weblogic.cluster.singleton
Class SimpleLeasingBasis

java.lang.Object
  weblogic.cluster.singleton.SimpleLeasingBasis

All Implemented Interfaces:

LeasingBasis

Direct Known Subclasses:

ReplicatedLeasingBasis

public class SimpleLeasingBasis
extends Object
implements LeasingBasis

Dumb LeasingBasis that holds leases in-memory. Should only be used in conjunction with replication or for testing purposes.

SimpleLeasingBasis

public SimpleLeasingBasis()

SimpleLeasingBasis

public SimpleLeasingBasis(Map leaseTable)

getLeaseTable

protected Map getLeaseTable()

acquire

public boolean acquire(String leaseName,
                       String owner,
                       int leaseTimeout)

Description copied from interface: LeasingBasis

Attempts to claim immediate ownership of a lease for this server. Returns true if the lease was successfully claimed or if it is already owned by the server. Returns false if the lease is owned by another server. Throws a LeasingException if there were infrastructure problems trying to get ownership. The leaseTimeout specifies how long the lease will last.

Specified by:

acquire in interface LeasingBasis

leaseTimeout - in milliseconds

Returns:

true if the lease was aquired

release

public void release(String leaseName,
                    String owner)
             throws IOException

Description copied from interface: LeasingBasis

If the lease is owned by this server, attempts to give up ownership. Otherwise does nothing. Throws a LeasingException if infrastructure problems make it impossible to access the lease.

Specified by:

release in interface LeasingBasis

Throws:

IOException

findOwner

public String findOwner(String leaseName)

Description copied from interface: LeasingBasis

Returns the identity of the server that currently owns the lease. Returns null if the lease is not owned. The lease is not considered to be owned if it has been claimed by a server that has missed heartbeats. This is a best-effort result in that the answer may change after the value is returned. Throws a LeasingException if infrastructure problems make it impossible to determine who owns the lease.

Specified by:

findOwner in interface LeasingBasis

Returns:

name of the owner

findPreviousOwner

public String findPreviousOwner(String leaseName)

Specified by:

findPreviousOwner in interface LeasingBasis

renewAllLeases

public int renewAllLeases(int healthCheckPeriod,
                          String owner)
                   throws MissedHeartbeatException

Description copied from interface: LeasingBasis

Attempts to send a heartbeat to prove the health of the server. Determines whether or not the heartbeat was sent in a timely manner. This determination should ideally be precise. If it is not, then it has to err on the safe side, i.e., it is better to falsely indicate that a Heartbeat was missed than to fail to indicate that a Heartbeat was missed. The heartbeat is sent for the next period even if the last one was missed. This minimizes the chances of damage while the system is signaling for corrective action. This is semantically equivalent to renewing all of the outstanding leases.

Specified by:

renewAllLeases in interface LeasingBasis

Parameters:

healthCheckPeriod - in milliseconds

Returns:

number of owned leases

Throws:

MissedHeartbeatException

renewLeases

public int renewLeases(String owner,
                       Set leases,
                       int healthCheckPeriod)
                throws MissedHeartbeatException

Description copied from interface: LeasingBasis

Attempts to renew all the currently held leases.

Specified by:

renewLeases in interface LeasingBasis

leases - to be renewed

healthCheckPeriod - in milliseconds

Returns:

number of leases renewed

Throws:

MissedHeartbeatException

findExpiredLeases

public String[] findExpiredLeases(int gracePeriod)

Description copied from interface: LeasingBasis

Returns a list of the servers that have consistently missed sending heartbeats in a timely manner, and failed to do so for longer than their grace period. INVARIANT: If a server stops heartbeating PERMANENTLY, then it will EVENTUALLY be returned in this list, although there is no guarantee as to how long that will take.

Specified by:

findExpiredLeases in interface LeasingBasis

Parameters:

gracePeriod - in milliseconds