[otlp] Deserialize GrpcStatusDetailsHeader to Retrieve Grpc Retry Del…

…ay (#5980)

Co-authored-by: Mikel Blanchard <mblanchard@macrosssoftware.com>

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/Grpc/GrpcStatusDeserializer.cs

@@ -0,0 +1,312 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using System.Text;
+
+namespace OpenTelemetry.Exporter.OpenTelemetryProtocol.Implementation.ExportClient.Grpc;
+
+internal static class GrpcStatusDeserializer
+{
+#pragma warning disable SA1310 // Field names should not contain underscore
+    // Wire types in protocol buffers
+    private const int WIRETYPE_VARINT = 0;
+    private const int WIRETYPE_FIXED64 = 1;
+    private const int WIRETYPE_LENGTH_DELIMITED = 2;
+    private const int WIRETYPE_FIXED32 = 5;
+#pragma warning restore SA1310 // Field names should not contain underscore
+
+    internal static TimeSpan? TryGetGrpcRetryDelay(string? grpcStatusDetailsHeader)
+    {
+        try
+        {
+            var retryInfo = ExtractRetryInfo(grpcStatusDetailsHeader);
+            if (retryInfo?.RetryDelay != null)
+            {
+                return TimeSpan.FromSeconds(retryInfo.Value.RetryDelay.Value.Seconds) +
+                       TimeSpan.FromTicks(retryInfo.Value.RetryDelay.Value.Nanos / 100); // Convert nanos to ticks
+            }
+        }
+        catch
+        {
+            // TODO: Log exception to event source.
+            return null;
+        }
+
+        return null;
+    }
+
+    // Marked as internal for test.
+    internal static Status? DeserializeStatus(string? grpcStatusDetailsBin)
+    {
+        if (string.IsNullOrWhiteSpace(grpcStatusDetailsBin))
+        {
+            return null;
+        }
+
+        var status = new Status();
+        byte[] data = Convert.FromBase64String(grpcStatusDetailsBin);
+        using (var stream = new MemoryStream(data))
+        {
+            while (stream.Position < stream.Length)
+            {
+                var tag = DecodeTag(stream);
+                var fieldNumber = tag >> 3;
+                var wireType = tag & 0x7;
+
+                switch (fieldNumber)
+                {
+                    case 1: // code
+                        status.Code = DecodeInt32(stream);
+                        break;
+                    case 2: // message
+                        status.Message = DecodeString(stream);
+                        break;
+                    case 3: // details
+                        status.Details.Add(DecodeAny(stream));
+                        break;
+                    default:
+                        SkipField(stream, wireType);
+                        break;
+                }
+            }
+        }
+
+        return status;
+    }
+
+    // Marked as internal for test.
+    internal static RetryInfo? ExtractRetryInfo(string? grpcStatusDetailsBin)
+    {
+        var status = DeserializeStatus(grpcStatusDetailsBin);
+        if (status == null)
+        {
+            return null;
+        }
+
+        foreach (var detail in status.Value.Details)
+        {
+            if (detail.TypeUrl != null && detail.TypeUrl.EndsWith("/google.rpc.RetryInfo"))
+            {
+                return DeserializeRetryInfo(detail.Value!);
+            }
+        }
+
+        return null;
+    }
+
+    private static RetryInfo? DeserializeRetryInfo(byte[] data)
+    {
+        RetryInfo? retryInfo = null;
+        using (var stream = new MemoryStream(data))
+        {
+            while (stream.Position < stream.Length)
+            {
+                var tag = DecodeTag(stream);
+                var fieldNumber = tag >> 3;
+                var wireType = tag & 0x7;
+
+                switch (fieldNumber)
+                {
+                    case 1: // retry_delay
+                        retryInfo = new RetryInfo(DecodeDuration(stream));
+                        break;
+                    default:
+                        SkipField(stream, wireType);
+                        break;
+                }
+            }
+        }
+
+        return retryInfo;
+    }
+
+    private static Duration DecodeDuration(Stream stream)
+    {
+        var length = DecodeVarint(stream);
+        var endPosition = stream.Position + length;
+        long seconds = 0;
+        int nanos = 0;
+
+        while (stream.Position < endPosition)
+        {
+            var tag = DecodeTag(stream);
+            var fieldNumber = tag >> 3;
+            var wireType = tag & 0x7;
+
