HDFS-15890. Improve the Logs for File Concat Operation. Contributed by Bhavik Patel.

(cherry picked from commit 9ba60c33d8e68766aec49e50ec4c86519c6f9889)

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

@@ -52,9 +52,9 @@ class FSDirConcatOp {
       String target, String[] srcs, boolean logRetryCache) throws IOException {
     validatePath(target, srcs);
     assert srcs != null;
-    if (FSDirectory.LOG.isDebugEnabled()) {
-      FSDirectory.LOG.debug("concat {} to {}", Arrays.toString(srcs), target);
-    }
+    NameNode.stateChangeLog.debug("DIR* NameSystem.concat: {} to {}",
+        Arrays.toString(srcs), target);
+
     final INodesInPath targetIIP = fsd.resolvePath(pc, target, DirOp.WRITE);
     // write permission for the target
     if (fsd.isPermissionEnabled()) {
@@ -66,11 +66,6 @@ class FSDirConcatOp {
     // check the srcs
     INodeFile[] srcFiles = verifySrcFiles(fsd, srcs, targetIIP, pc);
 
-    if(NameNode.stateChangeLog.isDebugEnabled()) {
-      NameNode.stateChangeLog.debug("DIR* NameSystem.concat: " +
-          Arrays.toString(srcs) + " to " + target);
-    }
-
     long timestamp = now();
     fsd.writeLock();
     try {
@@ -234,10 +229,8 @@ class FSDirConcatOp {
   static void unprotectedConcat(FSDirectory fsd, INodesInPath targetIIP,
       INodeFile[] srcList, long timestamp) throws IOException {
     assert fsd.hasWriteLock();
-    if (NameNode.stateChangeLog.isDebugEnabled()) {
-      NameNode.stateChangeLog.debug("DIR* FSNamesystem.concat to "
-          + targetIIP.getPath());
-    }
+    NameNode.stateChangeLog.debug("DIR* NameSystem.concat to {}",
+        targetIIP.getPath());
 
     final INodeFile trgInode = targetIIP.getLastINode().asFile();
     QuotaCounts deltas = computeQuotaDeltas(fsd, trgInode, srcList);

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

@@ -1054,6 +1054,8 @@ public class NameNodeRpcServer implements NamenodeProtocols {
   @Override // ClientProtocol
   public void concat(String trg, String[] src) throws IOException {
     checkNNStartup();
+    stateChangeLog.debug("*DIR* NameNode.concat: src path {} to" +
+        " target path {}", Arrays.toString(src), trg);
     namesystem.checkOperation(OperationCategory.WRITE);
     CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
     if (cacheEntry != null && cacheEntry.isSuccess()) {