Package me.ahoo.cosid.proxy

Class ProxyMachineLeaseStore

java.lang.Object

me.ahoo.cosid.proxy.ProxyMachineLeaseStore

All Implemented Interfaces:

MachineLeaseStore

public class ProxyMachineLeaseStore
extends Object
implements MachineLeaseStore

MachineLeaseStore through a CosId proxy server's version 2 lease API: each primitive is one HTTP call to the server, which passes it to its backend store. The server clock is the backend store's.

Constructor Summary

Constructors

Constructor	Description
ProxyMachineLeaseStore(MachineLeaseApi leaseApi)

Method Summary

Modifier and Type	Method	Description
Optional<Lease>	claimExpired(String namespace, InstanceId instanceId, int maxMachineId, long expiredBefore, long now)	Take over a machine id whose owner has not renewed it since expiredBefore.
Optional<Lease>	claimNew(String namespace, InstanceId instanceId, int maxMachineId, long now)	Take the next machine id that was never used in the namespace.
Optional<Lease>	claimReleased(String namespace, InstanceId instanceId, int maxMachineId, long now)	Take a machine id that a non-stable instance released on shutdown.
Optional<Lease>	claimSelf(String namespace, InstanceId instanceId, long now)	Take back the lease this instance already holds, renewing it to now, whether or not it has expired.
boolean	release(Lease lease, long watermark)	Release a lease on shutdown, if it is still the current version.
Optional<Lease>	renew(Lease lease, long now)	Renew a lease to now if it is still the current version, even when now is before the stored renewed at (the store clock moved back).
long	serverTime()	The backend store's clock, through the server.

Methods inherited from class java.lang.Object

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

Constructor Details

ProxyMachineLeaseStore

public ProxyMachineLeaseStore(MachineLeaseApi leaseApi)

Method Details

claimSelf

public Optional<Lease> claimSelf(String namespace,
 InstanceId instanceId,
 long now)

Description copied from interface: MachineLeaseStore

Take back the lease this instance already holds, renewing it to now, whether or not it has expired. The watermark is raised to at least now and the stored renewed at.

Specified by:

claimSelf in interface MachineLeaseStore

Returns:

the renewed lease, or empty if the instance holds none (it was released or recycled)

claimReleased

public Optional<Lease> claimReleased(String namespace,
 InstanceId instanceId,
 int maxMachineId,
 long now)

Description copied from interface: MachineLeaseStore

Take a machine id that a non-stable instance released on shutdown.

Specified by:

claimReleased in interface MachineLeaseStore

maxMachineId - the largest machine id allowed: released ids above it (left over from a larger machine bit) are never returned

Returns:

the new lease, or empty if no released machine id up to maxMachineId is left

claimNew

public Optional<Lease> claimNew(String namespace,
 InstanceId instanceId,
 int maxMachineId,
 long now)

Description copied from interface: MachineLeaseStore

Take the next machine id that was never used in the namespace.

Specified by:

claimNew in interface MachineLeaseStore

maxMachineId - the largest machine id allowed

Returns:

the new lease, or empty if every machine id up to maxMachineId is in use

claimExpired

public Optional<Lease> claimExpired(String namespace,
 InstanceId instanceId,
 int maxMachineId,
 long expiredBefore,
 long now)

Description copied from interface: MachineLeaseStore

Take over a machine id whose owner has not renewed it since expiredBefore. Leases of stable instances are never taken over.

Specified by:

claimExpired in interface MachineLeaseStore

maxMachineId - the largest machine id allowed: expired ids above it are never returned

expiredBefore - leases renewed at or before this time are expired

Returns:

the new lease, or empty if no lease up to maxMachineId has expired

renew

public Optional<Lease> renew(Lease lease,
 long now)

Description copied from interface: MachineLeaseStore

Renew a lease to now if it is still the current version, even when now is before the stored renewed at (the store clock moved back). The watermark is unchanged.

Specified by:

renew in interface MachineLeaseStore

Returns:

the renewed lease, or empty if the lease was taken over, released or changed since

release

public boolean release(Lease lease,
 long watermark)

Description copied from interface: MachineLeaseStore

Release a lease on shutdown, if it is still the current version. A stable instance keeps its machine id (only the watermark is updated); otherwise the machine id becomes available to MachineLeaseStore.claimReleased(java.lang.String, me.ahoo.cosid.machine.InstanceId, int, long).

Specified by:

release in interface MachineLeaseStore

watermark - the generator's last timestamp: the watermark becomes at least this, so that the next owner waits if its clock is behind

Returns:

false if the lease was taken over or changed since

serverTime

public long serverTime()

The backend store's clock, through the server.

Specified by:

serverTime in interface MachineLeaseStore