*/
package org.opendaylight.controller.md.sal.common.api.data;
-import java.util.concurrent.Future;
-
import org.opendaylight.controller.md.sal.common.api.TransactionStatus;
import org.opendaylight.yangtools.concepts.Path;
import org.opendaylight.yangtools.yang.common.RpcResult;
-public interface AsyncWriteTransaction<P extends Path<P>, D> extends AsyncTransaction<P, D> {
+import com.google.common.util.concurrent.ListenableFuture;
+
+/**
+ * Write transaction provides mutation capabilities for a data tree.
+ *
+ * <p>
+ * Initial state of write transaction is a stable snapshot of the current data tree.
+ * The state is captured when the transaction is created and its state and underlying
+ * data tree are not affected by other concurrently running transactions.
+ * <p>
+ * Write transactions are isolated from other concurrent write transactions. All
+ * writes are local to the transaction and represent only a proposal of state
+ * change for the data tree and it is not visible to any other concurrently running
+ * transaction.
+ * <p>
+ * Applications publish the changes proposed in the transaction by calling {@link #commit}
+ * on the transaction. This seals the transaction
+ * (preventing any further writes using this transaction) and submits it to be
+ * processed and applied to global conceptual data tree.
+ * <p>
+ * The transaction commit may fail due to a concurrent transaction modifying and committing data in
+ * an incompatible way. See {@link #commit()} for more concrete commit failure examples.
+ *
+ *
+ * <p>
+ * <b>Implementation Note:</b> This interface is not intended to be implemented
+ * by users of MD-SAL, but only to be consumed by them.
+ *
+ * @param <P>
+ * Type of path (subtree identifier), which represents location in
+ * tree
+ * @param <D>
+ * Type of data (payload), which represents data payload
+ */
+public interface AsyncWriteTransaction<P extends Path<P>, D> extends AsyncTransaction<P, D> {
/**
- * Cancels transaction.
+ * Cancels the transaction.
*
- * Transaction could be only cancelled if it's status
- * is {@link TransactionStatus#NEW} or {@link TransactionStatus#SUBMITED}
+ * Transactions can only be cancelled if it's status is
+ * {@link TransactionStatus#NEW} or {@link TransactionStatus#SUBMITED}
*
- * Invoking cancel() on {@link TransactionStatus#FAILED} or {@link TransactionStatus#CANCELED}
- * will have no effect.
+ * Invoking cancel() on {@link TransactionStatus#FAILED} or
+ * {@link TransactionStatus#CANCELED} will have no effect, and transaction
+ * is considered cancelled.
*
- * @throws IllegalStateException If transaction status is {@link TransactionStatus#COMMITED}
+ * Invoking cancel() on finished transaction (future returned by {@link #commit()}
+ * already completed with {@link TransactionStatus#COMMITED}) will always
+ * fail (return false).
+ *
+ * @return <tt>false</tt> if the task could not be cancelled,
+ * typically because it has already completed normally;
+ * <tt>true</tt> otherwise
*
*/
- public void cancel();
+ public boolean cancel();
/**
- * Store a piece of data at specified path. This acts as a add / replace operation,
- * which is to say that whole subtree will be replaced by specified path.
+ * Store a piece of data at specified path. This acts as an add / replace
+ * operation, which is to say that whole subtree will be replaced by
+ * specified path. Performing the following put operations:
+ *
+ * <pre>
+ * 1) container { list [ a ] }
+ * 2) container { list [ b ] }
+ * </pre>
+ *
+ * will result in the following data being present:
*
- * If you need add or merge of current object with specified use {@link #merge(LogicalDatastoreType, Path, Object)}
+ * <pre>
+ * container { list [ b ] }
+ * </pre>
*
- * @param store Logical data store which should be modified
- * @param path Data object path
- * @param data Data object to be written to specified path
- * @throws IllegalStateException if the transaction is no longer {@link TransactionStatus#NEW}
+ *
+ * If you need to make sure that a parent object exists, but you do not want modify
+ * its preexisting state by using put, consider using
+ * {@link #merge(LogicalDatastoreType, Path, Object)}
+ *
+ * @param store
+ * Logical data store which should be modified
+ * @param path
+ * Data object path
+ * @param data
+ * Data object to be written to specified path
+ * @throws IllegalStateException
+ * if the transaction is no longer {@link TransactionStatus#NEW}
*/
public void put(LogicalDatastoreType store, P path, D data);
/**
- * Store a piece of data at specified path. This acts as a merge operation,
+ * Store a piece of data at the specified path. This acts as a merge operation,
* which is to say that any pre-existing data which is not explicitly
* overwritten will be preserved. This means that if you store a container,
- * its child lists will be merged. Performing the following put operations:
+ * its child lists will be merged. Performing the following merge
+ * operations:
*
+ * <pre>
* 1) container { list [ a ] }
* 2) container { list [ b ] }
+ * </pre>
*
* will result in the following data being present:
*
+ * <pre>
* container { list [ a, b ] }
+ * </pre>
*
- * This also means that storing the container will preserve any augmentations
- * which have been attached to it.
