org.omg.CosTransactions
Interface ResourceOperations
- All Known Subinterfaces:
- Resource, SubtransactionAwareResource, SubtransactionAwareResourceOperations
- All Known Implementing Classes:
- _ResourceStub, _SubtransactionAwareResourceStub, ResourcePOA, SubCoordinator, SubtransactionAwareResourcePOA
- public interface ResourceOperations
The Transaction Service uses a two-phase commitment protocol to complete a top-level
transaction with each registered resource. The Resource interface defines the
operations invoked by the transaction service on each resource. Each object supporting
the Resource interface is implicitly associated with a single top-level transaction. Note
that in the case of failure, the completion sequence will continue after the failure is
repaired. A resource should be prepared to receive duplicate requests for the commit or
rollback operation and to respond consistently.
Method Summary |
void |
commit_one_phase()
If possible, the resource should commit all changes made as part of the transaction. |
void |
commit()
If necessary, the resource should commit all changes made as part of the transaction. |
void |
forget()
This operation is performed only if the resource raised a heuristic outcome exception
to rollback, commit, or commit_one_phase. |
Vote |
prepare()
This operation is invoked to begin the two-phase commit protocol on the resource. |
void |
rollback()
If necessary, the resource should rollback all changes made as part of the transaction. |
prepare
public Vote prepare()
throws HeuristicMixed,
HeuristicHazard
- This operation is invoked to begin the two-phase commit protocol on the resource. The
resource can respond in several ways, represented by the Vote result.
If no persistent data associated with the resource has been modified by the transaction,
the resource can return VoteReadOnly. After receiving this response, the Transaction
Service is not required to perform any additional operations on this resource.
Furthermore, the resource can forget all knowledge of the transaction.
If the resource is able to write (or has already written) all the data needed to commit
the transaction to stable storage, as well as an indication that it has prepared the
transaction, it can return VoteCommit. After receiving this response, the Transaction
Service is required to eventually perform either the commit or the rollback operation on
this object. To support recovery, the resource should store the RecoveryCoordinator
object reference in stable storage.
The resource can return VoteRollback under any circumstances, including not having
any knowledge about the transaction (which might happen after a crash). If this
response is returned, the transaction must be rolled back. Furthermore, the Transaction
Service is not required to perform any additional operations on this resource. After
returning this response, the resource can forget all knowledge of the transaction.
The resource reports inconsistent outcomes using the HeuristicMixed and HeuristicHazard
exceptions. Heuristic outcomes occur when a resource acts as a sub-coordinator and at least
one of its resources takes a heuristic decision after a VoteCommit return.
- Throws:
HeuristicMixed
HeuristicHazard
rollback
public void rollback()
throws HeuristicCommit,
HeuristicMixed,
HeuristicHazard
- If necessary, the resource should rollback all changes made as part of the transaction.
If the resource has forgotten the transaction, it should do nothing.
The heuristic outcome exceptions are used
to report heuristic decisions related to the resource. If a heuristic outcome exception is
raised, the resource must remember this outcome until the forget operation is performed
so that it can return the same outcome in case rollback is performed again. Otherwise,
the resource can immediately forget all knowledge of the transaction.
- Throws:
HeuristicCommit
HeuristicMixed
HeuristicHazard
commit
public void commit()
throws NotPrepared,
HeuristicRollback,
HeuristicMixed,
HeuristicHazard
- If necessary, the resource should commit all changes made as part of the transaction. If
the resource has forgotten the transaction, it should do nothing.
The heuristic outcome exceptions are used
to report heuristic decisions related to the resource. If a heuristic outcome exception is
raised, the resource must remember this outcome until the forget operation is performed
so that it can return the same outcome in case commit is performed again. Otherwise,
the resource can immediately forget all knowledge of the transaction.
The NotPrepared exception is raised if the commit operation is performed without first
performing the prepare operation.
- Throws:
NotPrepared
HeuristicRollback
HeuristicMixed
HeuristicHazard
commit_one_phase
public void commit_one_phase()
throws HeuristicHazard
- If possible, the resource should commit all changes made as part of the transaction. If
it cannot, it should raise the TRANSACTION_ROLLEDBACK standard exception.
If a failure occurs during commit_one_phase, it must be retried when the failure is
repaired. Since their can only be a single resource, the HeuristicHazard exception is used
to report heuristic decisions related to that resource. If a heuristic exception is raised,
the resource must remember this outcome until the forget operation is performed so that
it can return the same outcome in case commit_one_phase is performed again. Otherwise,
the resource can immediately forget all knowledge of the transaction.
- Throws:
HeuristicHazard
forget
public void forget()
- This operation is performed only if the resource raised a heuristic outcome exception
to rollback, commit, or commit_one_phase. Once the coordinator has determined that the
heuristic situation has been addressed, it should issue forget on the resource. The
resource can forget all knowledge of the transaction.