Fix server.port type and trace tag source

src/NATS.Client.Core/Internal/Telemetry.cs

@@ -139,18 +139,19 @@ public static TagList BuildMetricTags(INatsConnection? connection, string operat
             if (replyTo is not null)
                 len++;
 
-            var serverPort = conn.ServerInfo.Port.ToString();
+            var serverPort = conn.BoxedServerPort; // boxed once per ServerInfo change, reused for server.port and network.peer.port
+            var serverHost = conn.ServerHost; // grabbed once per ServerInfo change
             tags = new KeyValuePair<string, object?>[len];
             tags[0] = new KeyValuePair<string, object?>(Constants.SystemKey, Constants.SystemVal);
             tags[1] = new KeyValuePair<string, object?>(Constants.OpKey, Constants.OpPub);
             tags[2] = new KeyValuePair<string, object?>(Constants.DestName, subject);
 
-            tags[3] = new KeyValuePair<string, object?>(Constants.ClientId, conn.ServerInfo.ClientId.ToString());
-            tags[4] = new KeyValuePair<string, object?>(Constants.ServerAddress, conn.ServerInfo.Host);
+            tags[3] = new KeyValuePair<string, object?>(Constants.ClientId, conn.ClientId);
+            tags[4] = new KeyValuePair<string, object?>(Constants.ServerAddress, serverHost);
             tags[5] = new KeyValuePair<string, object?>(Constants.ServerPort, serverPort);
             tags[6] = new KeyValuePair<string, object?>(Constants.NetworkProtoName, "nats");
             tags[7] = new KeyValuePair<string, object?>(Constants.NetworkTransport, "tcp");
-            tags[8] = new KeyValuePair<string, object?>(Constants.NetworkPeerAddress, conn.ServerInfo.Host);
+            tags[8] = new KeyValuePair<string, object?>(Constants.NetworkPeerAddress, serverHost);
             tags[9] = new KeyValuePair<string, object?>(Constants.NetworkPeerPort, serverPort);
             tags[10] = new KeyValuePair<string, object?>(Constants.NetworkLocalAddress, conn.ServerInfo.ClientIp);
 
@@ -238,7 +239,8 @@ public static void AddTraceContextHeaders(Activity? activity, ref NatsHeaders? h
         KeyValuePair<string, object?>[] tags;
         if (connection is NatsConnection { ServerInfo: not null } conn)
         {
-            var serverPort = conn.ServerInfo.Port.ToString();
+            var serverPort = conn.BoxedServerPort; // boxed once per ServerInfo change, reused for server.port and network.peer.port
+            var serverHost = conn.ServerHost; // grabbed once per ServerInfo change
 
             var len = 17;
             if (replyTo is not null)
@@ -256,12 +258,12 @@ public static void AddTraceContextHeaders(Activity? activity, ref NatsHeaders? h
             tags[6] = new KeyValuePair<string, object?>(Constants.DestPubName, subject);
             tags[7] = new KeyValuePair<string, object?>(Constants.MsgBodySize, bodySize.ToString());
             tags[8] = new KeyValuePair<string, object?>(Constants.MsgTotalSize, size.ToString());
-            tags[9] = new KeyValuePair<string, object?>(Constants.ClientId, conn.ServerInfo.ClientId.ToString());
-            tags[10] = new KeyValuePair<string, object?>(Constants.ServerAddress, conn.ServerInfo.Host);
+            tags[9] = new KeyValuePair<string, object?>(Constants.ClientId, conn.ClientId);
+            tags[10] = new KeyValuePair<string, object?>(Constants.ServerAddress, serverHost);
             tags[11] = new KeyValuePair<string, object?>(Constants.ServerPort, serverPort);
             tags[12] = new KeyValuePair<string, object?>(Constants.NetworkProtoName, "nats");
             tags[13] = new KeyValuePair<string, object?>(Constants.NetworkTransport, "tcp");
-            tags[14] = new KeyValuePair<string, object?>(Constants.NetworkPeerAddress, conn.ServerInfo.Host);
+            tags[14] = new KeyValuePair<string, object?>(Constants.NetworkPeerAddress, serverHost);
             tags[15] = new KeyValuePair<string, object?>(Constants.NetworkPeerPort, serverPort);
             tags[16] = new KeyValuePair<string, object?>(Constants.NetworkLocalAddress, conn.ServerInfo.ClientIp);
 

src/NATS.Client.Core/NatsConnection.cs

@@ -58,6 +58,9 @@ public partial class NatsConnection : INatsConnection
 
     private ServerInfo? _writableServerInfo;
     private KeyValuePair<string, object?>[]? _metricTagsPrefix;
+    private object? _boxedServerPort;
+    private string? _serverHost;
+    private string? _clientId;
     private int _pongCount;
     private int _connectionState;
     private int _isDisposed;
@@ -164,34 +167,50 @@ internal ServerInfo? WritableServerInfo
             }
 
