Predefine Vector Capacity for LogRecord Attributes

opentelemetry-appender-tracing/benches/logs.rs

@@ -10,7 +10,7 @@
     | noop_layer_disabled         | 12 ns       |
     | noop_layer_enabled          | 25 ns       |
     | ot_layer_disabled           | 19 ns       |
-    | ot_layer_enabled            | 371 ns      |
+    | ot_layer_enabled            | 270 ns      |
 */
 
 use async_trait::async_trait;

opentelemetry-sdk/src/logs/record.rs

@@ -5,7 +5,9 @@ use opentelemetry::{
 };
 use std::{borrow::Cow, time::SystemTime};
 
-#[derive(Debug, Default, Clone)]
+const PREALLOCATED_ATTRIBUTE_CAPACITY: usize = 8;
+
+#[derive(Debug, Clone)]
 #[non_exhaustive]
 /// LogRecord represents all data carried by a log record, and
 /// is provided to `LogExporter`s as input.
@@ -37,6 +39,22 @@ pub struct LogRecord {
     pub attributes: Option<Vec<(Key, AnyValue)>>,
 }
 
+impl Default for LogRecord {
+    fn default() -> Self {
+        LogRecord {
+            event_name: None,
+            target: None,
+            timestamp: None,
+            observed_timestamp: None,
+            trace_context: None,
+            severity_text: None,
+            severity_number: None,
+            body: None,
+            attributes: Some(Vec::with_capacity(PREALLOCATED_ATTRIBUTE_CAPACITY)), // Pre-allocate for perf optimization. This may change in future.
+        }
+    }
+}
+
 impl opentelemetry::logs::LogRecord for LogRecord {
     fn set_event_name<T>(&mut self, name: T)
     where