org.javagroups.service.lease
Interface LeaseFactory

All Known Implementing Classes:

LeaseFactoryClient

public interface LeaseFactory

LeaseFactory is responsible for granting new leases, renewing existing leases and canceling leases when it is no longer needed. For batch purposes, LeaseFactory creates instances of LeaseGroup.

Author:

Roman Rokytskyy (rrokytskyy@acm.org)

Field Summary

static long	DURATION_ANY This constant represents arbitrary duration.
static long	DURATION_FOREVER This constant represents maximum possible duration.

Method Summary

void	cancelLease(Lease existingLease) Cancels existing lease.
Lease	newLease(java.lang.Object leaseTarget, java.lang.Object tenant, long requestedDuration, boolean isAbsolute) Obtain new lease.
Lease	renewLease(Lease existingLease, long requestedDuration, boolean isAbsolute) Renew existing lease.

Field Detail

DURATION_ANY

static final long DURATION_ANY

This constant represents arbitrary duration. When passed to LeaseFactory#newLease(Object, long, boolean), implementation grants lease for a duration that best fits leased resource.

See Also:

Constant Field Values

DURATION_FOREVER

static final long DURATION_FOREVER

This constant represents maximum possible duration. When passed to LeaseFactory#newLease(Object, long, boolean), implementation usually will grant lease for a maximum possible duration for leased resource.

See Also:

Constant Field Values

Method Detail

newLease

Lease newLease(java.lang.Object leaseTarget,
               java.lang.Object tenant,
               long requestedDuration,
               boolean isAbsolute)
               throws LeaseDeniedException

Obtain new lease. When client wants to access to resource that is protected by leasing mechanism, he needs to obtain lease. Each lease contains lease target that is unique identifier of resource and lease duration, either relative or absolute. LeaseFactory checks its internal lease map and decides if the lease can be granted or not. In latter case, LeaseDeniedException is thrown.

Parameters:

leaseTarget - unique identifier of resource to be leased.

tenant - unique identifier of entity that requests lease.

leaseDuration - duration of lease in milliseconds.

isAbsolute - specified if lease duration is absolute or relative.

Returns:

instance of Lease representing granted lease. Note, granted lease might have different duration than requested.

Throws:

LeaseDeniedException - if lease cannot be granted.

renewLease

Lease renewLease(Lease existingLease,
                 long requestedDuration,
                 boolean isAbsolute)
                 throws LeaseDeniedException

Renew existing lease. This method extends lease duration from now for a specified duration. If existingLease has expired, an exception is thrown. In this case client has to use #newLease(Object, long, boolean) method to obtain a lease.

Parameters:

leaseTarget - unique identifier of resource to be leased.

leaseDuration - duration of lease in milliseconds.

isAbsolute - specified if lease duration is absolute or relative.

Returns:

instance of Lease representing granted lease. Note, granted lease might have different duration than requested.

Throws:

LeaseDeniedException - if lease cannot be granted.

cancelLease

void cancelLease(Lease existingLease)
                 throws UnknownLeaseException

Cancels existing lease. After invoking this method leased resource is free.

Parameters:

existingLease - lease to cancel.

Throws:

UnknownLeaseException - if existingLease is unknown for this lease factory. Usually means that lease was granted by another factory.