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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.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Net.Http.Headers;
using System.Threading;
using System.Threading.Tasks;
namespace System.Net.Http
{
/// <summary>
/// DiagnosticHandler notifies DiagnosticSource subscribers about outgoing Http requests
/// </summary>
internal sealed class DiagnosticsHandler : HttpMessageHandlerStage
{
private static readonly DiagnosticListener s_diagnosticListener = new DiagnosticListener(DiagnosticsHandlerLoggingStrings.DiagnosticListenerName);
private static readonly ActivitySource s_activitySource = new ActivitySource(DiagnosticsHandlerLoggingStrings.Namespace);
private readonly HttpMessageHandler _innerHandler;
private readonly DistributedContextPropagator _propagator;
private readonly HeaderDescriptor[]? _propagatorFields;
public DiagnosticsHandler(HttpMessageHandler innerHandler, DistributedContextPropagator propagator, bool autoRedirect = false)
{
Debug.Assert(IsGloballyEnabled());
Debug.Assert(innerHandler is not null && propagator is not null);
_innerHandler = innerHandler;
_propagator = propagator;
// Prepare HeaderDescriptors for fields we need to clear when following redirects
if (autoRedirect && _propagator.Fields is IReadOnlyCollection<string> fields && fields.Count > 0)
{
var fieldDescriptors = new List<HeaderDescriptor>(fields.Count);
foreach (string field in fields)
{
if (field is not null && HeaderDescriptor.TryGet(field, out HeaderDescriptor descriptor))
{
fieldDescriptors.Add(descriptor);
}
}
_propagatorFields = fieldDescriptors.ToArray();
}
}
private static bool IsEnabled()
{
// check if there is a parent Activity or if someone listens to "System.Net.Http" ActivitySource or "HttpHandlerDiagnosticListener" DiagnosticListener.
return Activity.Current != null ||
s_activitySource.HasListeners() ||
s_diagnosticListener.IsEnabled();
}
private static Activity? CreateActivity(HttpRequestMessage requestMessage)
{
Activity? activity = null;
if (s_activitySource.HasListeners())
{
activity = s_activitySource.CreateActivity(DiagnosticsHandlerLoggingStrings.ActivityName, ActivityKind.Client);
}
if (activity is null)
{
if (Activity.Current is not null || s_diagnosticListener.IsEnabled(DiagnosticsHandlerLoggingStrings.ActivityName, requestMessage))
{
activity = new Activity(DiagnosticsHandlerLoggingStrings.ActivityName);
}
}
return activity;
}
internal static bool IsGloballyEnabled() => GlobalHttpSettings.DiagnosticsHandler.EnableActivityPropagation;
internal override ValueTask<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool async, CancellationToken cancellationToken)
{
if (IsEnabled())
{
return SendAsyncCore(request, async, cancellationToken);
}
else
{
return async ?
new ValueTask<HttpResponseMessage>(_innerHandler.SendAsync(request, cancellationToken)) :
new ValueTask<HttpResponseMessage>(_innerHandler.Send(request, cancellationToken));
}
}
private async ValueTask<HttpResponseMessage> SendAsyncCore(HttpRequestMessage request, bool async, CancellationToken cancellationToken)
{
// HttpClientHandler is responsible to call static DiagnosticsHandler.IsEnabled() before forwarding request here.
// It will check if propagation is on (because parent Activity exists or there is a listener) or off (forcibly disabled)
// This code won't be called unless consumer unsubscribes from DiagnosticListener right after the check.
