Add option to enable propagation of parent span tags

DoumanAsh · DoumanAsh · commit de85f123f92d · 2025-04-11T19:28:42.000+09:00
diff --git a/sentry-core/src/performance.rs b/sentry-core/src/performance.rs
@@ -526,6 +526,22 @@ pub struct Transaction {
     pub(crate) inner: TransactionArc,
 }
 
+/// Iterable for a transaction's [tags attributes](protocol::Transaction::tags).
+pub struct TransactionTags<'a>(MutexGuard<'a, TransactionInner>);
+impl<'a> TransactionTags<'a> {
+    #[inline]
+    /// Returns iterator over available tags, if transaction is sampled
+    pub fn iter(&'a self) -> Option<impl Iterator<Item = (&'a String, &'a String)> + 'a> {
+        self.0.transaction.as_ref().map(|tx| tx.tags.iter())
+    }
+
+    #[inline]
+    /// Converts self into data pointer
+    pub fn into_data(self) -> TransactionData<'a> {
+        TransactionData(self.0)
+    }
+}
+
 /// Iterable for a transaction's [data attributes](protocol::TraceContext::data).
 pub struct TransactionData<'a>(MutexGuard<'a, TransactionInner>);
 
@@ -647,6 +663,12 @@ impl Transaction {
         TransactionData(self.inner.lock().unwrap())
     }
 
+    /// Returns an iterating accessor to the transaction's
+    /// [tags attributes](protocol::Transaction::tags).
+    pub fn tags(&self) -> TransactionTags {
+        TransactionTags(self.inner.lock().unwrap())
+    }
+
     /// Get the TransactionContext of the Transaction.
     ///
     /// Note that this clones the underlying value.
@@ -756,6 +778,38 @@ impl Transaction {
     }
 }
 
+/// A smart pointer to a span's [`tags` field](protocol::Span::tags).
+pub struct Tags<'a>(MutexGuard<'a, protocol::Span>);
+
+impl<'a> Tags<'a> {
+    /// Set some tag to be sent with this Span.
+    pub fn set_tag(&mut self, key: String, value: String) {
+        self.0.tags.insert(key, value);
+    }
+
+    #[inline]
+    /// Moves pointer to [`data` field](protocol::Span::data)
+    pub fn into_data(self) -> Data<'a> {
+        Data(self.0)
+    }
+}
+
+impl Deref for Tags<'_> {
+    type Target = BTreeMap<String, String>;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.0.tags
+    }
+}
+
+impl DerefMut for Tags<'_> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0.tags
+    }
+}
+
 /// A smart pointer to a span's [`data` field](protocol::Span::data).
 pub struct Data<'a>(MutexGuard<'a, protocol::Span>);
 
@@ -826,6 +880,11 @@ impl Span {
         Data(self.span.lock().unwrap())
     }
 
+    /// Returns a smart pointer to the span's [`tags` field](protocol::Span::tags).
+    pub fn tags(&self) -> Tags {
+        Tags(self.span.lock().unwrap())
+    }
+
     /// Get the TransactionContext of the Span.
     ///
     /// Note that this clones the underlying value.
diff --git a/sentry-tracing/src/converters.rs b/sentry-tracing/src/converters.rs
@@ -9,7 +9,7 @@ use tracing_subscriber::layer::Context;
 use tracing_subscriber::registry::LookupSpan;
 
 use super::layer::SentrySpanData;
-use crate::TAGS_PREFIX;
+use crate::{SpanPropagation, TAGS_PREFIX};
 
 /// Converts a [`tracing_core::Level`] to a Sentry [`Level`]
 fn convert_tracing_level(level: &tracing_core::Level) -> Level {
@@ -54,39 +54,55 @@ fn extract_event_data(event: &tracing_core::Event) -> (Option<String>, FieldVisi
 
 fn extract_event_data_with_context<S>(
     event: &tracing_core::Event,
-    ctx: Option<Context<S>>,
+    ctx: Context<S>,
+    propagation: Option<SpanPropagation>,
 ) -> (Option<String>, FieldVisitor)
 where
     S: Subscriber + for<'a> LookupSpan<'a>,
 {
     let (message, mut visitor) = extract_event_data(event);
 
