fix: Align metrics implementation with spec

- Default enable_metrics to true (spec requirement)
- Gate user PII attributes (user.id, user.name, user.email) on
  send_default_pii
- Add trace_metric rate limiting category so server-sent rate limits
  for metrics are properly respected

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jjbayer

sentry-core/src/batcher.rs

@@ -268,14 +268,17 @@ mod tests {
         }
 
         #[test]
-        fn test_metrics_disabled_by_default() {
+        fn test_metrics_disabled_explicitly() {
             let envelopes = test::with_captured_envelopes_options(
                 || {
                     for i in 0..10 {
                         crate::Hub::current().capture_metric(test_metric(&format!("metric.{i}")));
                     }
                 },
-                crate::ClientOptions::default(),
+                crate::ClientOptions {
+                    enable_metrics: false,
+                    ..Default::default()
+                },
             );
 
             assert_eq!(0, envelopes.len());

sentry-core/src/client.rs

@@ -579,7 +579,7 @@ impl Client {
     /// processing it through `before_send_metric`.
     #[cfg(feature = "metrics")]
     fn prepare_metric(&self, mut metric: TraceMetric, scope: &Scope) -> Option<TraceMetric> {
-        scope.apply_to_metric(&mut metric);
+        scope.apply_to_metric(&mut metric, self.options.send_default_pii);
 
         if let Some(default_attributes) = self.default_metric_attributes.as_ref() {
             for (key, val) in default_attributes.iter() {

sentry-core/src/clientoptions.rs

@@ -174,7 +174,7 @@ pub struct ClientOptions {
     /// Determines whether captured structured logs should be sent to Sentry (defaults to false).
     #[cfg(feature = "logs")]
     pub enable_logs: bool,
-    /// Determines whether captured trace metrics should be sent to Sentry (defaults to false).
+    /// Determines whether captured trace metrics should be sent to Sentry (defaults to true).
     #[cfg(feature = "metrics")]
     pub enable_metrics: bool,
     /// Callback that is executed for each TraceMetric being added.
@@ -337,7 +337,7 @@ impl Default for ClientOptions {
             #[cfg(feature = "logs")]
             before_send_log: None,
             #[cfg(feature = "metrics")]
-            enable_metrics: false,
+            enable_metrics: true,
             #[cfg(feature = "metrics")]
             before_send_metric: None,
         }

sentry-core/src/scope/noop.rs

@@ -123,8 +123,9 @@ impl Scope {
 
     /// Applies the contained scoped data to fill a trace metric.
     #[cfg(feature = "metrics")]
-    pub fn apply_to_metric(&self, metric: &mut TraceMetric) {
+    pub fn apply_to_metric(&self, metric: &mut TraceMetric, send_default_pii: bool) {
         let _metric = metric;
+        let _send_default_pii = send_default_pii;
         minimal_unreachable!();
     }
 

sentry-core/src/scope/real.rs

@@ -405,9 +405,10 @@ impl Scope {
     }
 
     /// Applies the contained scoped data to a trace metric, setting the `trace_id`, `span_id`,
-    /// and certain default attributes.
+    /// and certain default attributes. User PII attributes are only attached when
+    /// `send_default_pii` is `true`.
     #[cfg(feature = "metrics")]
-    pub fn apply_to_metric(&self, metric: &mut TraceMetric) {
+    pub fn apply_to_metric(&self, metric: &mut TraceMetric, send_default_pii: bool) {
         if let Some(span) = self.span.as_ref() {
             metric.trace_id = span.get_trace_context().trace_id;
         } else {
@@ -426,29 +427,31 @@ impl Scope {
             }
         }
 
-        if let Some(user) = self.user.as_ref() {
-            if !metric.attributes.contains_key("user.id") {
-                if let Some(id) = user.id.as_ref() {
-                    metric
-                        .attributes
-                        .insert("user.id".to_owned(), LogAttribute(id.to_owned().into()));
+        if send_default_pii {
+            if let Some(user) = self.user.as_ref() {
+                if !metric.attributes.contains_key("user.id") {
+                    if let Some(id) = user.id.as_ref() {
+                        metric
+                            .attributes
+                            .insert("user.id".to_owned(), LogAttribute(id.to_owned().into()));
+                    }
                 }
-            }
 
