org.apache.hadoop.hbase.regionserver

Class Leases

java.lang.Object

org.apache.hadoop.hbase.util.HasThread

org.apache.hadoop.hbase.regionserver.Leases

All Implemented Interfaces:

Runnable

@InterfaceAudience.Private
public class Leases
extends HasThread

Leases There are several server classes in HBase that need to track external clients that occasionally send heartbeats.

These external clients hold resources in the server class. Those resources need to be released if the external client fails to send a heartbeat after some interval of time passes.

The Leases class is a general reusable class for this kind of pattern. An instance of the Leases class will create a thread to do its dirty work. You should close() the instance if you want to clean up the thread properly.

NOTE: This class extends Thread rather than Chore because the sleep time can be interrupted when there is something to do, rather than the Chore sleep time which is invariant.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
(package private) static class	Leases.Lease This class tracks a single Lease.
static class	Leases.LeaseStillHeldException Thrown if we are asked to create a lease but lease on passed name already exists.

Field Summary

Fields

Modifier and Type	Field and Description
protected int	leaseCheckFrequency
private Map<String,Leases.Lease>	leases
private static org.slf4j.Logger	LOG
static int	MIN_WAIT_TIME
protected boolean	stopRequested

Constructor Summary

Constructors

Constructor and Description
Leases(int leaseCheckFrequency) Creates a lease monitor

Method Summary

Modifier and Type	Method and Description
void	addLease(Leases.Lease lease) Inserts lease.
void	cancelLease(String leaseName) Client explicitly cancels a lease.
void	close() Shut down this Leases instance.
void	closeAfterLeasesExpire() Shuts down this lease instance when all outstanding leases expire.
Leases.Lease	createLease(String leaseName, int leaseTimeoutPeriod, LeaseListener listener) Create a lease and insert it to the map of leases.
(package private) Leases.Lease	removeLease(String leaseName) Remove named lease.
void	renewLease(String leaseName) Renew a lease
void	run()

Methods inherited from class org.apache.hadoop.hbase.util.HasThread

getName, getThread, interrupt, isAlive, isInterrupted, join, join, join, setDaemon, setName, setPriority, setUncaughtExceptionHandler, start

Methods inherited from class java.lang.Object

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

Field Detail

LOG

private static final org.slf4j.Logger LOG

MIN_WAIT_TIME

public static final int MIN_WAIT_TIME

See Also:

Constant Field Values

leases

private final Map<String,Leases.Lease> leases

leaseCheckFrequency

protected final int leaseCheckFrequency

stopRequested

protected volatile boolean stopRequested

Constructor Detail

Leases

public Leases(int leaseCheckFrequency)

Creates a lease monitor

Parameters:

leaseCheckFrequency - - how often the lease should be checked (milliseconds)

Method Detail

run

public void run()

Specified by:

run in interface Runnable

Specified by:

run in class HasThread

See Also:

Thread.run()

closeAfterLeasesExpire

public void closeAfterLeasesExpire()

Shuts down this lease instance when all outstanding leases expire. Like close() but rather than violently end all leases, waits first on extant leases to finish. Use this method if the lease holders could lose data, leak locks, etc. Presumes client has shutdown allocation of new leases.

close

public void close()

Shut down this Leases instance. All pending leases will be destroyed, without any cancellation calls.

createLease

public Leases.Lease createLease(String leaseName,
                                int leaseTimeoutPeriod,
                                LeaseListener listener)
                         throws Leases.LeaseStillHeldException

Create a lease and insert it to the map of leases.

Parameters:

leaseName - name of the lease

leaseTimeoutPeriod - length of the lease in milliseconds

listener - listener that will process lease expirations

Returns:

The lease created.

Throws:

Leases.LeaseStillHeldException

addLease

public void addLease(Leases.Lease lease)
              throws Leases.LeaseStillHeldException

Inserts lease. Resets expiration before insertion.

Parameters:

lease -

Throws:

Leases.LeaseStillHeldException

renewLease

public void renewLease(String leaseName)
                throws LeaseException

Renew a lease

Parameters:

leaseName - name of lease

Throws:

LeaseException

cancelLease

public void cancelLease(String leaseName)
                 throws LeaseException

Client explicitly cancels a lease.

Parameters:

leaseName - name of lease

Throws:

LeaseException

removeLease

Leases.Lease removeLease(String leaseName)
                  throws LeaseException

Remove named lease. Lease is removed from the map of leases. Lease can be reinserted using addLease(Lease)

Parameters:

leaseName - name of lease

Returns:

Removed lease

Throws:

LeaseException