TAG" >> $GITHUB_OUTPUT

    - name: Build
      run: dotnet build Mostlylucid.Markdig.FetchExtension/Mostlylucid.Markdig.FetchExtension.csproj --configuration Release -p:Version=${{ steps.get_version.outputs.VERSION }}

    - name: Pack
      run: dotnet pack Mostlylucid.Markdig.FetchExtension/Mostlylucid.Markdig.FetchExtension.csproj --configuration Release --no-build -p:PackageVersion=${{ steps.get_version.outputs.VERSION }} --output ./artifacts

    - name: Login to NuGet (OIDC)
      id: nuget_login
      uses: NuGet/login@v1
      with:
        user: 'mostlylucid'

    - name: Publish to NuGet
      run: dotnet nuget push ./artifacts/*.nupkg --api-key ${{ steps.nuget_login.outputs.NUGET_API_KEY }} --source https://api.nuget.org/v3/index.json --skip-duplicate

Dit patroon heet

oud-while-revalidate

En het is uitstekend voor betrouwbaarheid.

# My NuGet Package Documentation

Here's the official README from GitHub:

# Umami.Net

## UmamiClient

This is a .NET Core client for the Umami tracking API.
It's based on the Umami Node client, which can be found [here](https://github.com/umami-software/node).

You can see how to set up Umami as a docker
container [here](https://www.mostlylucid.net/blog/usingumamiforlocalanalytics).
You can read more detail about it's creation on my
blog [here](https://www.mostlylucid.net/blog/addingumamitrackingclientfollowup).

