HDFS-6355. Fix divide-by-zero, improper use of wall-clock time in BlockPoolSliceScanner (cmccabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1594338 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -466,6 +466,9 @@ Release 2.5.0 - UNRELEASED
     HDFS-6305. WebHdfs response decoding may throw RuntimeExceptions (Daryn
     Sharp via jeagles)
 
+    HDFS-6355. Fix divide-by-zero, improper use of wall-clock time in
+    BlockPoolSliceScanner (cmccabe)
+
 Release 2.4.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES

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

@@ -97,7 +97,7 @@ class BlockPoolSliceScanner {
   private long totalTransientErrors = 0;
   private final AtomicInteger totalBlocksScannedInLastRun = new AtomicInteger(); // Used for test only
   
-  private long currentPeriodStart = Time.now();
+  private long currentPeriodStart = Time.monotonicNow();
   private long bytesLeft = 0; // Bytes to scan in this period
   private long totalBytesToScan = 0;
   private boolean isNewPeriod = true;
@@ -260,7 +260,7 @@ class BlockPoolSliceScanner {
     long period = Math.min(scanPeriod, 
                            Math.max(blockMap.size(),1) * 600 * 1000L);
     int periodInt = Math.abs((int)period);
-    return Time.now() - scanPeriod + 
+    return Time.monotonicNow() - scanPeriod +
         DFSUtil.getRandom().nextInt(periodInt);
   }
 
@@ -322,7 +322,7 @@ class BlockPoolSliceScanner {
       info = new BlockScanInfo(block);
     }
     
-    long now = Time.now();
+    long now = Time.monotonicNow();
     info.lastScanType = type;
     info.lastScanTime = now;
     info.lastScanOk = scanOk;
@@ -399,8 +399,9 @@ class BlockPoolSliceScanner {
   }
   
   private synchronized void adjustThrottler() {
-    long timeLeft = currentPeriodStart+scanPeriod - Time.now();
-    long bw = Math.max(bytesLeft*1000/timeLeft, MIN_SCAN_RATE);
+    long timeLeft = Math.max(1L,
+        currentPeriodStart + scanPeriod - Time.monotonicNow());
+    long bw = Math.max((bytesLeft * 1000) / timeLeft, MIN_SCAN_RATE);
     throttler.setBandwidth(Math.min(bw, MAX_SCAN_RATE));
   }
   
@@ -523,7 +524,7 @@ class BlockPoolSliceScanner {
   private boolean assignInitialVerificationTimes() {
     //First updates the last verification times from the log file.
     if (verificationLog != null) {
-      long now = Time.now();
+      long now = Time.monotonicNow();
       RollingLogs.LineIterator logIterator = null;
       try {
         logIterator = verificationLog.logs.iterator(false);
@@ -574,7 +575,7 @@ class BlockPoolSliceScanner {
       // Initially spread the block reads over half of scan period
       // so that we don't keep scanning the blocks too quickly when restarted.
       long verifyInterval = Math.min(scanPeriod/(2L * numBlocks), 10*60*1000L);
-      long lastScanTime = Time.now() - scanPeriod;
+      long lastScanTime = Time.monotonicNow() - scanPeriod;
 
       if (!blockInfoSet.isEmpty()) {
         BlockScanInfo info;
@@ -601,16 +602,16 @@ class BlockPoolSliceScanner {
 
     // reset the byte counts :
     bytesLeft = totalBytesToScan;
-    currentPeriodStart = Time.now();
+    currentPeriodStart = Time.monotonicNow();
     isNewPeriod = true;
   }
   
   private synchronized boolean workRemainingInCurrentPeriod() {
-    if (bytesLeft <= 0 && Time.now() < currentPeriodStart + scanPeriod) {
+    if (bytesLeft <= 0 && Time.monotonicNow() < currentPeriodStart + scanPeriod) {
       if (LOG.isDebugEnabled()) {
         LOG.debug("Skipping scan since bytesLeft=" + bytesLeft + ", Start=" +
                   currentPeriodStart + ", period=" + scanPeriod + ", now=" +
-                  Time.now() + " " + blockPoolId);
+                  Time.monotonicNow() + " " + blockPoolId);
       }
       return false;
     } else {
@@ -633,7 +634,7 @@ class BlockPoolSliceScanner {
       scan();
     } finally {
       totalBlocksScannedInLastRun.set(processedBlocks.size());
-      lastScanTime.set(Time.now());
+      lastScanTime.set(Time.monotonicNow());
     }
   }
 
