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.yangtools.concepts.Path;
15 * Write transaction provides mutation capabilities for a data tree.
18 * Initial state of write transaction is a stable snapshot of the current data tree.
19 * The state is captured when the transaction is created and its state and underlying
20 * data tree are not affected by other concurrently running transactions.
23 * Write transactions are isolated from other concurrent write transactions. All
24 * writes are local to the transaction and represent only a proposal of state
25 * change for the data tree and it is not visible to any other concurrently running
29 * Applications make changes to the local data tree in the transaction by via the
30 * <b>put</b>, <b>merge</b>, and <b>delete</b> operations.
32 * <h2>Put operation</h2>
33 * Stores a piece of data at a specified path. This acts as an add / replace
34 * operation, which is to say that whole subtree will be replaced by the
38 * Performing the following put operations:
41 * 1) container { list [ a ] }
42 * 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
53 * which is not explicitly overwritten will be preserved. This means that if you store a container,
54 * its child lists will be merged.
57 * Performing the following merge operations:
60 * 1) container { list [ a ] }
61 * 2) container { list [ b ] }
65 * will result in the following data being present:
68 * container { list [ a, b ] }
72 * This also means that storing the container will preserve any
73 * augmentations which have been attached to it.
75 * <h2>Delete operation</h2>
76 * Removes a piece of data from a specified path.
79 * After applying changes to the local data tree, applications publish the changes proposed in the
80 * transaction by calling {@link #submit} on the transaction. This seals the transaction
81 * (preventing any further writes using this transaction) and submits it to be
82 * processed and applied to global conceptual data tree.
85 * The transaction commit may fail due to a concurrent transaction modifying and committing data in
86 * an incompatible way. See {@link #submit} for more concrete commit failure examples.
89 * <b>Implementation Note:</b> This interface is not intended to be implemented
90 * by users of MD-SAL, but only to be consumed by them.
93 * Type of path (subtree identifier), which represents location in
96 * Type of data (payload), which represents data payload
98 public interface AsyncWriteTransaction<P extends Path<P>, D> extends AsyncTransaction<P, D> {
100 * Cancels the transaction.
103 * Transactions can only be cancelled if it's state is new or submitted.
106 * Invoking cancel() on a failed or cancelled transaction will have no effect, and transaction
107 * is considered cancelled.
110 * Invoking cancel() on a finished transaction (future returned by {@link #submit()} already completed will always
111 * fail (return false).
113 * @return <tt>false</tt> if the task could not be cancelled, typically because it has already completed normally
114 * <tt>true</tt> otherwise
120 * Removes a piece of data from specified path. This operation does not fail
121 * if the specified path does not exist.
124 * Logical data store which should be modified
127 * @throws IllegalStateException
128 * if the transaction as already been submitted or cancelled
130 void delete(LogicalDatastoreType store, P path);
133 * Submits this transaction to be asynchronously applied to update the logical data tree.
134 * The returned CheckedFuture conveys the result of applying the data changes.
137 * <b>Note:</b> It is strongly recommended to process the CheckedFuture result in an asynchronous
138 * manner rather than using the blocking get() method. See example usage below.
141 * This call logically seals the transaction, which prevents the client from
142 * further changing data tree using this transaction. Any subsequent calls to
143 * {@link #delete(LogicalDatastoreType, Path)} will fail with
144 * {@link IllegalStateException}.
147 * The transaction is marked as submitted and enqueued into the data store back-end for processing.
150 * Whether or not the commit is successful is determined by versioning
151 * of the data tree and validation of registered commit participants
152 * ({@link AsyncConfigurationCommitHandler}) if the transaction changes the data tree.
155 * The effects of a successful commit of data depends on data change listeners
156 * ({@link AsyncDataChangeListener}) and commit participants
157 * ({@link AsyncConfigurationCommitHandler}) that are registered with the data broker.
159 * <h3>Example usage:</h3>
161 * private void doWrite( final int tries ) {
162 * WriteTransaction writeTx = dataBroker.newWriteOnlyTransaction();
164 * MyDataObject data = ...;
165 * InstanceIdentifier<MyDataObject> path = ...;
166 * writeTx.put( LogicalDatastoreType.OPERATIONAL, path, data );
168 * Futures.addCallback( writeTx.submit(), new FutureCallback<Void>() {
169 * public void onSuccess( Void result ) {
173 * public void onFailure( Throwable t ) {
174 * if( t instanceof OptimisticLockFailedException ) {
175 * if( ( tries - 1 ) > 0 ) {
177 * doWrite( tries - 1 );
182 * // failed due to another type of TransactionCommitFailedException.
189 * <h2>Failure scenarios</h2>
192 * Transaction may fail because of multiple reasons, such as
194 * <li>Another transaction finished earlier and modified the same node in a
195 * non-compatible way (see below). In this case the returned future will fail with an
196 * {@link OptimisticLockFailedException}. It is the responsibility of the
197 * caller to create a new transaction and submit the same modification again in
198 * order to update data tree. <i><b>Warning</b>: In most cases, retrying after an
199 * OptimisticLockFailedException will result in a high probability of success.
