org.neo4j.kernel
Class AvailabilityGuard

java.lang.Object
  org.neo4j.kernel.AvailabilityGuard

public class AvailabilityGuard
extends Object

The availability guard is what ensures that the database will only take calls when it is in an ok state. It allows query handling to easily determine if it is ok to call the database by calling isAvailable(long).

The implementation uses an atomic integer that is initialized to the nr of conditions that must be met for the database to be available. Each such condition will then call grant/deny accordingly, and if the integer becomes 0 access is granted.

Nested Class Summary

static interface

AvailabilityGuard.AvailabilityListener

Constructor Summary

AvailabilityGuard(Clock clock, int conditionCount)

Method Summary

void	addListener(AvailabilityGuard.AvailabilityListener listener)
void	deny()
void	grant()
boolean	isAvailable(long millis) Determines if the database is available for transactions to use.
void	removeListener(AvailabilityGuard.AvailabilityListener listener)
void	shutdown()

Methods inherited from class java.lang.Object

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

Constructor Detail

AvailabilityGuard

public AvailabilityGuard(Clock clock,
                         int conditionCount)

Method Detail

deny

public void deny()

grant

public void grant()

shutdown

public void shutdown()

isAvailable

public boolean isAvailable(long millis)

Determines if the database is available for transactions to use.

Parameters:

millis - to wait if not yet available.

Returns:

true if it is available, otherwise false. Returns false immediately if shutdown.

addListener

public void addListener(AvailabilityGuard.AvailabilityListener listener)

removeListener

public void removeListener(AvailabilityGuard.AvailabilityListener listener)