feat(datadog): add sampling priority tag in datadog spans

.github/workflows/ci.yml

@@ -68,7 +68,7 @@ jobs:
     - uses: actions-rs/toolchain@v1
       with:
         profile: minimal
-        toolchain: 1.55.0
+        toolchain: 1.59.0
         override: true
     - name: Run tests
       run: cargo --version &&

opentelemetry-datadog/src/exporter/model/mod.rs

@@ -10,6 +10,9 @@ use url::ParseError;
 mod v03;
 mod v05;
 
+// https://github.com/DataDog/dd-trace-js/blob/c89a35f7d27beb4a60165409376e170eacb194c5/packages/dd-trace/src/constants.js#L4
+static SAMPLING_PRIORITY_KEY: &str = "_sampling_priority_v1";
+
 /// Custom mapping between opentelemetry spans and datadog spans.
 ///
 /// User can provide custom function to change the mapping. It currently supports customizing the following
@@ -242,7 +245,7 @@ pub(crate) mod tests {
             None,
         )?);
 
-        assert_eq!(encoded.as_str(), "kZGLpHR5cGWjd2Vip3NlcnZpY2Wsc2VydmljZV9uYW1lpG5hbWWpY29tcG9uZW50qHJlc291cmNlqHJlc291cmNlqHRyYWNlX2lkzwAAAAAAAAAHp3NwYW5faWTPAAAAAAAAAGOpcGFyZW50X2lkzwAAAAAAAAABpXN0YXJ00wAAAAAAAAAAqGR1cmF0aW9u0wAAAAA7msoApWVycm9y0gAAAACkbWV0YYGpc3Bhbi50eXBlo3dlYg==");
+        assert_eq!(encoded.as_str(), "kZGLpHR5cGWjd2Vip3NlcnZpY2Wsc2VydmljZV9uYW1lpG5hbWWpY29tcG9uZW50qHJlc291cmNlqHJlc291cmNlqHRyYWNlX2lkzwAAAAAAAAAHp3NwYW5faWTPAAAAAAAAAGOpcGFyZW50X2lkzwAAAAAAAAABpXN0YXJ00wAAAAAAAAAAqGR1cmF0aW9u0wAAAAA7msoApWVycm9y0gAAAACkbWV0YYGpc3Bhbi50eXBlo3dlYqdtZXRyaWNzgbVfc2FtcGxpbmdfcHJpb3JpdHlfdjHLAAAAAAAAAAA=");
 
         Ok(())
     }
@@ -263,7 +266,7 @@ pub(crate) mod tests {
         )?);
 
         assert_eq!(encoded.as_str(),
-                   "kpWjd2VirHNlcnZpY2VfbmFtZaljb21wb25lbnSocmVzb3VyY2Wpc3Bhbi50eXBlkZGczgAAAAHOAAAAAs4AAAADzwAAAAAAAAAHzwAAAAAAAABjzwAAAAAAAAAB0wAAAAAAAAAA0wAAAAA7msoA0gAAAACBzgAAAATOAAAAAIDOAAAAAA==");
+                   "kpajd2VirHNlcnZpY2VfbmFtZaljb21wb25lbnSocmVzb3VyY2Wpc3Bhbi50eXBltV9zYW1wbGluZ19wcmlvcml0eV92MZGRnM4AAAABzgAAAALOAAAAA88AAAAAAAAAB88AAAAAAAAAY88AAAAAAAAAAdMAAAAAAAAAANMAAAAAO5rKANIAAAAAgc4AAAAEzgAAAACBzgAAAAXLAAAAAAAAAADOAAAAAA==");
 
         Ok(())
     }

opentelemetry-datadog/src/exporter/model/v03.rs

@@ -1,4 +1,4 @@
-use crate::exporter::model::Error;
+use crate::exporter::model::{Error, SAMPLING_PRIORITY_KEY};
 use crate::exporter::ModelConfig;
 use opentelemetry::sdk::export::trace;
 use opentelemetry::sdk::export::trace::SpanData;
@@ -95,6 +95,18 @@ where
                 rmp::encode::write_str(&mut encoded, key.as_str())?;
                 rmp::encode::write_str(&mut encoded, value.as_str().as_ref())?;
             }
+
+            rmp::encode::write_str(&mut encoded, "metrics")?;
+            rmp::encode::write_map_len(&mut encoded, 1)?;
+            rmp::encode::write_str(&mut encoded, SAMPLING_PRIORITY_KEY)?;
+            rmp::encode::write_f64(
+                &mut encoded,
+                if span.span_context.is_sampled() {
+                    1.0
+                } else {
+                    0.0
+                },
+            )?;
         }
     }
 

opentelemetry-datadog/src/exporter/model/v05.rs

@@ -1,4 +1,5 @@
 use crate::exporter::intern::StringInterner;
+use crate::exporter::model::SAMPLING_PRIORITY_KEY;
 use crate::exporter::{Error, ModelConfig};
 use opentelemetry::sdk::export::trace;
 use opentelemetry::sdk::export::trace::SpanData;
@@ -161,7 +162,16 @@ where
                 rmp::encode::write_u32(&mut encoded, interner.intern(key.as_str()))?;
                 rmp::encode::write_u32(&mut encoded, interner.intern(value.as_str().as_ref()))?;
             }
-            rmp::encode::write_map_len(&mut encoded, 0)?;
+            rmp::encode::write_map_len(&mut encoded, 1)?;
+            rmp::encode::write_u32(&mut encoded, interner.intern(SAMPLING_PRIORITY_KEY))?;
+            rmp::encode::write_f64(
+                &mut encoded,
+                if span.span_context.is_sampled() {
+                    1.0
+                } else {
+                    0.0
+                },
+            )?;
             rmp::encode::write_u32(&mut encoded, span_type)?;
         }
     }