[Api] support for adding default tags to tracer

src/OpenTelemetry.Api/.publicApi/Stable/PublicAPI.Shipped.txt

@@ -151,7 +151,9 @@ OpenTelemetry.Trace.Tracer.StartRootSpan(string! name, OpenTelemetry.Trace.SpanK
 OpenTelemetry.Trace.Tracer.StartSpan(string! name, OpenTelemetry.Trace.SpanKind kind = OpenTelemetry.Trace.SpanKind.Internal, in OpenTelemetry.Trace.SpanContext parentContext = default(OpenTelemetry.Trace.SpanContext), OpenTelemetry.Trace.SpanAttributes? initialAttributes = null, System.Collections.Generic.IEnumerable<OpenTelemetry.Trace.Link>? links = null, System.DateTimeOffset startTime = default(System.DateTimeOffset)) -> OpenTelemetry.Trace.TelemetrySpan!
 OpenTelemetry.Trace.Tracer.StartSpan(string! name, OpenTelemetry.Trace.SpanKind kind, in OpenTelemetry.Trace.TelemetrySpan? parentSpan, OpenTelemetry.Trace.SpanAttributes? initialAttributes = null, System.Collections.Generic.IEnumerable<OpenTelemetry.Trace.Link>? links = null, System.DateTimeOffset startTime = default(System.DateTimeOffset)) -> OpenTelemetry.Trace.TelemetrySpan!
 OpenTelemetry.Trace.TracerProvider
-OpenTelemetry.Trace.TracerProvider.GetTracer(string! name, string? version = null) -> OpenTelemetry.Trace.Tracer!
+OpenTelemetry.Trace.TracerProvider.GetTracer(string! name) -> OpenTelemetry.Trace.Tracer!
+OpenTelemetry.Trace.TracerProvider.GetTracer(string! name, string? version = "") -> OpenTelemetry.Trace.Tracer!
+OpenTelemetry.Trace.TracerProvider.GetTracer(string! name, string? version = "", System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string!, object?>>? tags = null) -> OpenTelemetry.Trace.Tracer!
 OpenTelemetry.Trace.TracerProvider.TracerProvider() -> void
 OpenTelemetry.Trace.TracerProviderBuilder
 OpenTelemetry.Trace.TracerProviderBuilder.TracerProviderBuilder() -> void

src/OpenTelemetry.Api/Trace/TracerProvider.cs

@@ -27,6 +27,18 @@ protected TracerProvider()
     /// </summary>
     public static TracerProvider Default { get; } = new TracerProvider();
 
+    /// <summary>
+    /// Gets a tracer with given name and version.
+    /// </summary>
+    /// <param name="name">Name identifying the instrumentation library.</param>
+    /// <returns>Tracer instance.</returns>
+    public Tracer GetTracer(
+#if NET
+        [AllowNull]
+#endif
+        string name) =>
+        this.GetTracer(name, string.Empty, null);
+
     /// <summary>
     /// Gets a tracer with given name and version.
     /// </summary>
@@ -38,7 +50,23 @@ public Tracer GetTracer(
         [AllowNull]
 #endif
         string name,
-        string? version = null)
+        string? version = "") =>
+        this.GetTracer(name, version, null);
+
+    /// <summary>
+    /// Gets a tracer with given name, version and tags.
+    /// </summary>
+    /// <param name="name">Name identifying the instrumentation library.</param>
+    /// <param name="version">Version of the instrumentation library.</param>
+    /// <param name="tags">Tags associated with the tracer.</param>
+    /// <returns>Tracer instance.</returns>
+    public Tracer GetTracer(
+#if NET
+        [AllowNull]
+#endif
+        string name,
+        string? version = "",
+        IEnumerable<KeyValuePair<string, object?>>? tags = null)
     {
         var tracers = this.Tracers;
         if (tracers == null)
@@ -47,7 +75,7 @@ public Tracer GetTracer(
             return new(activitySource: null);
         }
 
-        var key = new TracerKey(name, version);
+        var key = new TracerKey(name, version, tags);
 
         if (!tracers.TryGetValue(key, out var tracer))
         {
@@ -60,12 +88,10 @@ public Tracer GetTracer(
                     return new(activitySource: null);
                 }
 
-                tracer = new(new(key.Name, key.Version));
-#if DEBUG
+                tracer = new(new(key.Name, key.Version, key.Tags));
                 bool result = tracers.TryAdd(key, tracer);
+#if DEBUG
                 System.Diagnostics.Debug.Assert(result, "Write into tracers cache failed");
-#else
-                tracers.TryAdd(key, tracer);
 #endif
             }
         }
@@ -103,11 +129,26 @@ internal readonly record struct TracerKey
     {
         public readonly string Name;
         public readonly string? Version;
+        public readonly IEnumerable<KeyValuePair<string, object?>>? Tags;
 
