Leases (Apache HBase 1.4.11 API)

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

static class Leases.LeaseStillHeldException
Thrown if we are asked to create a lease but lease on passed name already exists.

Nested Classes
Modifier and Type	Class and Description
`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

static int MIN_WAIT_TIME

protected boolean stopRequested

Fields
Modifier and Type	Field and Description
`protected int`	`leaseCheckFrequency`
`static int`	`MIN_WAIT_TIME`
`protected boolean`	`stopRequested`

Constructor Summary

Constructors
Constructor and Description

Leases(int leaseCheckFrequency)
Creates a lease monitor

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

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`addLease(org.apache.hadoop.hbase.regionserver.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.
`void`	`createLease(String leaseName, int leaseTimeoutPeriod, LeaseListener listener)` Create a lease and insert it to the map of leases.
`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
  - MIN_WAIT_TIME
```
public static final int MIN_WAIT_TIME
```
    See Also:
    Constant Field Values
  - 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 void 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
    
    Throws:
    
    Leases.LeaseStillHeldException
  - addLease
```
public void addLease(org.apache.hadoop.hbase.regionserver.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

Class Leases

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Field Detail

MIN_WAIT_TIME

leaseCheckFrequency

stopRequested

Constructor Detail

Leases

Method Detail

run

closeAfterLeasesExpire

close

createLease

addLease

renewLease

cancelLease