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 static com.google.common.base.Preconditions.checkState;
  11 import static java.util.Objects.requireNonNull;
  12
  13 import com.google.common.annotations.Beta;
  14 import java.util.AbstractMap.SimpleEntry;
  15 import java.util.Map.Entry;
  16 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
  17 import org.opendaylight.mdsal.dom.spi.store.SnapshotBackedReadTransaction.TransactionClosePrototype;
  18 import org.opendaylight.mdsal.dom.spi.store.SnapshotBackedWriteTransaction.TransactionReadyPrototype;
  19 import org.opendaylight.yangtools.yang.data.tree.api.DataTreeModification;
  20 import org.opendaylight.yangtools.yang.data.tree.api.DataTreeSnapshot;
  21 import org.slf4j.Logger;
  22 import org.slf4j.LoggerFactory;
  23
  24 /**
  25  * Abstract implementation of the {@link DOMStoreTransactionChain} interface relying on {@link DataTreeSnapshot}
  26  * supplier and backend commit coordinator.
  27  *
  28  * @param <T> transaction identifier type
  29  */
  30 @Beta
  31 public abstract class AbstractSnapshotBackedTransactionChain<T>
  32         extends TransactionReadyPrototype<T> implements DOMStoreTransactionChain, TransactionClosePrototype<T> {
  33     private abstract static sealed class State {
  34         /**
  35          * Allocate a new snapshot.
  36          *
  37          * @return A new snapshot
  38          */
  39         abstract DataTreeSnapshot getSnapshot();
  40     }
  41
  42     private static final class Idle extends State {
  43         private final AbstractSnapshotBackedTransactionChain<?> chain;
  44
  45         Idle(final AbstractSnapshotBackedTransactionChain<?> chain) {
  46             this.chain = requireNonNull(chain);
  47         }
  48
  49         @Override
  50         DataTreeSnapshot getSnapshot() {
  51             return chain.takeSnapshot();
  52         }
  53     }
  54
  55     /**
  56      * We have a transaction out there.
  57      */
  58     private static final class Allocated extends State {
  59         private static final AtomicReferenceFieldUpdater<Allocated, DataTreeSnapshot> SNAPSHOT_UPDATER =
  60                 AtomicReferenceFieldUpdater.newUpdater(Allocated.class, DataTreeSnapshot.class, "snapshot");
  61         private final DOMStoreWriteTransaction transaction;
  62         private volatile DataTreeSnapshot snapshot;
  63
  64         Allocated(final DOMStoreWriteTransaction transaction) {
  65             this.transaction = requireNonNull(transaction);
  66         }
  67
  68         DOMStoreWriteTransaction getTransaction() {
  69             return transaction;
  70         }
  71
  72         @Override
  73         DataTreeSnapshot getSnapshot() {
  74             final DataTreeSnapshot ret = snapshot;
  75             checkState(ret != null, "Previous transaction %s is not ready yet", transaction.getIdentifier());
  76             return ret;
  77         }
  78
  79         void setSnapshot(final DataTreeSnapshot snapshot) {
  80             final boolean success = SNAPSHOT_UPDATER.compareAndSet(this, null, snapshot);
  81             checkState(success, "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 = requireNonNull(message);
  93         }
  94
  95         @Override
  96         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
 110     private final Idle idleState;
 111     private volatile State state;
 112
 113     protected AbstractSnapshotBackedTransactionChain() {
 114         state = idleState = new Idle(this);
 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(final 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(final 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(final T transactionId) {
 167         Entry<State, DataTreeSnapshot> entry;
 168         DOMStoreWriteTransaction ret;
 169
 170         do {
 171             entry = getSnapshot();
 172             ret = new SnapshotBackedWriteTransaction<>(transactionId, getDebugTransactions(), entry.getValue(), this);
 173         } while (!recordTransaction(entry.getKey(), ret));
 174
 175         return ret;
 176     }
 177
 178     @Override
 179     protected final void transactionAborted(final SnapshotBackedWriteTransaction<T> tx) {
 180         final State localState = state;
 181         if (localState instanceof Allocated allocated) {
 182             if (allocated.getTransaction().equals(tx)) {
 183                 final boolean success = STATE_UPDATER.compareAndSet(this, localState, idleState);
 184                 if (!success) {
 185                     LOG.warn("Transaction {} aborted, but chain {} state already transitioned from {} to {}, "
 186                         + "very strange", tx, this, localState, state);
 187                 }
