Split TransactionChainProxy.combineWithPriorReadOnlyTxFutures()
[controller.git] / opendaylight / md-sal / sal-distributed-datastore / src / main / java / org / opendaylight / controller / cluster / datastore / TransactionChainProxy.java
1 /*
2  * Copyright (c) 2015 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.cluster.datastore;
9
10 import static com.google.common.base.Preconditions.checkState;
11 import static java.util.Objects.requireNonNull;
12
13 import akka.actor.ActorSelection;
14 import akka.dispatch.Futures;
15 import akka.dispatch.OnComplete;
16 import java.util.ArrayList;
17 import java.util.Collection;
18 import java.util.List;
19 import java.util.Map.Entry;
20 import java.util.concurrent.ConcurrentHashMap;
21 import java.util.concurrent.ConcurrentMap;
22 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
23 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
24 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
25 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
26 import org.opendaylight.controller.cluster.datastore.messages.PrimaryShardInfo;
27 import org.opendaylight.mdsal.dom.api.DOMTransactionChainClosedException;
28 import org.opendaylight.mdsal.dom.spi.store.DOMStoreReadTransaction;
29 import org.opendaylight.mdsal.dom.spi.store.DOMStoreReadWriteTransaction;
30 import org.opendaylight.mdsal.dom.spi.store.DOMStoreTransactionChain;
31 import org.opendaylight.mdsal.dom.spi.store.DOMStoreWriteTransaction;
32 import org.opendaylight.yangtools.yang.data.api.schema.tree.ReadOnlyDataTree;
33 import org.slf4j.Logger;
34 import org.slf4j.LoggerFactory;
35 import scala.concurrent.Future;
36 import scala.concurrent.Promise;
37
38 /**
39  * A chain of {@link TransactionProxy}s. It allows a single open transaction to be open
40  * at a time. For remote transactions, it also tracks the outstanding readiness requests
41  * towards the shard and unblocks operations only after all have completed.
42  */
43 final class TransactionChainProxy extends AbstractTransactionContextFactory<LocalTransactionChain>
44         implements DOMStoreTransactionChain {
45     private abstract static class State {
46         /**
47          * Check if it is okay to allocate a new transaction.
48          * @throws IllegalStateException if a transaction may not be allocated.
49          */
50         abstract void checkReady();
51
52         /**
53          * Return the future which needs to be waited for before shard information
54          * is returned (which unblocks remote transactions).
55          * @return Future to wait for, or null of no wait is necessary
56          */
57         abstract Future<?> previousFuture();
58     }
59
60     private abstract static class Pending extends State {
61         private final TransactionIdentifier transaction;
62         private final Future<?> previousFuture;
63
64         Pending(final TransactionIdentifier transaction, final Future<?> previousFuture) {
65             this.previousFuture = previousFuture;
66             this.transaction = requireNonNull(transaction);
67         }
68
69         @Override
70         final Future<?> previousFuture() {
71             return previousFuture;
72         }
73
74         final TransactionIdentifier getIdentifier() {
75             return transaction;
76         }
77     }
78
79     private static final class Allocated extends Pending {
80         Allocated(final TransactionIdentifier transaction, final Future<?> previousFuture) {
81             super(transaction, previousFuture);
82         }
83
84         @Override
85         void checkReady() {
86             throw new IllegalStateException(String.format("Previous transaction %s is not ready yet", getIdentifier()));
87         }
88     }
89
90     private static final class Submitted extends Pending {
91         Submitted(final TransactionIdentifier transaction, final Future<?> previousFuture) {
92             super(transaction, previousFuture);
93         }
94
95         @Override
96         void checkReady() {
97             // Okay to allocate
98         }
99     }
100
101     private abstract static class DefaultState extends State {
102         @Override
103         final Future<?> previousFuture() {
104             return null;
105         }
106     }
107
108     private static final State IDLE_STATE = new DefaultState() {
109         @Override
110         void checkReady() {
111             // Okay to allocate
112         }
113     };
114
115     private static final State CLOSED_STATE = new DefaultState() {
116         @Override
117         void checkReady() {
118             throw new DOMTransactionChainClosedException("Transaction chain has been closed");
119         }
120     };
121
122     private static final Logger LOG = LoggerFactory.getLogger(TransactionChainProxy.class);
123     private static final AtomicReferenceFieldUpdater<TransactionChainProxy, State> STATE_UPDATER =
124             AtomicReferenceFieldUpdater.newUpdater(TransactionChainProxy.class, State.class, "currentState");
125
126     private final TransactionContextFactory parent;
127     private volatile State currentState = IDLE_STATE;
128
129     /**
130      * This map holds Promise instances for each read-only tx. It is used to maintain ordering of tx creates
131      * wrt to read-only tx's between this class and a LocalTransactionChain since they're bridged by
132      * asynchronous futures. Otherwise, in the following scenario, eg:
133      * <p/>
134      *   1) Create write tx1 on chain
135      *   2) do write and submit
136      *   3) Create read-only tx2 on chain and issue read
137      *   4) Create write tx3 on chain, do write but do not submit
138      * <p/>
139      * if the sequence/timing is right, tx3 may create its local tx on the LocalTransactionChain before tx2,
140      * which results in tx2 failing b/c tx3 isn't ready yet. So maintaining ordering prevents this issue
141      * (see Bug 4774).
