public static Metadata ProcessHeaders(Metadata headers)
{
if (headers == null)
{
throw new ArgumentNullException(nameof(headers));
}
Metadata.Entry trackingEntry = headers.FirstOrDefault(x => string.CompareOrdinal(x.Key, s_TrackingContextKeyName) == 0);
// Retrieve the tracking context from the message header, if it exists.
if (trackingEntry != null)
{
// If an tracking context exists in the message header, always use it to replace the ambient context.
TrackingContext tc = TrackingContext.DeSerialize(trackingEntry.ValueBytes);
tc.SetAsCurrent();
}
else
{
// If no tracking context exists then create one.
TrackingContext.NewCurrentIfEmpty();
Debug.Assert(TrackingContext.Current != null);
// Copy the tracking context to the message header.
byte[] byteArray = TrackingContext.Serialize(TrackingContext.Current);
headers.Add(s_TrackingContextKeyName, byteArray);
}
return(headers);
}
private static void OverwriteTrackingContextHeader(
HttpContext httpContext,
IList <string> headerKeys,
Func <HttpContext, string> headerValueGenerator)
{
if (httpContext == null)
{
throw new ArgumentNullException(nameof(httpContext));
}
if (headerKeys == null)
{
throw new ArgumentNullException(nameof(headerKeys));
}
if (headerValueGenerator == null)
{
throw new ArgumentNullException(nameof(headerValueGenerator));
}
TrackingContext currentTrackingContext = TrackingContext.Current;
// Replace the http header value in the current Tracking Context, if the
// http header exists.
if (currentTrackingContext != null)
{
// Prepare the inputs for the new Tracking Context.
Guid callChainId = currentTrackingContext.CallChainId;
DateTime originatorUtcTimestamp = currentTrackingContext.OriginatorUtcTimestamp;
IDictionary <string, string> extraHeaders = currentTrackingContext
.ExtraHeaders
.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
// Cycle through each of the requested http header keys.
foreach (string headerKey in headerKeys)
{
if (extraHeaders.ContainsKey(headerKey))
{
// Overwrite the target http header value.
string headerValue = headerValueGenerator(httpContext);
extraHeaders[headerKey] = headerValue;
}
}
// Now recreate the current Tracking Context with the overwritten extra headers.
var newTrackingContext = new TrackingContext(
callChainId,
originatorUtcTimestamp,
extraHeaders);
newTrackingContext.SetAsCurrent();
}
}
private static void CreateTrackingContextFromHeaderValues(IEnumerable <string> values)
{
if (values == null)
{
throw new ArgumentNullException(nameof(values));
}
if (values.Count() > 1)
{
throw new InvalidOperationException(Properties.Resources.CannotHaveMoreThanOneSerializedTrackingContextInHTTPHeaders);
}
string tcBase64 = values.FirstOrDefault();
if (string.IsNullOrWhiteSpace(tcBase64))
{
TrackingContext.NewCurrentIfEmpty();
}
else
{
// If an tracking context exists in the message header then use it to replace the current context.
TrackingContext tc = TrackingContext.DeSerialize(tcBase64.Base64StringToByteArray());
tc.SetAsCurrent();
}
}
private static void MergeTrackingContextHeader(HttpContext httpContext)
{
if (httpContext == null)
{
throw new ArgumentNullException(nameof(httpContext));
}
TrackingContext previousTrackingContext = TrackingContext.Current;
// Take the Tracking Context (if it exists) from the http request headers and make it current.
TrackingContextHelper.ProcessHttpHeaders(httpContext.Request?.Headers);
// Check to see how the new current Tracking Context compares to the previous one.
if (previousTrackingContext != null)
{
TrackingContext currentTrackingContext = TrackingContext.Current;
Debug.Assert(currentTrackingContext != null);
// Prepare the inputs for the new Tracking Context.
Guid callChainId = currentTrackingContext.CallChainId;
DateTime originatorUtcTimestamp = currentTrackingContext.OriginatorUtcTimestamp;
IDictionary <string, string> extraHeaders = currentTrackingContext
.ExtraHeaders
.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
// Extract the extra headers that were in the previous Tracking Context, but
// are not in the inputs for the new Tracking Context.
IList <string> nowMissingHeaderNames = previousTrackingContext
.ExtraHeaders.Keys
.Except(extraHeaders.Keys)
.ToList();
// Add the missing extra headers back to the inputs for the new Tracking Context.
foreach (string headerName in nowMissingHeaderNames)
{
extraHeaders.Add(headerName, previousTrackingContext.ExtraHeaders[headerName]);
}
// Extract the extra headers that were in the previous Tracking Context, and
// also in inputs for the new Tracking Context, but whose values are not empty.
IList <string> sharedHeaderNames = extraHeaders
.Keys
.Except(nowMissingHeaderNames)
.ToList();
// Add the missing extra header values back to the inputs for the new Tracking Context.
foreach (string headerName in sharedHeaderNames)
{
if (string.IsNullOrWhiteSpace(extraHeaders[headerName]))
{
extraHeaders[headerName] = previousTrackingContext.ExtraHeaders[headerName];
}
}
// Now recreate the current Tracking Context with the refilled extra headers.
var newTrackingContext = new TrackingContext(
callChainId,
originatorUtcTimestamp,
extraHeaders);
newTrackingContext.SetAsCurrent();
}
}
