HDFS-11696. Fix warnings from Spotbugs in hadoop-hdfs. Contributed by Yiqun Lin.

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSClient.java

@@ -2857,9 +2857,12 @@ private void initThreadsNumForStripedReads(int numThreads) {
     }
     synchronized (DFSClient.class) {
       if (STRIPED_READ_THREAD_POOL == null) {
-        STRIPED_READ_THREAD_POOL = DFSUtilClient.getThreadPoolExecutor(1,
+        // Only after thread pool is fully constructed then save it to
+        // volatile field.
+        ThreadPoolExecutor threadPool = DFSUtilClient.getThreadPoolExecutor(1,
             numThreads, 60, "StripedRead-", true);
-        STRIPED_READ_THREAD_POOL.allowCoreThreadTimeOut(true);
+        threadPool.allowCoreThreadTimeOut(true);
+        STRIPED_READ_THREAD_POOL = threadPool;
       }
     }
   }

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/server/protocol/SlowDiskReports.java

@@ -101,8 +101,9 @@ public boolean equals(Object o) {
     }
 
     boolean areEqual;
-    for (String disk : this.slowDisks.keySet()) {
+    for (Map.Entry<String, Map<DiskOp, Double>> entry : this.slowDisks
-      if (!this.slowDisks.get(disk).equals(that.slowDisks.get(disk))) {
+        .entrySet()) {
+      if (!entry.getValue().equals(that.slowDisks.get(entry.getKey()))) {
         return false;
       }
     }

hadoop-hdfs-project/hadoop-hdfs/dev-support/findbugsExcludeFile.xml

@@ -252,4 +252,9 @@
         <Class name="org.apache.hadoop.hdfs.server.datanode.checker.AbstractFuture" />
         <Bug pattern="NS_DANGEROUS_NON_SHORT_CIRCUIT" />
     </Match>
+    <Match>
+        <Class name="org.apache.hadoop.hdfs.server.namenode.NNUpgradeUtil$1" />
+        <Method name="visitFile" />
+        <Bug pattern="NP_NULL_ON_SOME_PATH_FROM_RETURN_VALUE" />
+    </Match>
  </FindBugsFilter>

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/server/JournalNode.java

@@ -297,14 +297,18 @@ public boolean accept(File file) {
         return file.isDirectory();
       }
     });
-    for (File journalDir : journalDirs) {
+
-      String jid = journalDir.getName();
+    if (journalDirs != null) {
-      if (!status.containsKey(jid)) {
+      for (File journalDir : journalDirs) {
-        Map<String, String> jMap = new HashMap<String, String>();
+        String jid = journalDir.getName();
-        jMap.put("Formatted", "true");
+        if (!status.containsKey(jid)) {
-        status.put(jid, jMap);
+          Map<String, String> jMap = new HashMap<String, String>();
+          jMap.put("Formatted", "true");
+          status.put(jid, jMap);
+        }
       }
     }
+
     return JSON.toString(status);
   }
   

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/common/HdfsServerConstants.java

@@ -190,6 +190,8 @@ public NamenodeRole toNodeRole() {
     }
 
     public void setClusterId(String cid) {
+      Preconditions.checkState(this == UPGRADE || this == UPGRADEONLY
+          || this == FORMAT);
       clusterId = cid;
     }
 
@@ -214,6 +216,7 @@ public MetaRecoveryContext createRecoveryContext() {
     }
 
     public void setForce(int force) {
+      Preconditions.checkState(this == RECOVER);
       this.force = force;
     }
     
@@ -226,6 +229,7 @@ public boolean getForceFormat() {
     }
     
     public void setForceFormat(boolean force) {
+      Preconditions.checkState(this == FORMAT);
       isForceFormat = force;
     }
     
@@ -234,6 +238,7 @@ public boolean getInteractiveFormat() {
     }
     
     public void setInteractiveFormat(boolean interactive) {
+      Preconditions.checkState(this == FORMAT);
       isInteractiveFormat = interactive;
     }
     

