com.gigaspaces.cluster.activeelection.core

Class ActiveElectionManager

java.lang.Object

com.gigaspaces.cluster.activeelection.core.ActiveElectionManager

public class ActiveElectionManager
extends Object

ActiveElectionManager based on distributed naming service INamingService and provides a distributed active election algorithm to select only one active service between all candidates.

NOTE: The manage service must provide consistent equals() method implementation or implement ReferentUuid interface. Example:

   
    public class ServiceIDOrderFilter
      implements IActiveElectionDecisionFilter
    {
         ServiceID _srvID;

     public boolean isAcceptable(ActiveElectionState.State advanceState, List
 candidateSrv )
     {
       for( ServiceItem srvItem : candidateSrv )
       {
        // return true if _srvID is the greater from all candidateSrv.serviceID;
       }
     }
    }

    public class ElectionListener
                implements IActiveElectionListener
    {
      ActiveElectionManager _electManager;

      public void onActive( ActiveElectionEvent event )
      {
        System.out.println("OnActive -> Elected Active: " + event.getActiveServiceItem() );

        if ( _electManager.getState() == ActiveElectionState.State.ACTIVE )
          System.out.println("The manage service is an ACTIVE");
        else
          System.out.println("The manage service is an NOT an ACTIVE");

       }

       public void onSplitBrain( ActiveElectionEvent event )
       {
         System.out.println("OnSplit -> Elected Active: " + event.getActiveServiceItem() ); *
       }
     }

    public static void main( String[] args )
    {
     IJSpace space;
     ServiceTemplate srvTemplate;
     INamingService lookupSrv    = new LookupNamingService();
     ElectionListener listener   = new ElectionListener();
     ServiceIDOrderFilter filter = new ServiceIDOrderFilter();

     ActiveElectionManager electManager = new ActiveElectionManager( space, srvTemplate,
 lookupSrv, listener, filter );
     electManager.elect();
    }
   
 

Since:

6.0

Version:

1.0

Author:

Igor Goldenberg

See Also:

IActiveElectionDecisionFilter

Constructor Summary

Constructors

Constructor and Description

ActiveElectionManager(String nodeName, Object service, ServiceTemplate participantSrvTemplate, INamingService namingSrv, IActiveElectionListener activeElectionListener, IActiveElectionDecisionFilter decisionFilter, ActiveElectionConfig config, ClusterFailureDetector clusterFailureDetector, SplitBrainRecoveryHolder splitBrainRecoveryHolder) Constructs an instance of this class that will add ActiveElectionState to the set of service attributes see: #addNamingAttributes(Object, Entry[]).

Method Summary

Modifier and Type	Method and Description
protected boolean	changeState(ActiveElectionState.State oldState, ActiveElectionState.State newState, boolean force) Change the service state on naming service.
protected boolean	confirmPendingStateRegistration(int retryCount) Confirmation PENDING state registration on naming service.
void	elect() Elect the active service, this method will be blocked while the active service will be elected.
protected ServiceItem	findActive() Find an ACTIVE service with the election template.
void	forceMoveToPrimary() Forcefully make this space to be primary
ClusterFailureDetector	getClusterFailureDetector()
ActiveElectionConfig	getConfig()
ActiveElectionState.State	getState()
protected boolean	isAdvanceToStateAllowed(ActiveElectionState.State currentState, ActiveElectionState.State acquireState) Request to advance to the new state.
protected boolean	isTerminate()
protected List<ServiceItem>	lookup(ActiveElectionState.State state, int maxMatches) Lookup the services with desired state.
protected void	notifyListenerOnActive(ServiceItem activeService) notify the IActiveElectionListener about elected ACTIVE service or an ACTIVE on split-brain occurrence.
void	onActiveDiscoveryCheckExtraBackup(ServiceItem activeServiceItem) A backup Space verifies that it is a replication target of an active primary Space.
protected void	onActiveFailure() The callback method from ActiveFailureDetector on active failure.
protected void	onSplitBrain(List<ServiceItem> splitActives) The callback method from SplitBrainController on 2 or more identified ACTIVE services.
protected ServiceItem	pollStateUntilAvailable(ActiveElectionState.State pollingState) Poll the desired service state on naming service while available, when the pollingState is not available make an attempt to find an ACTIVE state, if ACTIVE was found notify the IActiveElectionListener and return the active service.
void	reelect() Re-elect the primary space.
protected void	startSplitBrainController() Start the split-brain controller which controls the collision of 2 or more ACTIVE services.
void	terminate() Terminate the ActiveElectionManager.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ActiveElectionManager

public ActiveElectionManager(String nodeName,
                             Object service,
                             ServiceTemplate participantSrvTemplate,
                             INamingService namingSrv,
                             IActiveElectionListener activeElectionListener,
                             IActiveElectionDecisionFilter decisionFilter,
                             ActiveElectionConfig config,
                             ClusterFailureDetector clusterFailureDetector,
                             SplitBrainRecoveryHolder splitBrainRecoveryHolder)
                      throws ActiveElectionException

Constructs an instance of this class that will add ActiveElectionState to the set of service attributes see: #addNamingAttributes(Object, Entry[]).

Parameters:

service - the service candidate which a participate in active election.
NOTE: the service must provide consistent equals() method implementation or implement ReferentUuid interface.

participantSrvTemplate - the template to match participant services with match attributes set.

namingSrv - the naming service provider to lookup services, change states and etc...

activeElectionListener - the listener implementation to receive notification about new active candidate.

decisionFilter - the decision filter is call to get acceptance to advance new state.

