2 * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
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
8 package org.opendaylight.mdsal.binding.api;
10 import com.google.common.util.concurrent.FluentFuture;
11 import edu.umd.cs.findbugs.annotations.CheckReturnValue;
12 import org.eclipse.jdt.annotation.NonNull;
13 import org.opendaylight.mdsal.common.api.CommitInfo;
14 import org.opendaylight.mdsal.common.api.DataValidationFailedException;
15 import org.opendaylight.mdsal.common.api.OptimisticLockFailedException;
16 import org.opendaylight.mdsal.common.api.TransactionCommitFailedException;
19 * A transaction that provides mutation capabilities on a data tree.
22 * Initial state of write transaction is a stable snapshot of the current data tree. The state is captured when
23 * the transaction is created and its state and underlying data tree are not affected by other concurrently running
27 * Write transactions are isolated from other concurrent write transactions. All writes are local to the transaction
28 * and represent only a proposal of state change for the data tree and it is not visible to any other concurrently
29 * running transaction.
32 * Applications make changes to the local data tree in the transaction by via the <b>put</b>, <b>merge</b>,
33 * and <b>delete</b> operations.
35 * <h2>Put operation</h2>
36 * Stores a piece of data at a specified path. This acts as an add / replace operation, which is to say that whole
37 * subtree will be replaced by the specified data.
40 * Performing the following put operations:
43 * 1) container { list [ a ] }
44 * 2) container { list [ b ] }
46 * will result in the following data being present:
49 * container { list [ b ] }
51 * <h2>Merge operation</h2>
52 * Merges a piece of data with the existing data at a specified path. Any pre-existing data which is not explicitly
53 * overwritten will be preserved. This means that if you store a container, its child lists will be merged.
56 * Performing the following merge operations:
59 * 1) container { list [ a ] }
60 * 2) container { list [ b ] }
62 * will result in the following data being present:
65 * container { list [ a, b ] }
67 * This also means that storing the container will preserve any augmentations which have been attached to it.
69 * <h2>Delete operation</h2>
70 * Removes a piece of data from a specified path.
73 * After applying changes to the local data tree, applications publish the changes proposed in the transaction
74 * by calling {@link #commit} on the transaction. This seals the transaction (preventing any further writes using this
75 * transaction) and commits it to be processed and applied to global conceptual data tree.
78 * The transaction commit may fail due to a concurrent transaction modifying and committing data in an incompatible way.
79 * See {@link #commit} for more concrete commit failure examples.
82 * <b>Implementation Note:</b> This interface is not intended to be implemented by users of MD-SAL, but only to be
85 public interface WriteTransaction extends Transaction, WriteOperations {
87 * Cancels the transaction. Transactions can only be cancelled if it was not yet committed.
88 * Invoking cancel() on failed or already canceled will have no effect, and transaction is considered cancelled.
89 * Invoking cancel() on finished transaction (future returned by {@link #commit()} already successfully completed)
90 * will always fail (return false).
92 * @return {@code false} if the task could not be cancelled, typically because it has already completed normally;
93 * {@code true} otherwise
98 * Commits this transaction to be asynchronously applied to update the logical data tree. The returned
99 * {@link FluentFuture} conveys the result of applying the data changes.
102 * This call logically seals the transaction, which prevents the client from further changing the data tree using
103 * this transaction. Any subsequent calls to <code>put(LogicalDatastoreType, Path, Object)</code>,
104 * <code>merge(LogicalDatastoreType, Path, Object)</code>, <code>delete(LogicalDatastoreType, Path)</code> will fail
105 * with {@link IllegalStateException}. The transaction is marked as committed and enqueued into the data store
106 * back-end for processing.
109 * Whether or not the commit is successful is determined by versioning of the data tree and validation of registered
110 * commit participants if the transaction changes the data tree.
113 * The effects of a successful commit of data depends on listeners and commit participants that are registered with
116 * <h3>Example usage:</h3>
118 * private void doWrite(final int tries) {
119 * WriteTransaction writeTx = dataBroker.newWriteOnlyTransaction();
120 * MyDataObject data = ...;
121 * InstanceIdentifier<MyDataObject> path = ...;
122 * writeTx.put(LogicalDatastoreType.OPERATIONAL, path, data);
123 * Futures.addCallback(writeTx.commit(), new FutureCallback<CommitInfo>() {
124 * public void onSuccess(CommitInfo result) {
127 * public void onFailure(Throwable t) {
128 * if (t instanceof OptimisticLockFailedException) {
129 * if(( tries - 1) > 0 ) {
131 * doWrite(tries - 1);
136 * // failed due to another type of TransactionCommitFailedException.
