/// <summary>
/// Diagnostic event handler method for 'Microsoft.AspNetCore.Hosting.HttpRequestIn.Start' event. This is from 2.XX runtime.
/// </summary>
public void OnHttpRequestInStart(HttpContext httpContext)
{
if (this.client.IsEnabled())
{
// It's possible to host multiple apps (ASP.NET Core or generic hosts) in the same process
// Each of this apps has it's own HostingDiagnosticListener and corresponding Http listener.
// We should ignore events for all of them except one
if (!SubscriptionManager.IsActive(this))
{
// AspNetCoreEventSource.Instance.NotActiveListenerNoTracking("Microsoft.AspNetCore.Hosting.HttpRequestIn.Start", Activity.Current?.Id);
return;
}
if (Activity.Current == null)
{
// AspNetCoreEventSource.Instance.LogHostingDiagnosticListenerOnHttpRequestInStartActivityNull();
return;
}
var currentActivity = ActivityShim.Current;
ActivityShim newActivity = default;
string originalParentId = currentActivity.ParentId;
string legacyRootId = null;
bool traceParentPresent = false;
var headers = httpContext.Request.Headers;
// 3 possibilities when TelemetryConfiguration.EnableW3CCorrelation = true
// 1. No incoming headers. originalParentId will be null. Simply use the Activity as such.
// 2. Incoming Request-ID Headers. originalParentId will be request-id, but Activity ignores this for ID calculations.
// If incoming ID is W3C compatible, ignore current Activity. Create new one with parent set to incoming W3C compatible rootid.
// If incoming ID is not W3C compatible, we can use Activity as such, but need to store originalParentID in custom property 'legacyRootId'
// 3. Incoming TraceParent header.
// 3a - 2.XX Need to ignore current Activity, and create new from incoming W3C TraceParent header.
// 3b - 3.XX Use Activity as such because 3.XX is W3C Aware.
// Another 3 possibilities when TelemetryConfiguration.EnableW3CCorrelation = false
// 1. No incoming headers. originalParentId will be null. Simply use the Activity as such.
// 2. Incoming Request-ID Headers. originalParentId will be request-id, Activity uses this for ID calculations.
// 3. Incoming TraceParent header. Will simply Ignore W3C headers, and Current Activity used as such.
// Attempt to find parent from incoming W3C Headers which 2.XX Hosting is unaware of.
if (this.aspNetCoreMajorVersion != AspNetCoreMajorVersion.Three &&
currentActivity.IdFormat == ActivityIdFormat.W3C &&
headers.TryGetValue(W3CConstants.TraceParentHeader, out StringValues traceParentValues) &&
traceParentValues != StringValues.Empty)
{
var parentTraceParent = StringUtilities.EnforceMaxLength(
traceParentValues.First(),
InjectionGuardConstants.TraceParentHeaderMaxLength);
originalParentId = parentTraceParent;
traceParentPresent = true;
// AspNetCoreEventSource.Instance.HostingListenerInformational(this.aspNetCoreMajorVersion, "Retrieved trace parent from headers.");
}
// Scenario #1. No incoming correlation headers.
if (originalParentId == null)
{
// Nothing to do here.
// AspNetCoreEventSource.Instance.HostingListenerInformational(this.aspNetCoreMajorVersion, "OriginalParentId is null.");
}
else if (traceParentPresent)
{
// Scenario #3. W3C-TraceParent
// We need to ignore the Activity created by Hosting, as it did not take W3CTraceParent into consideration.
newActivity = new ActivityShim(ActivityCreatedByHostingDiagnosticListener);
newActivity.SetParentId(originalParentId);
// AspNetCoreEventSource.Instance.HostingListenerInformational(this.aspNetCoreMajorVersion, "Ignoring original Activity from Hosting to create new one using traceparent header retrieved by sdk.");
// read and populate tracestate
ReadTraceState(httpContext.Request.Headers, newActivity);
}
else if (this.aspNetCoreMajorVersion == AspNetCoreMajorVersion.Three && headers.ContainsKey(W3CConstants.TraceParentHeader))
{
// AspNetCoreEventSource.Instance.HostingListenerInformational(this.aspNetCoreMajorVersion, "Incoming request has traceparent. Using Activity created from Hosting.");
// scenario #3b Use Activity created by Hosting layer when W3C Headers Present.
// but ignore parent if user disabled w3c.
if (currentActivity.IdFormat != ActivityIdFormat.W3C)
{
originalParentId = null;
}
}
else
{
// Scenario #2. RequestID
if (currentActivity.IdFormat == ActivityIdFormat.W3C)
{
if (TryGetW3CCompatibleTraceId(originalParentId, out var traceId))
{
newActivity = new ActivityShim(ActivityCreatedByHostingDiagnosticListener);
newActivity.SetParentId(ActivityTraceId.CreateFromString(traceId), default(ActivitySpanId), ActivityTraceFlags.None);
// AspNetCoreEventSource.Instance.HostingListenerInformational(this.aspNetCoreMajorVersion, "Ignoring original Activity from Hosting to create new one using w3c compatible request-id.");
foreach (var bag in currentActivity.Baggage)
{
newActivity.AddBaggage(bag.Key, bag.Value);
}
}
else
{
// store rootIdFromOriginalParentId in custom Property
legacyRootId = ExtractOperationIdFromRequestId(originalParentId);
// AspNetCoreEventSource.Instance.HostingListenerInformational(this.aspNetCoreMajorVersion, "Incoming Request-ID is not W3C Compatible, and hence will be ignored for ID generation, but stored in custom property legacy_rootID.");
}
}
}
if (!newActivity.IsDefault)
{
newActivity.Start();
currentActivity = newActivity;
}
// Read Correlation-Context is all scenarios irrespective of presence of either request-id or traceparent headers.
ReadCorrelationContext(httpContext.Request.Headers, currentActivity);
var requestTelemetry = this.InitializeRequestTelemetry(httpContext, currentActivity, Stopwatch.GetTimestamp(), legacyRootId);
requestTelemetry.Context.Operation.ParentId =
GetParentId(currentActivity, originalParentId, requestTelemetry.Context.Operation.Id);
this.AddAppIdToResponseIfRequired(httpContext, requestTelemetry);
}
}