[HttpClient] Add error.type for traces and metrics (#5005)

Co-authored-by: Utkarsh Umesan Pillai <66651184+utpilla@users.noreply.github.com>
Co-authored-by: Timothy Mothra <tilee@microsoft.com>
Co-authored-by: Mikel Blanchard <mblanchard@macrosssoftware.com>

src/OpenTelemetry.Instrumentation.Http/CHANGELOG.md

@@ -18,6 +18,22 @@
   `http` or `http/dup`.
   ([#5003](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5003))
 
+* An additional attribute `error.type` will be added to activity and
+  `http.client.request.duration` metric in case of failed requests as per the
+  [specification](https://github.com/open-telemetry/semantic-conventions/blob/v1.23.0/docs/http/http-spans.md#common-attributes).
+
+  Users moving to `net8.0` or newer frameworks from lower versions will see
+  difference in values in case of an exception. `net8.0` or newer frameworks add
+  the ability to further drill down the exceptions to a specific type through
+  [HttpRequestError](https://learn.microsoft.com/dotnet/api/system.net.http.httprequesterror?view=net-8.0)
+  enum. For lower versions, the individual types will be rolled in to a single
+  type. This could be a **breaking change** if alerts are set based on the values.
+
+  The attribute will only be added when `OTEL_SEMCONV_STABILITY_OPT_IN`
+  environment variable is set to `http` or `http/dup`.
+
+  ([#5005](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5005))
+
 ## 1.6.0-beta.2
 
 Released 2023-Oct-26

src/OpenTelemetry.Instrumentation.Http/Implementation/HttpHandlerDiagnosticListener.cs

@@ -271,6 +271,11 @@ public void OnStopActivity(Activity activity, object payload)
 
             if (TryFetchResponse(payload, out HttpResponseMessage response))
             {
+                if (currentStatusCode == ActivityStatusCode.Unset)
+                {
+                    activity.SetStatus(SpanHelper.ResolveSpanStatusForHttpStatusCode(activity.Kind, (int)response.StatusCode));
+                }
+
                 if (this.emitOldAttributes)
                 {
                     activity.SetTag(SemanticConventions.AttributeHttpStatusCode, TelemetryHelper.GetBoxedStatusCode(response.StatusCode));
@@ -279,11 +284,10 @@ public void OnStopActivity(Activity activity, object payload)
                 if (this.emitNewAttributes)
                 {
                     activity.SetTag(SemanticConventions.AttributeHttpResponseStatusCode, TelemetryHelper.GetBoxedStatusCode(response.StatusCode));
-                }
-
-                if (currentStatusCode == ActivityStatusCode.Unset)
-                {
-                    activity.SetStatus(SpanHelper.ResolveSpanStatusForHttpStatusCode(activity.Kind, (int)response.StatusCode));
+                    if (activity.Status == ActivityStatusCode.Error)
+                    {
+                        activity.SetTag(SemanticConventions.AttributeErrorType, TelemetryHelper.GetBoxedStatusCode(response.StatusCode));
+                    }
                 }
 
                 try
@@ -337,6 +341,11 @@ public void OnException(Activity activity, object payload)
                 return;
             }
 
+            if (this.emitNewAttributes)
+            {
+                activity.SetTag(SemanticConventions.AttributeErrorType, GetErrorType(exc));
+            }
+
             if (this.options.RecordException)
             {
                 activity.RecordException(exc);
@@ -372,4 +381,33 @@ static bool TryFetchException(object payload, out Exception exc)
             return true;
         }
     }
+
+    private static string GetErrorType(Exception exc)
+    {
+#if NET8_0_OR_GREATER
+        // For net8.0 and above exception type can be found using HttpRequestError.
+        // https://learn.microsoft.com/dotnet/api/system.net.http.httprequesterror?view=net-8.0
+        if (exc is HttpRequestException httpRequestException)
+        {
+            return httpRequestException.HttpRequestError switch
+            {
+                HttpRequestError.NameResolutionError => "name_resolution_error",
+                HttpRequestError.ConnectionError => "connection_error",
+                HttpRequestError.SecureConnectionError => "secure_connection_error",
+                HttpRequestError.HttpProtocolError => "http_protocol_error",
+                HttpRequestError.ExtendedConnectNotSupported => "extended_connect_not_supported",
+                HttpRequestError.VersionNegotiationError => "version_negotiation_error",
+                HttpRequestError.UserAuthenticationError => "user_authentication_error",
+                HttpRequestError.ProxyTunnelError => "proxy_tunnel_error",
+                HttpRequestError.InvalidResponse => "invalid_response",
+                HttpRequestError.ResponseEnded => "response_ended",
+                HttpRequestError.ConfigurationLimitExceeded => "configuration_limit_exceeded",
+
+                // Fall back to the exception type name in case of HttpRequestError.Unknown
+                _ => exc.GetType().FullName,
+            };
+        }
+#endif
+        return exc.GetType().FullName;
+    }
 }