[close #435] SimpleDateFormat is not threadsafe (#479)

Author: marsishandsome

src/main/java/org/tikv/common/log/SlowLogImpl.java

@@ -32,8 +32,6 @@ public class SlowLogImpl implements SlowLog {
 
   private static final int MAX_SPAN_SIZE = 1024;
 
-  public static final SimpleDateFormat DATE_FORMAT = new SimpleDateFormat("HH:mm:ss.SSS");
-
   private final List<SlowLogSpan> slowLogSpans = new ArrayList<>();
   private Throwable error = null;
 
@@ -85,10 +83,11 @@ public void log() {
   }
 
   private String getSlowLogString(long currentMS) {
+    SimpleDateFormat dateFormat = getSimpleDateFormat();
     JsonObject jsonObject = new JsonObject();
 
-    jsonObject.addProperty("start", DATE_FORMAT.format(startMS));
-    jsonObject.addProperty("end", DATE_FORMAT.format(currentMS));
+    jsonObject.addProperty("start", dateFormat.format(startMS));
+    jsonObject.addProperty("end", dateFormat.format(currentMS));
     jsonObject.addProperty("duration", (currentMS - startMS) + "ms");
     if (error != null) {
       jsonObject.addProperty("error", error.getMessage());
@@ -106,4 +105,8 @@ private String getSlowLogString(long currentMS) {
 
     return jsonObject.toString();
   }
+
+  public static SimpleDateFormat getSimpleDateFormat() {
+    return new SimpleDateFormat("HH:mm:ss.SSS");
+  }
 }

src/main/java/org/tikv/common/log/SlowLogSpanImpl.java

@@ -17,10 +17,11 @@
 
 package org.tikv.common.log;
 
-import static org.tikv.common.log.SlowLogImpl.DATE_FORMAT;
+import static org.tikv.common.log.SlowLogImpl.getSimpleDateFormat;
 
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
+import java.text.SimpleDateFormat;
 
 public class SlowLogSpanImpl implements SlowLogSpan {
   private final String name;
@@ -60,27 +61,28 @@ public void end() {
 
   @Override
   public JsonElement toJsonElement() {
+    SimpleDateFormat simpleDateFormat = getSimpleDateFormat();
     JsonObject jsonObject = new JsonObject();
     jsonObject.addProperty("name", name);
-    jsonObject.addProperty("start", getStartString());
-    jsonObject.addProperty("end", getEndString());
+    jsonObject.addProperty("start", getStartString(simpleDateFormat));
+    jsonObject.addProperty("end", getEndString(simpleDateFormat));
     jsonObject.addProperty("duration", getDurationString());
 
     return jsonObject;
   }
 
-  private String getStartString() {
+  private String getStartString(SimpleDateFormat simpleDateFormat) {
     if (startMS == 0) {
       return "N/A";
     }
-    return DATE_FORMAT.format(startMS);
+    return simpleDateFormat.format(startMS);
   }
 
-  private String getEndString() {
+  private String getEndString(SimpleDateFormat simpleDateFormat) {
     if (endMS == 0) {
       return "N/A";
     }
-    return DATE_FORMAT.format(endMS);
+    return simpleDateFormat.format(endMS);
   }
 
   private String getDurationString() {