HDFS-10485. Fix findbugs warning in FSEditLog.java. (aajisaka)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLog.java

@@ -27,6 +27,7 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicLong;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -174,7 +175,7 @@ public class FSEditLog implements LogsPurgeable {
   
   // these are statistics counters.
   private long numTransactions;        // number of transactions
-  private long numTransactionsBatchedInSync;
+  private final AtomicLong numTransactionsBatchedInSync = new AtomicLong();
   private long totalTimeTransactions;  // total time for all transactions
   private NameNodeMetrics metrics;
 
@@ -672,7 +673,7 @@ public class FSEditLog implements LogsPurgeable {
       if (metrics != null) { // Metrics non-null only when used inside name node
         metrics.addSync(elapsed);
         metrics.incrTransactionsBatchedInSync(editsBatchedInSync);
-        numTransactionsBatchedInSync += editsBatchedInSync;
+        numTransactionsBatchedInSync.addAndGet(editsBatchedInSync);
       }
       
     } finally {
@@ -712,7 +713,7 @@ public class FSEditLog implements LogsPurgeable {
     buf.append(" Total time for transactions(ms): ");
     buf.append(totalTimeTransactions);
     buf.append(" Number of transactions batched in Syncs: ");
-    buf.append(numTransactionsBatchedInSync);
+    buf.append(numTransactionsBatchedInSync.get());
     buf.append(" Number of syncs: ");
     buf.append(editLogStream.getNumSync());
     buf.append(" SyncTimes(ms): ");
@@ -1281,7 +1282,9 @@ public class FSEditLog implements LogsPurgeable {
         "Cannot start log segment at txid %s when next expected " +
         "txid is %s", segmentTxId, txid + 1);
     
-    numTransactions = totalTimeTransactions = numTransactionsBatchedInSync = 0;
+    numTransactions = 0;
+    totalTimeTransactions = 0;
+    numTransactionsBatchedInSync.set(0L);
 
     // TODO no need to link this back to storage anymore!
     // See HDFS-2174.