144 * <h2>Failure scenarios</h2>
147 * Transaction may fail because of multiple reasons, such as
150 * Another transaction finished earlier and modified the same node in a non-compatible way (see below). In this
151 * case the returned future will fail with an {@link OptimisticLockFailedException}. It is the responsibility
152 * of the caller to create a new transaction and commit the same modification again in order to update data
155 * <b>Warning</b>: In most cases, retrying after an OptimisticLockFailedException will result in a high
156 * probability of success. However, there are scenarios, albeit unusual, where any number of retries will
157 * not succeed. Therefore it is strongly recommended to limit the number of retries (2 or 3) to avoid
161 * <li>Data change introduced by this transaction did not pass validation by commit handlers or data was
162 * incorrectly structured. Returned future will fail with a {@link DataValidationFailedException}. User
163 * should not retry to create new transaction with same data, since it probably will fail again.
167 * <h3>Change compatibility</h3>
168 * There are several sets of changes which could be considered incompatible between two transactions which are
169 * derived from same initial state. Rules for conflict detection applies recursively for each subtree level.
171 * <h4>Change compatibility of leafs, leaf-list items</h4>
172 * Following table shows state changes and failures between two concurrent transactions, which are based on same
173 * initial state, Tx 1 completes successfully before Tx 2 is committed.
176 * <caption>Change compatibility of leaf values</caption>
178 * <th>Initial state</th>
187 * <td>Tx 2 will fail, state is A=1</td>
192 * <td>merge(A,2)</td>
198 * <td>merge(A,1)</td>
200 * <td>Tx 2 will fail, state is A=1</td>
204 * <td>merge(A,1)</td>
205 * <td>merge(A,2)</td>
214 * <td>Tx 2 will fail, A=1</td>
219 * <td>merge(A,2)</td>
224 * <td>merge(A,1)</td>
226 * <td>Tx 2 will fail, A=1</td>
230 * <td>merge(A,1)</td>
231 * <td>merge(A,2)</td>
239 * <td>Tx 2 will fail, A does not exists</td>
244 * <td>merge(A,2)</td>
249 * <h4>Change compatibility of subtrees</h4>
250 * Following table shows state changes and failures between two concurrent transactions, which are based on same
251 * initial state, Tx 1 completes successfully before Tx 2 is committed.
254 * <caption>Change compatibility of containers</caption>
256 * <th>Initial state</th>
264 * <td>put(TOP,[])</td>
265 * <td>put(TOP,[])</td>
266 * <td>Tx 2 will fail, state is TOP=[]</td>
270 * <td>put(TOP,[])</td>
271 * <td>merge(TOP,[])</td>
277 * <td>put(TOP,[FOO=1])</td>
278 * <td>put(TOP,[BAR=1])</td>
279 * <td>Tx 2 will fail, state is TOP=[FOO=1]</td>
283 * <td>put(TOP,[FOO=1])</td>
284 * <td>merge(TOP,[BAR=1])</td>
285 * <td>TOP=[FOO=1,BAR=1]</td>
290 * <td>merge(TOP,[FOO=1])</td>
291 * <td>put(TOP,[BAR=1])</td>
292 * <td>Tx 2 will fail, state is TOP=[FOO=1]</td>
296 * <td>merge(TOP,[FOO=1])</td>
297 * <td>merge(TOP,[BAR=1])</td>
298 * <td>TOP=[FOO=1,BAR=1]</td>
303 * <td>put(TOP,[FOO=1])</td>
304 * <td>put(TOP,[BAR=1])</td>
305 * <td>Tx 2 will fail, state is TOP=[FOO=1]</td>
309 * <td>put(TOP,[FOO=1])</td>
310 * <td>merge(TOP,[BAR=1])</td>
311 * <td>state is TOP=[FOO=1,BAR=1]</td>
315 * <td>merge(TOP,[FOO=1])</td>
316 * <td>put(TOP,[BAR=1])</td>
317 * <td>Tx 2 will fail, state is TOP=[FOO=1]</td>
321 * <td>merge(TOP,[FOO=1])</td>
322 * <td>merge(TOP,[BAR=1])</td>
323 * <td>state is TOP=[FOO=1,BAR=1]</td>
327 * <td>delete(TOP)</td>
328 * <td>put(TOP,[BAR=1])</td>
329 * <td>Tx 2 will fail, state is empty store</td>
333 * <td>delete(TOP)</td>