             KeyValuePair<string, object?>[]? prefix = null;
+            object? port = null;
+            string? host = null;
+            string? clientId = null;
             if (value is not null)
             {
                 // ServerInfo.Host/Port is the server's bind address (often 0.0.0.0); use the
                 // address the client actually dialled for OTel server.address/server.port.
                 var connectUri = _currentConnectUri;
-                var host = connectUri?.Host ?? value.Host;
-                var port = connectUri?.Port ?? value.Port;
+                host = connectUri?.Host ?? value.Host;
+                port = connectUri?.Port ?? value.Port;
+                clientId = value.ClientId.ToString();
                 prefix = new[]
                 {
                     new KeyValuePair<string, object?>(Telemetry.Constants.SystemKey, Telemetry.Constants.SystemVal),
                     new KeyValuePair<string, object?>(Telemetry.Constants.ServerAddress, host),
-                    new KeyValuePair<string, object?>(Telemetry.Constants.ServerPort, (object)port),
+                    new KeyValuePair<string, object?>(Telemetry.Constants.ServerPort, port),
                     new KeyValuePair<string, object?>(Telemetry.Constants.NetworkProtoName, "nats"),
                     new KeyValuePair<string, object?>(Telemetry.Constants.NetworkTransport, "tcp"),
                 };
             }
 
-            // Publish prefix before ServerInfo so any reader observing the new ServerInfo
-            // is guaranteed to also observe the matching prefix. Today no single reader
-            // reads both, but #1156 will unify the trace and metric tag sources and start
-            // relying on this ordering.
+            // Cache the trace-tag host, boxed port and client id once per ServerInfo change so the
+            // per-message trace path can reuse them instead of re-boxing the port and re-allocating
+            // the client id string on every message. Host and port come from the connect URI, so the
+            // trace and metric tags now share the same source.
+            Volatile.Write(ref _boxedServerPort, port);
+            Volatile.Write(ref _serverHost, host);
+            Volatile.Write(ref _clientId, clientId);
+
+            // Publish the cached fields before ServerInfo so any reader observing the new ServerInfo
+            // is guaranteed to also observe the matching tags.
             Volatile.Write(ref _metricTagsPrefix, prefix);
             Interlocked.Exchange(ref _writableServerInfo, value);
         }
     }
 
     internal KeyValuePair<string, object?>[]? MetricTagsPrefix => Volatile.Read(ref _metricTagsPrefix);
 
+    internal object? BoxedServerPort => Volatile.Read(ref _boxedServerPort);
+
+    internal string? ServerHost => Volatile.Read(ref _serverHost);
+
+    internal string? ClientId => Volatile.Read(ref _clientId);
+
     internal bool IsDisposed
     {
         get => Interlocked.CompareExchange(ref _isDisposed, 0, 0) == 1;

tests/NATS.Net.OpenTelemetry.Tests/OpenTelemetryTest.cs

@@ -27,7 +27,9 @@ public async Task Publish_subscribe_activities()
 
         await sub.Msgs.ReadAsync(cts.Token);
 
-        AssertActivityData("foo", tracker.Started);
+        var expectedHost = new Uri(server.Url).Host;
+        var expectedClientId = nats.ServerInfo!.ClientId.ToString();
+        AssertActivityData("foo", tracker.Started, expectedHost, expectedClientId);
         tracker.AssertAllStopped();
     }
 
@@ -424,7 +426,7 @@ public async Task Direct_request_reply_receive_activity_is_disposed()
         await reg;
     }
 
-    private void AssertActivityData(string subject, IReadOnlyList<Activity> activityList)
+    private void AssertActivityData(string subject, IReadOnlyList<Activity> activityList, string expectedHost, string expectedClientId)
     {
         var activities = activityList.ToArray();
         Assert.NotEmpty(activities);
@@ -457,6 +459,23 @@ private void AssertActivityData(string subject, IReadOnlyList<Activity> activity
         // Verify network.protocol.version is no longer present
         Assert.Null(sendActivity.GetTagItem("network.protocol.version"));
         Assert.Null(receiveActivity.GetTagItem("network.protocol.version"));
+
+        // server.port and network.peer.port are integers per OTel semconv, not strings
+        AssertIntTag(sendActivity, "server.port");
+        AssertIntTag(sendActivity, "network.peer.port");
+        AssertIntTag(receiveActivity, "server.port");
+        AssertIntTag(receiveActivity, "network.peer.port");
+
+        // server.address/network.peer.address come from the connect URI, not ServerInfo.Host
+        // (the server bind address, often 0.0.0.0)
+        Assert.Equal(expectedHost, sendActivity.GetTagItem("server.address"));
+        Assert.Equal(expectedHost, sendActivity.GetTagItem("network.peer.address"));
+        Assert.Equal(expectedHost, receiveActivity.GetTagItem("server.address"));
+        Assert.Equal(expectedHost, receiveActivity.GetTagItem("network.peer.address"));
+
+        // messaging.client_id is the server-assigned client id, cached per ServerInfo change
+        Assert.Equal(expectedClientId, sendActivity.GetTagItem("messaging.client_id"));
+        Assert.Equal(expectedClientId, receiveActivity.GetTagItem("messaging.client_id"));
     }
 
     private void AssertStringTagNotNullOrEmpty(Activity activity, string name)
@@ -466,6 +485,13 @@ private void AssertStringTagNotNullOrEmpty(Activity activity, string name)
         Assert.False(string.IsNullOrEmpty(tag));
     }
 
+    private void AssertIntTag(Activity activity, string name)
+    {
+        var tag = activity.GetTagItem(name);
+        Assert.NotNull(tag);
+        Assert.IsType<int>(tag);
+    }
+
     private sealed class ActivityTracker : IDisposable
     {
         private readonly List<Activity> _started = new();