dom/mdsal-dom-spi/src/main/java/org/opendaylight/mdsal/dom/spi/store/AbstractSnapshotBackedTransactionChain.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 com.google.common.annotations.Beta;
  11 import com.google.common.base.Preconditions;
  12 import java.util.AbstractMap.SimpleEntry;
  13 import java.util.Map.Entry;
  14 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
  15 import org.opendaylight.mdsal.dom.spi.store.SnapshotBackedReadTransaction.TransactionClosePrototype;
  16 import org.opendaylight.mdsal.dom.spi.store.SnapshotBackedWriteTransaction.TransactionReadyPrototype;
  17 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeModification;
  18 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeSnapshot;
  19 import org.slf4j.Logger;
  20 import org.slf4j.LoggerFactory;
  21
  22 /**
  23  * Abstract implementation of the {@link DOMStoreTransactionChain}
  24  * interface relying on {@link DataTreeSnapshot} supplier
  25  * and backend commit coordinator.
  26  * @param <T> transaction identifier type
  27  */
  28 @Beta
  29 public abstract class AbstractSnapshotBackedTransactionChain<T>
  30         extends TransactionReadyPrototype<T> implements DOMStoreTransactionChain, TransactionClosePrototype<T> {
  31     private abstract static class State {
  32         /**
  33          * Allocate a new snapshot.
  34          *
  35          * @return A new snapshot
  36          */
  37         protected abstract DataTreeSnapshot getSnapshot();
  38     }
  39
  40     private static final class Idle extends State {
  41         private final AbstractSnapshotBackedTransactionChain<?> chain;
  42
  43         Idle(final AbstractSnapshotBackedTransactionChain<?> chain) {
  44             this.chain = Preconditions.checkNotNull(chain);
  45         }
  46
  47         @Override
  48         protected DataTreeSnapshot getSnapshot() {
  49             return chain.takeSnapshot();
  50         }
  51     }
  52
  53     /**
  54      * We have a transaction out there.
  55      */
  56     private static final class Allocated extends State {
  57         private static final AtomicReferenceFieldUpdater<Allocated, DataTreeSnapshot> SNAPSHOT_UPDATER =
  58                 AtomicReferenceFieldUpdater.newUpdater(Allocated.class, DataTreeSnapshot.class, "snapshot");
  59         private final DOMStoreWriteTransaction transaction;
  60         private volatile DataTreeSnapshot snapshot;
  61
  62         Allocated(final DOMStoreWriteTransaction transaction) {
  63             this.transaction = Preconditions.checkNotNull(transaction);
  64         }
  65
  66         public DOMStoreWriteTransaction getTransaction() {
  67             return transaction;
  68         }
  69
  70         @Override
  71         protected DataTreeSnapshot getSnapshot() {
  72             final DataTreeSnapshot ret = snapshot;
  73             Preconditions.checkState(ret != null,
  74                     "Previous transaction %s is not ready yet", transaction.getIdentifier());
  75             return ret;
  76         }
  77
  78         void setSnapshot(final DataTreeSnapshot snapshot) {
  79             final boolean success = SNAPSHOT_UPDATER.compareAndSet(this, null, snapshot);
  80             Preconditions.checkState(success,
  81                     "Transaction %s has already been marked as ready", transaction.getIdentifier());
  82         }
  83     }
  84
  85     /**
  86      * Chain is logically shut down, no further allocation allowed.
