From d3260243f5ecae35bcd51b8772d992139612490c Mon Sep 17 00:00:00 2001
From: Guillaume Polaert <gpolaert@gmail.com>
Date: Wed, 26 Jul 2017 12:47:16 +0200
Subject: [PATCH] make thread safe for nanoTime()

---
 .../java/com/datadoghq/trace/DDBaseSpan.java  |  9 ++--
 .../java/com/datadoghq/trace/DDTracer.java    | 49 ++++++++++---------
 .../java/com/datadoghq/trace/util/Clock.java  |  8 +++
 3 files changed, 38 insertions(+), 28 deletions(-)
 create mode 100644 dd-trace/src/main/java/com/datadoghq/trace/util/Clock.java

diff --git a/dd-trace/src/main/java/com/datadoghq/trace/DDBaseSpan.java b/dd-trace/src/main/java/com/datadoghq/trace/DDBaseSpan.java
index 20c828a131..cd65b1d741 100644
--- a/dd-trace/src/main/java/com/datadoghq/trace/DDBaseSpan.java
+++ b/dd-trace/src/main/java/com/datadoghq/trace/DDBaseSpan.java
@@ -1,5 +1,6 @@
 package com.datadoghq.trace;
 
+import com.datadoghq.trace.util.Clock;
 import com.fasterxml.jackson.annotation.JsonGetter;
 import com.fasterxml.jackson.annotation.JsonIgnore;
 import io.opentracing.BaseSpan;
@@ -13,14 +14,14 @@ import lombok.extern.slf4j.Slf4j;
 @Slf4j
 public abstract class DDBaseSpan<S extends BaseSpan> implements BaseSpan<S> {
 
+  /** The context attached to the span */
+  protected final DDSpanContext context;
   /** StartTime stores the creation time of the span in milliseconds */
   protected long startTimeMicro;
   /** StartTimeNano stores the only the nanoseconds for more accuracy */
   protected long startTimeNano;
   /** The duration in nanoseconds computed using the startTimeMicro and startTimeNano */
   protected long durationNano;
-  /** The context attached to the span */
-  protected final DDSpanContext context;
 
   /**
    * A simple constructor. Currently, users have
@@ -38,14 +39,14 @@ public abstract class DDBaseSpan<S extends BaseSpan> implements BaseSpan<S> {
     } else {
       this.startTimeMicro = timestampMicro;
     }
-    this.startTimeNano = System.nanoTime();
+    this.startTimeNano = Clock.nowNanos();
 
     // track each span of the trace
     this.context.getTrace().add(this);
   }
 
   public final void finish() {
-    this.durationNano = System.nanoTime() - startTimeNano;
+    this.durationNano = Clock.nowNanos() - startTimeNano;
     afterFinish();
   }
 
diff --git a/dd-trace/src/main/java/com/datadoghq/trace/DDTracer.java b/dd-trace/src/main/java/com/datadoghq/trace/DDTracer.java
index f560b8b1fe..4fa24d8e06 100644
--- a/dd-trace/src/main/java/com/datadoghq/trace/DDTracer.java
+++ b/dd-trace/src/main/java/com/datadoghq/trace/DDTracer.java
@@ -5,6 +5,7 @@ import com.datadoghq.trace.propagation.Codec;
 import com.datadoghq.trace.propagation.HTTPCodec;
 import com.datadoghq.trace.sampling.AllSampler;
 import com.datadoghq.trace.sampling.Sampler;
+import com.datadoghq.trace.util.Clock;
 import com.datadoghq.trace.writer.LoggingWriter;
 import com.datadoghq.trace.writer.Writer;
 import io.opentracing.ActiveSpan;
@@ -136,6 +137,24 @@ public class DDTracer extends ThreadLocalActiveSpanSource implements io.opentrac
     writer.close();
   }
 
+  @Override
+  public String toString() {
+    return "DDTracer{" + "writer=" + writer + ", sampler=" + sampler + '}';
+  }
+
+  private static class CodecRegistry {
+
+    private final Map<Format<?>, Codec<?>> codecs = new HashMap<>();
+
+    <T> Codec<T> get(final Format<T> format) {
+      return (Codec<T>) codecs.get(format);
+    }
+
+    public <T> void register(final Format<T> format, final Codec<T> codec) {
+      codecs.put(format, codec);
+    }
+  }
+
   /** Spans are built using this builder */
   public class DDSpanBuilder implements SpanBuilder {
     private final ActiveSpanSource spanSource;
@@ -153,6 +172,11 @@ public class DDTracer extends ThreadLocalActiveSpanSource implements io.opentrac
     private String spanType;
     private boolean ignoreActiveSpan = false;
 
+    public DDSpanBuilder(final String operationName, final ActiveSpanSource spanSource) {
+      this.operationName = operationName;
+      this.spanSource = spanSource;
+    }
+
     @Override
     public SpanBuilder ignoreActiveSpan() {
       this.ignoreActiveSpan = true;
@@ -206,11 +230,6 @@ public class DDTracer extends ThreadLocalActiveSpanSource implements io.opentrac
       return withTag(tag, (Object) bool);
     }
 
-    public DDSpanBuilder(final String operationName, final ActiveSpanSource spanSource) {
-      this.operationName = operationName;
-      this.spanSource = spanSource;
-    }
-
     @Override
     public DDSpanBuilder withStartTimestamp(final long timestampMillis) {
       this.timestamp = timestampMillis;
@@ -271,7 +290,7 @@ public class DDTracer extends ThreadLocalActiveSpanSource implements io.opentrac
     }
 
     private long generateNewId() {
-      return System.nanoTime();
+      return Clock.nowNanos();
     }
 
     /**
@@ -344,22 +363,4 @@ public class DDTracer extends ThreadLocalActiveSpanSource implements io.opentrac
       return context;
     }
   }
-
-  private static class CodecRegistry {
-
-    private final Map<Format<?>, Codec<?>> codecs = new HashMap<>();
-
-    <T> Codec<T> get(final Format<T> format) {
-      return (Codec<T>) codecs.get(format);
-    }
-
-    public <T> void register(final Format<T> format, final Codec<T> codec) {
-      codecs.put(format, codec);
-    }
-  }
-
-  @Override
-  public String toString() {
-    return "DDTracer{" + "writer=" + writer + ", sampler=" + sampler + '}';
-  }
 }
diff --git a/dd-trace/src/main/java/com/datadoghq/trace/util/Clock.java b/dd-trace/src/main/java/com/datadoghq/trace/util/Clock.java
new file mode 100644
index 0000000000..2c2186428b
--- /dev/null
+++ b/dd-trace/src/main/java/com/datadoghq/trace/util/Clock.java
@@ -0,0 +1,8 @@
+package com.datadoghq.trace.util;
+
+public class Clock {
+
+  public synchronized static long nowNanos() {
+    return System.nanoTime();
+  }
+}