+            switch (fieldNumber)
+            {
+                case 1: // seconds
+                    seconds = DecodeInt64(stream);
+                    break;
+                case 2: // nanos
+                    nanos = DecodeInt32(stream);
+                    break;
+                default:
+                    SkipField(stream, wireType);
+                    break;
+            }
+        }
+
+        return new Duration(seconds, nanos);
+    }
+
+    private static Any DecodeAny(Stream stream)
+    {
+        var length = DecodeVarint(stream);
+        var endPosition = stream.Position + length;
+
+        string? typeUrl = null;
+        byte[]? value = null;
+
+        while (stream.Position < endPosition)
+        {
+            var tag = DecodeTag(stream);
+            var fieldNumber = tag >> 3;
+            var wireType = tag & 0x7;
+
+            switch (fieldNumber)
+            {
+                case 1: // type_url
+                    typeUrl = DecodeString(stream);
+                    break;
+                case 2: // value
+                    value = DecodeBytes(stream);
+                    break;
+                default:
+                    SkipField(stream, wireType);
+                    break;
+            }
+        }
+
+        return new Any(typeUrl, value);
+    }
+
+    private static uint DecodeTag(Stream stream)
+    {
+        return (uint)DecodeVarint(stream);
+    }
+
+    private static long DecodeVarint(Stream stream)
+    {
+        long result = 0;
+        int shift = 0;
+
+        while (true)
+        {
+            int b = stream.ReadByte();
+            if (b == -1)
+            {
+                throw new EndOfStreamException();
+            }
+
+            result |= (long)(b & 0x7F) << shift;
+            if ((b & 0x80) == 0)
+            {
+                return result;
+            }
+
+            shift += 7;
+            if (shift >= 64)
+            {
+                throw new InvalidDataException("Invalid varint");
+            }
+        }
+    }
+
+    private static int DecodeInt32(Stream stream) => (int)DecodeVarint(stream);
+
+    private static long DecodeInt64(Stream stream) => DecodeVarint(stream);
+
+    private static string DecodeString(Stream stream)
+    {
+        var bytes = DecodeBytes(stream);
+        return Encoding.UTF8.GetString(bytes);
+    }
+
+    private static byte[] DecodeBytes(Stream stream)
+    {
+        var length = (int)DecodeVarint(stream);
+        var buffer = new byte[length];
+        int read = stream.Read(buffer, 0, length);
+        if (read != length)
+        {
+            throw new EndOfStreamException();
+        }
+
+        return buffer;
+    }
+
+    private static void SkipField(Stream stream, uint wireType)
+    {
+        switch (wireType)
+        {
+            case WIRETYPE_VARINT:
+                DecodeVarint(stream);
+                break;
+            case WIRETYPE_FIXED64:
+                stream.Position += 8;
+                break;
+            case WIRETYPE_LENGTH_DELIMITED:
+                var length = DecodeVarint(stream);
+                stream.Position += length;
+                break;
+            case WIRETYPE_FIXED32:
+                stream.Position += 4;
+                break;
+            default:
+                throw new InvalidDataException($"Unknown wire type: {wireType}");
+        }
+    }
+
+    internal readonly struct Duration
+    {
+        internal Duration(long seconds, int nanos)
+        {
+            this.Seconds = seconds;
+            this.Nanos = nanos;
+        }
+
+        public long Seconds { get; }
+
+        public int Nanos { get; }
+    }
+
+    internal readonly struct RetryInfo
+    {
+        public RetryInfo(Duration? retryDelay)
+        {
+            this.RetryDelay = retryDelay;
+        }
+
+        public Duration? RetryDelay { get; }
+    }
+
+    internal readonly struct Any
+    {
+        public Any(string? typeUrl, byte[]? value)
+        {
+            this.TypeUrl = typeUrl;
+            this.Value = value;
+        }
+
+        public string? TypeUrl { get; }
+
+        public byte[]? Value { get; }
+    }
+
+    internal struct Status
+    {
+        public Status()
+        {
+            this.Code = 0;
+            this.Message = null;
+            this.Details = [];
+        }
+
+        public int Code { get; set; }
+
+        public string? Message { get; set; }
+
+        public List<Any> Details { get; set; }
+    }
+}