more perf

Author: jack-berg

sdk/common/src/main/java/io/opentelemetry/sdk/internal/StackTraceRenderer.java

@@ -40,13 +40,15 @@ String render() {
   }
 
   private void appendStackTrace() {
-    if (appendLine(throwable.toString())) {
+    builder.append(throwable).append(System.lineSeparator());
+    if (isOverLimit()) {
       return;
     }
 
     StackTraceElement[] stackTraceElements = throwable.getStackTrace();
     for (StackTraceElement stackTraceElement : stackTraceElements) {
-      if (appendLine("\tat " + stackTraceElement)) {
+      builder.append("\tat ").append(stackTraceElement).append(System.lineSeparator());
+      if (isOverLimit()) {
         return;
       }
     }
@@ -75,7 +77,13 @@ private boolean appendInnerStacktrace(
       String caption,
       Set<Throwable> seen) {
     if (seen.contains(innerThrowable)) {
-      appendLine(prefix + caption + "[CIRCULAR REFERENCE: " + innerThrowable + "]");
+      builder
+          .append(prefix)
+          .append(caption)
+          .append("[CIRCULAR REFERENCE: ")
+          .append(innerThrowable)
+          .append("]")
+          .append(System.lineSeparator());
       return true;
     }
     seen.add(innerThrowable);
@@ -96,20 +104,32 @@ private boolean appendInnerStacktrace(
       lastSharedFrameIndex--;
     }
 
-    if (appendLine(prefix + caption + innerThrowable)) {
+    builder.append(prefix).append(caption).append(innerThrowable).append(System.lineSeparator());
+    if (isOverLimit()) {
       return true;
     }
 
     for (int i = 0; i <= lastSharedFrameIndex; i++) {
       StackTraceElement stackTraceElement = currentElements[i];
-      if (appendLine(prefix + "\tat " + stackTraceElement)) {
+      builder
+          .append(prefix)
+          .append("\tat ")
+          .append(stackTraceElement)
+          .append(System.lineSeparator());
+      if (isOverLimit()) {
         return true;
       }
     }
 
     int duplicateFrames = currentElements.length - 1 - lastSharedFrameIndex;
     if (duplicateFrames != 0) {
-      if (appendLine(prefix + "\t... " + duplicateFrames + " more")) {
+      builder
+          .append(prefix)
+          .append("\t... ")
+          .append(duplicateFrames)
+          .append(" more")
+          .append(System.lineSeparator());
+      if (isOverLimit()) {
         return true;
       }
     }
@@ -128,12 +148,7 @@ private boolean appendInnerStacktrace(
     return false;
   }
 
-  /**
-   * Append the string as a new line on {@link #builder}, returning {@code true} if the builder now
-   * exceeds the length limit.
-   */
-  private boolean appendLine(String s) {
-    builder.append(s).append(System.lineSeparator());
+  private boolean isOverLimit() {
     return builder.length() >= lengthLimit;
   }
 }

sdk/common/src/test/java/io/opentelemetry/sdk/internal/StackTraceRendererTest.java

@@ -9,16 +9,30 @@
 
 import java.io.PrintWriter;
 import java.io.StringWriter;
+import java.util.Random;
 import java.util.stream.Stream;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
 
 class StackTraceRendererTest {
 
+  private static final Random random = new Random();
+
+  @ParameterizedTest
+  @MethodSource("renderStacktraceArgs")
+  void renderStacktrace_randomLength(Throwable throwable) {
+    // Test equal stacktrace for random lengths to test edges
+    for (int i = 0; i < 100; i++) {
+      int length = random.nextInt(10_000);
+      assertThat(new StackTraceRenderer(throwable, length).render())
+          .isEqualTo(jdkStackTrace(throwable, length));
+    }
+  }
+
   @ParameterizedTest
   @MethodSource("renderStacktraceArgs")
-  void renderStacktrace(Throwable throwable) {
+  void renderStacktrace_fixedLengths(Throwable throwable) {
     assertThat(new StackTraceRenderer(throwable, 10).render())
         .isEqualTo(jdkStackTrace(throwable, 10));
     assertThat(new StackTraceRenderer(throwable, 100).render())