dom/mdsal-dom-spi/src/main/java/org/opendaylight/mdsal/dom/spi/store/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.mdsal.dom.spi.store;
   9
  10 import static java.util.Objects.requireNonNull;
  11
  12 import com.google.common.annotations.Beta;
  13 import com.google.common.util.concurrent.FluentFuture;
  14 import com.google.common.util.concurrent.MoreExecutors;
  15 import java.util.Optional;
  16 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
  17 import org.opendaylight.mdsal.common.api.ReadFailedException;
  18 import org.opendaylight.yangtools.util.concurrent.FluentFutures;
  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} which delegates most
  27  * of its calls to similar methods provided by underlying snapshot.
  28  *
  29  * @param <T> identifier type
  30  */
  31 @Beta
  32 public final class SnapshotBackedReadTransaction<T> extends
  33         AbstractDOMStoreTransaction<T> implements DOMStoreReadTransaction, SnapshotBackedTransaction {
  34     private static final Logger LOG = LoggerFactory.getLogger(SnapshotBackedReadTransaction.class);
  35
  36     @SuppressWarnings("rawtypes")
  37     private static final AtomicReferenceFieldUpdater<SnapshotBackedReadTransaction, DataTreeSnapshot> SNAPSHOT_UPDATER =
  38             AtomicReferenceFieldUpdater.newUpdater(SnapshotBackedReadTransaction.class, DataTreeSnapshot.class,
  39                 "stableSnapshot");
  40
  41     // Guarded by stableSnapshot CAS, hence it does not need to be volatile
  42     private TransactionClosePrototype<T> closeImpl;
  43     private volatile DataTreeSnapshot stableSnapshot;
  44
  45     /**
  46      * Creates a new read-only transaction.
  47      *
  48      * @param identifier Transaction Identifier
  49      * @param debug Enable transaction debugging
  50      * @param snapshot Snapshot which will be modified.
  51      */
  52     SnapshotBackedReadTransaction(final T identifier, final boolean debug, final DataTreeSnapshot snapshot,
  53             final TransactionClosePrototype<T> closeImpl) {
  54         super(identifier, debug);
  55         this.stableSnapshot = requireNonNull(snapshot);
  56         this.closeImpl = closeImpl;
  57         LOG.debug("ReadOnly Tx: {} allocated with snapshot {}", identifier, snapshot);
  58     }
  59
  60     @Override
  61     public void close() {
  62         final DataTreeSnapshot prev = SNAPSHOT_UPDATER.getAndSet(this, null);
  63         if (prev == null) {
  64             LOG.debug("Store transaction: {} : previously closed", getIdentifier());
  65             return;
  66         }
  67
  68         LOG.debug("Store transaction: {} : Closed", getIdentifier());
  69         if (closeImpl != null) {
  70             closeImpl.transactionClosed(this);
  71             closeImpl = null;
  72         }
  73     }
  74
  75     @SuppressWarnings("checkstyle:IllegalCatch")
  76     @Override
  77     public FluentFuture<Optional<NormalizedNode>> read(final YangInstanceIdentifier path) {
  78         LOG.debug("Tx: {} Read: {}", getIdentifier(), path);
  79         requireNonNull(path, "Path must not be null.");
  80
  81         final DataTreeSnapshot snapshot = stableSnapshot;
  82         if (snapshot == null) {
  83             return FluentFutures.immediateFailedFluentFuture(new ReadFailedException("Transaction is closed"));
  84         }
  85
  86         try {
  87             return FluentFutures.immediateFluentFuture(snapshot.readNode(path));
  88         } catch (Exception e) {
  89             LOG.error("Tx: {} Failed Read of {}", getIdentifier(), path, e);
  90             return FluentFutures.immediateFailedFluentFuture(new ReadFailedException("Read failed", e));
  91         }
  92     }
  93
  94     @Override
  95     public FluentFuture<Boolean> exists(final YangInstanceIdentifier path) {
  96         LOG.debug("Tx: {} Exists: {}", getIdentifier(), path);
  97         requireNonNull(path, "Path must not be null.");
  98
  99         return read(path).transform(Optional::isPresent, MoreExecutors.directExecutor());
 100     }
 101
 102     @Override
 103     public Optional<DataTreeSnapshot> getSnapshot() {
 104         return Optional.ofNullable(stableSnapshot);
 105     }
 106
 107     /**
 108      * Prototype implementation of {@link SnapshotBackedReadTransaction#close()}.
 109      *
 110      * <p>
 111      * This class is intended to be implemented by Transaction factories responsible for allocation
 112      * of {@link org.opendaylight.mdsal.dom.spi.store.SnapshotBackedReadTransaction} and
 113      * providing underlying logic for applying implementation.
 114      *
 115      * @param <T> identifier type
 116      */
 117     public interface TransactionClosePrototype<T> {
 118         /**
 119          * Called when a transaction is closed. This is not invoked at most once for every transaction.
 120          *
 121          * @param tx Transaction which got closed.
 122          */
 123         void transactionClosed(SnapshotBackedReadTransaction<T> tx);
 124     }
 125 }