opentelemetry: slightly improve OpentemetrySubscriber's performance…

… by pre-determined the attribute length
tokio-rs · Apr 2, 2021 · c812e42 · c812e42
1 parent 0e8f920
commit c812e42
Showing 1 changed file with 14 additions and 24 deletions.
diff --git a/tracing-opentelemetry/src/subscriber.rs b/tracing-opentelemetry/src/subscriber.rs
@@ -171,29 +171,28 @@ impl<'a> field::Visit for SpanEventVisitor<'a> {
 
 struct SpanAttributeVisitor<'a>(&'a mut otel::SpanBuilder);
 
+impl<'a> SpanAttributeVisitor<'a> {
+    fn record(&mut self, attribute: KeyValue) {
+        debug_assert!(self.0.attributes.is_some());
+        if let Some(v) = self.0.attributes.as_mut() {
+            v.push(attribute);
+        }
+    }
+}
+
 impl<'a> field::Visit for SpanAttributeVisitor<'a> {
     /// Set attributes on the underlying OpenTelemetry [`Span`] from `bool` values.
     ///
     /// [`Span`]: opentelemetry::trace::Span
     fn record_bool(&mut self, field: &field::Field, value: bool) {
-        let attribute = KeyValue::new(field.name(), value);
-        if let Some(attributes) = &mut self.0.attributes {
-            attributes.push(attribute);
-        } else {
-            self.0.attributes = Some(vec![attribute]);
-        }
+        self.record(KeyValue::new(field.name(), value));
     }
 
     /// Set attributes on the underlying OpenTelemetry [`Span`] from `i64` values.
     ///
     /// [`Span`]: opentelemetry::trace::Span
     fn record_i64(&mut self, field: &field::Field, value: i64) {
-        let attribute = KeyValue::new(field.name(), value);
-        if let Some(attributes) = &mut self.0.attributes {
-            attributes.push(attribute);
-        } else {
-            self.0.attributes = Some(vec![attribute]);
-        }
+        self.record(KeyValue::new(field.name(), value));
     }
 
     /// Set attributes on the underlying OpenTelemetry [`Span`] from `&str` values.
@@ -205,12 +204,7 @@ impl<'a> field::Visit for SpanAttributeVisitor<'a> {
         } else if field.name() == SPAN_KIND_FIELD {
             self.0.span_kind = str_to_span_kind(value);
         } else {
-            let attribute = KeyValue::new(field.name(), value.to_string());
-            if let Some(attributes) = &mut self.0.attributes {
-                attributes.push(attribute);
-            } else {
-                self.0.attributes = Some(vec![attribute]);
-            }
+            self.record(KeyValue::new(field.name(), value.to_string()));
         }
     }
 
@@ -224,12 +218,7 @@ impl<'a> field::Visit for SpanAttributeVisitor<'a> {
         } else if field.name() == SPAN_KIND_FIELD {
             self.0.span_kind = str_to_span_kind(&format!("{:?}", value));
         } else {
-            let attribute = Key::new(field.name()).string(format!("{:?}", value));
-            if let Some(attributes) = &mut self.0.attributes {
-                attributes.push(attribute);
-            } else {
-                self.0.attributes = Some(vec![attribute]);
-            }
+            self.record(Key::new(field.name()).string(format!("{:?}", value)));
         }
     }
 }
@@ -418,6 +407,7 @@ where
             builder.trace_id = Some(self.tracer.new_trace_id());
         }
 
+        builder.attributes = Some(Vec::with_capacity(attrs.metadata().fields().len()));
         attrs.record(&mut SpanAttributeVisitor(&mut builder));
         extensions.insert(builder);
     }