opendaylight/md-sal/sal-dom-broker/src/main/java/org/opendaylight/controller/md/sal/dom/broker/impl/PingPongTransactionChain.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.md.sal.dom.broker.impl;
   9
  10 import com.google.common.base.Optional;
  11 import com.google.common.base.Preconditions;
  12 import com.google.common.util.concurrent.CheckedFuture;
  13 import com.google.common.util.concurrent.FutureCallback;
  14 import com.google.common.util.concurrent.Futures;
  15 import com.google.common.util.concurrent.ListenableFuture;
  16 import javax.annotation.concurrent.GuardedBy;
  17 import org.opendaylight.controller.md.sal.common.api.TransactionStatus;
  18 import org.opendaylight.controller.md.sal.common.api.data.AsyncTransaction;
  19 import org.opendaylight.controller.md.sal.common.api.data.LogicalDatastoreType;
  20 import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
  21 import org.opendaylight.controller.md.sal.common.api.data.TransactionChain;
  22 import org.opendaylight.controller.md.sal.common.api.data.TransactionChainListener;
  23 import org.opendaylight.controller.md.sal.common.api.data.TransactionCommitFailedException;
  24 import org.opendaylight.controller.md.sal.dom.api.DOMDataBroker;
  25 import org.opendaylight.controller.md.sal.dom.api.DOMDataReadOnlyTransaction;
  26 import org.opendaylight.controller.md.sal.dom.api.DOMDataReadWriteTransaction;
  27 import org.opendaylight.controller.md.sal.dom.api.DOMDataWriteTransaction;
  28 import org.opendaylight.controller.md.sal.dom.api.DOMTransactionChain;
  29 import org.opendaylight.controller.md.sal.dom.spi.ForwardingDOMDataReadWriteTransaction;
  30 import org.opendaylight.yangtools.yang.common.RpcResult;
  31 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  32 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  33 import org.slf4j.Logger;
  34 import org.slf4j.LoggerFactory;
  35
  36 /**
  37  * An implementation of {@link DOMTransactionChain}, which has a very specific
  38  * behavior, which some users may find surprising. If keeps the general
  39  * intent of the contract, but it makes sure there are never more than two
  40  * transactions allocated at any given time: one of them is being committed,
  41  * and while that is happening, the other one acts as the scratch pad. Once
  42  * the committing transaction completes successfully, the scratch transaction
  43  * is enqueued as soon as it is ready.
  44  *
  45  * This mode of operation means that there is no inherent isolation between
  46  * the front-end transactions and transactions cannot be reasonably cancelled.
  47  *
  48  * It furthermore means that the transactions returned by {@link #newReadOnlyTransaction()}
  49  * counts as an outstanding transaction and the user may not allocate multiple
  50  * read-only transactions at the same time.
  51  */
  52 public final class PingPongTransactionChain implements DOMTransactionChain {
  53     private static final Logger LOG = LoggerFactory.getLogger(PingPongTransactionChain.class);
  54     private final DOMTransactionChain delegate;
  55
  56     @GuardedBy("this")
  57     private PingPongTransaction bufferTransaction;
  58     @GuardedBy("this")
  59     private PingPongTransaction inflightTransaction;
  60     @GuardedBy("this")
  61     private boolean haveLocked;
  62     @GuardedBy("this")
  63     private boolean failed;
  64
  65     PingPongTransactionChain(final DOMDataBroker broker, final TransactionChainListener listener) {
  66         this.delegate = broker.createTransactionChain(new TransactionChainListener() {
  67             @Override
  68             public void onTransactionChainFailed(final TransactionChain<?, ?> chain, final AsyncTransaction<?, ?> transaction, final Throwable cause) {
  69                 LOG.debug("Delegate chain {} reported failure in {}", chain, transaction, cause);
  70
  71                 final DOMDataReadWriteTransaction frontend;
  72                 if (inflightTransaction == null) {
  73                     LOG.warn("Transaction chain {} failed with no pending transactions", chain);
  74                     frontend = null;
  75                 } else {
  76                     frontend = inflightTransaction.getFrontendTransaction();
  77                 }
  78
  79                 listener.onTransactionChainFailed(PingPongTransactionChain.this, frontend , cause);
  80                 delegateFailed();
  81             }
  82
  83             @Override
  84             public void onTransactionChainSuccessful(final TransactionChain<?, ?> chain) {
  85                 listener.onTransactionChainSuccessful(PingPongTransactionChain.this);
  86             }
  87         });
  88     }
  89
  90     private synchronized void delegateFailed() {
  91         failed = true;
  92         if (!haveLocked) {
  93             processBuffer();
  94         }
  95     }
  96
  97     private synchronized PingPongTransaction allocateTransaction() {
  98         Preconditions.checkState(!haveLocked, "Attempted to start a transaction while a previous one is still outstanding");
  99         Preconditions.checkState(!failed, "Attempted to use a failed chain");
 100
 101         if (bufferTransaction == null) {
 102             bufferTransaction = new PingPongTransaction(delegate.newReadWriteTransaction());
 103         }
 104
 105         haveLocked = true;
 106         return bufferTransaction;
 107     }
 108