To use this client you need the following appsettings.json configuration:

```json
{
  "Analytics":{
    "UmamiPath" : "https://umamilocal.mostlylucid.net",
    "WebsiteId" : "32c2aa31-b1ac-44c0-b8f3-ff1f50403bee"
  },
}

Where UmamiPath is the path to your Umami instance and WebsiteId is the id of the website you want to track.

To use the client you need to add the following to your Program.cs:

using Umami.Net;

services.SetupUmamiClient(builder.Configuration);

This will add the Umami client to the services collection.

You can then use the client in two ways:

Track

  1. Inject the UmamiClient into your class and call the Track method:
 // Inject UmamiClient umamiClient
 await umamiClient.Track("Search", new UmamiEventData(){{"query", encodedQuery}});
  1. Use the UmamiBackgroundSender to track events in the background (this uses an IHostedService to send events in the background):
 // Inject UmamiBackgroundSender umamiBackgroundSender
await umamiBackgroundSender.Track("Search", new UmamiEventData(){{"query", encodedQuery}});

The client will send the event to the Umami API and it will be stored.

The UmamiEventData is a dictionary of key value pairs that will be sent to the Umami API as the event data.

There are additionally more low level methods that can be used to send events to the Umami API.

Track PageView

There's also a convenience method to track a page view. This will send an event to the Umami API with the url set (which counts as a pageview).

  await  umamiBackgroundSender.TrackPageView("api/search/" + encodedQuery, "searchEvent", eventData: new UmamiEventData(){{"query", encodedQuery}});
  
   await umamiClient.TrackPageView("api/search/" + encodedQuery, "searchEvent", eventData: new UmamiEventData(){{"query", encodedQuery}});

Here we're setting the url to "api/search/" + encodedQuery and the event type to "searchEvent". We're also passing in a dictionary of key value pairs as the event data.

Raw 'Send' method

On both the UmamiClient and UmamiBackgroundSender you can call the following method.



 Send(UmamiPayload? payload = null, UmamiEventData? eventData = null,
        string eventType = "event")

If you don't pass in a UmamiPayload object, the client will create one for you using the WebsiteId from the appsettings.json.

    public  UmamiPayload GetPayload(string? url = null, UmamiEventData? data = null)
    {
        var httpContext = httpContextAccessor.HttpContext;
        var request = httpContext?.Request;

        var payload = new UmamiPayload
        {
            Website = settings.WebsiteId,
            Data = data,
            Url = url ?? httpContext?.Request?.Path.Value,
            IpAddress = httpContext?.Connection?.RemoteIpAddress?.ToString(),
            UserAgent = request?.Headers["User-Agent"].FirstOrDefault(),
            Referrer = request?.Headers["Referer"].FirstOrDefault(),
           Hostname = request?.Host.Host,
        };
        
        return payload;
    }

You can see that this populates the UmamiPayload object with the WebsiteId from the appsettings.json, the Url, IpAddress, UserAgent, Referrer and Hostname from the HttpContext.

NOTE: eventType can only be "event" or "identify" as per the Umami API.

UmamiData

There's also a service that can be used to pull data from the Umami API. This is a service that allows me to pull data from my Umami instance to use in stuff like sorting posts by popularity etc...

To set it up you need to add a username and password for your umami instance to the Analytics element in your settings file:

    "Analytics":{
        "UmamiPath" : "https://umami.mostlylucid.net",
        "WebsiteId" : "1e3b7657-9487-4857-a9e9-4e1920aa8c42",
        "UserName": "admin",
        "Password": ""
     
    }

Then in your Program.cs you set up the UmamiDataService as follows:

    services.SetupUmamiData(config);

You can then inject the UmamiDataService into your class and use it to pull data from the Umami API.

Usage

Now you have the UmamiDataService in your service collection you can start using it!

Methods

The methods are all from the Umami API definition you can read about them here: https://umami.is/docs/api/website-stats

All returns are wrapped in an UmamiResults<T> object which has a Success property and a Result property. The Result property is the object returned from the Umami API.

public record UmamiResult<T>(HttpStatusCode Status, string Message, T? Data);

All requests apart from ActiveUsers have a base request object with two compulsory properties. I added convenience DateTimes to the base request object to make it easier to set the start and end dates.

public class BaseRequest
{
    [QueryStringParameter("startAt", isRequired: true)]
    public long StartAt => StartAtDate.ToMilliseconds(); // Timestamp (in ms) of starting date
    [QueryStringParameter("endAt", isRequired: true)]
    public long EndAt => EndAtDate.ToMilliseconds(); // Timestamp (in ms) of end date
    public DateTime StartAtDate { get; set; }
    public DateTime EndAtDate { get; set; }
}

The service has the following methods:

Active Users

This just gets the total number of CURRENT active users on the site

public async Task<UmamiResult<ActiveUsersResponse>> GetActiveUsers()

Stats

This returns a bunch of statistics about the site, including the number of users, page views, etc.

public async Task<UmamiResult<StatsResponseModels>> GetStats(StatsRequest statsRequest)    

You may set a number of parameters to filter the data returned from the API. For instance using url will return the stats for a specific URL.

StatsRequest object
public class StatsRequest : BaseRequest
{
    [QueryStringParameter("url")]
    public string? Url { get; set; } // Name of URL
    
    [QueryStringParameter("referrer")]
    public string? Referrer { get; set; } // Name of referrer
    
    [QueryStringParameter("title")]
    public string? Title { get; set; } // Name of page title
    
    [QueryStringParameter("query")]
    public string? Query { get; set; } // Name of query
    
    [QueryStringParameter("event")]
    public string? Event { get; set; } // Name of event
    
    [QueryStringParameter("host")]
