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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Diagnostics;
using Microsoft.AspNetCore.Http;
namespace Microsoft.AspNetCore.MiddlewareAnalysis;
/// <summary>
/// Middleware that is inserted before and after each other middleware in the pipeline by <see cref="AnalysisBuilder"/>
/// to log to a <see cref="DiagnosticSource"/> when other middleware starts, finishes and throws.
/// </summary>
public class AnalysisMiddleware
{
private readonly Guid _instanceId = Guid.NewGuid();
private readonly RequestDelegate _next;
private readonly DiagnosticSource _diagnostics;
private readonly string _middlewareName;
/// <summary>
/// Initializes a new instance of <see cref="AnalysisMiddleware"/>.
/// </summary>
/// <param name="next">The next middleware in the pipeline.</param>
/// <param name="diagnosticSource">The <see cref="DiagnosticSource"/> to log when other middleware starts, finishes and throws.</param>
/// <param name="middlewareName">
/// The name of the next middleware in the pipeline. This name is typically retrieved from <see cref="Builder.IApplicationBuilder.Properties"/>
/// using the "analysis.NextMiddlewareName" key.
/// </param>
public AnalysisMiddleware(RequestDelegate next, DiagnosticSource diagnosticSource, string middlewareName)
{
_next = next;
_diagnostics = diagnosticSource;
if (string.IsNullOrEmpty(middlewareName))
{
middlewareName = next.Target!.GetType().FullName!;
}
_middlewareName = middlewareName;
}
/// <summary>
/// Executes the middleware that logs to a <see cref="DiagnosticSource"/> when the next middleware starts, finishes and throws.
/// </summary>
/// <param name="httpContext">The <see cref="HttpContext"/> for the current request.</param>
public async Task Invoke(HttpContext httpContext)
{
var startTimestamp = Stopwatch.GetTimestamp();
if (_diagnostics.IsEnabled("Microsoft.AspNetCore.MiddlewareAnalysis.MiddlewareStarting"))
{
_diagnostics.Write(
"Microsoft.AspNetCore.MiddlewareAnalysis.MiddlewareStarting",
new
{
name = _middlewareName,
httpContext = httpContext,
instanceId = _instanceId,
timestamp = startTimestamp,
});
}
try
{
await _next(httpContext);
if (_diagnostics.IsEnabled("Microsoft.AspNetCore.MiddlewareAnalysis.MiddlewareFinished"))
{
var currentTimestamp = Stopwatch.GetTimestamp();
_diagnostics.Write(
"Microsoft.AspNetCore.MiddlewareAnalysis.MiddlewareFinished",
new
{
name = _middlewareName,
httpContext = httpContext,
instanceId = _instanceId,
timestamp = currentTimestamp,
duration = currentTimestamp - startTimestamp,
});
}
}
catch (Exception ex)
{
if (_diagnostics.IsEnabled("Microsoft.AspNetCore.MiddlewareAnalysis.MiddlewareException"))
{
var currentTimestamp = Stopwatch.GetTimestamp();
_diagnostics.Write(
"Microsoft.AspNetCore.MiddlewareAnalysis.MiddlewareException",
new
{
name = _middlewareName,
httpContext = httpContext,
instanceId = _instanceId,
timestamp = currentTimestamp,
duration = currentTimestamp - startTimestamp,
exception = ex,
});
}
throw;
}
}
}
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