// So some requests happening right after subscription starts might not be instrumented. Similarly,
// when consumer unsubscribes, extra requests might be instrumented
// Since we are reusing the request message instance on redirects, clear any existing headers
// Do so before writing DiagnosticListener events as instrumentations use those to inject headers
if (request.WasRedirected() && _propagatorFields is HeaderDescriptor[] fields)
{
foreach (HeaderDescriptor field in fields)
{
request.Headers.Remove(field);
}
}
DiagnosticListener diagnosticListener = s_diagnosticListener;
Guid loggingRequestId = Guid.Empty;
Activity? activity = CreateActivity(request);
// Start activity anyway if it was created.
if (activity is not null)
{
activity.Start();
// Only send start event to users who subscribed for it.
if (diagnosticListener.IsEnabled(DiagnosticsHandlerLoggingStrings.ActivityStartName))
{
Write(diagnosticListener, DiagnosticsHandlerLoggingStrings.ActivityStartName, new ActivityStartData(request));
}
}
// Try to write System.Net.Http.Request event (deprecated)
if (diagnosticListener.IsEnabled(DiagnosticsHandlerLoggingStrings.RequestWriteNameDeprecated))
{
long timestamp = Stopwatch.GetTimestamp();
loggingRequestId = Guid.NewGuid();
Write(diagnosticListener, DiagnosticsHandlerLoggingStrings.RequestWriteNameDeprecated,
new RequestData(
request,
loggingRequestId,
timestamp));
}
if (activity is not null)
{
InjectHeaders(activity, request);
}
HttpResponseMessage? response = null;
TaskStatus taskStatus = TaskStatus.RanToCompletion;
try
{
response = async ?
await _innerHandler.SendAsync(request, cancellationToken).ConfigureAwait(false) :
_innerHandler.Send(request, cancellationToken);
return response;
}
catch (OperationCanceledException)
{
taskStatus = TaskStatus.Canceled;
// we'll report task status in HttpRequestOut.Stop
throw;
}
catch (Exception ex)
{
taskStatus = TaskStatus.Faulted;
if (diagnosticListener.IsEnabled(DiagnosticsHandlerLoggingStrings.ExceptionEventName))
{
// If request was initially instrumented, Activity.Current has all necessary context for logging
// Request is passed to provide some context if instrumentation was disabled and to avoid
// extensive Activity.Tags usage to tunnel request properties
Write(diagnosticListener, DiagnosticsHandlerLoggingStrings.ExceptionEventName, new ExceptionData(ex, request));
}
throw;
}
finally
{
// Always stop activity if it was started.
if (activity is not null)
{
activity.SetEndTime(DateTime.UtcNow);
// Only send stop event to users who subscribed for it.
if (diagnosticListener.IsEnabled(DiagnosticsHandlerLoggingStrings.ActivityStopName))
{
Write(diagnosticListener, DiagnosticsHandlerLoggingStrings.ActivityStopName, new ActivityStopData(response, request, taskStatus));
}
activity.Stop();
}
// Try to write System.Net.Http.Response event (deprecated)
if (diagnosticListener.IsEnabled(DiagnosticsHandlerLoggingStrings.ResponseWriteNameDeprecated))
{
long timestamp = Stopwatch.GetTimestamp();
Write(diagnosticListener, DiagnosticsHandlerLoggingStrings.ResponseWriteNameDeprecated,
new ResponseData(
response,
loggingRequestId,
timestamp,
taskStatus));
}
}
}
protected override void Dispose(bool disposing)
{
if (disposing)
{
_innerHandler.Dispose();
}
base.Dispose(disposing);
}
#region private
private sealed class ActivityStartData
{
// matches the properties selected in https://github.com/dotnet/diagnostics/blob/ffd0254da3bcc47847b1183fa5453c0877020abd/src/Microsoft.Diagnostics.Monitoring.EventPipe/Configuration/HttpRequestSourceConfiguration.cs#L36-L40
[DynamicDependency(nameof(HttpRequestMessage.RequestUri), typeof(HttpRequestMessage))]
[DynamicDependency(nameof(HttpRequestMessage.Method), typeof(HttpRequestMessage))]
[DynamicDependency(nameof(Uri.Host), typeof(Uri))]
[DynamicDependency(nameof(Uri.Port), typeof(Uri))]
internal ActivityStartData(HttpRequestMessage request)
{
Request = request;
}
public HttpRequestMessage Request { get; }
