opendaylight/md-sal/sal-dom-spi/src/main/java/org/opendaylight/controller/sal/core/spi/data/SnapshotBackedReadTransaction.java

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.controller.sal.core.spi.data;
   9
  10 import static com.google.common.base.Preconditions.checkNotNull;
  11
  12 import com.google.common.annotations.Beta;
  13 import com.google.common.base.Optional;
  14 import com.google.common.base.Preconditions;
  15 import com.google.common.util.concurrent.CheckedFuture;
  16 import com.google.common.util.concurrent.Futures;
  17 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
  18 import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
  19 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  20 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  21 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeSnapshot;
  22 import org.slf4j.Logger;
  23 import org.slf4j.LoggerFactory;
  24
  25 /**
  26  * Implementation of read-only transaction backed by {@link DataTreeSnapshot}.
  27  *
  28  * <p>
  29  * Implementation of read-only transaction backed by {@link DataTreeSnapshot}
  30  * which delegates most of its calls to similar methods provided by underlying snapshot.
  31  *
  32  * @param <T> identifier type
  33  */
  34 @Beta
  35 public final class SnapshotBackedReadTransaction<T> extends AbstractDOMStoreTransaction<T>
  36         implements DOMStoreReadTransaction {
  37     private static final Logger LOG = LoggerFactory.getLogger(SnapshotBackedReadTransaction.class);
  38
  39     @SuppressWarnings("rawtypes")
  40     private static final AtomicReferenceFieldUpdater<SnapshotBackedReadTransaction, DataTreeSnapshot> SNAPSHOT_UPDATER =
  41             AtomicReferenceFieldUpdater.newUpdater(SnapshotBackedReadTransaction.class, DataTreeSnapshot.class,
  42                 "stableSnapshot");
  43
  44     // Guarded by stableSnapshot CAS, hence it does not need to be volatile
  45     private TransactionClosePrototype<T> closeImpl;
  46     private volatile DataTreeSnapshot stableSnapshot;
  47
  48     /**
  49      * Creates a new read-only transaction.
  50      *
  51      * @param identifier Transaction Identifier
  52      * @param debug Enable transaction debugging
  53      * @param snapshot Snapshot which will be modified.
  54      */
  55     SnapshotBackedReadTransaction(final T identifier, final boolean debug, final DataTreeSnapshot snapshot,
  56             final TransactionClosePrototype<T> closeImpl) {
  57         super(identifier, debug);
  58         this.stableSnapshot = Preconditions.checkNotNull(snapshot);
  59         this.closeImpl = closeImpl;
  60         LOG.debug("ReadOnly Tx: {} allocated with snapshot {}", identifier, snapshot);
  61     }
  62
  63     @Override
  64     public void close() {
  65         final DataTreeSnapshot prev = SNAPSHOT_UPDATER.getAndSet(this, null);
  66         if (prev == null) {
  67             LOG.debug("Store transaction: {} : previously closed", getIdentifier());
  68             return;
  69         }
  70
  71         LOG.debug("Store transaction: {} : Closed", getIdentifier());
  72         if (closeImpl != null) {
  73             closeImpl.transactionClosed(this);
  74             closeImpl = null;
  75         }
  76     }
  77
  78     @Override
  79     @SuppressWarnings("checkstyle:IllegalCatch")
  80     public CheckedFuture<Optional<NormalizedNode<?,?>>, ReadFailedException> read(final YangInstanceIdentifier path) {
  81         LOG.debug("Tx: {} Read: {}", getIdentifier(), path);
  82         checkNotNull(path, "Path must not be null.");
  83
  84         final DataTreeSnapshot snapshot = stableSnapshot;
  85         if (snapshot == null) {
  86             return Futures.immediateFailedCheckedFuture(new ReadFailedException("Transaction is closed"));
  87         }
  88
  89         try {
  90             return Futures.immediateCheckedFuture(Optional.fromJavaUtil(snapshot.readNode(path)));
  91         } catch (RuntimeException e) {
  92             LOG.error("Tx: {} Failed Read of {}", getIdentifier(), path, e);
  93             return Futures.immediateFailedCheckedFuture(new ReadFailedException("Read failed",e));
  94         }
  95     }
  96
  97     @Override
  98     public CheckedFuture<Boolean, ReadFailedException> exists(final YangInstanceIdentifier path) {
  99         LOG.debug("Tx: {} Exists: {}", getIdentifier(), path);
 100         checkNotNull(path, "Path must not be null.");
 101
 102         try {
 103             return Futures.immediateCheckedFuture(read(path).checkedGet().isPresent());
 104         } catch (ReadFailedException e) {
 105             return Futures.immediateFailedCheckedFuture(e);
 106         }
 107     }
 108
 109     /**
 110      * Prototype implementation of {@link SnapshotBackedReadTransaction#close()}.
 111      *
 112      * <p>
 113      * This class is intended to be implemented by Transaction factories responsible for allocation
 114      * of {@link org.opendaylight.mdsal.dom.spi.store.SnapshotBackedReadTransaction} and
 115      * providing underlying logic for applying implementation.
 116      *
 117      * @param <T> identifier type
 118      */
 119     public interface TransactionClosePrototype<T> {
 120         /**
 121          * Called when a transaction is closed. This is not invoked at most once for every transaction.
 122          *
 123          * @param tx Transaction which got closed.
 124          */
 125         void transactionClosed(SnapshotBackedReadTransaction<T> tx);
 126     }
 127 }