Passing the traceid/context across page reloads?

Just a quick question/thought and I have a basic understanding of Open Telemetry.

Aare there a standard/recommendation for passing the traceId/context across page redirects in the browser? (like does the browser support passing the context across a 30x redirect?).

What I wanted to do was to visualize the authentication flow when using OpenID-Connect and I thought it would be very cool if I could pass the traceId across redirects to get a complete picture of all the page loads.

Assuming that I could get the auth service to support it).

I don't see what language/platform/framework you are using. So, I'll assume it's .NET.

We do not have standard/recommendation for redirects. I had the same problem with redirects and this is what I came up with:

Create new Propagator to check if request has trace in cookies

public class CookiePropagator : TextMapPropagator
{
    public const string IdpTraceid = "IdP-TraceId";
    public const string IdpTraceState = "Idp-TraceState";
    
    public  static readonly int TraceparentLengthV0 = "00-0af7651916cd43dd8448eb211c80319c-00f067aa0ba902b7-00".Length;


    public override void Inject<T>(PropagationContext context, T carrier, Action<T, string, string> setter)
    {
        // We're ignoring setter because it is used for Headers in HTTP requests only.
    }

    public override PropagationContext Extract<T>(PropagationContext context, T carrier,
        Func<T, string, IEnumerable<string>> getter)
    {
        // We're ignoring getter because it is used for Headers only. It's the way OpenTelemetry works for now.

        if (carrier == null)
        {
            return context;
        }

        // Let's check if we have it in the cookie
        if (carrier is HttpRequest
            {
                Path.Value: "/login1"
                or "/login2"
                or "/authorize"
                or "/challenge" // all workflows you want to track with 302 cookie
            } request
            && request.Cookies[IdpTraceid] != null)
        {
            // You can use TryExtractTraceParent from 
            // https://github.com/open-telemetry/opentelemetry-dotnet/blob/ba8a0e4c131054217555aae5c8a210da3a4b7c39/src/OpenTelemetry.Api/Context/Propagation/TraceContextPropagator.cs
            var parsed = TryExtractTraceParent(request.Cookies[IdpTraceid], out var traceId, out var spanId, out var traceoptions); 

            if (!parsed)
            {
                return context;
            }

            string tracestate = null;
            var traceStateFromCookie = request.Cookies[IdpTraceState];
            if (!string.IsNullOrWhiteSpace(traceStateFromCookie))
            {
                // You can use TryExtractTraceState from 
                // https://github.com/open-telemetry/opentelemetry-dotnet/blob/ba8a0e4c131054217555aae5c8a210da3a4b7c39/src/OpenTelemetry.Api/Context/Propagation/TraceContextPropagator.cs
                TryExtractTraceState([traceStateFromCookie], out tracestate);
            }
            return new PropagationContext(
                new ActivityContext(traceId, spanId, traceoptions, tracestate, isRemote: true),
                context.Baggage);
        }

        return context;
    }
}

You will have to put traceId in cookie, so it could be done in middleware:

app.Use(async (ctx, next) =>
    {
        await next.Invoke(ctx);

        if (ctx.Request.Path == "first/path/to/start/tracking" && Activity.Current != null)
        {
            var cookieOptions = new CookieOptions
            {
                // Two minutes should suffice for most login use cases
                Expires = DateTimeOffset.Now.AddMinutes(2)
            };

            // To make your WriteTraceParentIntoSpan you can check:
            // https://github.com/open-telemetry/opentelemetry-dotnet/blob/ba8a0e4c131054217555aae5c8a210da3a4b7c39/src/OpenTelemetry.Api/Context/Propagation/TraceContextPropagator.cs
            var traceParent = string.Create(CookiePropagator.TraceparentLengthV0, Activity.Current, CookiePropagator.WriteTraceParentIntoSpan);
            ctx.Response.Cookies.Append(CookiePropagator.IdpTraceid, traceParent, cookieOptions);
            ctx.Response.Cookies.Append(CookiePropagator.IdpTraceState, Activity.Current.TraceStateString ?? string.Empty, cookieOptions);
        }

        // Removing cookies after last redirect
        if (ctx.Request.Path == "/last/call/to/stop/tracking")
        {
            ctx.Response.Cookies.Delete(CookiePropagator.IdpTraceid);
            ctx.Response.Cookies.Delete(CookiePropagator.IdpTraceState);
        }
    });

Don't forget to add new propagator to SDK!!!

Sdk.SetDefaultTextMapPropagator(new CompositeTextMapPropagator(new TextMapPropagator[]
{
    new TraceContextPropagator(),
    new CookiePropagator()
}));