com.sleepycat.je.rep.arbitration

Class DesignatedPrimaryProvider

java.lang.Object

com.sleepycat.je.rep.arbitration.DesignatedPrimaryProvider

All Implemented Interfaces:

ArbiterProvider

public class DesignatedPrimaryProvider
extends Object
implements ArbiterProvider

Designated Primary arbitration relies on the configuration parameter je.rep.designatedPrimary. This form of arbitration is only effective when the electable group size is 2. When one of the two electable nodes goes down, the remaining node is permitted to win elections, retain authoritative mastership, and commit transactions without any participation from its dead sibling, if and only if it has been configured as designated primary.

The user is responsible for ensuring that only one node at any time is annointed as the designated primary. There is some sanity checking that designated primary is only set by one node by master/replica syncups. The parameter is mutable.

Method Summary

Modifier and Type	Method and Description
boolean	activationPossible() Return true if this node is in a 2-node group and is configured as the Designated Primary, and is therefore capable of entering active arbitration.
boolean	attemptActivation() Try to activate this node as a Primary, if it has been configured as such and if the group size is two.
void	endArbitration() No cleannup is needed when exiting designated primary arbitration.
int	getAckCount(Durability.ReplicaAckPolicy ackPolicy) Always returns 0, no replica acks are needed when acting under designated primary arbitration.
int	getElectionQuorumSize(QuorumPolicy quorumPolicy) When operating under designated primary arbitration, the election quorum is 1 for a group with electable group size of 2,
boolean	shouldEndArbitration(ReplicationMutableConfig newConfig) Return true if this node is no longer configured as the designated primary under the new configuration.

Methods inherited from class java.lang.Object

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

Method Detail

attemptActivation

public boolean attemptActivation()

Try to activate this node as a Primary, if it has been configured as such and if the group size is two. This method is invoked when an operation falls short of quorum requirements and is ready to trade durability for availability. More specifically it's invoked when an election fails, or there is an insufficient number of replicas during a begin transaction or a transaction commit. Active arbitration ends when the Non-Primary contacts it.

Specified by:

attemptActivation in interface ArbiterProvider

Returns:

true if the primary was activated.

activationPossible

public boolean activationPossible()

Return true if this node is in a 2-node group and is configured as the Designated Primary, and is therefore capable of entering active arbitration.

Specified by:

activationPossible in interface ArbiterProvider

endArbitration

public void endArbitration()

No cleannup is needed when exiting designated primary arbitration.

Specified by:

endArbitration in interface ArbiterProvider

getElectionQuorumSize

public int getElectionQuorumSize(QuorumPolicy quorumPolicy)

When operating under designated primary arbitration, the election quorum is 1 for a group with electable group size of 2,

Specified by:

getElectionQuorumSize in interface ArbiterProvider

getAckCount

public int getAckCount(Durability.ReplicaAckPolicy ackPolicy)

Always returns 0, no replica acks are needed when acting under designated primary arbitration. TODO: is this still true with non voting nodes?

Specified by:

getAckCount in interface ArbiterProvider

shouldEndArbitration

public boolean shouldEndArbitration(ReplicationMutableConfig newConfig)

Return true if this node is no longer configured as the designated primary under the new configuration.

Specified by:

shouldEndArbitration in interface ArbiterProvider