142      * <p/>
143      * A Promise is added via newReadOnlyTransaction. When the parent class completes the primary shard
144      * lookup and creates the TransactionContext (either success or failure), onTransactionContextCreated is
145      * called which completes the Promise. A write tx that is created prior to completion will wait on the
146      * Promise's Future via findPrimaryShard.
147      */
148     private final ConcurrentMap<TransactionIdentifier, Promise<Object>> priorReadOnlyTxPromises =
149             new ConcurrentHashMap<>();
150
151     TransactionChainProxy(final TransactionContextFactory parent, final LocalHistoryIdentifier historyId) {
152         super(parent.getActorUtils(), historyId);
153         this.parent = parent;
154     }
155
156     @Override
157     public DOMStoreReadTransaction newReadOnlyTransaction() {
158         currentState.checkReady();
159         TransactionProxy transactionProxy = new TransactionProxy(this, TransactionType.READ_ONLY);
160         priorReadOnlyTxPromises.put(transactionProxy.getIdentifier(), Futures.<Object>promise());
161         return transactionProxy;
162     }
163
164     @Override
165     public DOMStoreReadWriteTransaction newReadWriteTransaction() {
166         getActorUtils().acquireTxCreationPermit();
167         return allocateWriteTransaction(TransactionType.READ_WRITE);
168     }
169
170     @Override
171     public DOMStoreWriteTransaction newWriteOnlyTransaction() {
172         getActorUtils().acquireTxCreationPermit();
173         return allocateWriteTransaction(TransactionType.WRITE_ONLY);
174     }
175
176     @Override
177     public void close() {
178         currentState = CLOSED_STATE;
179
180         // Send a close transaction chain request to each and every shard
181
182         getActorUtils().broadcast(version -> new CloseTransactionChain(getHistoryId(), version).toSerializable(),
183                 CloseTransactionChain.class);
184     }
185
186     private TransactionProxy allocateWriteTransaction(final TransactionType type) {
187         State localState = currentState;
188         localState.checkReady();
189
190         final TransactionProxy ret = new TransactionProxy(this, type);
191         currentState = new Allocated(ret.getIdentifier(), localState.previousFuture());
192         return ret;
193     }
194
195     @Override
196     protected LocalTransactionChain factoryForShard(final String shardName, final ActorSelection shardLeader,
197             final ReadOnlyDataTree dataTree) {
198         final LocalTransactionChain ret = new LocalTransactionChain(this, shardLeader, dataTree);
199         LOG.debug("Allocated transaction chain {} for shard {} leader {}", ret, shardName, shardLeader);
200         return ret;
201     }
202
203     /**
204      * This method is overridden to ensure the previous Tx's ready operations complete
205      * before we initiate the next Tx in the chain to avoid creation failures if the
206      * previous Tx's ready operations haven't completed yet.
207      */
208     @SuppressWarnings({ "unchecked", "rawtypes" })
209     @Override
210     protected Future<PrimaryShardInfo> findPrimaryShard(final String shardName, final TransactionIdentifier txId) {
211         // Read current state atomically
212         final State localState = currentState;
213
214         // There are no outstanding futures, shortcut
215         Future<?> previous = localState.previousFuture();
216         if (previous == null) {
217             return combineFutureWithPossiblePriorReadOnlyTxFutures(parent.findPrimaryShard(shardName, txId), txId);
218         }
219
220         final String previousTransactionId;
221
222         if (localState instanceof Pending) {
223             previousTransactionId = ((Pending) localState).getIdentifier().toString();
224             LOG.debug("Tx: {} - waiting for ready futures with pending Tx {}", txId, previousTransactionId);
225         } else {
226             previousTransactionId = "";
227             LOG.debug("Waiting for ready futures on chain {}", getHistoryId());
228         }
229
230         previous = combineFutureWithPossiblePriorReadOnlyTxFutures(previous, txId);
231
232         // Add a callback for completion of the combined Futures.
