Fix misuses of CopyOnWriteArrayList

CHANGELOG.md

@@ -5,6 +5,8 @@
 ### Fixes
 
 - Add support for setting in-app-includes/in-app-excludes via AndroidManifest.xml ([#4240](https://github.com/getsentry/sentry-java/pull/4240))
+- Avoid unnecessary copies and ensure thread-safety when using `CopyOnWriteArrayList` ([#4247](https://github.com/getsentry/sentry-java/pull/4247))
+  - This affects in particular `SentryTracer.getLatestActiveSpan` which would have previously unnecessarily copied all children spans, with high impact on memory usage
 
 ### Features
 

sentry/src/main/java/io/sentry/Scope.java

@@ -759,7 +759,7 @@ public void removeContexts(final @NotNull String key) {
   @NotNull
   @Override
   public List<Attachment> getAttachments() {
-    return new CopyOnWriteArrayList<>(attachments);
+    return attachments;
   }
 
   /**

sentry/src/main/java/io/sentry/SentryTracer.java

@@ -7,7 +7,6 @@
 import io.sentry.util.AutoClosableReentrantLock;
 import io.sentry.util.Objects;
 import io.sentry.util.SpanUtils;
-import java.util.ArrayList;
 import java.util.List;
 import java.util.ListIterator;
 import java.util.Map;
@@ -155,7 +154,10 @@ private void onDeadlineTimeoutReached() {
     // abort all child-spans first, this ensures the transaction can be finished,
     // even if waitForChildren is true
     // iterate in reverse order to ensure leaf spans are processed before their parents
-    @NotNull final ListIterator<Span> iterator = children.listIterator(children.size());
+    @NotNull final ListIterator<Span> iterator = this.children.listIterator();
+    while (iterator.hasNext()) {
+      iterator.next();
+    }
     while (iterator.hasPrevious()) {
       @NotNull final Span span = iterator.previous();
       span.setSpanFinishedCallback(null);
@@ -677,14 +679,13 @@ private void updateBaggageValues(final @NotNull Baggage baggage) {
   }
 
   private boolean hasAllChildrenFinished() {
-    final List<Span> spans = new ArrayList<>(this.children);
-    if (!spans.isEmpty()) {
-      for (final Span span : spans) {
-        // This is used in the spanFinishCallback, when the span isn't finished, but has a finish
-        // date
-        if (!span.isFinished() && span.getFinishDate() == null) {
-          return false;
-        }
+    @NotNull final ListIterator<Span> iterator = this.children.listIterator();
+    while (iterator.hasNext()) {
+      @NotNull final Span span = iterator.next();
+      // This is used in the spanFinishCallback, when the span isn't finished, but has a finish
+      // date
+      if (!span.isFinished() && span.getFinishDate() == null) {
+        return false;
       }
     }
     return true;
@@ -909,12 +910,14 @@ public void setName(@NotNull String name, @NotNull TransactionNameSource transac
 
   @Override
   public @Nullable ISpan getLatestActiveSpan() {
-    final List<Span> spans = new ArrayList<>(this.children);
-    if (!spans.isEmpty()) {
-      for (int i = spans.size() - 1; i >= 0; i--) {
-        if (!spans.get(i).isFinished()) {
-          return spans.get(i);
-        }
+    @NotNull final ListIterator<Span> iterator = this.children.listIterator();
+    while (iterator.hasNext()) {
+      iterator.next();
+    }
+    while (iterator.hasPrevious()) {
+      @NotNull final Span span = iterator.previous();
+      if (!span.isFinished()) {
+        return span;
       }
     }
     return null;