-    // Add the context fields of every parent span.
-    let current_span = ctx.as_ref().and_then(|ctx| {
+    // Add the context fields of every parent span, if propagation is enabled
+    let propagation_span = propagation.and_then(|propagation| {
         event
             .parent()
-            .and_then(|id| ctx.span(id))
-            .or_else(|| ctx.lookup_current())
+            .and_then(|id| ctx.span(id).map(|span| (propagation, span)))
+            .or_else(|| ctx.lookup_current().map(|span| (propagation, span)))
     });
-    if let Some(span) = current_span {
+    if let Some((propagation, span)) = propagation_span {
         for span in span.scope() {
             let name = span.name();
             let ext = span.extensions();
             if let Some(span_data) = ext.get::<SentrySpanData>() {
                 match &span_data.sentry_span {
                     TransactionOrSpan::Span(span) => {
-                        for (key, value) in span.data().iter() {
-                            if key != "message" {
-                                let key = format!("{}:{}", name, key);
-                                visitor.json_values.insert(key, value.clone());
+                        let tags = span.tags();
+
+                        if propagation.is_tags_enabled() {
+                            for (key, value) in tags.iter() {
+                                visitor.propagate_span_tag(key, value);
+                            }
+                        }
+
+                        if propagation.is_attrs_enabled() {
+                            for (key, value) in tags.into_data().iter() {
+                                visitor.propagate_span_attr(key, value, name);
                             }
                         }
                     }
                     TransactionOrSpan::Transaction(transaction) => {
-                        for (key, value) in transaction.data().iter() {
-                            if key != "message" {
-                                let key = format!("{}:{}", name, key);
-                                visitor.json_values.insert(key, value.clone());
+                        let tags = transaction.tags();
+                        if propagation.is_tags_enabled() {
+                            if let Some(tags) = tags.iter() {
+                                for (key, value) in tags {
+                                    visitor.propagate_span_tag(key, value);
+                                }
+                            }
+                        }
+
+                        if propagation.is_attrs_enabled() {
+                            for (key, value) in tags.into_data().iter() {
+                                visitor.propagate_span_attr(key, value, name);
                             }
                         }
                     }
@@ -106,6 +122,19 @@ pub(crate) struct FieldVisitor {
 }
 
 impl FieldVisitor {
+    fn propagate_span_tag(&mut self, key: &str, value: &str) {
+        //Propagate tags as it is, it will be extracted later on
+        let tag = format!("{TAGS_PREFIX}{key}");
+        self.json_values.entry(tag).or_insert_with(|| value.into());
+    }
+
+    fn propagate_span_attr(&mut self, key: &str, value: &Value, span_name: &str) {
+        if key != "message" {
+            let key = format!("{}:{}", span_name, key);
+            self.json_values.insert(key, value.clone());
+        }
+    }
+
     fn record<T: Into<Value>>(&mut self, field: &Field, value: T) {
         self.json_values
             .insert(field.name().to_owned(), value.into());
@@ -144,12 +173,19 @@ impl Visit for FieldVisitor {
 /// Creates a [`Breadcrumb`] from a given [`tracing_core::Event`]
 pub fn breadcrumb_from_event<'context, S>(
     event: &tracing_core::Event,
-    ctx: impl Into<Option<Context<'context, S>>>,
+    ctx: Context<'context, S>,
+    mut propagation: Option<SpanPropagation>,
 ) -> Breadcrumb
 where
     S: Subscriber + for<'a> LookupSpan<'a>,
 {
-    let (message, visitor) = extract_event_data_with_context(event, ctx.into());
+    if let Some(propagation) = propagation.as_mut() {
+        if propagation.is_attrs_enabled() {
+            //Breadcrumb has no tags, so propagate only attributes
+            *propagation = SpanPropagation::Attributes;
+        }
+    }
+    let (message, visitor) = extract_event_data_with_context(event, ctx, propagation);
 
     let FieldVisitor {
         exceptions,
@@ -232,10 +268,11 @@ fn contexts_from_event(
     context
 }
 
-/// Creates an [`Event`] (possibly carrying an exception) from a given [`tracing_core::Event`]
+/// Creates an [`Event`] from a given [`tracing_core::Event`]
 pub fn event_from_event<'context, S>(
     event: &tracing_core::Event,
-    ctx: impl Into<Option<Context<'context, S>>>,
+    ctx: Context<'context, S>,
+    propagation: Option<SpanPropagation>,
 ) -> Event<'static>
 where
     S: Subscriber + for<'a> LookupSpan<'a>,
@@ -245,7 +282,7 @@ where
     // information for this. However, it may contain a serialized error which we can parse to emit
     // an exception record.
     #[allow(unused_mut)]
-    let (mut message, visitor) = extract_event_data_with_context(event, ctx.into());
+    let (mut message, visitor) = extract_event_data_with_context(event, ctx, propagation);
     let FieldVisitor {
         mut exceptions,
         mut json_values,
diff --git a/sentry-tracing/src/layer.rs b/sentry-tracing/src/layer.rs
@@ -11,7 +11,7 @@ use tracing_subscriber::layer::{Context, Layer};
 use tracing_subscriber::registry::LookupSpan;
 
 use crate::converters::*;
-use crate::TAGS_PREFIX;
+use crate::{SpanPropagation, TAGS_PREFIX};
 
