Makes traceIdHigh convertable to AWS X-Ray

This customizes the trace ID generator to make the high bits convertable
to Amazon X-Ray trace ID format v1.

See openzipkin/zipkin#1754

brave/src/main/java/brave/Tracer.java

@@ -240,7 +240,7 @@ TraceContext nextContext(@Nullable TraceContext parent, SamplingFlags samplingFl
     return TraceContext.newBuilder()
         .sampled(sampled)
         .debug(samplingFlags.debug())
-        .traceIdHigh(traceId128Bit ? Platform.get().randomLong() : 0L).traceId(nextId)
+        .traceIdHigh(traceId128Bit ? Platform.get().nextTraceIdHigh() : 0L).traceId(nextId)
         .spanId(nextId).build();
   }
 

brave/src/main/java/brave/internal/Platform.java

@@ -2,6 +2,7 @@
 
 import brave.Clock;
 import brave.Tracer;
+import brave.Tracing;
 import com.google.auto.value.AutoValue;
 import java.net.InetAddress;
 import java.net.NetworkInterface;
@@ -112,6 +113,15 @@ static Platform findPlatform() {
    */
   public abstract long randomLong();
 
+  /**
+   * Returns the high 8-bytes for use in {@link Tracing.Builder#traceId128Bit 128-bit trace IDs}.
+   *
+   * <p>The upper 4-bytes are epoch seconds and the lower 4-bytes are random. This makes it
+   * convertible to <a href="http://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-request-tracing.html"></a>Amazon
+   * X-Ray trace ID format v1</a>.
+   */
+  public abstract long nextTraceIdHigh();
+
   /** gets a timestamp based on duration since the create tick. */
   @Override
   public long currentTimeMicroseconds() {
@@ -136,6 +146,15 @@ static Jre7 buildIfSupported(boolean zipkinV1Present) {
     @Override public long randomLong() {
       return java.util.concurrent.ThreadLocalRandom.current().nextLong();
     }
+
+    @IgnoreJRERequirement
+    @Override public long nextTraceIdHigh() {
+      return nextTraceIdHigh(java.util.concurrent.ThreadLocalRandom.current());
+    }
+  }
+
+  static long nextTraceIdHigh(Random prng) {
+    return ((System.currentTimeMillis() / 1000) << 32) + prng.nextInt();
   }
 
   @AutoValue
@@ -149,5 +168,9 @@ static Jre6 build(boolean zipkinV1Present) {
     @Override public long randomLong() {
       return prng().nextLong();
     }
+
+    @Override public long nextTraceIdHigh() {
+      return nextTraceIdHigh(prng());
+    }
   }
 }

brave/src/test/java/brave/internal/PlatformTest.java

@@ -5,8 +5,10 @@
 import java.net.InetAddress;
 import java.net.NetworkInterface;
 import java.net.SocketException;
+import java.time.Instant;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Random;
 import java.util.Set;
 import java.util.Vector;
 import java.util.concurrent.Callable;
@@ -47,13 +49,27 @@ public class PlatformTest {
       @Override public long randomLong() {
         return 1L;
       }
+
+      @Override public long nextTraceIdHigh() {
+        return 1L;
+      }
     };
 
     when(System.nanoTime()).thenReturn(1000L); // 1 microsecond
 
     assertThat(platform.currentTimeMicroseconds()).isEqualTo(1);
   }
 
+  // example from X-Amzn-Trace-Id: Root=1-5759e988-bd862e3fe1be46a994272793;Sampled=1
+  @Test public void randomLong_epochSecondsPlusRandom() {
+    mockStatic(System.class);
+    when(System.currentTimeMillis()).thenReturn(1465510280_000L); // Thursday, June 9, 2016 10:11:20 PM
+
+    long traceIdHigh = platform.nextTraceIdHigh();
+
+    assertThat(HexCodec.toLowerHex(traceIdHigh)).startsWith("5759e988");
+  }
+
   @Test public void zipkinV1Absent() throws ClassNotFoundException {
     mockStatic(Class.class);
     when(Class.forName(zipkin.Endpoint.class.getName()))

instrumentation/benchmarks/src/main/java/brave/internal/PlatformBenchmarks.java

@@ -0,0 +1,111 @@
+/**
+ * Copyright 2015-2016 The OpenZipkin Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package brave.internal;
+
+import java.util.concurrent.TimeUnit;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Group;
+import org.openjdk.jmh.annotations.GroupThreads;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.RunnerException;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+@Measurement(iterations = 5, time = 1)
+@Warmup(iterations = 10, time = 1)
+@Fork(3)
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.MICROSECONDS)
+@State(Scope.Group)
+public class PlatformBenchmarks {
+  Platform jre6 = Platform.Jre6.build(false);
+  Platform jre7 = Platform.Jre7.buildIfSupported(false);
+
+  @Benchmark @Group("no_contention") @GroupThreads(1)
+  public long no_contention_nextTraceIdHigh_jre6() {
+    return jre6.nextTraceIdHigh();
+  }
+
+  @Benchmark @Group("mild_contention") @GroupThreads(2)
+  public long mild_contention_nextTraceIdHigh_jre6() {
+    return jre6.nextTraceIdHigh();
+  }
+
+  @Benchmark @Group("high_contention") @GroupThreads(8)
+  public long high_contention_nextTraceIdHigh_jre6() {
+    return jre6.nextTraceIdHigh();
+  }
+
+  @Benchmark @Group("no_contention") @GroupThreads(1)
+  public long no_contention_randomLong_jre6() {
+    return jre6.randomLong();
+  }
+
+  @Benchmark @Group("mild_contention") @GroupThreads(2)
+  public long mild_contention_randomLong_jre6() {
+    return jre6.randomLong();
+  }
+
+  @Benchmark @Group("high_contention") @GroupThreads(8)
+  public long high_contention_randomLong_jre6() {
+    return jre6.randomLong();
+  }
+
+  @Benchmark @Group("no_contention") @GroupThreads(1)
+  public long no_contention_nextTraceIdHigh_jre7() {
+    return jre7.nextTraceIdHigh();
+  }
+
+  @Benchmark @Group("mild_contention") @GroupThreads(2)
+  public long mild_contention_nextTraceIdHigh_jre7() {
+    return jre7.nextTraceIdHigh();
+  }
+
+  @Benchmark @Group("high_contention") @GroupThreads(8)
+  public long high_contention_nextTraceIdHigh_jre7() {
+    return jre7.nextTraceIdHigh();
+  }
+
+  @Benchmark @Group("no_contention") @GroupThreads(1)
+  public long no_contention_randomLong_jre7() {
+    return jre7.randomLong();
+  }
+
+  @Benchmark @Group("mild_contention") @GroupThreads(2)
+  public long mild_contention_randomLong_jre7() {
+    return jre7.randomLong();
+  }
+
+  @Benchmark @Group("high_contention") @GroupThreads(8)
+  public long high_contention_randomLong_jre7() {
+    return jre7.randomLong();
+  }
+
+  // Convenience main entry-point
+  public static void main(String[] args) throws RunnerException {
+    Options opt = new OptionsBuilder()
+        .include(".*" + PlatformBenchmarks.class.getSimpleName() + ".*")
+        .build();
+
+    new Runner(opt).run();
+  }
+}