X-Git-Url: https://git.opendaylight.org/gerrit/gitweb?a=blobdiff_plain;f=opendaylight%2Fmd-sal%2Fsal-common-api%2Fsrc%2Fmain%2Fjava%2Forg%2Fopendaylight%2Fcontroller%2Fmd%2Fsal%2Fcommon%2Fapi%2Fdata%2FAsyncReadWriteTransaction.java;h=16b4ed4fe2ed14d7cf7db8e5e88621df801d9f1c;hb=5c2c22d99e522ccdc164287757fd2defa62a9f9c;hp=ce740bf41d9d798bb69bf42c573f4a6a98ecbaa9;hpb=d5759c52d69ba8725d9bbdc18e81848f319861d1;p=controller.git diff --git a/opendaylight/md-sal/sal-common-api/src/main/java/org/opendaylight/controller/md/sal/common/api/data/AsyncReadWriteTransaction.java b/opendaylight/md-sal/sal-common-api/src/main/java/org/opendaylight/controller/md/sal/common/api/data/AsyncReadWriteTransaction.java index ce740bf41d..16b4ed4fe2 100644 --- a/opendaylight/md-sal/sal-common-api/src/main/java/org/opendaylight/controller/md/sal/common/api/data/AsyncReadWriteTransaction.java +++ b/opendaylight/md-sal/sal-common-api/src/main/java/org/opendaylight/controller/md/sal/common/api/data/AsyncReadWriteTransaction.java @@ -10,12 +10,128 @@ package org.opendaylight.controller.md.sal.common.api.data; import org.opendaylight.yangtools.concepts.Path; /** - * Transaction enabling client to have combined transaction, - * which provides read and write capabilities. + * Transaction enabling a client to have a combined read/write capabilities. * + *
+ * The initial state of the write transaction is stable snapshot of current data tree + * state captured when transaction was created and it's state and underlying + * data tree are not affected by other concurrently running transactions. * - * @param
Path Type
- * @param
+ * Write transactions are isolated from other concurrent write transactions. All
+ * writes are local to the transaction and represents only a proposal of state
+ * change for data tree and it is not visible to any other concurrently running
+ * transactions.
+ *
+ *
+ * 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.
+ *
+ *
+ * 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.
+ *
+ * Implementation Note: This interface is not intended to be implemented
+ * by users of MD-SAL, but only to be consumed by them.
+ *
+ *
+ * Note: examples contains blocking calls on future only to illustrate
+ * that action happened after other asynchronous action. Use of blocking call
+ * {@link com.google.common.util.concurrent.ListenableFuture#get()} is discouraged for most uses and you should
+ * use
+ * {@link com.google.common.util.concurrent.Futures#addCallback(com.google.common.util.concurrent.ListenableFuture, com.google.common.util.concurrent.FutureCallback)}
+ * or other functions from {@link com.google.common.util.concurrent.Futures} to
+ * register more specific listeners.
+ *
+ * @see AsyncReadTransaction
+ * @see AsyncWriteTransaction
+ *
+ * @param
+ * Type of path (subtree identifier), which represents location in
+ * tree
+ * @param , D> extends AsyncReadTransaction ,
AsyncWriteTransaction {
Examples
+ *
+ * Transaction local state
+ *
+ * Let assume initial state of data tree for PATH
is A
+ * .
+ *
+ *
+ * txWrite = broker.newReadWriteTransaction(); // concurrent write transaction
+ *
+ * txWrite.read(OPERATIONAL,PATH).get() // will return Optional containing A
+ * txWrite.put(OPERATIONAL,PATH,B); // writes B to PATH
+ * txWrite.read(OPERATIONAL,PATH).get() // will return Optional Containing B
+ *
+ * txWrite.commit().get(); // data tree is updated, PATH contains B
+ *
+ * tx1afterCommit = broker.newReadOnlyTransaction(); // read Transaction is snapshot of new state
+ * tx1afterCommit.read(OPERATIONAL,PATH).get(); // returns Optional containing B
+ *
+ *
+ * As you could see read-write transaction provides capabilities as
+ * {@link AsyncWriteTransaction} but also allows for reading proposed changes as
+ * if they already happened.
+ *
+ * Transaction isolation (read transaction, read-write transaction)
Let
+ * assume initial state of data tree for PATH
is A
.
+ *
+ *
+ * txRead = broker.newReadOnlyTransaction(); // read Transaction is snapshot of data
+ * txWrite = broker.newReadWriteTransaction(); // concurrent write transaction
+ *
+ * txRead.read(OPERATIONAL,PATH).get(); // will return Optional containing A
+ * txWrite.read(OPERATIONAL,PATH).get() // will return Optional containing A
+ *
+ * txWrite.put(OPERATIONAL,PATH,B); // writes B to PATH
+ * txWrite.read(OPERATIONAL,PATH).get() // will return Optional Containing B
+ *
+ * txRead.read(OPERATIONAL,PATH).get(); // concurrent read transaction still returns
+ * // Optional containing A
+ *
+ * txWrite.commit().get(); // data tree is updated, PATH contains B
+ * txRead.read(OPERATIONAL,PATH).get(); // still returns Optional containing A
+ *
+ * tx1afterCommit = broker.newReadOnlyTransaction(); // read Transaction is snapshot of new state
+ * tx1afterCommit.read(OPERATIONAL,PATH).get(); // returns Optional containing B
+ *
+ *
+ * Transaction isolation (2 concurrent read-write transactions)
Let
+ * assume initial state of data tree for PATH
is A
.
+ *
+ *
+ * tx1 = broker.newReadWriteTransaction(); // read Transaction is snapshot of data
+ * tx2 = broker.newReadWriteTransaction(); // concurrent write transaction
+ *
+ * tx1.read(OPERATIONAL,PATH).get(); // will return Optional containing A
+ * tx2.read(OPERATIONAL,PATH).get() // will return Optional containing A
+ *
+ * tx2.put(OPERATIONAL,PATH,B); // writes B to PATH
+ * tx2.read(OPERATIONAL,PATH).get() // will return Optional Containing B
+ *
+ * tx1.read(OPERATIONAL,PATH).get(); // tx1 read-write transaction still sees Optional
+ * // containing A since is isolated from tx2
+ * tx1.put(OPERATIONAL,PATH,C); // writes C to PATH
+ * tx1.read(OPERATIONAL,PATH).get() // will return Optional Containing C
+ *
+ * tx2.read(OPERATIONAL,PATH).get() // tx2 read-write transaction still sees Optional
+ * // containing B since is isolated from tx1
+ *
+ * tx2.commit().get(); // data tree is updated, PATH contains B
+ * tx1.read(OPERATIONAL,PATH).get(); // still returns Optional containing C since is isolated from tx2
+ *
+ * tx1afterCommit = broker.newReadOnlyTransaction(); // read Transaction is snapshot of new state
+ * tx1afterCommit.read(OPERATIONAL,PATH).get(); // returns Optional containing B
+ *
+ * tx1.commit() // Will fail with OptimisticLockFailedException
+ * // which means concurrent transaction changed the same PATH
+ *
+ *
+ *
+ *