com.amazonaws.services.kinesis.leases.impl

Class LeaseCoordinator<T extends Lease>

java.lang.Object

com.amazonaws.services.kinesis.leases.impl.LeaseCoordinator<T>

public class LeaseCoordinator<T extends Lease>
extends java.lang.Object

LeaseCoordinator abstracts away LeaseTaker and LeaseRenewer from the application code that's using leasing. It owns the scheduling of the two previously mentioned components as well as informing LeaseRenewer when LeaseTaker takes new leases.

Field Summary

Fields

Modifier and Type	Field and Description
protected IMetricsFactory	metricsFactory
static java.lang.String	WORKER_IDENTIFIER_METRIC

Constructor Summary

Constructors

Constructor and Description
LeaseCoordinator(ILeaseManager<T> leaseManager, java.lang.String workerIdentifier, long leaseDurationMillis, long epsilonMillis) Constructor.
LeaseCoordinator(ILeaseManager<T> leaseManager, java.lang.String workerIdentifier, long leaseDurationMillis, long epsilonMillis, IMetricsFactory metricsFactory) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
java.util.Collection<T>	getAssignments()
T	getCurrentlyHeldLease(java.lang.String leaseKey)
java.lang.String	getWorkerIdentifier()
boolean	isRunning()
protected void	runRenewer() Runs a single iteration of the lease renewer - used by integration tests.
protected void	runTaker() Runs a single iteration of the lease taker - used by integration tests.
void	start() Start background LeaseHolder and LeaseTaker threads.
void	stop() Stops background threads.
boolean	updateLease(T lease, java.util.UUID concurrencyToken) Updates application-specific lease values in DynamoDB.

Methods inherited from class java.lang.Object

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

Field Detail

WORKER_IDENTIFIER_METRIC

public static final java.lang.String WORKER_IDENTIFIER_METRIC

See Also:

Constant Field Values

metricsFactory

protected final IMetricsFactory metricsFactory

Constructor Detail

LeaseCoordinator

public LeaseCoordinator(ILeaseManager<T> leaseManager,
                java.lang.String workerIdentifier,
                long leaseDurationMillis,
                long epsilonMillis)

Constructor.

Parameters:

leaseManager - LeaseManager instance to use

workerIdentifier - Identifies the worker (e.g. useful to track lease ownership)

leaseDurationMillis - Duration of a lease

epsilonMillis - Allow for some variance when calculating lease expirations

LeaseCoordinator

public LeaseCoordinator(ILeaseManager<T> leaseManager,
                java.lang.String workerIdentifier,
                long leaseDurationMillis,
                long epsilonMillis,
                IMetricsFactory metricsFactory)

Constructor.

Parameters:

leaseManager - LeaseManager instance to use

workerIdentifier - Identifies the worker (e.g. useful to track lease ownership)

leaseDurationMillis - Duration of a lease

epsilonMillis - Allow for some variance when calculating lease expirations

metricsFactory - Used to publish metrics about lease operations

Method Detail

start

public void start()
           throws DependencyException,
                  InvalidStateException,
                  ProvisionedThroughputException

Start background LeaseHolder and LeaseTaker threads.

Throws:

ProvisionedThroughputException - If we can't talk to DynamoDB due to insufficient capacity.

InvalidStateException - If the lease table doesn't exist

DependencyException - If we encountered exception taking to DynamoDB

runTaker

protected void runTaker()
                 throws DependencyException,
                        InvalidStateException

Runs a single iteration of the lease taker - used by integration tests.

Throws:

InvalidStateException

DependencyException

runRenewer

protected void runRenewer()
                   throws DependencyException,
                          InvalidStateException

Runs a single iteration of the lease renewer - used by integration tests.

Throws:

InvalidStateException

DependencyException

getAssignments

public java.util.Collection<T> getAssignments()

Returns:

currently held leases

getCurrentlyHeldLease

public T getCurrentlyHeldLease(java.lang.String leaseKey)

Parameters:

leaseKey - lease key to fetch currently held lease for

Returns:

deep copy of currently held Lease for given key, or null if we don't hold the lease for that key

getWorkerIdentifier

public java.lang.String getWorkerIdentifier()

Returns:

workerIdentifier

stop

public void stop()

Stops background threads.

isRunning

public boolean isRunning()

Returns:

true if this LeaseCoordinator is running

updateLease

public boolean updateLease(T lease,
                  java.util.UUID concurrencyToken)
                    throws DependencyException,
                           InvalidStateException,
                           ProvisionedThroughputException

Updates application-specific lease values in DynamoDB.

Parameters:

lease - lease object containing updated values

concurrencyToken - obtained by calling Lease.getConcurrencyToken for a currently held lease

Returns:

true if update succeeded, false otherwise

Throws:

InvalidStateException - if lease table does not exist

ProvisionedThroughputException - if DynamoDB update fails due to lack of capacity

DependencyException - if DynamoDB update fails in an unexpected way