PassThroughPropagator.cs

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using System.Collections.Generic;
 
namespace System.Diagnostics;
 
internal sealed class PassThroughPropagator : DistributedContextPropagator
{
    internal static DistributedContextPropagator Instance { get; } = new PassThroughPropagator();
 
 
    public override IReadOnlyCollection<string> Fields { get; } = LegacyPropagator.Instance.Fields;
 
 
    public override void Inject(Activity activity, object carrier, PropagatorSetterCallback setter)
    {
        if (setter == null)
        {
            return;
        }
        GetRootId(out var parentId, out var traceState, out var isW3c, out var baggage);
        if (parentId != null)
        {
            setter(carrier, isW3c ? "traceparent" : "Request-Id", parentId);
            if (!string.IsNullOrEmpty(traceState))
            {
                setter(carrier, "tracestate", traceState);
            }
            if (baggage != null)
            {
                DistributedContextPropagator.InjectBaggage(carrier, baggage, setter);
            }
        }
    }
 
    public override void ExtractTraceIdAndState(object carrier, PropagatorGetterCallback getter, out string traceId, out string traceState)
    {
        LegacyPropagator.Instance.ExtractTraceIdAndState(carrier, getter, out traceId, out traceState);
    }
 
    public override IEnumerable<KeyValuePair<string, string>> ExtractBaggage(object carrier, PropagatorGetterCallback getter)
    {
        return LegacyPropagator.Instance.ExtractBaggage(carrier, getter);
    }
 
    private static void GetRootId(out string parentId, out string traceState, out bool isW3c, out IEnumerable<KeyValuePair<string, string>> baggage)
    {
        Activity activity = Activity.Current;
        while (true)
        {
            Activity activity2 = activity?.Parent;
            if (activity2 == null)
            {
                break;
            }
            activity = activity2;
        }
        traceState = activity?.TraceStateString;
        parentId = activity?.ParentId ?? activity?.Id;
        isW3c = parentId != null && Activity.TryConvertIdToContext(parentId, traceState, out var _);
        baggage = activity?.Baggage;
    }
}