-            if !metric.attributes.contains_key("user.name") {
-                if let Some(name) = user.username.as_ref() {
-                    metric
-                        .attributes
-                        .insert("user.name".to_owned(), LogAttribute(name.to_owned().into()));
+                if !metric.attributes.contains_key("user.name") {
+                    if let Some(name) = user.username.as_ref() {
+                        metric
+                            .attributes
+                            .insert("user.name".to_owned(), LogAttribute(name.to_owned().into()));
+                    }
                 }
-            }
 
-            if !metric.attributes.contains_key("user.email") {
-                if let Some(email) = user.email.as_ref() {
-                    metric.attributes.insert(
-                        "user.email".to_owned(),
-                        LogAttribute(email.to_owned().into()),
-                    );
+                if !metric.attributes.contains_key("user.email") {
+                    if let Some(email) = user.email.as_ref() {
+                        metric.attributes.insert(
+                            "user.email".to_owned(),
+                            LogAttribute(email.to_owned().into()),
+                        );
+                    }
                 }
             }
         }

sentry/src/transports/ratelimit.rs

@@ -14,6 +14,7 @@ pub struct RateLimiter {
     transaction: Option<SystemTime>,
     attachment: Option<SystemTime>,
     log_item: Option<SystemTime>,
+    trace_metric: Option<SystemTime>,
 }
 
 impl RateLimiter {
@@ -59,6 +60,7 @@ impl RateLimiter {
                     "transaction" => self.transaction = new_time,
                     "attachment" => self.attachment = new_time,
                     "log_item" => self.log_item = new_time,
+                    "trace_metric" => self.trace_metric = new_time,
                     _ => {}
                 }
             }
@@ -93,6 +95,7 @@ impl RateLimiter {
             RateLimitingCategory::Transaction => self.transaction,
             RateLimitingCategory::Attachment => self.attachment,
             RateLimitingCategory::LogItem => self.log_item,
+            RateLimitingCategory::TraceMetric => self.trace_metric,
         }?;
         time_left.duration_since(SystemTime::now()).ok()
     }
@@ -119,6 +122,9 @@ impl RateLimiter {
                 EnvelopeItem::ItemContainer(ItemContainer::Logs(_)) => {
                     RateLimitingCategory::LogItem
                 }
+                EnvelopeItem::ItemContainer(ItemContainer::TraceMetrics(_)) => {
+                    RateLimitingCategory::TraceMetric
+                }
                 _ => RateLimitingCategory::Any,
             })
         })
@@ -140,6 +146,8 @@ pub enum RateLimitingCategory {
     Attachment,
     /// Rate Limit pertaining to Log Items.
     LogItem,
+    /// Rate Limit pertaining to Trace Metrics.
+    TraceMetric,
 }
 
 #[cfg(test)]
@@ -155,6 +163,7 @@ mod tests {
         assert!(rl.is_disabled(RateLimitingCategory::Session).unwrap() <= Duration::from_secs(60));
         assert!(rl.is_disabled(RateLimitingCategory::Transaction).is_none());
         assert!(rl.is_disabled(RateLimitingCategory::LogItem).is_none());
+        assert!(rl.is_disabled(RateLimitingCategory::TraceMetric).is_none());
         assert!(rl.is_disabled(RateLimitingCategory::Any).is_none());
 
         rl.update_from_sentry_header(
@@ -185,6 +194,9 @@ mod tests {
         assert!(
             rl.is_disabled(RateLimitingCategory::Attachment).unwrap() <= Duration::from_secs(120)
         );
+        assert!(
+            rl.is_disabled(RateLimitingCategory::TraceMetric).unwrap() <= Duration::from_secs(120)
+        );
         assert!(rl.is_disabled(RateLimitingCategory::Any).unwrap() <= Duration::from_secs(120));
     }