+ * This also means that storing the container will preserve any
+ * augmentations which have been attached to it.
+ *<p>
+ * If you require an explicit replace operation, use
+ * {@link #put(LogicalDatastoreType, Path, Object)} instead.
*
- * If you require an explicit replace operation, use {@link #put(LogicalDatastoreType, Path, Object)} instead.
- *
- * @param store Logical data store which should be modified
- * @param path Data object path
- * @param data Data object to be written to specified path
- * @throws IllegalStateException if the transaction is no longer {@link TransactionStatus#NEW}
+ * @param store
+ * Logical data store which should be modified
+ * @param path
+ * Data object path
+ * @param data
+ * Data object to be written to specified path
+ * @throws IllegalStateException
+ * if the transaction is no longer {@link TransactionStatus#NEW}
*/
public void merge(LogicalDatastoreType store, P path, D data);
* Remove a piece of data from specified path. This operation does not fail
* if the specified path does not exist.
*
- * @param store Logical data store which should be modified
- * @param path Data object path
- * @throws IllegalStateException if the transaction is no longer {@link TransactionStatus#NEW}
+ * @param store
+ * Logical data store which should be modified
+ * @param path
+ * Data object path
+ * @throws IllegalStateException
+ * if the transaction is no longer {@link TransactionStatus#NEW}
*/
public void delete(LogicalDatastoreType store, P path);
/**
+ * Submits transaction to be applied to update logical data tree.
+ * <p>
+ * This call logically seals the transaction, which prevents the client from
+ * further changing data tree using this transaction. Any subsequent calls to
+ * {@link #put(LogicalDatastoreType, Path, Object)},
+ * {@link #merge(LogicalDatastoreType, Path, Object)} or
+ * {@link #delete(LogicalDatastoreType, Path)} will fail with
+ * {@link IllegalStateException}.
*
- * Closes transaction and resources allocated to the transaction.
- *
- * This call does not change Transaction status. Client SHOULD
- * explicitly {@link #commit()} or {@link #cancel()} transaction.
- *
- * @throws IllegalStateException if the transaction has not been
- * updated by invoking {@link #commit()} or {@link #cancel()}.
- */
- @Override
- public void close();
-
- /**
- * Initiates a commit of modification. This call logically seals the
- * transaction, preventing any the client from interacting with the
- * data stores. The transaction is marked as {@link TransactionStatus#SUBMITED}
- * and enqueued into the data store backed for processing.
+ * The transaction is marked as {@link TransactionStatus#SUBMITED} and
+ * enqueued into the data store backed for processing.
*
* <p>
- * The successful commit changes the state of the system and may affect
- * several components.
+ * Whether or not the commit is successful is determined by versioning
+ * of data tree and validation of registered commit participants
+ * {@link AsyncConfigurationCommitHandler}
+ * if transaction changes {@link LogicalDatastoreType#CONFIGURATION} data tree.
+ *<p>
+ * The effects of successful commit of data depends on
+ * other data change listeners {@link AsyncDataChangeListener} and
+ * {@link AsyncConfigurationCommitHandler}, which was registered to the
+ * same {@link AsyncDataBroker}, to which this transaction belongs.
*
+ * <h2>Failure scenarios</h2>
* <p>
- * The effects of successful commit of data are described in the
- * specifications and YANG models describing the Provider components of
- * controller. It is assumed that Consumer has an understanding of this
- * changes.
- *
- * @see DataCommitHandler for further information how two-phase commit is
- * processed.
- * @param store Identifier of the store, where commit should occur.
+ * Transaction may fail because of multiple reasons, such as
+ * <ul>
+ * <li>Another transaction finished earlier and modified the same node in
+ * non-compatible way (see below). In this case the returned future will fail with
+ * {@link OptimisticLockFailedException}. It is the responsibility of the
+ * caller to create a new transaction and submit the same modification again in
+ * order to update data tree.</li>
+ * <li>Data change introduced by this transaction did not pass validation by
+ * commit handlers or data was incorrectly structured. Returned future will
+ * fail with {@link DataValidationFailedException}. User should not retry to
+ * create new transaction with same data, since it probably will fail again.
+ * </li>
+ * </ul>
+ *
+ * <h3>Change compatibility</h3>
+ *
+ * There are several sets of changes which could be considered incompatible
+ * between two transactions which are derived from same initial state.
+ * Rules for conflict detection applies recursively for each subtree
+ * level.
+ *
+ * <h4>Change compatibility of leafs, leaf-list items</h4>
+ *
+ * Following table shows state changes and failures between two concurrent transactions,
+ * which are based on same initial state, Tx 1 completes successfully
+ * before Tx 2 is submitted.