-        public TracerKey(string? name, string? version)
+        public TracerKey(string? name, string? version, IEnumerable<KeyValuePair<string, object?>>? tags)
         {
             this.Name = name ?? string.Empty;
             this.Version = version;
+            this.Tags = GetOrderedTags(tags);
+        }
+
+        private static IEnumerable<KeyValuePair<string, object?>>? GetOrderedTags(
+            IEnumerable<KeyValuePair<string, object?>>? tags)
+        {
+            if (tags is null)
+            {
+                return null;
+            }
+
+            var orderedTagList = new List<KeyValuePair<string, object?>>(tags);
+            orderedTagList.Sort((left, right) => string.Compare(left.Key, right.Key, StringComparison.Ordinal));
+            return orderedTagList.AsReadOnly();
         }
     }
 }

test/OpenTelemetry.Api.Tests/Trace/TracerTest.cs

@@ -303,8 +303,8 @@ public void TracerBecomesNoopWhenParentProviderIsDisposedTest()
         Tracer? tracer1;
 
         using (var tracerProvider = Sdk.CreateTracerProviderBuilder()
-            .AddSource("mytracer")
-            .Build())
+                   .AddSource("mytracer")
+                   .Build())
         {
             provider = tracerProvider;
             tracer1 = tracerProvider.GetTracer("mytracer");
@@ -408,6 +408,82 @@ static void InnerTest()
         }
     }
 
+    [Fact]
+    public void GetTracer_WithTags_ReturnsSameInstanceForSameTags()
+    {
+        var tags1 = new List<KeyValuePair<string, object?>> { new("tag1", "value1"), new("tag2", "value2") };
+        var tags2 = new List<KeyValuePair<string, object?>> { new("tag1", "value1"), new("tag2", "value2") };
+
+        using var tracerProvider = new TestTracerProvider();
+        var tracer1 = tracerProvider.GetTracer("test", "1.0.0", tags1);
+        var tracer2 = tracerProvider.GetTracer("test", "1.0.0", tags2);
+
+        Assert.Equivalent(tracer1, tracer2);
+    }
+
+    [Fact]
+    public void GetTracer_WithTags_ReturnsDifferentInstancesForDifferentTags()
+    {
+        var tags1 = new List<KeyValuePair<string, object?>> { new("tag1", "value1") };
+        var tags2 = new List<KeyValuePair<string, object?>> { new("tag2", "value2") };
+
+        using var tracerProvider = new TestTracerProvider();
+        var tracer1 = tracerProvider.GetTracer("test", "1.0.0", tags1);
+        var tracer2 = tracerProvider.GetTracer("test", "1.0.0", tags2);
+
+        Assert.NotEqual(tracer1, tracer2);
+    }
+
+    [Fact]
+    public void GetTracer_WithTags_OrdersTagsByKey()
+    {
+        var tags1 = new List<KeyValuePair<string, object?>> { new("tag2", "value2"), new("tag1", "value1"), };
+        var tags2 = new List<KeyValuePair<string, object?>> { new("tag1", "value1"), new("tag2", "value2"), };
+
+        using var tracerProvider = new TestTracerProvider();
+        var tracer1 = tracerProvider.GetTracer("test", "1.0.0", tags1);
+        var tracer2 = tracerProvider.GetTracer("test", "1.0.0", tags2);
+
+        Assert.Equivalent(tracer1, tracer2);
+    }
+
+    [Fact]
+    public void GetTracer_WithTagsAndWithoutTags_ReturnsDifferentInstances()
+    {
+        var tags = new List<KeyValuePair<string, object?>> { new("tag1", "value1") };
+
+        using var tracerProvider = new TestTracerProvider();
+        var tracerWithTags = tracerProvider.GetTracer("test", "1.0.0", tags);
+        var tracerWithoutTags = tracerProvider.GetTracer("test", "1.0.0");
+
+        Assert.NotSame(tracerWithTags, tracerWithoutTags);
+    }
+
+    [Fact]
+    public void GetTracer_WithTags_AppliesTagsToActivities()
+    {
+        var exportedItems = new List<Activity>();
+        var tags = new List<KeyValuePair<string, object?>> { new("tracerTag", "tracerValue") };
+
+        using var tracerProvider = Sdk.CreateTracerProviderBuilder()
+            .AddSource("test")
+            .AddInMemoryExporter(exportedItems)
+            .SetSampler(new AlwaysOnSampler())
+            .Build();
+
+        var tracer = tracerProvider.GetTracer("test", "1.0.0", tags);
+
+        using (var span = tracer.StartActiveSpan("TestSpan"))
+        {
+            // Activity started by the tracer with tags
+        }
+
+        Assert.Single(exportedItems);
+        var activity = exportedItems[0];
+
+        Assert.Contains(activity.Source.Tags!, kvp => kvp.Key == "tracerTag" && (string)kvp.Value! == "tracerValue");
+    }
+
     public void Dispose()
     {
         Activity.Current = null;