GracefulShutdownMonitor (org.codehaus.gpars)

groovyx.gpars.dataflow.operator.component.GracefulShutdownMonitor

All Implemented Interfaces and Traits:

OperatorStateMonitor
```
public final class GracefulShutdownMonitor
extends java.lang.Object
```
The monitor will orchestrate a graceful shutdown, when its shutdownNetwork() method is called. For this mechanism to work, all selectors/operators in the network have to have their own instance of GracefulShutdownListener added and these listeners have to share the same GracefulShutdownMonitor instance. Each listener observes the activity in the input channels of its corresponding operator/selector. Upon graceful shutdown initialization, the listeners also start watching the state of their operators/selectors. The GracefulShutdownMonitor then repeatedly watches, whether listeners report activity in the operators. When the activity ceases, the monitor will poll all listeners about the state of their operator/selector and its input channels. If all listeners report no activity and no incoming messages, the monitor can safely terminate all operators.
Authors:
Vaclav Pech

Field Summary

Fields
Modifiers	Name	Description
`private static long`	`DEFAULT_DELAY`
`private long`	`delay`
`private java.util.Collection<GracefulShutdownListener>`	`listeners`	All listeners that watch the operators/selectors in the network
`private java.util.concurrent.atomic.AtomicBoolean`	`notificationArrivedFlag`	Indicates, whether some activity has been reported since last time
`private DataflowVariable<java.lang.Boolean>`	`result`	The final latch that indicates the network has been shutdown
`private boolean`	`shutdownFlag`	Indicates whether shutdown has been initialized

Constructor Summary

Constructors
Constructor and description
`GracefulShutdownMonitor ()` Uses the default timer delay
`GracefulShutdownMonitor (long delay)` Allows to use a customized delay

Methods Summary

Methods
Type	Name and description
`private boolean`	`checkWhetherAnyEventsHaveArrived()` Checks the notification flag whether there has been some activity since last timer run.
`void`	`onTimer()` Checks, whether the network is no longer active.
`void`	`registerProcessorListener(GracefulShutdownListener listener)` Invoked by GracefulShutdownListeners, which listen on operators/selectors for lifecycle events, to get registered with the monitor.
`private void`	`schedule()` Clears the notification flag so as we know whether some activity happens between subsequent checks.
`Promise<java.lang.Boolean>`	`shutdownNetwork()` Initializes the shutdown process.
`void`	`stateChanged()` Invoked whenever a processor changes state

Inherited Methods Summary

Inherited Methods
Methods inherited from class	Name
`class java.lang.Object`	`java.lang.Object#wait(), java.lang.Object#wait(long, int), java.lang.Object#wait(long), java.lang.Object#equals(java.lang.Object), java.lang.Object#toString(), java.lang.Object#hashCode(), java.lang.Object#getClass(), java.lang.Object#notify(), java.lang.Object#notifyAll()`

- Field Detail
  - private static final long DEFAULT_DELAY
  - private final long delay
  - private final java.util.Collection<GracefulShutdownListener> listeners
    
    All listeners that watch the operators/selectors in the network
  - private final java.util.concurrent.atomic.AtomicBoolean notificationArrivedFlag
    
    Indicates, whether some activity has been reported since last time
  - private final DataflowVariable<java.lang.Boolean> result
    
    The final latch that indicates the network has been shutdown
  - private boolean shutdownFlag
    
    Indicates whether shutdown has been initialized
- Constructor Detail
  - public GracefulShutdownMonitor()
    
    Uses the default timer delay
  - public GracefulShutdownMonitor(long delay)
    
    Allows to use a customized delay
    Parameters:
    delay - A timeout in milliseconds to wait between two subsequent polls on processors' state. Lower values will reduce the wait time for network shutdown, but maz have impact on the performance when the shutdown process gets initialized.
- Method Detail
  - private boolean checkWhetherAnyEventsHaveArrived()
    
    Checks the notification flag whether there has been some activity since last timer run.
    Returns:
    True, if events have been registered since last time, false otherwise.
  - void onTimer()
    
    Checks, whether the network is no longer active. To reduce effect on system performance, cheap criteria are being checked first.
  - @java.lang.Override public void registerProcessorListener(GracefulShutdownListener listener)
    
    Invoked by GracefulShutdownListeners, which listen on operators/selectors for lifecycle events, to get registered with the monitor. The monitor will query these registered listeners about their respective operator/selector state when performing graceful shutdown.
    Parameters:
    listener - The listener to register
  - private void schedule()
    
    Clears the notification flag so as we know whether some activity happens between subsequent checks. Schedules the timer to run again after the delay set on the monitor.
  - public Promise<java.lang.Boolean> shutdownNetwork()
    
    Initializes the shutdown process. New listeners cannot be registered after this point. New messages should not enter the dataflow network from the outside, since this may prevent the network from terminating.
    Returns:
    A Promise, which may be used to wait for or get notified about the shutdown success.
  - @java.lang.Override public void stateChanged()
    
    Invoked whenever a processor changes state

Summary:
Field
Constructor
Method

| Detail:
Field
Constructor
Method

[Java] Class GracefulShutdownMonitor

Field Summary

Constructor Summary

Methods Summary

Inherited Methods Summary

Field Detail

private static final long DEFAULT_DELAY

private final long delay

private final java.util.Collection<GracefulShutdownListener> listeners

private final java.util.concurrent.atomic.AtomicBoolean notificationArrivedFlag

private final DataflowVariable<java.lang.Boolean> result

private boolean shutdownFlag

Constructor Detail

public GracefulShutdownMonitor()

public GracefulShutdownMonitor(long delay)

Method Detail

private boolean checkWhetherAnyEventsHaveArrived()

void onTimer()

@java.lang.Override public void registerProcessorListener(GracefulShutdownListener listener)

private void schedule()

public Promise<java.lang.Boolean> shutdownNetwork()

@java.lang.Override public void stateChanged()