CP-44752: propagate System.Diagnostics tracing information using W3C traceparent header

[edwintorok]

The newer System.Net.Http would propagate this automatically, but the older WebRequest doesn't.

Retrieve the span identifier and add the header ourselves. The WebRequest object is fresh for each request, so setting the headers shouldn't cause race conditions.

This adds a dependency on a library that is part of .Net source repository, but distributed outside of it on NuGet: System.Diagnostics. Lock the dependency to a given hash to avoid accidental/malicious changes.
This dependency is not available on .Net45, so all the code and build dependencies are wrapped with appropriate conditional compilation directives (which may look kind of ugly, they can be dropped once XenServer.dll drops support for .Net45 and switches to .Net462 minimum).

No new instrumentation is created, so if the application using XenServer.dll is not configured/set up to use OpenTelemetry or System.Diagnostics.DiagnosticSource, then this is a no-op.

I've tested this using the Powershell 7 module.

Draft PR because:

• I haven't tested the version with the locked dependencies yet
• There is one TODO in the code about obtaining a version number

[edwintorok]

Internal build succeeded with locked package dependencies too.

[edwintorok]

I think I'll also need NET462_OR_GREATER otherwise XC won't pick this up.

[danilo-delbusso]

haven't tested it yet but I spotted a couple of things on the first run

for SDK PRs also please request reviews manually, because we don't monitor the repo as often as toolstack does, so it helps to see PR reviews under https://github.com/pulls

[kc284]

As above.

[edwintorok]

I've addressed the review comments, and tested a build, the traceparent is sent correctly:

POST /jsonrpc HTTP/1.1
Host: lcy2-dt72.xenrt.citrite.net
Accept: application/json
User-Agent: XenServerPSModule/25.2.0.0
Connection: Keep-Alive
traceparent: 00-a29a037790a77a956ab8ce8887d1287d-900ac8ca433ee4f4-01
Content-Type: application/json
Content-Length: 100

[edwintorok]

I'll add a small self-contained example here on how the output looks with OpenTelemetry instrumentation enabled.

[edwintorok]

dotnet new console -o sample1
dotnet add package OpenTelemetry.Exporter.Console --version 1.9.0
dotnet add package OpenTelemetry --version 1.9.0
dotnet nuget add source --name 'Offline Packages' E:\myfolder\xen-api\sdk\sdk\XenServer-SDK\XenServer.NET\
dotnet add package XenServer.NET -s 'Offline Packages'

// See https://aka.ms/new-console-template for more information
using System.Net;
using System;
using System.Collections.Generic;
using XenAPI;
using System.Runtime.InteropServices;
using System.ComponentModel.DataAnnotations;
using OpenTelemetry;
using OpenTelemetry.Resources;
using OpenTelemetry.Trace;
using System.Diagnostics;

ActivitySource source = new ActivitySource("Sample.DistributedTracing", "1.0.0");

using var tracerProvider = Sdk.CreateTracerProviderBuilder()
                .SetResourceBuilder(ResourceBuilder.CreateDefault().AddService("MySample"))
                .AddSource("*")
                .AddConsoleExporter()
                .Build();

using (Activity activity = source.StartActivity("SomeWork"))
{
    //Trust all certificates. This is a test workaround. DO NOT USE IN PRODUCTION CODE!
    ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;

    string hostUrl = args[0], username = args[1], password = args[2];
    Session session = new Session(hostUrl);
    try
    {
        session.login_with_password(username, password, "", "XenSdkSample");

        var hosts = Host.get_all(session);
        System.Console.WriteLine("Got hosts: " + hosts.Count);
    }
    finally
    {
        session.logout();
    }
}

The output looks like this (the application can choose which activity sources to enable, if they want just the XenServer on, they can enable 'XenServer.*'):
https://gist.github.com/edwintorok/d1528660c588d6916363c8bb0565ba50

[edwintorok]

Tested using a slightly tweaked version of the above sample (using OTLP to send to jaeger), and confirmed that we get a joined Client + Server trace in Jaeger.

Review comments addressed in new commits. Removing stale review marker, and requested new review.

[mg12]

The code changes and output looks good to me, and the joined Client + Server trace in Jaeger shows it's working as intended. Perhaps someone more used to the SDK build system could check the dependency changes @kc284 @danilo-delbusso