ProcedureScheduler (Apache HBase 2.3.0 API)

All Known Implementing Classes:

AbstractProcedureScheduler, MasterProcedureScheduler, SimpleProcedureScheduler
```
@InterfaceAudience.Private
public interface ProcedureScheduler
```
Keep track of the runnable procedures

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`void`	`addBack(Procedure proc)` Inserts the specified element at the end of this queue.
`void`	`addBack(Procedure proc, boolean notify)` Inserts the specified element at the end of this queue.
`void`	`addFront(Iterator<Procedure> procedureIterator)` Inserts all elements in the iterator at the front of this queue.
`void`	`addFront(Procedure proc)` Inserts the specified element at the front of this queue.
`void`	`addFront(Procedure proc, boolean notify)` Inserts the specified element at the front of this queue.
`void`	`clear()` Clear current state of scheduler such that it is equivalent to newly created scheduler.
`void`	`completionCleanup(Procedure proc)` The procedure in execution completed.
`LockedResource`	`getLockResource(LockedResourceType resourceType, String resourceName)`
`List<LockedResource>`	`getLocks()` List lock queues.
`boolean`	`hasRunnables()`
`Procedure`	`poll()` Fetch one Procedure from the queue
`Procedure`	`poll(long timeout, TimeUnit unit)` Fetch one Procedure from the queue
`void`	`signalAll()` In case the class is blocking on poll() waiting for items to be added, this method should awake poll() and poll() should return.
`int`	`size()` Returns the number of elements in this queue.
`void`	`start()` Start the scheduler
`void`	`stop()` Stop the scheduler
`void`	`yield(Procedure proc)` The procedure can't run at the moment.

- Method Detail
  - start
```
void start()
```
    Start the scheduler
  - stop
```
void stop()
```
    Stop the scheduler
  - signalAll
```
void signalAll()
```
    In case the class is blocking on poll() waiting for items to be added, this method should awake poll() and poll() should return.
  - addFront
```
void addFront(Procedure proc)
```
    Inserts the specified element at the front of this queue.
    
    Parameters:
    
    proc - the Procedure to add
  - addFront
```
void addFront(Procedure proc,
              boolean notify)
```
    Inserts the specified element at the front of this queue.
    
    Parameters:
    
    proc - the Procedure to add
    
    notify - whether need to notify worker
  - addFront
```
void addFront(Iterator<Procedure> procedureIterator)
```
    Inserts all elements in the iterator at the front of this queue.
  - addBack
```
void addBack(Procedure proc)
```
    Inserts the specified element at the end of this queue.
    
    Parameters:
    
    proc - the Procedure to add
  - addBack
```
void addBack(Procedure proc,
             boolean notify)
```
    Inserts the specified element at the end of this queue.
    
    Parameters:
    
    proc - the Procedure to add
    
    notify - whether need to notify worker
  - yield
```
void yield(Procedure proc)
```
    The procedure can't run at the moment. add it back to the queue, giving priority to someone else.
    
    Parameters:
    
    proc - the Procedure to add back to the list
  - completionCleanup
```
void completionCleanup(Procedure proc)
```
    The procedure in execution completed. This can be implemented to perform cleanups.
    
    Parameters:
    
    proc - the Procedure that completed the execution.
  - hasRunnables
```
boolean hasRunnables()
```
    Returns:
    
    true if there are procedures available to process, otherwise false.
  - poll
```
Procedure poll()
```
    Fetch one Procedure from the queue
    
    Returns:
    
    the Procedure to execute, or null if nothing present.
  - poll
```
Procedure poll(long timeout,
               TimeUnit unit)
```
    Fetch one Procedure from the queue
    
    Parameters:
    
    timeout - how long to wait before giving up, in units of unit
    
    unit - a TimeUnit determining how to interpret the timeout parameter
    
    Returns:
    
    the Procedure to execute, or null if nothing present.
  - getLocks
```
List<LockedResource> getLocks()
```
    List lock queues.
    
    Returns:
    
    the locks
  - getLockResource
```
LockedResource getLockResource(LockedResourceType resourceType,
                               String resourceName)
```
    Returns:
    
    LockedResource for resource of specified type & name. null if resource is not locked.
  - size
```
int size()
```
    Returns the number of elements in this queue.
    
    Returns:
    
    the number of elements in this queue.
  - clear
```
void clear()
```
    Clear current state of scheduler such that it is equivalent to newly created scheduler. Used for testing failure and recovery. To emulate server crash/restart, ProcedureExecutor resets its own state and calls clear() on scheduler.

Interface ProcedureScheduler

Method Summary

Method Detail

start

stop

signalAll

addFront

addFront

addFront

addBack

addBack

yield

completionCleanup

hasRunnables

poll

poll

getLocks

getLockResource

size

clear