 109     @GuardedBy("this")
 110     private void processBuffer() {
 111         final PingPongTransaction tx = bufferTransaction;
 112
 113         if (tx != null) {
 114             if (failed) {
 115                 LOG.debug("Cancelling transaction {}", tx);
 116                 tx.getTransaction().cancel();
 117                 bufferTransaction = null;
 118                 return;
 119             }
 120
 121             LOG.debug("Submitting transaction {}", tx);
 122             final CheckedFuture<Void, ?> f = tx.getTransaction().submit();
 123             bufferTransaction = null;
 124             inflightTransaction = tx;
 125
 126             Futures.addCallback(f, new FutureCallback<Void>() {
 127                 @Override
 128                 public void onSuccess(final Void result) {
 129                     transactionSuccessful(tx, result);
 130                 }
 131
 132                 @Override
 133                 public void onFailure(final Throwable t) {
 134                     transactionFailed(tx, t);
 135                 }
 136             });
 137         }
 138     }
 139
 140     private void transactionSuccessful(final PingPongTransaction tx, final Void result) {
 141         LOG.debug("Transaction {} completed successfully", tx);
 142
 143         synchronized (this) {
 144             Preconditions.checkState(inflightTransaction == tx, "Successful transaction %s while %s was submitted", tx, inflightTransaction);
 145             inflightTransaction = null;
 146
 147             if (!haveLocked) {
 148                 processBuffer();
 149             }
 150         }
 151
 152         // Can run unsynchronized
 153         tx.onSuccess(result);
 154     }
 155
 156     private void transactionFailed(final PingPongTransaction tx, final Throwable t) {
 157         LOG.debug("Transaction {} failed", tx, t);
 158
 159         synchronized (this) {
 160             Preconditions.checkState(inflightTransaction == tx, "Failed transaction %s while %s was submitted", tx, inflightTransaction);
 161             inflightTransaction = null;
 162         }
 163
 164         tx.onFailure(t);
 165     }
 166
 167     private synchronized void readyTransaction(final PingPongTransaction tx) {
 168         Preconditions.checkState(haveLocked, "Attempted to submit transaction while it is not outstanding");
 169         Preconditions.checkState(bufferTransaction == tx, "Attempted to submit transaction %s while we have %s", tx, bufferTransaction);
 170
 171         haveLocked = false;
 172         LOG.debug("Transaction {} unlocked", bufferTransaction);
 173
 174         if (inflightTransaction == null) {
 175             processBuffer();
 176         }
 177     }
 178
 179     @Override
 180     public synchronized void close() {
 181         Preconditions.checkState(!haveLocked, "Attempted to close chain while a transaction is outstanding");
 182         processBuffer();
 183         delegate.close();
 184     }
 185
 186     @Override
 187     public DOMDataReadOnlyTransaction newReadOnlyTransaction() {
 188         final PingPongTransaction tx = allocateTransaction();
 189
 190         return new DOMDataReadOnlyTransaction() {
 191             @Override
 192             public CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> read(final LogicalDatastoreType store,
 193                     final YangInstanceIdentifier path) {
 194                 return tx.getTransaction().read(store, path);
 195             }
 196
 197             @Override
 198             public CheckedFuture<Boolean, ReadFailedException> exists(final LogicalDatastoreType store,
 199                     final YangInstanceIdentifier path) {
 200                 return tx.getTransaction().exists(store, path);
 201             }
 202
 203             @Override
 204             public Object getIdentifier() {
 205                 return tx.getTransaction().getIdentifier();
 206             }
 207
 208             @Override
 209             public void close() {
 210                 readyTransaction(tx);
 211             }
 212         };
 213     }
 214
 215     @Override
 216     public DOMDataReadWriteTransaction newReadWriteTransaction() {
 217         final PingPongTransaction tx = allocateTransaction();
 218         final DOMDataReadWriteTransaction ret = new ForwardingDOMDataReadWriteTransaction() {
 219             @Override
 220             protected DOMDataReadWriteTransaction delegate() {
 221                 return tx.getTransaction();
 222             }
 223
 224             @Override
 225             public CheckedFuture<Void, TransactionCommitFailedException> submit() {
 226                 readyTransaction(tx);
 227                 return tx.getSubmitFuture();
 228             }
 229
 230             @Override
 231             public ListenableFuture<RpcResult<TransactionStatus>> commit() {
 232                 readyTransaction(tx);
 233                 return tx.getCommitFuture();
 234             }
 235
 236             @Override
 237             public boolean cancel() {
 238                 throw new UnsupportedOperationException("Transaction cancellation is not supported");
 239             }
 240         };
 241
 242         tx.recordFrontendTransaction(ret);
 243         return ret;
 244     }
 245
 246     @Override
 247     public DOMDataWriteTransaction newWriteOnlyTransaction() {
 248         return newReadWriteTransaction();
 249     }
 250 }