334 * <td>merge(TOP,[BAR=1])</td>
335 * <td>state is TOP=[BAR=1]</td>
340 * <td>put(TOP/FOO,1)</td>
341 * <td>put(TOP/BAR,1])</td>
342 * <td>state is TOP=[FOO=1,BAR=1]</td>
346 * <td>put(TOP/FOO,1)</td>
347 * <td>merge(TOP/BAR,1)</td>
348 * <td>state is TOP=[FOO=1,BAR=1]</td>
352 * <td>merge(TOP/FOO,1)</td>
353 * <td>put(TOP/BAR,1)</td>
354 * <td>state is TOP=[FOO=1,BAR=1]</td>
358 * <td>merge(TOP/FOO,1)</td>
359 * <td>merge(TOP/BAR,1)</td>
360 * <td>state is TOP=[FOO=1,BAR=1]</td>
364 * <td>delete(TOP)</td>
365 * <td>put(TOP/BAR,1)</td>
366 * <td>Tx 2 will fail, state is empty store</td>
370 * <td>delete(TOP)</td>
371 * <td>merge(TOP/BAR,1]</td>
372 * <td>Tx 2 will fail, state is empty store</td>
376 * <td>TOP=[FOO=1]</td>
377 * <td>put(TOP/FOO,2)</td>
378 * <td>put(TOP/BAR,1)</td>
379 * <td>state is TOP=[FOO=2,BAR=1]</td>
382 * <td>TOP=[FOO=1]</td>
383 * <td>put(TOP/FOO,2)</td>
384 * <td>merge(TOP/BAR,1)</td>
385 * <td>state is TOP=[FOO=2,BAR=1]</td>
388 * <td>TOP=[FOO=1]</td>
389 * <td>merge(TOP/FOO,2)</td>
390 * <td>put(TOP/BAR,1)</td>
391 * <td>state is TOP=[FOO=2,BAR=1]</td>
394 * <td>TOP=[FOO=1]</td>
395 * <td>merge(TOP/FOO,2)</td>
396 * <td>merge(TOP/BAR,1)</td>
397 * <td>state is TOP=[FOO=2,BAR=1]</td>
400 * <td>TOP=[FOO=1]</td>
401 * <td>delete(TOP/FOO)</td>
402 * <td>put(TOP/BAR,1)</td>
403 * <td>state is TOP=[BAR=1]</td>
406 * <td>TOP=[FOO=1]</td>
407 * <td>delete(TOP/FOO)</td>
408 * <td>merge(TOP/BAR,1]</td>
409 * <td>state is TOP=[BAR=1]</td>
414 * <h3>Examples of failure scenarios</h3>
416 * <h4>Conflict of two transactions</h4>
417 * This example illustrates two concurrent transactions, which derived from same initial state
418 * of data tree and proposes conflicting modifications.
421 * txA = broker.newWriteTransaction(); // allocates new transaction, data tree is empty
422 * txB = broker.newWriteTransaction(); // allocates new transaction, data tree is empty
423 * txA.put(CONFIGURATION, PATH, A); // writes to PATH value A
424 * txB.put(CONFIGURATION, PATH, B) // writes to PATH value B
425 * ListenableFuture futureA = txA.commit(); // transaction A is sealed and committed
426 * ListenebleFuture futureB = txB.commit(); // transaction B is sealed and committed
428 * Commit of transaction A will be processed asynchronously and data tree will be updated to
429 * contain value <code>A</code> for <code>PATH</code>. Returned {@link FluentFuture} will
430 * successfully complete once state is applied to data tree.
431 * Commit of Transaction B will fail, because previous transaction also modified path in a
432 * concurrent way. The state introduced by transaction B will not be applied. Returned
433 * {@link FluentFuture} object will fail with {@link OptimisticLockFailedException}
434 * exception, which indicates to client that concurrent transaction prevented the committed
435 * transaction from being applied. <br>
438 * A successful commit produces implementation-specific {@link CommitInfo} structure, which is used to communicate
439 * post-condition information to the caller. Such information can contain commit-id, timing information or any
440 * other information the implementation wishes to share.
442 * @return a FluentFuture containing the result of the commit information. The Future blocks until the commit
443 * operation is complete. A successful commit returns nothing. On failure, the Future will fail with a
444 * {@link TransactionCommitFailedException} or an exception derived from TransactionCommitFailedException.
445 * @throws IllegalStateException if the transaction is already committed or was canceled.
448 @NonNull FluentFuture<? extends @NonNull CommitInfo> commit();