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.controller.md.sal.common.api.data;
10 import com.google.common.util.concurrent.CheckedFuture;
11 import com.google.common.util.concurrent.ListenableFuture;
12 import org.opendaylight.controller.md.sal.common.api.TransactionStatus;
13 import org.opendaylight.yangtools.concepts.Path;
14 import org.opendaylight.yangtools.yang.common.RpcResult;
17 * Write transaction provides mutation capabilities for a data tree.
20 * Initial state of write transaction is a stable snapshot of the current data tree.
21 * The state is captured when the transaction is created and its state and underlying
22 * data tree are not affected by other concurrently running transactions.
25 * Write transactions are isolated from other concurrent write transactions. All
26 * writes are local to the transaction and represent only a proposal of state
27 * change for the data tree and it is not visible to any other concurrently running
31 * Applications make changes to the local data tree in the transaction by via the
32 * <b>put</b>, <b>merge</b>, and <b>delete</b> operations.
34 * <h2>Put operation</h2>
35 * Stores a piece of data at a specified path. This acts as an add / replace
36 * operation, which is to say that whole subtree will be replaced by the
40 * Performing the following put operations:
43 * 1) container { list [ a ] }
44 * 2) container { list [ b ] }
48 * will result in the following data being present:
51 * container { list [ b ] }
53 * <h2>Merge operation</h2>
54 * Merges a piece of data with the existing data at a specified path. Any pre-existing data
55 * which is not explicitly overwritten will be preserved. This means that if you store a container,
56 * its child lists will be merged.
59 * Performing the following merge operations:
62 * 1) container { list [ a ] }
63 * 2) container { list [ b ] }
67 * will result in the following data being present:
70 * container { list [ a, b ] }
74 * This also means that storing the container will preserve any
75 * augmentations which have been attached to it.
77 * <h2>Delete operation</h2>
78 * Removes a piece of data from a specified path.
81 * After applying changes to the local data tree, applications publish the changes proposed in the
82 * transaction by calling {@link #submit} on the transaction. This seals the transaction
83 * (preventing any further writes using this transaction) and submits it to be
84 * processed and applied to global conceptual data tree.
87 * The transaction commit may fail due to a concurrent transaction modifying and committing data in
88 * an incompatible way. See {@link #submit} for more concrete commit failure examples.
91 * <b>Implementation Note:</b> This interface is not intended to be implemented
92 * by users of MD-SAL, but only to be consumed by them.
95 * Type of path (subtree identifier), which represents location in
98 * Type of data (payload), which represents data payload
100 public interface AsyncWriteTransaction<P extends Path<P>, D> extends AsyncTransaction<P, D> {
102 * Cancels the transaction.
105 * Transactions can only be cancelled if it's state is new or submitted.
108 * Invoking cancel() on a failed or cancelled transaction will have no effect, and transaction
109 * is considered cancelled.
112 * Invoking cancel() on a finished transaction (future returned by {@link #submit()} already completed will always
113 * fail (return false).
115 * @return <tt>false</tt> if the task could not be cancelled, typically because it has already completed normally
116 * <tt>true</tt> otherwise
122 * Removes a piece of data from specified path. This operation does not fail
123 * if the specified path does not exist.
126 * Logical data store which should be modified
129 * @throws IllegalStateException
130 * if the transaction as already been submitted or cancelled
132 void delete(LogicalDatastoreType store, P path);
135 * Submits this transaction to be asynchronously applied to update the logical data tree.
136 * The returned CheckedFuture conveys the result of applying the data changes.
139 * <b>Note:</b> It is strongly recommended to process the CheckedFuture result in an asynchronous
140 * manner rather than using the blocking get() method. See example usage below.
143 * This call logically seals the transaction, which prevents the client from
144 * further changing data tree using this transaction. Any subsequent calls to
145 * {@link #delete(LogicalDatastoreType, Path)} will fail with
146 * {@link IllegalStateException}.
149 * The transaction is marked as submitted and enqueued into the data store back-end for processing.
152 * Whether or not the commit is successful is determined by versioning
153 * of the data tree and validation of registered commit participants
154 * ({@link AsyncConfigurationCommitHandler}) if the transaction changes the data tree.
157 * The effects of a successful commit of data depends on data change listeners
158 * ({@link AsyncDataChangeListener}) and commit participants
159 * ({@link AsyncConfigurationCommitHandler}) that are registered with the data broker.
161 * <h3>Example usage:</h3>
163 * private void doWrite( final int tries ) {
164 * WriteTransaction writeTx = dataBroker.newWriteOnlyTransaction();
166 * MyDataObject data = ...;
167 * InstanceIdentifier<MyDataObject> path = ...;
168 * writeTx.put( LogicalDatastoreType.OPERATIONAL, path, data );
170 * Futures.addCallback( writeTx.submit(), new FutureCallback<Void>() {
171 * public void onSuccess( Void result ) {
175 * public void onFailure( Throwable t ) {
176 * if( t instanceof OptimisticLockFailedException ) {
177 * if( ( tries - 1 ) > 0 ) {
179 * doWrite( tries - 1 );
184 * // failed due to another type of TransactionCommitFailedException.
