com.atomikos.icatch
Interface Participant

All Superinterfaces:

Serializable

All Known Implementing Classes:

CoordinatorImp, ReadOnlyParticipant, RollbackOnlyParticipant, SubTransactionCoordinatorParticipant, XAResourceTransaction

public interface Participant
extends Serializable

A participant for 2PC of composite transactions. Implementations can be added as a 2PC participant in the icatch kernel. VERY IMPORTANT: implementations should also override the default equals and hashCode methods, in order for 2PC to work!

Field Summary

static int

READ_ONLY Indicates that no commit/rollback needed after prepare.

Method Summary

HeuristicMessage[]	commit(boolean onePhase) Commit the participant's work.
void	forget() Indicate that a heuristic participant can forget about its work.
HeuristicMessage[]	getHeuristicMessages() Get any heuristic messages so far.
String	getURI() Gets a unique URI for this participant.
int	prepare() Prepare the participant.
boolean	recover() Recover this instance.
HeuristicMessage[]	rollback() Rollback the participant's work.
void	setCascadeList(Dictionary allParticipants) For cascading 2PC, this method sets the information needed to cascade.
void	setGlobalSiblingCount(int count) Set by the root coordinator: the total no of siblings detected.

Field Detail

READ_ONLY

static final int READ_ONLY

Indicates that no commit/rollback needed after prepare.

See Also:

Constant Field Values

Method Detail

recover

boolean recover()
                throws SysException

Recover this instance. Called by the transaction manager (TM) at recovery time, and this should reconstruct the internal state.

Returns:

boolean False iff the instance could not be recovered. It is up to the TM to determine the severity of this case.

Throws:

SysException - On failure.

getURI

String getURI()

Gets a unique URI for this participant. Local participants should merely return null.

Returns:

String The URI for this participant, or null if not applicable.

setCascadeList

void setCascadeList(Dictionary allParticipants)
                    throws SysException

For cascading 2PC, this method sets the information needed to cascade. This method is relevant only for transaction monitors; leave empty otherwise!

Parameters:

allParticipants - The information needed by the transaction monitor for

Throws:

SysException - For unexpected failures.

setGlobalSiblingCount

void setGlobalSiblingCount(int count)

Set by the root coordinator: the total no of siblings detected. This method is relevant only for transaction monitors; leave empty otherwise!

Parameters:

count - The global count.

prepare

int prepare()
            throws RollbackException,
                   HeurHazardException,
                   HeurMixedException,
                   SysException

Prepare the participant. Any locks for this participant's work should be recoverable (either saved to an external file OR be part of the instance's non-transient state so that they can be flushed into the transaction manager's log).

Returns:

int If this is READ_ONLY, then no second round is needed. Participants that return this value on prepare will not be called by commit or rollback afterwards.

Throws:

RollbackException - For a NO vote. This indicates that the participant has already rolled back (or marked for rollback) the work on behalf of this participant.

HeurHazardException - On possible conflicts. This happens for remote participants instances, in case of communication failures.

HeurMixedException - If some subordinate participants voted YES, timed out and committed heuristically whereas afterwards some NO votes where received.

SysException - Unexpected errors.

commit

HeuristicMessage[] commit(boolean onePhase)
                          throws HeurRollbackException,
                                 HeurHazardException,
                                 HeurMixedException,
                                 RollbackException,
                                 SysException

Commit the participant's work. NOTE: custom participant implementations should preferably be made for the server's local VM (e.g., it is better not to do this over RMI). Also, they should rely on the icatch transaction manager for heuristic timeout (and NOT decide to terminate heuristically themselves). In that case, implementations never need to throw any of the heuristic exceptions of this method.

Parameters:

onePhase - If true, one-phase commit is being started. If the participant has received a prepare call earlier, then it should throw a SysException here.

Returns:

HeuristicMessage[] An array of messages, null if none.

Throws:

HeuristicRollbackException - If the participant has rolled back.

HeuristicMixedException - If part of it was rolled back.

HeurHazardException - On possible conflicts.

RollbackException - In case of one-phase commit, and the transaction has been rolled back at the time commit is called.

SysException - Unexpected failure.

HeurRollbackException

HeurMixedException

rollback

HeuristicMessage[] rollback()
                            throws HeurCommitException,
                                   HeurMixedException,
                                   HeurHazardException,
                                   SysException

Rollback the participant's work. NOTE: custom participant implementations should preferably be made for the server's local VM (e.g., it is better not to do this over RMI). Also, they should rely on the icatch transaction manager for heuristic timeout (and NOT decide to terminate heuristically themselves). In that case, implementations never need to throw any of the heuristic exceptions of this method.

Returns:

HeuristicMessage[] An array of messages, null if none.

Throws:

HeurCommitException - If the participant committed.

HeurHazardException - If the participant's final state is unsure.

HeurMixedException - If part of it was rolled back.

SysException - Unexpected failure.

forget

void forget()

Indicate that a heuristic participant can forget about its work. If implementations rely on the transaction manager to decide when to do heuristics (rather then deciding in the participant implementation), then leave this method empty.

getHeuristicMessages

HeuristicMessage[] getHeuristicMessages()

Get any heuristic messages so far. The transaction manager used this method to get information after preparing this participant.

Returns:

HeuristicMessage[] An array of heuristic messages, or null if none.