    public string? Host { get; set; } // Name of hostname
    
    [QueryStringParameter("os")]
    public string? Os { get; set; } // Name of operating system
    
    [QueryStringParameter("browser")]
    public string? Browser { get; set; } // Name of browser
    
    [QueryStringParameter("device")]
    public string? Device { get; set; } // Name of device (e.g., Mobile)
    
    [QueryStringParameter("country")]
    public string? Country { get; set; } // Name of country
    
    [QueryStringParameter("region")]
    public string? Region { get; set; } // Name of region/state/province
    
    [QueryStringParameter("city")]
    public string? City { get; set; } // Name of city
}

The JSON object Umami returns is as follows.

{
  "pageviews": { "value": 5, "change": 5 },
  "visitors": { "value": 1, "change": 1 },
  "visits": { "value": 3, "change": 2 },
  "bounces": { "value": 0, "change": 0 },
  "totaltime": { "value": 4, "change": 4 }
}

This is wrapped inside my StatsResponseModel object.

namespace Umami.Net.UmamiData.Models.ResponseObjects;

public class StatsResponseModels
{
    public Pageviews pageviews { get; set; }
    public Visitors visitors { get; set; }
    public Visits visits { get; set; }
    public Bounces bounces { get; set; }
    public Totaltime totaltime { get; set; }


    public class Pageviews
    {
        public int value { get; set; }
        public int prev { get; set; }
    }

    public class Visitors
    {
        public int value { get; set; }
        public int prev { get; set; }
    }

    public class Visits
    {
        public int value { get; set; }
        public int prev { get; set; }
    }

    public class Bounces
    {
        public int value { get; set; }
        public int prev { get; set; }
    }

    public class Totaltime
    {
        public int value { get; set; }
        public int prev { get; set; }
    }
}

Metrics

Metrics in Umami provide you the number of views for specific types of properties.

Events

One example of these is Events`:

'Events' in Umami are specific items you can track on a site. When tracking events using Umami.Net you can set a number of properties which are tracked with the event name. For instance here I track Search requests with the URL and the search term.

       await  umamiBackgroundSender.Track( "searchEvent", eventData: new UmamiEventData(){{"query", encodedQuery}});

To fetch data about this event you would use the Metrics method:

public async Task<UmamiResult<MetricsResponseModels[]>> GetMetrics(MetricsRequest metricsRequest)

As with the other methods this accepts the MetricsRequest object (with the compulsory BaseRequest properties) and a number of optional properties to filter the data.

MetricsRequest object
public class MetricsRequest : BaseRequest
{
    [QueryStringParameter("type", isRequired: true)]
    public MetricType Type { get; set; } // Metrics type

    [QueryStringParameter("url")]
    public string? Url { get; set; } // Name of URL
    
    [QueryStringParameter("referrer")]
    public string? Referrer { get; set; } // Name of referrer
    
    [QueryStringParameter("title")]
    public string? Title { get; set; } // Name of page title
    
    [QueryStringParameter("query")]
    public string? Query { get; set; } // Name of query
    
    [QueryStringParameter("host")]
    public string? Host { get; set; } // Name of hostname
    
    [QueryStringParameter("os")]
    public string? Os { get; set; } // Name of operating system
    
    [QueryStringParameter("browser")]
    public string? Browser { get; set; } // Name of browser
    
    [QueryStringParameter("device")]
    public string? Device { get; set; } // Name of device (e.g., Mobile)
    
    [QueryStringParameter("country")]
    public string? Country { get; set; } // Name of country
    
    [QueryStringParameter("region")]
    public string? Region { get; set; } // Name of region/state/province
    
    [QueryStringParameter("city")]
    public string? City { get; set; } // Name of city
    
    [QueryStringParameter("language")]
    public string? Language { get; set; } // Name of language
    
    [QueryStringParameter("event")]
    public string? Event { get; set; } // Name of event
    
    [QueryStringParameter("limit")]
    public int? Limit { get; set; } = 500; // Number of events returned (default: 500)
}

Here you can see that you can specify a number of properties in the request element to specify what metrics you want to return.

You can also set a Limit property to limit the number of results returned.

For instance to get the event over the past day I mentioned above you would use the following request:

var metricsRequest = new MetricsRequest
{
    StartAtDate = DateTime.Now.AddDays(-1),
    EndAtDate = DateTime.Now,
    Type = MetricType.@event,
    Event = "searchEvent"
};

The JSON object returned from the API is as follows:

[
  { "x": "searchEvent", "y": 46 }
]

And again I wrap this in my MetricsResponseModels object.

public class MetricsResponseModels
{
    public string x { get; set; }
    public int y { get; set; }
}

Where x is the event name and y is the number of times it has been triggered.

Page Views

One of the most useful metrics is the number of page views. This is the number of times a page has been viewed on the site. Below is the test I use to get the number of page views over the past 30 days. You'll note the Type parameter is set as MetricType.url however this is also the default value so you don't need to set it.

  [Fact]
    public async Task Metrics_StartEnd()
    {
        var setup = new SetupUmamiData();
        var serviceProvider = setup.Setup();
        var websiteDataService = serviceProvider.GetRequiredService<UmamiDataService>();
        
        var metrics = await websiteDataService.GetMetrics(new MetricsRequest()
        {
            StartAtDate = DateTime.Now.AddDays(-30),
            EndAtDate = DateTime.Now,
            Type = MetricType.url,
            Limit = 500
        });
        Assert.NotNull(metrics);
        Assert.Equal( HttpStatusCode.OK, metrics.Status);

    }

This returns a MetricsResponse object which has the following JSON structure:

[
  {
    "x": "/",
    "y": 1
  },
  {
