ProcedureScheduler (Apache HBase - Procedure 2.0.0-alpha4 API)

All Known Implementing Classes:

AbstractProcedureScheduler, 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`	`addFront(Procedure proc)` 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`	`suspendEvent(ProcedureEvent event)` Mark the event as not ready.
`boolean`	`waitEvent(ProcedureEvent event, Procedure procedure)` Suspend the procedure if the event is not ready yet.
`void`	`wakeEvent(ProcedureEvent event)` Wake every procedure waiting for the specified event (By design each event has only one "wake" caller)
`void`	`wakeEvents(int count, ProcedureEvent... events)` Wake every procedure waiting for the specified events.
`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
  - addBack
```
void addBack(Procedure proc)
```
    Inserts the specified element at the end of this queue.
    
    Parameters:
    
    proc - the Procedure to add
  - 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.
  - suspendEvent
```
void suspendEvent(ProcedureEvent event)
```
    Mark the event as not ready. Procedures calling waitEvent() will be suspended.
    
    Parameters:
    
    event - the event to mark as suspended/not ready
  - wakeEvent
```
void wakeEvent(ProcedureEvent event)
```
    Wake every procedure waiting for the specified event (By design each event has only one "wake" caller)
    
    Parameters:
    
    event - the event to wait
  - wakeEvents
```
void wakeEvents(int count,
                ProcedureEvent... events)
```
    Wake every procedure waiting for the specified events. (By design each event has only one "wake" caller)
    
    Parameters:
    
    count - the number of events in the array to wake
    
    events - the list of events to wake
  - waitEvent
```
boolean waitEvent(ProcedureEvent event,
                  Procedure procedure)
```
    Suspend the procedure if the event is not ready yet.
    
    Parameters:
    
    event - the event to wait on
    
    procedure - the procedure waiting on the event
    
    Returns:
    
    true if the procedure has to wait for the event to be ready, false otherwise.
  - 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

addBack

yield

completionCleanup

hasRunnables

poll

poll

suspendEvent

wakeEvent

wakeEvents

waitEvent

getLocks

getLockResource

size

clear