Throws:

ActiveElectionException - Failed to initialize ActiveElectionManager, naming service communication problem.

Method Detail

confirmPendingStateRegistration

protected boolean confirmPendingStateRegistration(int retryCount)
                                           throws ActiveElectionException

Confirmation PENDING state registration on naming service.

Returns:

true if registration confirmed, otherwise false.

Throws:

ActiveElectionException - failed to confirm, the process might be interrupted.

lookup

protected List<ServiceItem> lookup(ActiveElectionState.State state,
                                   int maxMatches)
                            throws InterruptedException

Lookup the services with desired state.

Parameters:

state - The state to find.

maxMatches - maximum number of matched services.

Returns:

The matched services or null if no service was found.

Throws:

InterruptedException

changeState

protected boolean changeState(ActiveElectionState.State oldState,
                              ActiveElectionState.State newState,
                              boolean force)
                       throws RemoteException

Change the service state on naming service.

Parameters:

oldState - oldState the old service state.

newState - newState the new service state.

force - true if the newState must be changed without throwing RemoteException. This operation will continue with retrying until the change state operation will be succeed or election manager was terminated.

Throws:

RemoteException - Failed to change state on naming-service, the reason might be a network problem.

pollStateUntilAvailable

protected ServiceItem pollStateUntilAvailable(ActiveElectionState.State pollingState)
                                       throws InterruptedException

Poll the desired service state on naming service while available, when the pollingState is not available make an attempt to find an ACTIVE state, if ACTIVE was found notify the IActiveElectionListener and return the active service.

Parameters:

pollingState - the polling service state.

Returns:

The ACTIVE service or null if ACTIVE was not found and polling state is not available on naming service..

Throws:

InterruptedException

isAdvanceToStateAllowed

protected boolean isAdvanceToStateAllowed(ActiveElectionState.State currentState,
                                          ActiveElectionState.State acquireState)
                                   throws RemoteException,
                                          InterruptedException

Request to advance to the new state. This method collects all candidates with currentState and only if IActiveElectionDecisionFilter.isAcceptable(com.gigaspaces.cluster.activeelection.core.ActiveElectionState.State, java.util.List<net.jini.core.lookup.ServiceItem>) return true this manage service can advance to the acquireState state.

Parameters:

currentState - the current state.

acquireState - the requesting state to acquire.

Returns:

true the manage service can advance the state from currentState to acquireState, false another candidate should advance first, or current state not in lookup.

Throws:

RemoteException - Failed to communicate with Naming Service.

InterruptedException - current thread was interrupted.

findActive

protected ServiceItem findActive()
                          throws InterruptedException

Find an ACTIVE service with the election template. If an active was found this service:
1. Register to the ActiveFailureDetector, so that to get notification on active failure.
2. Notify the IActiveElectionListener about new active service. If split-brain has been identified( two or more active services were found), lookup again the active while the split-bran will be resolved.

Returns:

the active service or null active not found.

Throws:

InterruptedException - throws when operation was interrupted.

elect

public void elect()
           throws InterruptedException,
                  ActiveElectionException

Elect the active service, this method will be blocked while the active service will be elected.

Throws:

InterruptedException - thrown when operation was interrupted.

ActiveElectionException - failed to elect active service, might be INamingService communication.

forceMoveToPrimary

public void forceMoveToPrimary()
                        throws RemoteException

Forcefully make this space to be primary

Throws:

RemoteException

notifyListenerOnActive

protected void notifyListenerOnActive(ServiceItem activeService)

notify the IActiveElectionListener about elected ACTIVE service or an ACTIVE on split-brain occurrence.

onSplitBrain

protected void onSplitBrain(List<ServiceItem> splitActives)
                     throws RemoteException,
                            InterruptedException,
                            ActiveElectionException

The callback method from SplitBrainController on 2 or more identified ACTIVE services. This method should resolve the split-brain and only 1 ACTIVE service should stay in the network.

Throws:

RemoteException - Failed to communicate with naming service.

ActiveElectionException - Election failed

InterruptedException - on split brain resolution was interrupted.

onActiveDiscoveryCheckExtraBackup

public void onActiveDiscoveryCheckExtraBackup(ServiceItem activeServiceItem)

A backup Space verifies that it is a replication target of an active primary Space. If the primary Space is already connected to a backup by the same name, but a different service ID then this backup should move to stopped state and be declared 'unhealthy'.

Parameters:

activeServiceItem - the primary service received from the LUS

onActiveFailure

protected void onActiveFailure()
                        throws InterruptedException,
                               ActiveElectionException

The callback method from ActiveFailureDetector on active failure.

Throws:

ActiveElectionException - Failed to elect new Active.

InterruptedException - operation was interrupted.

startSplitBrainController

protected void startSplitBrainController()
                                  throws RemoteException

Start the split-brain controller which controls the collision of 2 or more ACTIVE services.

Throws:

RemoteException

terminate

public void terminate()

Terminate the ActiveElectionManager.

getState

public ActiveElectionState.State getState()

Returns:

the current state.

getConfig

public ActiveElectionConfig getConfig()

Returns:

active election configuration.

isTerminate

protected boolean isTerminate()

Returns:

true if the manager should terminate, otherwise false.

toString

public String toString()

Overrides:

toString in class Object

reelect

public void reelect()
             throws InterruptedException,
                    ActiveElectionException,
                    RemoteException

Re-elect the primary space. The elector state is reset and election is performed

Throws:

InterruptedException

ActiveElectionException

RemoteException

getClusterFailureDetector

public ClusterFailureDetector getClusterFailureDetector()