 /// The action that Sentry should perform for a [`Metadata`]
 #[derive(Debug, Clone, Copy)]
@@ -68,7 +68,7 @@ pub struct SentryLayer<S> {
 
     span_filter: Box<dyn Fn(&Metadata) -> bool + Send + Sync>,
 
-    with_span_attributes: bool,
+    span_propagation: Option<SpanPropagation>,
 }
 
 impl<S> SentryLayer<S> {
@@ -121,8 +121,14 @@ impl<S> SentryLayer<S> {
     /// the [traces_sample_rate][sentry_core::ClientOptions::traces_sample_rate] to `1.0`
     /// while configuring your sentry client.
     #[must_use]
-    pub fn enable_span_attributes(mut self) -> Self {
-        self.with_span_attributes = true;
+    pub fn enable_span_attributes(self) -> Self {
+        self.enable_span_propagation(SpanPropagation::Attributes)
+    }
+
+    #[must_use]
+    /// Configures span propagation for events' creation
+    pub fn enable_span_propagation(mut self, propagation: SpanPropagation) -> Self {
+        self.span_propagation = Some(propagation);
         self
     }
 }
@@ -138,7 +144,7 @@ where
 
             span_filter: Box::new(default_span_filter),
 
-            with_span_attributes: false,
+            span_propagation: None,
         }
     }
 }
@@ -207,16 +213,17 @@ where
     fn on_event(&self, event: &Event, ctx: Context<'_, S>) {
         let item = match &self.event_mapper {
             Some(mapper) => mapper(event, ctx),
-            None => {
-                let span_ctx = self.with_span_attributes.then_some(ctx);
-                match (self.event_filter)(event.metadata()) {
-                    EventFilter::Ignore => EventMapping::Ignore,
-                    EventFilter::Breadcrumb => {
-                        EventMapping::Breadcrumb(breadcrumb_from_event(event, span_ctx))
-                    }
-                    EventFilter::Event => EventMapping::Event(event_from_event(event, span_ctx)),
+            None => match (self.event_filter)(event.metadata()) {
+                EventFilter::Ignore => EventMapping::Ignore,
+                EventFilter::Breadcrumb => EventMapping::Breadcrumb(breadcrumb_from_event(
+                    event,
+                    ctx,
+                    self.span_propagation,
+                )),
+                EventFilter::Event => {
+                    EventMapping::Event(event_from_event(event, ctx, self.span_propagation))
                 }
-            }
+            },
         };
 
         match item {
diff --git a/sentry-tracing/src/lib.rs b/sentry-tracing/src/lib.rs
@@ -147,3 +147,32 @@ pub use converters::*;
 pub use layer::*;
 
 const TAGS_PREFIX: &str = "tags.";
+
+#[derive(Debug, Clone, Copy)]
+/// Controls propagation of span data when creating event
+///
+/// Note that the root span is considered a [transaction][sentry_core::protocol::Transaction]
+/// so its context will only be grabbed only if you set the transaction to be sampled.
+/// The most straightforward way to do this is to set
+/// the [traces_sample_rate][sentry_core::ClientOptions::traces_sample_rate] to `1.0`
+/// while configuring your sentry client.
+pub enum SpanPropagation {
+    /// Collects all attributes prefixed with span name
+    Attributes,
+    /// Accumulates tags from within attributes as event tags, without overriding existing tags
+    Tags,
+    /// Collects both tags and attributes
+    All,
+}
+
+impl SpanPropagation {
+    #[inline(always)]
+    pub(crate) const fn is_tags_enabled(&self) -> bool {
+        matches!(self, Self::Tags | Self::All)
+    }
+
+    #[inline(always)]
+    pub(crate) const fn is_attrs_enabled(&self) -> bool {
+        matches!(self, Self::Attributes | Self::All)
+    }
+}
diff --git a/sentry-tracing/tests/shared.rs b/sentry-tracing/tests/shared.rs
@@ -1,5 +1,6 @@
 use sentry::{ClientOptions, Hub};
 use sentry_core::test::TestTransport;
+use sentry_tracing::SpanPropagation;
 
 use std::sync::Arc;
 
@@ -17,7 +18,7 @@ pub fn init_sentry(traces_sample_rate: f32) -> Arc<TestTransport> {
     Hub::current().bind_client(Some(Arc::new(options.into())));
 
     let _ = tracing_subscriber::registry()
-        .with(sentry_tracing::layer().enable_span_attributes())
+        .with(sentry_tracing::layer().enable_span_propagation(SpanPropagation::All))
         .try_init();
 
     transport
diff --git a/sentry-tracing/tests/smoke.rs b/sentry-tracing/tests/smoke.rs
@@ -19,6 +19,13 @@ fn should_instrument_function_with_event() {
         unexpected => panic!("Expected event, but got {:#?}", unexpected),
     };
 
+    //Event must be get tag attached
+    let event_tag = event
+        .tags
+        .get("tag")
+        .expect("event should be associated with span's tag");
+    assert_eq!(event_tag, "key");
+
     //Validate transaction is created
     let trace = match event.contexts.get("trace").expect("to get 'trace' context") {
         sentry::protocol::Context::Trace(trace) => trace,