@@ -656,7 +657,7 @@ class BlockPoolSliceScanner {
       while (datanode.shouldRun
           && !datanode.blockScanner.blockScannerThread.isInterrupted()
           && datanode.isBPServiceAlive(blockPoolId)) {
-        long now = Time.now();
+        long now = Time.monotonicNow();
         synchronized (this) {
           if ( now >= (currentPeriodStart + scanPeriod)) {
             startNewPeriod();
@@ -714,7 +715,7 @@ class BlockPoolSliceScanner {
     
     int total = blockInfoSet.size();
     
-    long now = Time.now();
+    long now = Time.monotonicNow();
     
     Date date = new Date();
     

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDatanodeBlockScanner.java

@@ -87,15 +87,15 @@ public class TestDatanodeBlockScanner {
   throws IOException, TimeoutException {
     URL url = new URL("http://localhost:" + infoPort +
                       "/blockScannerReport?listblocks");
-    long lastWarnTime = Time.now();
+    long lastWarnTime = Time.monotonicNow();
     if (newTime <= 0) newTime = 1L;
     long verificationTime = 0;
     
     String block = DFSTestUtil.getFirstBlock(fs, file).getBlockName();
     long failtime = (timeout <= 0) ? Long.MAX_VALUE 
-        : Time.now() + timeout;
+        : Time.monotonicNow() + timeout;
     while (verificationTime < newTime) {
-      if (failtime < Time.now()) {
+      if (failtime < Time.monotonicNow()) {
         throw new TimeoutException("failed to achieve block verification after "
             + timeout + " msec.  Current verification timestamp = "
             + verificationTime + ", requested verification time > " 
@@ -118,7 +118,7 @@ public class TestDatanodeBlockScanner {
       }
       
       if (verificationTime < newTime) {
-        long now = Time.now();
+        long now = Time.monotonicNow();
         if ((now - lastWarnTime) >= 5*1000) {
           LOG.info("Waiting for verification of " + block);
           lastWarnTime = now; 
@@ -134,7 +134,7 @@ public class TestDatanodeBlockScanner {
 
   @Test
   public void testDatanodeBlockScanner() throws IOException, TimeoutException {
-    long startTime = Time.now();
+    long startTime = Time.monotonicNow();
     
     Configuration conf = new HdfsConfiguration();
     MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf).build();
@@ -344,7 +344,7 @@ public class TestDatanodeBlockScanner {
     conf.setLong(DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_KEY, 3L);
     conf.setBoolean(DFSConfigKeys.DFS_NAMENODE_REPLICATION_CONSIDERLOAD_KEY, false);
 
-    long startTime = Time.now();
+    long startTime = Time.monotonicNow();
     MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf)
                                                .numDataNodes(REPLICATION_FACTOR)
                                                .build();
@@ -428,10 +428,10 @@ public class TestDatanodeBlockScanner {
   private static void waitForBlockDeleted(ExtendedBlock blk, int dnIndex,
       long timeout) throws TimeoutException, InterruptedException {
     File blockFile = MiniDFSCluster.getBlockFile(dnIndex, blk);
-    long failtime = Time.now() 
+    long failtime = Time.monotonicNow()
                     + ((timeout > 0) ? timeout : Long.MAX_VALUE);
     while (blockFile != null && blockFile.exists()) {
-      if (failtime < Time.now()) {
+      if (failtime < Time.monotonicNow()) {
         throw new TimeoutException("waited too long for blocks to be deleted: "
             + blockFile.getPath() + (blockFile.exists() ? " still exists; " : " is absent; "));
       }
@@ -462,7 +462,7 @@ public class TestDatanodeBlockScanner {
 
   @Test
   public void testDuplicateScans() throws Exception {
-    long startTime = Time.now();
+    long startTime = Time.monotonicNow();
     MiniDFSCluster cluster = new MiniDFSCluster.Builder(new Configuration())
         .numDataNodes(1).build();
     FileSystem fs = null;