Use constant for baggage validation bitsets (#3274)

* Use constant for baggage validation bitsets

* Spot

* Move to element

* private

api/all/src/jmh/java/io/opentelemetry/api/baggage/propagation/W3CBaggagePropagatorBenchmark.java

@@ -8,8 +8,11 @@ package io.opentelemetry.api.baggage.propagation;
 import io.opentelemetry.context.Context;
 import io.opentelemetry.context.propagation.TextMapGetter;
 import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
 import javax.annotation.Nullable;
 import org.openjdk.jmh.annotations.Benchmark;
 import org.openjdk.jmh.annotations.BenchmarkMode;
@@ -25,12 +28,14 @@ import org.openjdk.jmh.annotations.Warmup;
 @State(Scope.Thread)
 public class W3CBaggagePropagatorBenchmark {
 
-  // pre-allocate the keys & values to remove one possible confounding factor
+  private static final Map<String, String> SMALL_BAGGAGE;
-  private static String header;
+  private static final Map<String, String> LARGE_BAGGAGE;
 
   static {
-    for (int i = 0; i < 100; i++) {
+    List<String> baggages =
-      header +=
+        IntStream.range(0, 100)
+            .mapToObj(
+                i ->
                     "key"
                         + i
                         + " = value"
@@ -41,8 +46,10 @@ public class W3CBaggagePropagatorBenchmark {
                         + i
                         + ",broken)key"
                         + i
-              + "=value,";
+                        + "=value")
-    }
+            .collect(Collectors.toList());
+    SMALL_BAGGAGE = Collections.singletonMap("baggage", String.join(",", baggages.subList(0, 5)));
+    LARGE_BAGGAGE = Collections.singletonMap("baggage", String.join(",", baggages));
   }
 
   private static final TextMapGetter<Map<String, String>> getter =
@@ -61,13 +68,23 @@ public class W3CBaggagePropagatorBenchmark {
 
   @Benchmark
   @BenchmarkMode({Mode.AverageTime})
-  @Fork(1)
+  @Fork(3)
   @Measurement(iterations = 15, time = 1)
-  @OutputTimeUnit(TimeUnit.NANOSECONDS)
+  @OutputTimeUnit(TimeUnit.MICROSECONDS)
   @Warmup(iterations = 5, time = 1)
-  public Context defaultPropagatorExtractBenchmark() {
+  public Context smallBaggage() {
     W3CBaggagePropagator propagator = W3CBaggagePropagator.getInstance();
+    return propagator.extract(Context.root(), SMALL_BAGGAGE, getter);
+  }
 
-    return propagator.extract(Context.root(), Collections.singletonMap("baggage", header), getter);
+  @Benchmark
+  @BenchmarkMode({Mode.AverageTime})
+  @Fork(3)
+  @Measurement(iterations = 15, time = 1)
+  @OutputTimeUnit(TimeUnit.MICROSECONDS)
+  @Warmup(iterations = 5, time = 1)
+  public Context largeBaggage() {
+    W3CBaggagePropagator propagator = W3CBaggagePropagator.getInstance();
+    return propagator.extract(Context.root(), LARGE_BAGGAGE, getter);
   }
 }

api/all/src/main/java/io/opentelemetry/api/baggage/propagation/Element.java

@@ -14,7 +14,22 @@ import java.util.BitSet;
  */
 class Element {
 
-  private final BitSet excluded = new BitSet(128);
+  private static final BitSet EXCLUDED_KEY_CHARS = new BitSet(128);
+  private static final BitSet EXCLUDED_VALUE_CHARS = new BitSet(128);
+
+  static {
+    for (char c :
+        new char[] {
+          '(', ')', '<', '>', '@', ',', ';', ':', '\\', '"', '/', '[', ']', '?', '=', '{', '}'
+        }) {
+      EXCLUDED_KEY_CHARS.set(c);
+    }
+    for (char c : new char[] {'"', ',', ';', '\\'}) {
+      EXCLUDED_VALUE_CHARS.set(c);
+    }
+  }
+
+  private final BitSet excluded;
 
   private boolean leadingSpace;
   private boolean readingValue;
@@ -23,15 +38,21 @@ class Element {
   private int end;
   private String value;
 
+  static Element createKeyElement() {
+    return new Element(EXCLUDED_KEY_CHARS);
+  }
+
+  static Element createValueElement() {
+    return new Element(EXCLUDED_VALUE_CHARS);
+  }
+
   /**
    * Constructs element instance.
    *
-   * @param excludedChars characters that are not allowed for this type of an element
+   * @param excluded characters that are not allowed for this type of an element
    */
-  Element(char[] excludedChars) {
+  private Element(BitSet excluded) {
-    for (char excludedChar : excludedChars) {
+    this.excluded = excluded;
-      excluded.set(excludedChar);
-    }
     reset(0);
   }
 

api/all/src/main/java/io/opentelemetry/api/baggage/propagation/Parser.java

@@ -26,12 +26,8 @@ class Parser {
 
   private final String baggageHeader;
 
-  private final Element key =
+  private final Element key = Element.createKeyElement();
-      new Element(
+  private final Element value = Element.createValueElement();
-          new char[] {
-            '(', ')', '<', '>', '@', ',', ';', ':', '\\', '"', '/', '[', ']', '?', '=', '{', '}'
-          });
-  private final Element value = new Element(new char[] {'"', ',', ';', '\\'});
   private String meta;
 
   private State state;