feat(server): Serialize the DSC into event payloads

CHANGELOG.md

@@ -22,6 +22,7 @@
 - Copy root span data from `contexts.trace.data` when converting transaction events into raw spans. ([#3790](https://github.com/getsentry/relay/pull/3790))
 - Remove experimental double-write from spans to transactions. ([#3801](https://github.com/getsentry/relay/pull/3801))
 - Add feature flag to disable replay-video events. ([#3803](https://github.com/getsentry/relay/pull/3803))
+- Write the envelope's Dynamic Sampling Context (DSC) into event payloads for debugging. ([#3811](https://github.com/getsentry/relay/pull/3811))
 
 ## 24.6.0
 

relay-event-schema/src/protocol/event.rs

@@ -511,6 +511,10 @@ pub struct Event {
     #[metastructure(omit_from_schema)]
     pub _metrics_summary: Annotated<MetricsSummary>,
 
+    /// Value of the `DynamicSamplingContext` for this event.
+    #[metastructure(omit_from_schema)]
+    pub _dsc: Annotated<Value>,
+
     /// Additional arbitrary fields for forwards compatibility.
     #[metastructure(additional_properties, pii = "true")]
     pub other: Object<Value>,

relay-pii/src/snapshots/relay_pii__processor__tests__does_not_scrub_if_no_graphql.snap

@@ -109,5 +109,6 @@ Event {
     scraping_attempts: ~,
     _metrics: ~,
     _metrics_summary: ~,
+    _dsc: ~,
     other: {},
 }

relay-pii/src/snapshots/relay_pii__processor__tests__scrub_graphql_response_data_with_variables.snap

@@ -109,5 +109,6 @@ Event {
     scraping_attempts: ~,
     _metrics: ~,
     _metrics_summary: ~,
+    _dsc: ~,
     other: {},
 }

relay-pii/src/snapshots/relay_pii__processor__tests__scrub_graphql_response_data_without_variables.snap

@@ -90,5 +90,6 @@ Event {
     scraping_attempts: ~,
     _metrics: ~,
     _metrics_summary: ~,
+    _dsc: ~,
     other: {},
 }

relay-pii/src/snapshots/relay_pii__processor__tests__scrub_original_value.snap

@@ -122,5 +122,6 @@ Event {
     scraping_attempts: ~,
     _metrics: ~,
     _metrics_summary: ~,
+    _dsc: ~,
     other: {},
 }

relay-server/src/services/processor/event.rs

@@ -243,6 +243,12 @@ pub fn finalize<G: EventProcessing>(
                 );
             }
         }
+
+        if let Some(dsc) = envelope.dsc() {
+            if let Ok(Some(value)) = relay_protocol::to_value(dsc) {
+                event._dsc = Annotated::new(value);
+            }
+        }
     }
 
     let mut processor =