233         final Promise<PrimaryShardInfo> returnPromise = Futures.promise();
234
235         final OnComplete onComplete = new OnComplete() {
236             @Override
237             public void onComplete(final Throwable failure, final Object notUsed) {
238                 if (failure != null) {
239                     // A Ready Future failed so fail the returned Promise.
240                     LOG.error("Tx: {} - ready future failed for previous Tx {}", txId, previousTransactionId);
241                     returnPromise.failure(failure);
242                 } else {
243                     LOG.debug("Tx: {} - previous Tx {} readied - proceeding to FindPrimaryShard",
244                             txId, previousTransactionId);
245
246                     // Send the FindPrimaryShard message and use the resulting Future to complete the
247                     // returned Promise.
248                     returnPromise.completeWith(parent.findPrimaryShard(shardName, txId));
249                 }
250             }
251         };
252
253         previous.onComplete(onComplete, getActorUtils().getClientDispatcher());
254         return returnPromise.future();
255     }
256
257     private <T> Future<T> combineFutureWithPossiblePriorReadOnlyTxFutures(final Future<T> future,
258             final TransactionIdentifier txId) {
259         return priorReadOnlyTxPromises.isEmpty() || priorReadOnlyTxPromises.containsKey(txId) ? future
260                 // Tough luck, we need do some work
261                 : combineWithPriorReadOnlyTxFutures(future, txId);
262     }
263
264     // Split out of the common path
265     private <T> Future<T> combineWithPriorReadOnlyTxFutures(final Future<T> future, final TransactionIdentifier txId) {
266         // Take a stable snapshot, and check if we raced
267         final List<Entry<TransactionIdentifier, Promise<Object>>> priorReadOnlyTxPromiseEntries =
268                 new ArrayList<>(priorReadOnlyTxPromises.entrySet());
269         if (priorReadOnlyTxPromiseEntries.isEmpty()) {
270             return future;
271         }
272
273         final List<Future<Object>> priorReadOnlyTxFutures = new ArrayList<>(priorReadOnlyTxPromiseEntries.size());
274         for (Entry<TransactionIdentifier, Promise<Object>> entry: priorReadOnlyTxPromiseEntries) {
275             LOG.debug("Tx: {} - waiting on future for prior read-only Tx {}", txId, entry.getKey());
276             priorReadOnlyTxFutures.add(entry.getValue().future());
277         }
278
279         final Future<Iterable<Object>> combinedFutures = Futures.sequence(priorReadOnlyTxFutures,
280             getActorUtils().getClientDispatcher());
281
282         final Promise<T> returnPromise = Futures.promise();
283         final OnComplete<Iterable<Object>> onComplete = new OnComplete<>() {
284             @Override
285             public void onComplete(final Throwable failure, final Iterable<Object> notUsed) {
286                 LOG.debug("Tx: {} - prior read-only Tx futures complete", txId);
287
288                 // Complete the returned Promise with the original Future.
289                 returnPromise.completeWith(future);
290             }
291         };
292
293         combinedFutures.onComplete(onComplete, getActorUtils().getClientDispatcher());
294         return returnPromise.future();
295     }
296
297     @Override
298     protected <T> void onTransactionReady(final TransactionIdentifier transaction,
299             final Collection<Future<T>> cohortFutures) {
300         final State localState = currentState;
301         checkState(localState instanceof Allocated, "Readying transaction %s while state is %s", transaction,
302             localState);
303         final TransactionIdentifier currentTx = ((Allocated)localState).getIdentifier();
304         checkState(transaction.equals(currentTx), "Readying transaction %s while %s is allocated", transaction,
305             currentTx);
306
307         // Transaction ready and we are not waiting for futures -- go to idle
308         if (cohortFutures.isEmpty()) {
309             currentState = IDLE_STATE;
310             return;
311         }
312
313         // Combine the ready Futures into 1
314         final Future<Iterable<T>> combined = Futures.sequence(cohortFutures, getActorUtils().getClientDispatcher());
315
316         // Record the we have outstanding futures
317         final State newState = new Submitted(transaction, combined);
318         currentState = newState;
319
320         // Attach a completion reset, but only if we do not allocate a transaction
321         // in-between
322         combined.onComplete(new OnComplete<Iterable<T>>() {
323             @Override
324             public void onComplete(final Throwable arg0, final Iterable<T> arg1) {
325                 STATE_UPDATER.compareAndSet(TransactionChainProxy.this, newState, IDLE_STATE);
326             }
327         }, getActorUtils().getClientDispatcher());
328     }
329
330     @Override
331     protected void onTransactionContextCreated(final TransactionIdentifier transactionId) {
332         Promise<Object> promise = priorReadOnlyTxPromises.remove(transactionId);
333         if (promise != null) {
334             promise.success(null);
335         }
336     }
337 }

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