    "x": "/blog",
    "y": 1
  },
  {
    "x": "/blog/usingumamidataforwebsitestats",
    "y": 1
  }
]

Where x is the URL and y is the number of times it has been viewed.

PageViews

This returns the number of page views for a specific URL.

Again here is a test I use for this method:

    [Fact]
    public async Task PageViews_StartEnd_Day_Url()
    {
        var setup = new SetupUmamiData();
        var serviceProvider = setup.Setup();
        var websiteDataService = serviceProvider.GetRequiredService<UmamiDataService>();
    
        var pageViews = await websiteDataService.GetPageViews(new PageViewsRequest()
        {
            StartAtDate = DateTime.Now.AddDays(-7),
            EndAtDate = DateTime.Now,
            Unit = Unit.day,
            Url = "/blog"
        });
        Assert.NotNull(pageViews);
        Assert.Equal( HttpStatusCode.OK, pageViews.Status);

    }

This returns a PageViewsResponse object which has the following JSON structure:

[
  {
    "date": "2024-09-06 00:00",
    "value": 1
  }
]

Where date is the date and value is the number of page views, this is repeated for each day in the range specified ( or hour, month, etc. depending on the Unit property).

As with the other methods this accepts the PageViewsRequest object (with the compulsory BaseRequest properties) and a number of optional properties to filter the data.

PageViewsRequest object
public class PageViewsRequest : BaseRequest
{
    // Required properties

    [QueryStringParameter("unit", isRequired: true)]
    public Unit Unit { get; set; } = Unit.day; // Time unit (year | month | hour | day)
    
    [QueryStringParameter("timezone")]
    [TimeZoneValidator]
    public string Timezone { get; set; }

    // Optional properties
    [QueryStringParameter("url")]
    public string? Url { get; set; } // Name of URL
    [QueryStringParameter("referrer")]
    public string? Referrer { get; set; } // Name of referrer
    [QueryStringParameter("title")]
    public string? Title { get; set; } // Name of page title
    [QueryStringParameter("host")]
    public string? Host { get; set; } // Name of hostname
    [QueryStringParameter("os")]
    public string? Os { get; set; } // Name of operating system
    [QueryStringParameter("browser")]
    public string? Browser { get; set; } // Name of browser
    [QueryStringParameter("device")]
    public string? Device { get; set; } // Name of device (e.g., Mobile)
    [QueryStringParameter("country")]
    public string? Country { get; set; } // Name of country
    [QueryStringParameter("region")]
    public string? Region { get; set; } // Name of region/state/province
    [QueryStringParameter("city")]
    public string? City { get; set; } // Name of city
}

As with the other methods you can set a number of properties to filter the data returned from the API, for instance you could set the Country property to get the number of page views from a specific country.

Using the Service

In this site I have some code which lets me use this service to get the number of views each blog page has. In the code below I take a start and end date and a prefix (which is /blog in my case) and get the number of views for each page in the blog.

I then cache this data for an hour so I don't have to keep hitting the Umami API.

public class UmamiDataSortService(
    UmamiDataService dataService,
    IMemoryCache cache)
{
    public async Task<List<MetricsResponseModels>?> GetMetrics(DateTime startAt, DateTime endAt, string prefix="" )
    {
        using var activity = Log.Logger.StartActivity("GetMetricsWithPrefix");
        try
        {
            var cacheKey = $"Metrics_{startAt}_{endAt}_{prefix}";
            if (cache.TryGetValue(cacheKey, out List<MetricsResponseModels>? metrics))
            {
                activity?.AddProperty("CacheHit", true);
                return metrics;
            }
            activity?.AddProperty("CacheHit", false);
            var metricsRequest = new MetricsRequest()
            {
                StartAtDate = startAt,
                EndAtDate = endAt,
                Type = MetricType.url,
                Limit = 500
            };
            var metricRequest = await dataService.GetMetrics(metricsRequest);

            if(metricRequest.Status != HttpStatusCode.OK)
            {
                return null;
            }
            var filteredMetrics = metricRequest.Data.Where(x => x.x.StartsWith(prefix)).ToList();
            cache.Set(cacheKey, filteredMetrics, TimeSpan.FromHours(1));
            activity?.AddProperty("MetricsCount", filteredMetrics?.Count()?? 0);
            activity?.Complete();
            return filteredMetrics;
        }
        catch (Exception e)
        {
            activity?.Complete(LogEventLevel.Error, e);
         
            return null;
        }
    }

Installation

The package is available on NuGet...


Zelfs als je bron naar beneden gaat, blijft je site cache inhoud serveren.

# Cache verwijderen en beheren

Soms moet je de cache handmatig ongeldig maken:

1. **Of via webhooks wanneer de inhoud verandert:**Testen van de uitbreiding
2. **De uitbreiding omvat uitgebreide tests.**Hier is hoe ik ze structureer:
3. **Prestatieoverwegingen**De uitbreiding is ontworpen voor prestaties:
4. **Gelijktijdig woordenboek**- In-geheugen implementatie toepassingen
5. **voor draadveilige toegang**SemaforeSlim
6. **- File-based maakt gebruik van async vergrendeling om racevoorwaarden te voorkomen**Database-indexen

- Alle database providers hebben goede indexen op cache sleutels

- [HTTP-client pooling](https://www.nuget.org/packages/mostlylucid.Markdig.FetchExtension)
- [- Gebruikt](https://www.nuget.org/packages/mostlylucid.Markdig.FetchExtension.Postgres)
- [voor efficiënt hergebruik van verbindingen](https://www.nuget.org/packages/mostlylucid.Markdig.FetchExtension.Sqlite)
- [Async all the way](https://www.nuget.org/packages/mostlylucid.Markdig.FetchExtension.SqlServer)

- Geen telefoontjes blokkeren, alles is async.[Typische prestatienummers op mijn thuisserver:](https://github.com/scottgal/mostlylucidweb/tree/main/Mostlylucid.Markdig.FetchExtension)

Cache hit: < 1ms
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