200 * However, there are scenarios, albeit unusual, where any number of retries will
201 * not succeed. Therefore it is strongly recommended to limit the number of retries (2 or 3)
202 * to avoid an endless loop.</i>
204 * <li>Data change introduced by this transaction did not pass validation by
205 * commit handlers or data was incorrectly structured. Returned future will
206 * fail with a {@link DataValidationFailedException}. User should not retry to
207 * create new transaction with same data, since it probably will fail again.
211 * <h3>Change compatibility</h3>
214 * There are several sets of changes which could be considered incompatible
215 * between two transactions which are derived from same initial state.
216 * Rules for conflict detection applies recursively for each subtree
219 * <h4>Change compatibility of leafs, leaf-list items</h4>
222 * Following table shows state changes and failures between two concurrent transactions,
223 * which are based on same initial state, Tx 1 completes successfully
224 * before Tx 2 is submitted.
227 * <tr><th>Initial state</th><th>Tx 1</th><th>Tx 2</th><th>Result</th></tr>
228 * <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>
229 * <tr><td>Empty</td><td>put(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
231 * <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>
232 * <tr><td>Empty</td><td>merge(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
235 * <tr><td>A=0</td><td>put(A,1)</td><td>put(A,2)</td><td>Tx 2 will fail, A=1</td></tr>
236 * <tr><td>A=0</td><td>put(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
237 * <tr><td>A=0</td><td>merge(A,1)</td><td>put(A,2)</td><td>Tx 2 will fail, A=1</td></tr>
238 * <tr><td>A=0</td><td>merge(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
240 * <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>
241 * <tr><td>A=0</td><td>delete(A)</td><td>merge(A,2)</td><td>A=2</td></tr>
244 * <h4>Change compatibility of subtrees</h4>
247 * Following table shows state changes and failures between two concurrent transactions,
248 * which are based on same initial state, Tx 1 completes successfully
249 * before Tx 2 is submitted.
252 * <tr><th>Initial state</th><th>Tx 1</th><th>Tx 2</th><th>Result</th></tr>
254 * <tr><td>Empty</td><td>put(TOP,[])</td><td>put(TOP,[])</td><td>Tx 2 will fail, state is TOP=[]</td></tr>
255 * <tr><td>Empty</td><td>put(TOP,[])</td><td>merge(TOP,[])</td><td>TOP=[]</td></tr>
257 * <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]
259 * <tr><td>Empty</td><td>put(TOP,[FOO=1])</td><td>merge(TOP,[BAR=1])</td><td>TOP=[FOO=1,BAR=1]</td></tr>
261 * <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]
263 * <tr><td>Empty</td><td>merge(TOP,[FOO=1])</td><td>merge(TOP,[BAR=1])</td><td>TOP=[FOO=1,BAR=1]</td></tr>
265 * <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]
267 * <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>
268 * <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]
270 * <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>
271 * <tr><td>TOP=[]</td><td>delete(TOP)</td><td>put(TOP,[BAR=1])</td><td>Tx 2 will fail, state is empty store
273 * <tr><td>TOP=[]</td><td>delete(TOP)</td><td>merge(TOP,[BAR=1])</td><td>state is TOP=[BAR=1]</td></tr>
275 * <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>
276 * <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>
277 * <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>
278 * <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>
279 * <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>
280 * <tr><td>TOP=[]</td><td>delete(TOP)</td><td>merge(TOP/BAR,1]</td><td>Tx 2 will fail, state is empty store
283 * <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>
284 * <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>
285 * <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>
286 * <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]
288 * <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>
289 * <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>
293 * <h3>Examples of failure scenarios</h3>
295 * <h4>Conflict of two transactions</h4>
298 * This example illustrates two concurrent transactions, which derived from
299 * same initial state of data tree and proposes conflicting modifications.
302 * txA = broker.newWriteTransaction(); // allocates new transaction, data tree is empty
303 * txB = broker.newWriteTransaction(); // allocates new transaction, data tree is empty
305 * txA.put(CONFIGURATION, PATH, A); // writes to PATH value A
306 * txB.put(CONFIGURATION, PATH, B) // writes to PATH value B
308 * ListenableFuture futureA = txA.submit(); // transaction A is sealed and submitted
309 * ListenebleFuture futureB = txB.submit(); // transaction B is sealed and submitted
313 * Commit of transaction A will be processed asynchronously and data tree
314 * will be updated to contain value <code>A</code> for <code>PATH</code>.
315 * Returned {@link ListenableFuture} will successfully complete once
316 * state is applied to data tree.
319 * Commit of Transaction B will fail, because previous transaction also
320 * modified path in a concurrent way. The state introduced by transaction B
321 * will not be applied. Returned {@link ListenableFuture} object will fail
322 * with {@link OptimisticLockFailedException} exception, which indicates to
323 * client that concurrent transaction prevented the submitted transaction from being
326 * @return a CheckFuture containing the result of the commit. The Future blocks until the
327 * commit operation is complete. A successful commit returns nothing. On failure,
328 * the Future will fail with a {@link TransactionCommitFailedException} or an exception
329 * derived from TransactionCommitFailedException.
331 * @throws IllegalStateException
332 * if the transaction is not new
334 CheckedFuture<Void,TransactionCommitFailedException> submit();