chore(otlp source): initialize map size and reduce intermediate clone (#1202)

Author: andrewqian2001datadog

lib/saluki-components/src/common/otlp/traces/transform.rs

@@ -98,7 +98,7 @@ const DD_NAMESPACED_TO_APM_CONVENTIONS: &[(&str, &str)] = &[
 pub fn otel_span_to_dd_span(
     otel_span: &OtlpSpan, otel_resource: &Resource, instrumentation_scope: Option<&OtlpInstrumentationScope>,
     ignore_missing_fields: bool, compute_top_level_by_span_kind: bool, interner: &GenericMapInterner,
-    string_builder: &mut StringBuilder<GenericMapInterner>, trace_id_hex: Option<MetaString>,
+    string_builder: &mut StringBuilder<GenericMapInterner>, trace_id_hex: Option<&MetaString>,
 ) -> DdSpan {
     let span_attributes = &otel_span.attributes;
     let resource_attributes = &otel_resource.attributes;
@@ -131,7 +131,7 @@ pub fn otel_span_to_dd_span(
 
     if let Some(trace_id_hex) = trace_id_hex {
         if !trace_id_hex.is_empty() {
-            meta.insert(MetaString::from_static(OTEL_TRACE_ID_META_KEY), trace_id_hex);
+            meta.insert(MetaString::from_static(OTEL_TRACE_ID_META_KEY), trace_id_hex.clone());
         }
     } else if !otel_span.trace_id.is_empty() {
         meta.insert(

lib/saluki-components/src/common/otlp/traces/translator.rs

@@ -83,6 +83,8 @@ impl OtlpTracesTranslator {
         let string_builder = &mut self.string_builder;
         let resource_tags = resource_attributes_to_tagset(&resource.attributes, string_builder).into_shared();
         let mut traces_by_id: FastHashMap<u64, TraceEntry> = FastHashMap::default();
+        let trace_count_hint = resource_spans.scope_spans.len();
+        traces_by_id.reserve(trace_count_hint);
 
         for scope_spans in resource_spans.scope_spans {
             let scope = scope_spans.scope;
@@ -100,7 +102,6 @@ impl OtlpTracesTranslator {
                     entry.trace_id_hex = trace_id_hex_meta(&span.trace_id);
                 }
 
-                let trace_id_hex = entry.trace_id_hex.clone();
                 let dd_span = otel_span_to_dd_span(
                     &span,
                     &resource,
@@ -109,7 +110,7 @@ impl OtlpTracesTranslator {
                     compute_top_level,
                     interner,
                     string_builder,
-                    trace_id_hex,
+                    entry.trace_id_hex.as_ref(),
                 );
 
                 // Track last-seen priority for this trace (overwrites previous values)