 188             }
 189         }
 190     }
 191
 192     @Override
 193     protected final DOMStoreThreePhaseCommitCohort transactionReady(final SnapshotBackedWriteTransaction<T> tx,
 194             final DataTreeModification tree,
 195             final Exception readyError) {
 196         final State localState = state;
 197
 198         if (localState instanceof Allocated allocated) {
 199             final DOMStoreWriteTransaction transaction = allocated.getTransaction();
 200             checkState(tx.equals(transaction), "Mis-ordered ready transaction %s last allocated was %s", tx,
 201                 transaction);
 202             allocated.setSnapshot(tree);
 203         } else {
 204             LOG.debug("Ignoring transaction {} readiness due to state {}", tx, localState);
 205         }
 206
 207         return createCohort(tx, tree, readyError);
 208     }
 209
 210     @Override
 211     public final void close() {
 212         final State localState = state;
 213
 214         do {
 215             checkState(!CLOSED.equals(localState), "Transaction chain %s has been closed", this);
 216
 217             if (FAILED.equals(localState)) {
 218                 LOG.debug("Ignoring user close in failed state");
 219                 return;
 220             }
 221         } while (!STATE_UPDATER.compareAndSet(this, localState, CLOSED));
 222     }
 223
 224     /**
 225      * Notify the base logic that a previously-submitted transaction has been committed successfully.
 226      * @param transaction Transaction which completed successfully.
 227      */
 228     protected final void onTransactionCommited(final SnapshotBackedWriteTransaction<T> transaction) {
 229         // If the committed transaction was the one we allocated last,
 230         // we clear it and the ready snapshot, so the next transaction
 231         // allocated refers to the data tree directly.
 232         final State localState = state;
 233
 234         if (!(localState instanceof Allocated allocated)) {
 235             // This can legally happen if the chain is shut down before the transaction was committed
 236             // by the backend.
 237             LOG.debug("Ignoring successful transaction {} in state {}", transaction, localState);
 238             return;
 239         }
 240
 241         final DOMStoreWriteTransaction tx = allocated.getTransaction();
 242         if (!tx.equals(transaction)) {
 243             LOG.debug("Ignoring non-latest successful transaction {} in state {}", transaction, allocated);
 244             return;
 245         }
 246
 247         if (!STATE_UPDATER.compareAndSet(this, localState, idleState)) {
 248             LOG.debug("Transaction chain {} has already transitioned from {} to {}, not making it idle", this,
 249                 localState, state);
 250         }
 251     }
 252
 253     /**
 254      * Notify the base logic that a previously-submitted transaction has failed.
 255      * @param transaction Transaction which failed.
 256      * @param cause Failure cause
 257      */
 258     protected final void onTransactionFailed(
 259             final SnapshotBackedWriteTransaction<T> transaction, final Throwable cause) {
 260         LOG.debug("Transaction chain {} failed on transaction {}", this, transaction, cause);
 261         state = FAILED;
 262     }
 263
 264     /**
 265      * Return the next transaction identifier.
 266      *
 267      * @return transaction identifier.
 268      */
 269     protected abstract T nextTransactionIdentifier();
 270
 271     /**
 272      * Inquire as to whether transactions should record their allocation context.
 273      * @return True if allocation context should be recorded.
 274      */
 275     protected abstract boolean getDebugTransactions();
 276
 277     /**
 278      * Take a fresh {@link DataTreeSnapshot} from the backend.
 279      * @return A new snapshot.
 280      */
 281     protected abstract DataTreeSnapshot takeSnapshot();
 282
 283     /**
 284      * Create a cohort for driving the transaction through the commit process.
 285      * @param transaction Transaction handle
 286      * @param modification {@link DataTreeModification} which needs to be applied to the backend
 287      * @param operationError Any previous error that could be reported through three phase commit
 288      * @return A {@link DOMStoreThreePhaseCommitCohort} cohort.
 289      */
 290     protected abstract DOMStoreThreePhaseCommitCohort createCohort(SnapshotBackedWriteTransaction<T> transaction,
 291                                                                    DataTreeModification modification,
 292                                                                    Exception operationError);
 293 }