software.amazon.kinesis.leases

Interface LeaseTaker

All Known Implementing Classes:

DynamoDBLeaseTaker

public interface LeaseTaker

ILeaseTaker is used by LeaseCoordinator to take new leases, or leases that other workers fail to renew. Each LeaseCoordinator instance corresponds to one worker and uses exactly one ILeaseTaker to take leases for that worker.

Method Summary

Modifier and Type	Method and Description
default List<Lease>	allLeases() Default implementation returns an empty list and concrete implementaion is expected to return all leases for the application that are in the lease table either by reading lease table or from an internal cache.
String	getWorkerIdentifier()
Map<String,Lease>	takeLeases() Compute the set of leases available to be taken and attempt to take them.

Method Detail

takeLeases

Map<String,Lease> takeLeases()
                      throws DependencyException,
                             InvalidStateException

Compute the set of leases available to be taken and attempt to take them. Lease taking rules are: 1) If a lease's counter hasn't changed in long enough, try to take it. 2) If we see a lease we've never seen before, take it only if owner == null. If it's owned, odds are the owner is holding it. We can't tell until we see it more than once. 3) For load balancing purposes, you may violate rules 1 and 2 for EXACTLY ONE lease per call of takeLeases().

Returns:

map of shardId to Lease object for leases we just successfully took.

Throws:

DependencyException - on unexpected DynamoDB failures

InvalidStateException - if lease table does not exist

getWorkerIdentifier

String getWorkerIdentifier()

Returns:

workerIdentifier for this LeaseTaker

allLeases

default List<Lease> allLeases()

Default implementation returns an empty list and concrete implementaion is expected to return all leases for the application that are in the lease table either by reading lease table or from an internal cache.

Returns:

all leases for the application that are in the lease table