191 * <h2>Failure scenarios</h2>
194 * Transaction may fail because of multiple reasons, such as
196 * <li>Another transaction finished earlier and modified the same node in a
197 * non-compatible way (see below). In this case the returned future will fail with an
198 * {@link OptimisticLockFailedException}. It is the responsibility of the
199 * caller to create a new transaction and submit the same modification again in
200 * order to update data tree. <i><b>Warning</b>: In most cases, retrying after an
201 * OptimisticLockFailedException will result in a high probability of success.
202 * However, there are scenarios, albeit unusual, where any number of retries will
203 * not succeed. Therefore it is strongly recommended to limit the number of retries (2 or 3)
204 * to avoid an endless loop.</i>
206 * <li>Data change introduced by this transaction did not pass validation by
207 * commit handlers or data was incorrectly structured. Returned future will
208 * fail with a {@link DataValidationFailedException}. User should not retry to
209 * create new transaction with same data, since it probably will fail again.
213 * <h3>Change compatibility</h3>
216 * There are several sets of changes which could be considered incompatible
217 * between two transactions which are derived from same initial state.
218 * Rules for conflict detection applies recursively for each subtree
221 * <h4>Change compatibility of leafs, leaf-list items</h4>
224 * Following table shows state changes and failures between two concurrent transactions,
225 * which are based on same initial state, Tx 1 completes successfully
226 * before Tx 2 is submitted.
229 * <tr><th>Initial state</th><th>Tx 1</th><th>Tx 2</th><th>Result</th></tr>
230 * <tr><td>Empty</td><td>put(A,1)</td><td>put(A,2)</td><td>Tx 2 will fail, state is A=1</td></tr>
231 * <tr><td>Empty</td><td>put(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
233 * <tr><td>Empty</td><td>merge(A,1)</td><td>put(A,2)</td><td>Tx 2 will fail, state is A=1</td></tr>
234 * <tr><td>Empty</td><td>merge(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
237 * <tr><td>A=0</td><td>put(A,1)</td><td>put(A,2)</td><td>Tx 2 will fail, A=1</td></tr>
238 * <tr><td>A=0</td><td>put(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
239 * <tr><td>A=0</td><td>merge(A,1)</td><td>put(A,2)</td><td>Tx 2 will fail, A=1</td></tr>
240 * <tr><td>A=0</td><td>merge(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
242 * <tr><td>A=0</td><td>delete(A)</td><td>put(A,2)</td><td>Tx 2 will fail, A does not exists</td></tr>
243 * <tr><td>A=0</td><td>delete(A)</td><td>merge(A,2)</td><td>A=2</td></tr>
246 * <h4>Change compatibility of subtrees</h4>
249 * Following table shows state changes and failures between two concurrent transactions,
250 * which are based on same initial state, Tx 1 completes successfully
251 * before Tx 2 is submitted.
254 * <tr><th>Initial state</th><th>Tx 1</th><th>Tx 2</th><th>Result</th></tr>
256 * <tr><td>Empty</td><td>put(TOP,[])</td><td>put(TOP,[])</td><td>Tx 2 will fail, state is TOP=[]</td></tr>
257 * <tr><td>Empty</td><td>put(TOP,[])</td><td>merge(TOP,[])</td><td>TOP=[]</td></tr>
259 * <tr><td>Empty</td><td>put(TOP,[FOO=1])</td><td>put(TOP,[BAR=1])</td><td>Tx 2 will fail, state is TOP=[FOO=1]
261 * <tr><td>Empty</td><td>put(TOP,[FOO=1])</td><td>merge(TOP,[BAR=1])</td><td>TOP=[FOO=1,BAR=1]</td></tr>
263 * <tr><td>Empty</td><td>merge(TOP,[FOO=1])</td><td>put(TOP,[BAR=1])</td><td>Tx 2 will fail, state is TOP=[FOO=1]
265 * <tr><td>Empty</td><td>merge(TOP,[FOO=1])</td><td>merge(TOP,[BAR=1])</td><td>TOP=[FOO=1,BAR=1]</td></tr>
267 * <tr><td>TOP=[]</td><td>put(TOP,[FOO=1])</td><td>put(TOP,[BAR=1])</td><td>Tx 2 will fail, state is TOP=[FOO=1]
269 * <tr><td>TOP=[]</td><td>put(TOP,[FOO=1])</td><td>merge(TOP,[BAR=1])</td><td>state is TOP=[FOO=1,BAR=1]</td></tr>