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataStorage.java

@@ -1336,10 +1336,14 @@ public boolean accept(File dir, String name) {
           return name.startsWith(BLOCK_SUBDIR_PREFIX);
         }
       });
-    for(int i = 0; i < otherNames.length; i++)
+
-      linkBlocksHelper(new File(from, otherNames[i]),
+    if (otherNames != null) {
-          new File(to, otherNames[i]), oldLV, hl, upgradeToIdBasedLayout,
+      for (int i = 0; i < otherNames.length; i++) {
-          blockRoot, idBasedLayoutSingleLinks);
+        linkBlocksHelper(new File(from, otherNames[i]),
+            new File(to, otherNames[i]), oldLV, hl, upgradeToIdBasedLayout,
+            blockRoot, idBasedLayoutSingleLinks);
+      }
+    }
   }
 
   /**

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

@@ -255,24 +255,27 @@ public boolean accept(File dir, String name) {
     });
 
     // Check whether there is any work to do.
-    if (filesInStorage.length <= numCheckpointsToRetain) {
+    if (filesInStorage != null
+        && filesInStorage.length <= numCheckpointsToRetain) {
       return;
     }
 
     // Create a sorted list of txids from the file names.
     TreeSet<Long> sortedTxIds = new TreeSet<Long>();
-    for (String fName : filesInStorage) {
+    if (filesInStorage != null) {
-      // Extract the transaction id from the file name.
+      for (String fName : filesInStorage) {
-      long fTxId;
+        // Extract the transaction id from the file name.
-      try {
+        long fTxId;
-        fTxId = Long.parseLong(fName.substring(oivImagePrefix.length() + 1));
+        try {
-      } catch (NumberFormatException nfe) {
+          fTxId = Long.parseLong(fName.substring(oivImagePrefix.length() + 1));
-        // This should not happen since we have already filtered it.
+        } catch (NumberFormatException nfe) {
-        // Log and continue.
+          // This should not happen since we have already filtered it.
-        LOG.warn("Invalid file name. Skipping " + fName);
+          // Log and continue.
-        continue;
+          LOG.warn("Invalid file name. Skipping " + fName);
+          continue;
+        }
+        sortedTxIds.add(Long.valueOf(fTxId));
       }
-      sortedTxIds.add(Long.valueOf(fTxId));
     }
 
     int numFilesToDelete = sortedTxIds.size() - numCheckpointsToRetain;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/DFSAdmin.java

@@ -1917,7 +1917,7 @@ public int run(String[] argv) throws Exception {
         return exitCode;
       }
     } else if ("-report".equals(cmd)) {
-      if (argv.length < 1) {
+      if (argv.length > 4) {
         printUsage(cmd);
         return exitCode;
       }
@@ -1947,7 +1947,7 @@ public int run(String[] argv) throws Exception {
         return exitCode;
       }
     } else if (RollingUpgradeCommand.matches(cmd)) {
-      if (argv.length < 1 || argv.length > 2) {
+      if (argv.length > 2) {
         printUsage(cmd);
         return exitCode;
       }
@@ -2022,7 +2022,7 @@ public int run(String[] argv) throws Exception {
         return exitCode;
       }
     } else if ("-triggerBlockReport".equals(cmd)) {
-      if (argv.length < 1) {
+      if ((argv.length != 2) && (argv.length != 3)) {
         printUsage(cmd);
         return exitCode;
       }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/ImageLoaderCurrent.java

@@ -722,9 +722,13 @@ private void processINode(DataInputStream in, ImageVisitor v,
       if (supportSnapshot && supportInodeId) {
         dirNodeMap.put(inodeId, pathName);
       }
-      v.visit(ImageElement.NS_QUOTA, numBlocks == -1 ? in.readLong() : -1);
+
-      if (NameNodeLayoutVersion.supports(Feature.DISKSPACE_QUOTA, imageVersion))
+      v.visit(ImageElement.NS_QUOTA, in.readLong());
-        v.visit(ImageElement.DS_QUOTA, numBlocks == -1 ? in.readLong() : -1);
+      if (NameNodeLayoutVersion.supports(Feature.DISKSPACE_QUOTA,
+          imageVersion)) {
+        v.visit(ImageElement.DS_QUOTA, in.readLong());
+      }
+
       if (supportSnapshot) {
         boolean snapshottable = in.readBoolean();
         if (!snapshottable) {