public void OnNext(KeyValuePair <string, object> value)
{
if (value.Key == "Microsoft.AspNetCore.Hosting.HttpRequestIn.Start")
{
// This happens on incoming requests to ASP.NET. Grab the MS-CV header and store
// it on the HttpContext.
//
if (!(value.Value.GetType().GetProperty("HttpContext")?.GetValue(value.Value, null) is HttpContext httpContext))
{
return;
}
CorrelationVector correlationVector;
if (httpContext.Request.Headers.ContainsKey("MS-CV"))
{
correlationVector =
CorrelationVector.Extend(httpContext.Request.Headers["MS-CV"][0]);
}
else
{
correlationVector = new CorrelationVector();
}
CorrelationVector.Current = correlationVector;
}
else if (value.Key == "System.Net.Http.HttpRequestOut.Start")
{
// This happens on outgoing Http requests via Http Client. See if a Correlation
// Vector has been stored on the Request Message's properties and use it to
// stamp an MS-CV header (after incrementing the CV).
//
if (!(value.Value.GetType().GetProperty("Request")?.GetValue(value.Value, null) is HttpRequestMessage requestMessage))
{
return;
}
requestMessage.Properties.Add("TimeStamp", DateTime.Now.Ticks);
// If the application code explicitly passed along the cV header from the incoming request, then increment it prior to the outbound request.
CorrelationVector correlationVector = requestMessage.GetCorrelationVector();
if (correlationVector != null)
{
requestMessage.Headers.Add("MS-CV", correlationVector.Increment());
}
else
{
// This is the expected case where the application code is unaware of the cV and did not get it from the incoming request and set it on the
// outgoing request. Get the current cV from the AsyncLocal Instance, increment it, and add it to the outgoing request.
correlationVector = CorrelationVector.Current;
if (correlationVector != null)
{
requestMessage.Headers.Add("MS-CV", correlationVector.Increment());
}
else
{
// TODO: Should never hit this case. Just in case we do, initialize a new cV here.
}
}
}
else if (value.Key == "System.Net.Http.HttpRequestOut.Stop")
{
// This happens after an outgoing Http request via Http Client completes. We can use
// this as an opportunity to log the Outgoing Service Request event. Many of the
// properties used for logging can be gleaned from the Http request and response.
// Some of the properties need to be stamped on the request ahead of time by the
// service owner, such as the Dependency information.
//
if (!(value.Value.GetType().GetProperty("Response")?.GetValue(value.Value, null) is HttpResponseMessage responseMessage))
{
return;
}
long?latency = null;
if (responseMessage.RequestMessage.Properties.ContainsKey("TimeStamp") &&
responseMessage.RequestMessage.Properties["TimeStamp"] is long requestTimeStamp)
{
latency = (long)(DateTime.Now - new DateTime(requestTimeStamp)).TotalMilliseconds;
}
// Acquire a lock just so the console output isn't jumbled up by multiple threads
//
lock (_outgoingRequestLoggingLock)
{
// These properties can be gleaned from the Http request and response
//
Console.WriteLine("---------------------------------------");
Console.WriteLine("Logging the Outgoing Service Request...");
Console.WriteLine("Correlation Vector: {0}", responseMessage.RequestMessage.GetCorrelationVectorHeader());
Console.WriteLine("Target Uri: {0}", responseMessage.RequestMessage.RequestUri.ToString());
Console.WriteLine("Latency ms: {0}", latency.HasValue ? latency.Value.ToString() : string.Empty);
// TODO - need code to be able to read the service error code - should this code be common or customizable?
Console.WriteLine("Service error code: {0}", null);
Console.WriteLine("Succeeded: {0}", responseMessage.IsSuccessStatusCode);
Console.WriteLine("Request method: {0}", responseMessage.RequestMessage.Method);
Console.WriteLine("Protocol Status Code: {0}", (int)responseMessage.StatusCode);
Console.WriteLine("Response Size (bytes): {0}", responseMessage.Content.ReadAsByteArrayAsync().Result.Length);
// These properties need to be stamped on the request by the service owner
// through the use of DependencyClientHandler and a HttpClient.SendAsync
// extension method.
//
if (responseMessage.RequestMessage.Properties.ContainsKey(nameof(DependencyOperationInfo)) &&
responseMessage.RequestMessage.Properties[nameof(DependencyOperationInfo)] is DependencyOperationInfo dependencyInfo)
{
Console.WriteLine("Dependency Name: {0}", dependencyInfo.DependencyName);
Console.WriteLine("Dependency Type: {0}", dependencyInfo.DependencyType);
Console.WriteLine("Operation Name: {0}", dependencyInfo.OperationName);
Console.WriteLine("Dependency Operation Name: {0}", dependencyInfo.DependencyOperationName);
Console.WriteLine("Dependency Operation Version: {0}", dependencyInfo.DependencyOperationVersion);
}
Console.WriteLine("---------------------------------------");
}
}
}
public static void AddCorrelationVector(this HttpRequestMessage requestMessage, CorrelationVector correlationVector)
{
requestMessage.Properties.Add(nameof(CorrelationVector), correlationVector);
}