[incubator-zipkin-brave] branch master updated: Reuse buffer when converting long to hex. (#907)

[an...@apache.org]

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anuraaga pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/incubator-zipkin-brave.git


The following commit(s) were added to refs/heads/master by this push:
     new 44719d4  Reuse buffer when converting long to hex. (#907)
44719d4 is described below

commit 44719d4e5298a4be9b88a95dbd1e28a6e3758065
Author: Anuraag Agrawal <an...@gmail.com>
AuthorDate: Sun May 12 18:37:36 2019 +0900

    Reuse buffer when converting long to hex. (#907)
    
    * Reuse buffer when converting long to hex.
    
    * Move buffer to separate class to not deal with platformness.
---
 brave/src/main/java/brave/internal/HexCodec.java   |  4 +--
 .../java/brave/internal/RecyclableBuffers.java     | 36 ++++++++++++++++++++++
 .../main/java/brave/propagation/TraceContext.java  |  3 +-
 3 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/brave/src/main/java/brave/internal/HexCodec.java b/brave/src/main/java/brave/internal/HexCodec.java
index 76b1c1a..595e67c 100644
--- a/brave/src/main/java/brave/internal/HexCodec.java
+++ b/brave/src/main/java/brave/internal/HexCodec.java
@@ -52,9 +52,9 @@ public final class HexCodec {
 
   /** Inspired by {@code okio.Buffer.writeLong} */
   public static String toLowerHex(long v) {
-    char[] data = new char[16];
+    char[] data = RecyclableBuffers.idBuffer();
     writeHexLong(data, 0, v);
-    return new String(data);
+    return new String(data, 0, 16);
   }
 
   /** Inspired by {@code okio.Buffer.writeLong} */
diff --git a/brave/src/main/java/brave/internal/RecyclableBuffers.java b/brave/src/main/java/brave/internal/RecyclableBuffers.java
new file mode 100644
index 0000000..22e20d8
--- /dev/null
+++ b/brave/src/main/java/brave/internal/RecyclableBuffers.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2019 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;
+
+public final class RecyclableBuffers {
+
+  private static final ThreadLocal<char[]> ID_BUFFER = new ThreadLocal<>();
+
+  /**
+   * Returns a {@link ThreadLocal} reused {@code char[]} for use when decoding bytes into an ID hex
+   * string. The buffer should be immediately copied into a {@link String} after decoding within the
+   * same method.
+   */
+  public static char[] idBuffer() {
+    char[] idBuffer = ID_BUFFER.get();
+    if (idBuffer == null) {
+      idBuffer = new char[32];
+      ID_BUFFER.set(idBuffer);
+    }
+    return idBuffer;
+  }
+
+  private RecyclableBuffers() {}
+}
diff --git a/brave/src/main/java/brave/propagation/TraceContext.java b/brave/src/main/java/brave/propagation/TraceContext.java
index 7e7c809..bf509f8 100644
--- a/brave/src/main/java/brave/propagation/TraceContext.java
+++ b/brave/src/main/java/brave/propagation/TraceContext.java
@@ -4,6 +4,7 @@ import brave.Span;
 import brave.internal.InternalPropagation;
 import brave.internal.Nullable;
 import brave.internal.Platform;
+import brave.internal.RecyclableBuffers;
 import java.lang.ref.WeakReference;
 import java.util.Collections;
 import java.util.List;
@@ -185,7 +186,7 @@ public final class TraceContext extends SamplingFlags {
     String r = traceIdString;
     if (r == null) {
       if (traceIdHigh != 0) {
-        char[] result = new char[32];
+        char[] result = RecyclableBuffers.idBuffer();
         writeHexLong(result, 0, traceIdHigh);
         writeHexLong(result, 16, traceId);
         r = new String(result);