com.sleepycat.je.rep.impl.node

Class DurabilityQuorum

java.lang.Object

com.sleepycat.je.rep.impl.node.DurabilityQuorum

public class DurabilityQuorum
extends Object

Provides information about quorums needed for durability decisions.

Constructor Summary

Constructors

Constructor and Description
DurabilityQuorum(RepImpl repImpl)

Method Summary

Modifier and Type	Method and Description
void	ensureReplicasForCommit(MasterTxn txn, int insufficientReplicasTimeout) See if there are a sufficient number of replicas alive to support the commit for this transaction.
void	ensureSufficientAcks(FeederTxns.TxnInfo txnInfo, int timeoutMs) Determine if this transaction has been adequately acknowledged.
int	getCurrentRequiredAckCount(Durability.ReplicaAckPolicy ackPolicy) Returns the minimum number of acknowledgments required to satisfy the ReplicaAckPolicy for a given group size.
boolean	replicaAcksQualify(RepNodeImpl replica) Determine whether acknowledgments from the specified replica should be counted against transaction durability requirements.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DurabilityQuorum

public DurabilityQuorum(RepImpl repImpl)

Method Detail

ensureReplicasForCommit

public void ensureReplicasForCommit(MasterTxn txn,
                                    int insufficientReplicasTimeout)
                             throws DatabaseException,
                                    InterruptedException,
                                    InsufficientReplicasException

See if there are a sufficient number of replicas alive to support the commit for this transaction. Used as an optimizing step before any writes are executed, to reduce the number of outstanding writes that suffer from insufficient ack problems. If this node is not the master, just return. A different kind of check will catch the fact that this node cannot support writes. TODO: Read only transactions on the master should not have to wait. In the future, introduce either a read-only attribute as part of TransactionConfig or a read only transaction class to optimize this.

Parameters:

insufficientReplicasTimeout - timeout in ms

Throws:

InsufficientReplicasException - if there are not enough replicas connected to this feeder to be able to commit the transaction.

DatabaseException

InterruptedException

replicaAcksQualify

public boolean replicaAcksQualify(RepNodeImpl replica)

Determine whether acknowledgments from the specified replica should be counted against transaction durability requirements.

Parameters:

replica - the replica node

Returns:

whether acknowledgments from the replica should be counted

ensureSufficientAcks

public void ensureSufficientAcks(FeederTxns.TxnInfo txnInfo,
                                 int timeoutMs)
                          throws InsufficientAcksException

Determine if this transaction has been adequately acknowledged.

Throws:

InsufficientAcksException - if the transaction's durability requirements have not been met.

getCurrentRequiredAckCount

public int getCurrentRequiredAckCount(Durability.ReplicaAckPolicy ackPolicy)

Returns the minimum number of acknowledgments required to satisfy the ReplicaAckPolicy for a given group size. Does not include the master. The method factors in considerations like the current arbitration status of the environment and the composition of the replication group. TODO: it seems sufficient to return a number, as opposed to a set of qualified ack nodes, as long as replicaAcksQualify(com.sleepycat.je.rep.impl.RepNodeImpl) will only count qualified acks against the required count. That does mean that getCurrentRequiredAckCount and noteReplicaAcks for a transaction must be kept consistent.

Returns:

the number of nodes that are needed, not including the master.