+ *
+ * <table>
+ * <tr><th>Initial state</th><th>Tx 1</th><th>Tx 2</th><th>Result</th></tr>
+ * <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>
+ * <tr><td>Empty</td><td>put(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
+ *
+ * <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>
+ * <tr><td>Empty</td><td>merge(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
+ *
+ *
+ * <tr><td>A=0</td><td>put(A,1)</td><td>put(A,2)</td><td>Tx 2 will fail, A=1</td></tr>
+ * <tr><td>A=0</td><td>put(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
+ * <tr><td>A=0</td><td>merge(A,1)</td><td>put(A,2)</td><td>Tx 2 will fail, A=1</td></tr>
+ * <tr><td>A=0</td><td>merge(A,1)</td><td>merge(A,2)</td><td>A=2</td></tr>
+ *
+ * <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>
+ * <tr><td>A=0</td><td>delete(A)</td><td>merge(A,2)</td><td>A=2</td></tr>
+ * </table>
+ *
+ * <h4>Change compatibility of subtrees</h4>
+ *
+ * Following table shows state changes and failures between two concurrent transactions,
+ * which are based on same initial state, Tx 1 completes successfully
+ * before Tx 2 is submitted.
+ *
+ * <table>
+ * <tr><th>Initial state</th><th>Tx 1</th><th>Tx 2</th><th>Result</th></tr>
+ *
+ * <tr><td>Empty</td><td>put(TOP,[])</td><td>put(TOP,[])</td><td>Tx 2 will fail, state is TOP=[]</td></tr>
+ * <tr><td>Empty</td><td>put(TOP,[])</td><td>merge(TOP,[])</td><td>TOP=[]</td></tr>
+ *
+ * <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]</td></tr>
+ * <tr><td>Empty</td><td>put(TOP,[FOO=1])</td><td>merge(TOP,[BAR=1])</td><td>TOP=[FOO=1,BAR=1]</td></tr>
+ *
+ * <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]</td></tr>
+ * <tr><td>Empty</td><td>merge(TOP,[FOO=1])</td><td>merge(TOP,[BAR=1])</td><td>TOP=[FOO=1,BAR=1]</td></tr>
+ *
+ * <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]</td></tr>
+ * <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>
+ * <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]</td></tr>
+ * <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>
+ * <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>
+ * <tr><td>TOP=[]</td><td>delete(TOP)</td><td>merge(TOP,[BAR=1])</td><td>state is TOP=[BAR=1]</td></tr>
+ *
+ * <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>
+ * <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>
+ * <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>
+ * <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>
+ * <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>
+ * <tr><td>TOP=[]</td><td>delete(TOP)</td><td>merge(TOP/BAR,1]</td><td>Tx 2 will fail, state is empty store</td></tr>
+ *
+ * <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>
+ * <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>
+ * <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>
+ * <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]</td></tr>
+ * <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>
+ * <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>
+ * </table>
+ *
+ *
+ * <h3>Examples of failure scenarios</h3>
+ *
+ * <h4>Conflict of two transactions</h4>
+ *
+ * This example illustrates two concurrent transactions, which derived from
+ * same initial state of data tree and proposes conflicting modifications.
+ *
+ * <pre>
+ * txA = broker.newWriteTransaction(); // allocates new transaction, data tree is empty
+ * txB = broker.newWriteTransaction(); // allocates new transaction, data tree is empty
+ *
+ * txA.put(CONFIGURATION, PATH, A); // writes to PATH value A
+ * txB.put(CONFIGURATION, PATH, B) // writes to PATH value B
+ *
+ * ListenableFuture futureA = txA.commit(); // transaction A is sealed and committed
+ * ListenebleFuture futureB = txB.commit(); // transaction B is sealed and committed
+ * </pre>
+ *
+ * Commit of transaction A will be processed asynchronously and data tree
+ * will be updated to contain value <code>A</code> for <code>PATH</code>.
+ * Returned {@link ListenableFuture} will successfully complete once
+ * state is applied to data tree.
+ *
+ * Commit of Transaction B will fail, because previous transaction also
+ * modified path in a concurrent way. The state introduced by transaction B
+ * will not be applied. Returned {@link ListenableFuture} object will fail
+ * with {@link OptimisticLockFailedException} exception, which indicates to
+ * client that concurrent transaction prevented the submitted transaction from being
+ * applied.
+ *
* @return Result of the Commit, containing success information or list of
* encountered errors, if commit was not successful. The Future
- * blocks until {@link TransactionStatus#COMMITED} or
- * {@link TransactionStatus#FAILED} is reached.
- * @throws IllegalStateException if the transaction is not {@link TransactionStatus#NEW}
+ * blocks until {@link TransactionStatus#COMMITED} is reached.
+ * Future will fail with {@link TransactionCommitFailedException} if
+ * Commit of this transaction failed. TODO: Usability: Consider
+ * change from ListenableFuture to
+ * {@link com.google.common.util.concurrent.CheckedFuture} which
+ * will throw {@link TransactionCommitFailedException}.
+ *
+ * @throws IllegalStateException
+ * if the transaction is not {@link TransactionStatus#NEW}
*/
- public Future<RpcResult<TransactionStatus>> commit();
+ public ListenableFuture<RpcResult<TransactionStatus>> commit();
}
Code Review / controller.git / blobdiff