From c5b52e270bac95f74f970283ecc875070b49c71c Mon Sep 17 00:00:00 2001
From: Samuron <samuronchik@gmail.com>
Date: Sun, 17 Mar 2024 08:14:33 +0200
Subject: [PATCH 1/3] perf(eport): do not allocate arrays if resource has no
 pending async attributes

---
 .../src/export/BatchSpanProcessorBase.ts      | 23 +++++++++++--------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/packages/opentelemetry-sdk-trace-base/src/export/BatchSpanProcessorBase.ts b/packages/opentelemetry-sdk-trace-base/src/export/BatchSpanProcessorBase.ts
index f069aac0c7..776b7bea21 100644
--- a/packages/opentelemetry-sdk-trace-base/src/export/BatchSpanProcessorBase.ts
+++ b/packages/opentelemetry-sdk-trace-base/src/export/BatchSpanProcessorBase.ts
@@ -195,19 +195,24 @@ export abstract class BatchSpanProcessorBase<T extends BufferConfig>
               );
             }
           });
-        const pendingResources = spans
-          .map(span => span.resource)
-          .filter(resource => resource.asyncAttributesPending);
+
+        let pendingResources: Array<Promise<void>> | null = null;
+        for (let i = 0, len = spans.length; i < len; i++) {
+          const span = spans[i];
+          if (
+            span.resource.asyncAttributesPending &&
+            span.resource.waitForAsyncAttributes
+          ) {
+            pendingResources ??= [];
+            pendingResources.push(span.resource.waitForAsyncAttributes());
+          }
+        }
 
         // Avoid scheduling a promise to make the behavior more predictable and easier to test
-        if (pendingResources.length === 0) {
+        if (pendingResources === null) {
           doExport();
         } else {
-          Promise.all(
-            pendingResources.map(
-              resource => resource.waitForAsyncAttributes?.()
-            )
-          ).then(doExport, err => {
+          Promise.all(pendingResources).then(doExport, err => {
             globalErrorHandler(err);
             reject(err);
           });

From a4f45c723f5ed7b18e1c7e21c52e08a7e0b9701e Mon Sep 17 00:00:00 2001
From: Samuron <samuronchik@gmail.com>
Date: Sun, 17 Mar 2024 13:58:59 +0200
Subject: [PATCH 2/3] perf(export): do not use splice if fit in one batch

---
 CHANGELOG.md                                              | 2 ++
 .../src/export/BatchSpanProcessorBase.ts                  | 8 +++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f2980539eb..9f9162e86a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,8 @@ For experimental package changes, see the [experimental CHANGELOG](experimental/
 
 ### :rocket: (Enhancement)
 
+perf(sdk-trace-base): do not allocate arrays if resource has no pending async attributes
+
 ### :bug: (Bug Fix)
 
 * fix(sdk-metrics): increase the depth of the output to the console such that objects in the metric are printed fully to the console [#4522](https://github.com/open-telemetry/opentelemetry-js/pull/4522) @JacksonWeber
diff --git a/packages/opentelemetry-sdk-trace-base/src/export/BatchSpanProcessorBase.ts b/packages/opentelemetry-sdk-trace-base/src/export/BatchSpanProcessorBase.ts
index 776b7bea21..19e616dc08 100644
--- a/packages/opentelemetry-sdk-trace-base/src/export/BatchSpanProcessorBase.ts
+++ b/packages/opentelemetry-sdk-trace-base/src/export/BatchSpanProcessorBase.ts
@@ -181,7 +181,13 @@ export abstract class BatchSpanProcessorBase<T extends BufferConfig>
         // Reset the finished spans buffer here because the next invocations of the _flush method
         // could pass the same finished spans to the exporter if the buffer is cleared
         // outside the execution of this callback.
-        const spans = this._finishedSpans.splice(0, this._maxExportBatchSize);
+        let spans: ReadableSpan[];
+        if (this._finishedSpans.length <= this._maxExportBatchSize) {
+          spans = this._finishedSpans;
+          this._finishedSpans = [];
+        } else {
+          spans = this._finishedSpans.splice(0, this._maxExportBatchSize);
+        }
 
         const doExport = () =>
           this._exporter.export(spans, result => {

From fee30fde6bc473a2efd6ff79ca77179159224c72 Mon Sep 17 00:00:00 2001
From: Ievgen Makukh <Samuron@users.noreply.github.com>
Date: Fri, 22 Mar 2024 17:48:13 +0200
Subject: [PATCH 3/3] Update CHANGELOG.md

Co-authored-by: Marc Pichler <marc.pichler@dynatrace.com>
---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9f9162e86a..3c68dec71a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,7 +11,7 @@ For experimental package changes, see the [experimental CHANGELOG](experimental/
 
 ### :rocket: (Enhancement)
 
-perf(sdk-trace-base): do not allocate arrays if resource has no pending async attributes
+* perf(sdk-trace-base): do not allocate arrays if resource has no pending async attributes
 
 ### :bug: (Bug Fix)