Code review.

open-telemetry · May 6, 2024 · 7e455f0 · 7e455f0
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diff --git a/src/OpenTelemetry.Exporter.Zipkin/CHANGELOG.md b/src/OpenTelemetry.Exporter.Zipkin/CHANGELOG.md
@@ -2,11 +2,6 @@
 
 ## Unreleased
 
-* Zipkin will now write numeric, boolean, and floating-point tag values as
-  primitive types in its emitted JSON instead of converting the values to
-  strings.
-  ([#5590](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5590))
-
 ## 1.8.1
 
 Released 2024-Apr-17

diff --git a/src/OpenTelemetry.Exporter.Zipkin/Implementation/ZipkinSpan.cs b/src/OpenTelemetry.Exporter.Zipkin/Implementation/ZipkinSpan.cs
@@ -1,6 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+using System.Globalization;
 using System.Text.Json;
 using OpenTelemetry.Internal;
 
@@ -152,14 +153,27 @@ public void Write(Utf8JsonWriter writer)
             writer.WritePropertyName(ZipkinSpanJsonHelper.TagsPropertyName);
             writer.WriteStartObject();
 
-            foreach (var tag in this.LocalEndpoint.Tags ?? Enumerable.Empty<KeyValuePair<string, object>>())
+            // Note: The spec says "Primitive types MUST be converted to string using en-US culture settings"
+            // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/sdk_exporters/zipkin.md#attribute
+
+            var originalUICulture = Thread.CurrentThread.CurrentUICulture;
+            Thread.CurrentThread.CurrentUICulture = CultureInfo.InvariantCulture;
+
+            try
             {
-                ZipkinTagWriter.Instance.TryWriteTag(ref writer, tag);
+                foreach (var tag in this.LocalEndpoint.Tags ?? Enumerable.Empty<KeyValuePair<string, object>>())
+                {
+                    ZipkinTagWriter.Instance.TryWriteTag(ref writer, tag);
+                }
+
+                foreach (var tag in this.Tags)
+                {
+                    ZipkinTagWriter.Instance.TryWriteTag(ref writer, tag);
+                }
             }
-
-            foreach (var tag in this.Tags)
+            finally
             {
-                ZipkinTagWriter.Instance.TryWriteTag(ref writer, tag);
+                Thread.CurrentThread.CurrentUICulture = originalUICulture;
             }
 
             writer.WriteEndObject();

diff --git a/src/OpenTelemetry.Exporter.Zipkin/Implementation/ZipkinTagWriter.cs b/src/OpenTelemetry.Exporter.Zipkin/Implementation/ZipkinTagWriter.cs
@@ -3,27 +3,51 @@
 
 #nullable enable
 
+using System.Buffers.Text;
+using System.Globalization;
 using System.Text.Json;
 using OpenTelemetry.Internal;
 
 namespace OpenTelemetry.Exporter.Zipkin.Implementation;
 
 internal sealed class ZipkinTagWriter : JsonStringArrayTagWriter<Utf8JsonWriter>
 {
+    public const int StackallocByteThreshold = 256;
+
     private ZipkinTagWriter()
     {
     }
 
     public static ZipkinTagWriter Instance { get; } = new();
 
     protected override void WriteIntegralTag(ref Utf8JsonWriter writer, string key, long value)
-        => writer.WriteNumber(key, value);
+    {
+        Span<byte> destination = stackalloc byte[StackallocByteThreshold];
+        if (Utf8Formatter.TryFormat(value, destination, out int bytesWritten))
+        {
+            writer.WriteString(key, destination.Slice(0, bytesWritten));
+        }
+        else
+        {
+            writer.WriteString(key, value.ToString(CultureInfo.InvariantCulture));
+        }
+    }
 
     protected override void WriteFloatingPointTag(ref Utf8JsonWriter writer, string key, double value)
-        => writer.WriteNumber(key, value);
+    {
+        Span<byte> destination = stackalloc byte[StackallocByteThreshold];
+        if (Utf8Formatter.TryFormat(value, destination, out int bytesWritten))
+        {
+            writer.WriteString(key, destination.Slice(0, bytesWritten));
+        }
+        else
+        {
+            writer.WriteString(key, value.ToString(CultureInfo.InvariantCulture));
+        }
+    }
 
     protected override void WriteBooleanTag(ref Utf8JsonWriter writer, string key, bool value)
-        => writer.WriteBoolean(key, value);
+        => writer.WriteString(key, value ? "true" : "false");
 
     protected override void WriteStringTag(ref Utf8JsonWriter writer, string key, string value)
         => writer.WriteString(key, value);