  87      */
  88     private static final class Shutdown extends State {
  89         private final String message;
  90
  91         Shutdown(final String message) {
  92             this.message = Preconditions.checkNotNull(message);
  93         }
  94
  95         @Override
  96         protected DataTreeSnapshot getSnapshot() {
  97             throw new IllegalStateException(message);
  98         }
  99     }
 100
 101     @SuppressWarnings("rawtypes")
 102     private static final AtomicReferenceFieldUpdater<AbstractSnapshotBackedTransactionChain, State>
 103         STATE_UPDATER =
 104             AtomicReferenceFieldUpdater.newUpdater(AbstractSnapshotBackedTransactionChain.class,
 105                     State.class, "state");
 106     private static final Logger LOG = LoggerFactory.getLogger(AbstractSnapshotBackedTransactionChain.class);
 107     private static final Shutdown CLOSED = new Shutdown("Transaction chain is closed");
 108     private static final Shutdown FAILED = new Shutdown("Transaction chain has failed");
 109     private final Idle idleState;
 110     private volatile State state;
 111
 112     protected AbstractSnapshotBackedTransactionChain() {
 113         idleState = new Idle(this);
 114         state = idleState;
 115     }
 116
 117     private Entry<State, DataTreeSnapshot> getSnapshot() {
 118         final State localState = state;
 119         return new SimpleEntry<>(localState, localState.getSnapshot());
 120     }
 121
 122     private boolean recordTransaction(final State expected, final DOMStoreWriteTransaction transaction) {
 123         final State real = new Allocated(transaction);
 124         return STATE_UPDATER.compareAndSet(this, expected, real);
 125     }
 126
 127     @Override
 128     public final DOMStoreReadTransaction newReadOnlyTransaction() {
 129         return newReadOnlyTransaction(nextTransactionIdentifier());
 130     }
 131
 132     protected DOMStoreReadTransaction newReadOnlyTransaction(T transactionId) {
 133         final Entry<State, DataTreeSnapshot> entry = getSnapshot();
 134         return SnapshotBackedTransactions.newReadTransaction(transactionId,
 135                 getDebugTransactions(), entry.getValue(), this);
 136     }
 137
 138     @Override
 139     public void transactionClosed(final SnapshotBackedReadTransaction<T> tx) {
 140         // Defaults to no-op
 141     }
 142
 143     @Override
 144     public final DOMStoreReadWriteTransaction newReadWriteTransaction() {
 145         return newReadWriteTransaction(nextTransactionIdentifier());
 146     }
 147
 148     protected DOMStoreReadWriteTransaction newReadWriteTransaction(T transactionId) {
 149         Entry<State, DataTreeSnapshot> entry;
 150         DOMStoreReadWriteTransaction ret;
 151
 152         do {
 153             entry = getSnapshot();
 154             ret = new SnapshotBackedReadWriteTransaction<>(transactionId,
 155                     getDebugTransactions(), entry.getValue(), this);
 156         } while (!recordTransaction(entry.getKey(), ret));
 157
 158         return ret;
 159     }
 160
 161     @Override
 162     public final DOMStoreWriteTransaction newWriteOnlyTransaction() {
 163         return newWriteOnlyTransaction(nextTransactionIdentifier());
 164     }
 165
 166     protected DOMStoreWriteTransaction newWriteOnlyTransaction(T transactionId) {
 167         Entry<State, DataTreeSnapshot> entry;
 168         DOMStoreWriteTransaction ret;
 169
 170         do {
 171             entry = getSnapshot();
 172             ret = new SnapshotBackedWriteTransaction<>(transactionId,
 173                     getDebugTransactions(), entry.getValue(), this);
 174         } while (!recordTransaction(entry.getKey(), ret));
 175
 176         return ret;
 177     }
 178
 179     @Override
 180     protected final void transactionAborted(final SnapshotBackedWriteTransaction<T> tx) {
 181         final State localState = state;
 182         if (localState instanceof Allocated) {
 183             final Allocated allocated = (Allocated)localState;
 184             if (allocated.getTransaction().equals(tx)) {
 185                 final boolean success = STATE_UPDATER.compareAndSet(this, localState, idleState);
 186                 if (!success) {
 187                     LOG.warn("Transaction {} aborted, but chain {} state already transitioned from {} to {}, "
 188                         + "very strange", tx, this, localState, state);
 189                 }
 190             }
 191         }
 192     }
 193
 194     @Override
 195     protected final DOMStoreThreePhaseCommitCohort transactionReady(
 196             final SnapshotBackedWriteTransaction<T> tx,
 197             final DataTreeModification tree,
 198             final Exception readyError) {
 199         final State localState = state;
 200
 201         if (localState instanceof Allocated) {
 202             final Allocated allocated = (Allocated)localState;
 203             final DOMStoreWriteTransaction transaction = allocated.getTransaction();
 204             Preconditions.checkState(tx.equals(transaction),
 205                     "Mis-ordered ready transaction %s last allocated was %s", tx, transaction);
 206             allocated.setSnapshot(tree);
 207         } else {
 208             LOG.debug("Ignoring transaction {} readiness due to state {}", tx, localState);
 209         }
 210
 211         return createCohort(tx, tree, readyError);
 212     }
 213
 214     @Override
 215     public final void close() {
 216         final State localState = state;
 217
 218         do {
 219             Preconditions.checkState(!CLOSED.equals(localState),
 220                     "Transaction chain {} has been closed", this);
 221
 222             if (FAILED.equals(localState)) {
 223                 LOG.debug("Ignoring user close in failed state");
 224                 return;
 225             }
 226         } while (!STATE_UPDATER.compareAndSet(this, localState, CLOSED));
 227     }
 228
 229     /**
 230      * Notify the base logic that a previously-submitted transaction has been committed successfully.
