HBASE-13082 Coarsen StoreScanner locks to RegionScanner.

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java

@@ -5233,6 +5233,8 @@ public HRegionInfo getRegionInfo() {
           scan.getFamilyMap().entrySet()) {
         Store store = stores.get(entry.getKey());
         KeyValueScanner scanner = store.getScanner(scan, entry.getValue(), this.readPt);
+        // pass the RegionScanner object to lock out concurrent changes to set of readers
+        scanner.setReaderLock(this);
         if (this.filter == null || !scan.doLoadColumnFamiliesOnDemand()
           || this.filter.isFamilyEssential(entry.getKey())) {
           scanners.add(scanner);

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/KeyValueScanner.java

@@ -162,4 +162,11 @@ boolean requestSeek(Cell kv, boolean forward, boolean useBloom)
    * if known, or null otherwise
    */
   public Cell getNextIndexedKey();
+
+  /**
+   * Set the object to lock when the scanner's readers (if any) are updated (this is here so that the
+   * coprocessors creating {@link StoreScanner}'s do not have to change)
+   * @param obj lock object to use
+   */
+  public void setReaderLock(Object obj);
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/NonLazyKeyValueScanner.java

@@ -71,4 +71,7 @@ public boolean isFileScanner() {
   public Cell getNextIndexedKey() {
     return null;
   }
+
+  @Override
+  public void setReaderLock(Object obj) {/* NO OP */}
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ReversedStoreScanner.java

@@ -124,24 +124,13 @@ public boolean seek(Cell key) throws IOException {
 
   @Override
   public boolean seekToPreviousRow(Cell key) throws IOException {
-    lock.lock();
-    try {
-      checkReseek();
-      return this.heap.seekToPreviousRow(key);
-    } finally {
-      lock.unlock();
-    }
-
+    checkReseek();
+    return this.heap.seekToPreviousRow(key);
   }
 
   @Override
   public boolean backwardSeek(Cell key) throws IOException {
-    lock.lock();
-    try {
-      checkReseek();
-      return this.heap.backwardSeek(key);
-    } finally {
-      lock.unlock();
-    }
+    checkReseek();
+    return this.heap.backwardSeek(key);
   }
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreFileScanner.java

@@ -489,4 +489,7 @@ public boolean backwardSeek(Cell key) throws IOException {
   public Cell getNextIndexedKey() {
     return hfs.getNextIndexedKey();
   }
+
+  @Override
+  public void setReaderLock(Object obj) {/* NO OP */}
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java

@@ -25,7 +25,6 @@
 import java.util.List;
 import java.util.NavigableSet;
 import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.locks.ReentrantLock;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -103,10 +102,17 @@ public class StoreScanner extends NonReversedNonLazyKeyValueScanner
 
   // A flag whether use pread for scan
   private boolean scanUsePread = false;
-  protected ReentrantLock lock = new ReentrantLock();
 
   private final long readPt;
 
+  // lock to use for updateReaders
+  // creator needs to ensure that:
+  // 1. *all* calls to public methods (except updateReaders and close) are locked with this lock
+  //    (this can be done by passing the RegionScannerImpl object down)
+  // OR
+  // 2. updateReader is *never* called (such as in flushes or compactions)
+  private Object readerLock;
+
   // used by the injection framework to test race between StoreScanner construction and compaction
   enum StoreScannerCompactionRace {
     BEFORE_SEEK,
@@ -395,15 +401,10 @@ protected List<KeyValueScanner> selectScannersFrom(
 
   @Override
   public Cell peek() {
-    lock.lock();
-    try {
     if (this.heap == null) {
       return this.lastTop;
     }
     return this.heap.peek();
-    } finally {
-      lock.unlock();
-    }
   }
 
   @Override
@@ -414,8 +415,6 @@ public KeyValue next() {
 
   @Override
   public void close() {
-    lock.lock();
-    try {
     if (this.closing) return;
     this.closing = true;
     // under test, we dont have a this.store
@@ -425,21 +424,13 @@ public void close() {
       this.heap.close();
     this.heap = null; // CLOSED!
     this.lastTop = null; // If both are null, we are closed.
-    } finally {
-      lock.unlock();
-    }
   }
 
   @Override
   public boolean seek(Cell key) throws IOException {
-    lock.lock();
-    try {
     // reset matcher state, in case that underlying store changed
     checkReseek();
     return this.heap.seek(key);
-    } finally {
-      lock.unlock();
-    }
   }
 
   /**
@@ -464,8 +455,6 @@ public NextState next(List<Cell> outResult, int limit) throws IOException {
   @Override
   public NextState next(List<Cell> outResult, int limit, long remainingResultSize)
       throws IOException {
-    lock.lock();
-    try {
     if (checkReseek()) {
       return NextState.makeState(NextState.State.MORE_VALUES, 0);
     }
@@ -617,9 +606,6 @@ public NextState next(List<Cell> outResult, int limit, long remainingResultSize)
     // No more keys
     close();
     return NextState.makeState(NextState.State.NO_MORE_VALUES, totalHeapSize);
-    } finally {
-      lock.unlock();
-    }
   }
 
   /*
@@ -663,8 +649,7 @@ public NextState next(List<Cell> outResult) throws IOException {
   // Implementation of ChangedReadersObserver
   @Override
   public void updateReaders() throws IOException {
-    lock.lock();
-    try {
+    synchronized(readerLock) {
     if (this.closing) return;
 
     // All public synchronized API calls will call 'checkReseek' which will cause
@@ -684,8 +669,6 @@ public void updateReaders() throws IOException {
     this.heap = null; // the re-seeks could be slow (access HDFS) free up memory ASAP
 
     // Let the next() call handle re-creating and seeking
-    } finally {
-      lock.unlock();
     }
   }
 
@@ -776,8 +759,6 @@ protected boolean seekAsDirection(Cell kv)
 
   @Override
   public boolean reseek(Cell kv) throws IOException {
-    lock.lock();
-    try {
     //Heap will not be null, if this is called from next() which.
     //If called from RegionScanner.reseek(...) make sure the scanner
     //stack is reset if needed.
@@ -786,9 +767,6 @@ public boolean reseek(Cell kv) throws IOException {
       return heap.requestSeek(kv, true, useRowColBloom);
     }
     return heap.reseek(kv);
-    } finally {
-      lock.unlock();
-    }
   }
 
   @Override
@@ -863,5 +841,9 @@ public long getEstimatedNumberOfKvsScanned() {
   public Cell getNextIndexedKey() {
     return this.heap.getNextIndexedKey();
   }
-}
 
+  @Override
+  public void setReaderLock(Object obj) {
+    this.readerLock = obj;
+  }
+}