270 * <tr><td>TOP=[]</td><td>merge(TOP,[FOO=1])</td><td>put(TOP,[BAR=1])</td><td>Tx 2 will fail, state is TOP=[FOO=1]
272 * <tr><td>TOP=[]</td><td>merge(TOP,[FOO=1])</td><td>merge(TOP,[BAR=1])</td><td>state is TOP=[FOO=1,BAR=1]</td></tr>
273 * <tr><td>TOP=[]</td><td>delete(TOP)</td><td>put(TOP,[BAR=1])</td><td>Tx 2 will fail, state is empty store
275 * <tr><td>TOP=[]</td><td>delete(TOP)</td><td>merge(TOP,[BAR=1])</td><td>state is TOP=[BAR=1]</td></tr>
277 * <tr><td>TOP=[]</td><td>put(TOP/FOO,1)</td><td>put(TOP/BAR,1])</td><td>state is TOP=[FOO=1,BAR=1]</td></tr>
278 * <tr><td>TOP=[]</td><td>put(TOP/FOO,1)</td><td>merge(TOP/BAR,1)</td><td>state is TOP=[FOO=1,BAR=1]</td></tr>
279 * <tr><td>TOP=[]</td><td>merge(TOP/FOO,1)</td><td>put(TOP/BAR,1)</td><td>state is TOP=[FOO=1,BAR=1]</td></tr>
280 * <tr><td>TOP=[]</td><td>merge(TOP/FOO,1)</td><td>merge(TOP/BAR,1)</td><td>state is TOP=[FOO=1,BAR=1]</td></tr>
281 * <tr><td>TOP=[]</td><td>delete(TOP)</td><td>put(TOP/BAR,1)</td><td>Tx 2 will fail, state is empty store</td></tr>
282 * <tr><td>TOP=[]</td><td>delete(TOP)</td><td>merge(TOP/BAR,1]</td><td>Tx 2 will fail, state is empty store
285 * <tr><td>TOP=[FOO=1]</td><td>put(TOP/FOO,2)</td><td>put(TOP/BAR,1)</td><td>state is TOP=[FOO=2,BAR=1]</td></tr>
286 * <tr><td>TOP=[FOO=1]</td><td>put(TOP/FOO,2)</td><td>merge(TOP/BAR,1)</td><td>state is TOP=[FOO=2,BAR=1]</td></tr>
287 * <tr><td>TOP=[FOO=1]</td><td>merge(TOP/FOO,2)</td><td>put(TOP/BAR,1)</td><td>state is TOP=[FOO=2,BAR=1]</td></tr>
288 * <tr><td>TOP=[FOO=1]</td><td>merge(TOP/FOO,2)</td><td>merge(TOP/BAR,1)</td><td>state is TOP=[FOO=2,BAR=1]
290 * <tr><td>TOP=[FOO=1]</td><td>delete(TOP/FOO)</td><td>put(TOP/BAR,1)</td><td>state is TOP=[BAR=1]</td></tr>
291 * <tr><td>TOP=[FOO=1]</td><td>delete(TOP/FOO)</td><td>merge(TOP/BAR,1]</td><td>state is TOP=[BAR=1]</td></tr>
295 * <h3>Examples of failure scenarios</h3>
297 * <h4>Conflict of two transactions</h4>
300 * This example illustrates two concurrent transactions, which derived from
301 * same initial state of data tree and proposes conflicting modifications.
304 * txA = broker.newWriteTransaction(); // allocates new transaction, data tree is empty
305 * txB = broker.newWriteTransaction(); // allocates new transaction, data tree is empty
307 * txA.put(CONFIGURATION, PATH, A); // writes to PATH value A
308 * txB.put(CONFIGURATION, PATH, B) // writes to PATH value B
310 * ListenableFuture futureA = txA.submit(); // transaction A is sealed and submitted
311 * ListenebleFuture futureB = txB.submit(); // transaction B is sealed and submitted
315 * Commit of transaction A will be processed asynchronously and data tree
316 * will be updated to contain value <code>A</code> for <code>PATH</code>.
317 * Returned {@link ListenableFuture} will successfully complete once
318 * state is applied to data tree.
321 * Commit of Transaction B will fail, because previous transaction also
322 * modified path in a concurrent way. The state introduced by transaction B
323 * will not be applied. Returned {@link ListenableFuture} object will fail
324 * with {@link OptimisticLockFailedException} exception, which indicates to
325 * client that concurrent transaction prevented the submitted transaction from being
328 * @return a CheckFuture containing the result of the commit. The Future blocks until the
329 * commit operation is complete. A successful commit returns nothing. On failure,
330 * the Future will fail with a {@link TransactionCommitFailedException} or an exception
331 * derived from TransactionCommitFailedException.
333 * @throws IllegalStateException
334 * if the transaction is not new
336 CheckedFuture<Void,TransactionCommitFailedException> submit();
341 * @deprecated Use {@link #submit()} instead.
344 default ListenableFuture<RpcResult<TransactionStatus>> commit() {
345 throw new UnsupportedOperationException("commit() is deprecated, use submit() instead");