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using System;
using System.Threading;
using Microsoft.AspNetCore.Mvc.ApiExplorer;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Options;
using Microsoft.OpenApi.Models;
using Swashbuckle.AspNetCore.Swagger;
using Swashbuckle.AspNetCore.SwaggerGen;
namespace Jellyfin.Server.Filters;
/// <summary>
/// OpenApi provider with caching.
/// </summary>
internal sealed class CachingOpenApiProvider : ISwaggerProvider
{
private const string CacheKey = "openapi.json";
private static readonly MemoryCacheEntryOptions _cacheOptions = new() { SlidingExpiration = TimeSpan.FromMinutes(5) };
private static readonly SemaphoreSlim _lock = new(1, 1);
private static readonly TimeSpan _lockTimeout = TimeSpan.FromSeconds(1);
private readonly IMemoryCache _memoryCache;
private readonly SwaggerGenerator _swaggerGenerator;
private readonly SwaggerGeneratorOptions _swaggerGeneratorOptions;
/// <summary>
/// Initializes a new instance of the <see cref="CachingOpenApiProvider"/> class.
/// </summary>
/// <param name="optionsAccessor">The options accessor.</param>
/// <param name="apiDescriptionsProvider">The api descriptions provider.</param>
/// <param name="schemaGenerator">The schema generator.</param>
/// <param name="memoryCache">The memory cache.</param>
public CachingOpenApiProvider(
IOptions<SwaggerGeneratorOptions> optionsAccessor,
IApiDescriptionGroupCollectionProvider apiDescriptionsProvider,
ISchemaGenerator schemaGenerator,
IMemoryCache memoryCache)
{
_swaggerGeneratorOptions = optionsAccessor.Value;
_swaggerGenerator = new SwaggerGenerator(_swaggerGeneratorOptions, apiDescriptionsProvider, schemaGenerator);
_memoryCache = memoryCache;
}
/// <inheritdoc />
public OpenApiDocument GetSwagger(string documentName, string? host = null, string? basePath = null)
{
if (_memoryCache.TryGetValue(CacheKey, out OpenApiDocument? openApiDocument) && openApiDocument is not null)
{
return AdjustDocument(openApiDocument, host, basePath);
}
var acquired = _lock.Wait(_lockTimeout);
try
{
if (_memoryCache.TryGetValue(CacheKey, out openApiDocument) && openApiDocument is not null)
{
return AdjustDocument(openApiDocument, host, basePath);
}
if (!acquired)
{
throw new InvalidOperationException("OpenApi document is generating");
}
openApiDocument = _swaggerGenerator.GetSwagger(documentName);
_memoryCache.Set(CacheKey, openApiDocument, _cacheOptions);
return AdjustDocument(openApiDocument, host, basePath);
}
finally
{
if (acquired)
{
_lock.Release();
}
}
}
private OpenApiDocument AdjustDocument(OpenApiDocument document, string? host, string? basePath)
{
document.Servers = _swaggerGeneratorOptions.Servers.Count != 0
? _swaggerGeneratorOptions.Servers
: string.IsNullOrEmpty(host) && string.IsNullOrEmpty(basePath)
? []
: [new OpenApiServer { Url = $"{host}{basePath}" }];
return document;
}
}
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