/** Iterate through all items and detect timed-out items */
 void pendingReplicationCheck() {
   synchronized (pendingReplications) {
     Iterator iter = pendingReplications.entrySet().iterator();
     long now = FSNamesystem.now();
     FSNamesystem.LOG.debug("PendingReplicationMonitor checking Q");
     while (iter.hasNext()) {
       Map.Entry entry = (Map.Entry) iter.next();
       PendingBlockInfo pendingBlock = (PendingBlockInfo) entry.getValue();
       if (now > pendingBlock.getTimeStamp() + timeout) {
         Block block = (Block) entry.getKey();
         synchronized (timedOutItems) {
           timedOutItems.add(block);
         }
         FSNamesystem.LOG.warn("PendingReplicationMonitor timed out block " + block);
         iter.remove();
       }
     }
   }
 }
 void setTimeStamp() {
   timeStamp = FSNamesystem.now();
 }
 PendingBlockInfo(int numReplicas) {
   this.timeStamp = FSNamesystem.now();
   this.numReplicasInProgress = numReplicas;
 }