 231      * @param transaction Transaction which completed successfully.
 232      */
 233     protected final void onTransactionCommited(final SnapshotBackedWriteTransaction<T> transaction) {
 234         // If the committed transaction was the one we allocated last,
 235         // we clear it and the ready snapshot, so the next transaction
 236         // allocated refers to the data tree directly.
 237         final State localState = state;
 238
 239         if (!(localState instanceof Allocated)) {
 240             // This can legally happen if the chain is shut down before the transaction was committed
 241             // by the backend.
 242             LOG.debug("Ignoring successful transaction {} in state {}", transaction, localState);
 243             return;
 244         }
 245
 246         final Allocated allocated = (Allocated)localState;
 247         final DOMStoreWriteTransaction tx = allocated.getTransaction();
 248         if (!tx.equals(transaction)) {
 249             LOG.debug("Ignoring non-latest successful transaction {} in state {}", transaction, allocated);
 250             return;
 251         }
 252
 253         if (!STATE_UPDATER.compareAndSet(this, localState, idleState)) {
 254             LOG.debug("Transaction chain {} has already transitioned from "
 255                     + "{} to {}, not making it idle", this, localState, state);
 256         }
 257     }
 258
 259     /**
 260      * Notify the base logic that a previously-submitted transaction has failed.
 261      * @param transaction Transaction which failed.
 262      * @param cause Failure cause
 263      */
 264     protected final void onTransactionFailed(
 265             final SnapshotBackedWriteTransaction<T> transaction, final Throwable cause) {
 266         LOG.debug("Transaction chain {} failed on transaction {}", this, transaction, cause);
 267         state = FAILED;
 268     }
 269
 270     /**
 271      * Return the next transaction identifier.
 272      *
 273      * @return transaction identifier.
 274      */
 275     protected abstract T nextTransactionIdentifier();
 276
 277     /**
 278      * Inquire as to whether transactions should record their allocation context.
 279      * @return True if allocation context should be recorded.
 280      */
 281     protected abstract boolean getDebugTransactions();
 282
 283     /**
 284      * Take a fresh {@link DataTreeSnapshot} from the backend.
 285      * @return A new snapshot.
 286      */
 287     protected abstract DataTreeSnapshot takeSnapshot();
 288
 289     /**
 290      * Create a cohort for driving the transaction through the commit process.
 291      * @param transaction Transaction handle
 292      * @param modification {@link DataTreeModification} which needs to be applied to the backend
 293      * @param operationError Any previous error that could be reported through three phase commit
 294      * @return A {@link DOMStoreThreePhaseCommitCohort} cohort.
 295      */
 296     protected abstract DOMStoreThreePhaseCommitCohort createCohort(SnapshotBackedWriteTransaction<T> transaction,
 297                                                                    DataTreeModification modification,
 298                                                                    Exception operationError);
 299 }