public override string ToString() => $"{{ {nameof(Request)} = {Request} }}";
}
private sealed class ActivityStopData
{
internal ActivityStopData(HttpResponseMessage? response, HttpRequestMessage request, TaskStatus requestTaskStatus)
{
Response = response;
Request = request;
RequestTaskStatus = requestTaskStatus;
}
public HttpResponseMessage? Response { get; }
public HttpRequestMessage Request { get; }
public TaskStatus RequestTaskStatus { get; }
public override string ToString() => $"{{ {nameof(Response)} = {Response}, {nameof(Request)} = {Request}, {nameof(RequestTaskStatus)} = {RequestTaskStatus} }}";
}
private sealed class ExceptionData
{
// preserve the same properties as ActivityStartData above + common Exception properties
[DynamicDependency(nameof(HttpRequestMessage.RequestUri), typeof(HttpRequestMessage))]
[DynamicDependency(nameof(HttpRequestMessage.Method), typeof(HttpRequestMessage))]
[DynamicDependency(nameof(Uri.Host), typeof(Uri))]
[DynamicDependency(nameof(Uri.Port), typeof(Uri))]
[DynamicDependency(nameof(System.Exception.Message), typeof(Exception))]
[DynamicDependency(nameof(System.Exception.StackTrace), typeof(Exception))]
internal ExceptionData(Exception exception, HttpRequestMessage request)
{
Exception = exception;
Request = request;
}
public Exception Exception { get; }
public HttpRequestMessage Request { get; }
public override string ToString() => $"{{ {nameof(Exception)} = {Exception}, {nameof(Request)} = {Request} }}";
}
private sealed class RequestData
{
// preserve the same properties as ActivityStartData above
[DynamicDependency(nameof(HttpRequestMessage.RequestUri), typeof(HttpRequestMessage))]
[DynamicDependency(nameof(HttpRequestMessage.Method), typeof(HttpRequestMessage))]
[DynamicDependency(nameof(Uri.Host), typeof(Uri))]
[DynamicDependency(nameof(Uri.Port), typeof(Uri))]
internal RequestData(HttpRequestMessage request, Guid loggingRequestId, long timestamp)
{
Request = request;
LoggingRequestId = loggingRequestId;
Timestamp = timestamp;
}
public HttpRequestMessage Request { get; }
public Guid LoggingRequestId { get; }
public long Timestamp { get; }
public override string ToString() => $"{{ {nameof(Request)} = {Request}, {nameof(LoggingRequestId)} = {LoggingRequestId}, {nameof(Timestamp)} = {Timestamp} }}";
}
private sealed class ResponseData
{
[DynamicDependency(nameof(HttpResponseMessage.StatusCode), typeof(HttpResponseMessage))]
internal ResponseData(HttpResponseMessage? response, Guid loggingRequestId, long timestamp, TaskStatus requestTaskStatus)
{
Response = response;
LoggingRequestId = loggingRequestId;
Timestamp = timestamp;
RequestTaskStatus = requestTaskStatus;
}
public HttpResponseMessage? Response { get; }
public Guid LoggingRequestId { get; }
public long Timestamp { get; }
public TaskStatus RequestTaskStatus { get; }
public override string ToString() => $"{{ {nameof(Response)} = {Response}, {nameof(LoggingRequestId)} = {LoggingRequestId}, {nameof(Timestamp)} = {Timestamp}, {nameof(RequestTaskStatus)} = {RequestTaskStatus} }}";
}
private void InjectHeaders(Activity currentActivity, HttpRequestMessage request)
{
_propagator.Inject(currentActivity, request, static (carrier, key, value) =>
{
if (carrier is HttpRequestMessage request &&
key is not null &&
HeaderDescriptor.TryGet(key, out HeaderDescriptor descriptor) &&
!request.Headers.TryGetHeaderValue(descriptor, out _))
{
request.Headers.TryAddWithoutValidation(descriptor, value);
}
});
}
[UnconditionalSuppressMessage("ReflectionAnalysis", "IL2026:UnrecognizedReflectionPattern",
Justification = "The values being passed into Write have the commonly used properties being preserved with DynamicDependency.")]
private static void Write<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicProperties)] T>(
DiagnosticSource diagnosticSource,
string name,
T value)
{
diagnosticSource.Write(name, value);
}
#endregion
}
}
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