org.neo4j.kernel.ha.cluster.HighAvailabilityMemberState Maven / Gradle / Ivy
/*
* Copyright (c) 2002-2016 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see
* Here we are waiting for events that transitions this member either to becoming a master or slave.
*/
PENDING
{
@Override
public HighAvailabilityMemberState masterIsElected( HighAvailabilityMemberContext context,
InstanceId masterId )
{
assert context.getAvailableHaMaster() == null;
if ( masterId.equals( context.getMyId() ) && !context.isSlaveOnly() )
{
return TO_MASTER;
}
return PENDING;
}
@Override
public HighAvailabilityMemberState masterIsAvailable( HighAvailabilityMemberContext context,
InstanceId masterId, URI masterHaURI )
{
if ( masterId.equals( context.getMyId() ) )
{
HighAvailabilityMemberState result = ILLEGAL;
result.setErrorMessage( "Received a MasterIsAvailable event for my InstanceId while in" +
" PENDING state" );
return result;
}
return TO_SLAVE;
}
@Override
public HighAvailabilityMemberState slaveIsAvailable( HighAvailabilityMemberContext context,
InstanceId slaveId,
URI slaveUri )
{
if ( slaveId.equals( context.getMyId() ) )
{
HighAvailabilityMemberState result = ILLEGAL;
result.setErrorMessage( "Cannot go from pending to slave" );
return result;
}
return this;
}
@Override
public boolean isEligibleForElection()
{
return true;
}
@Override
public boolean isAccessAllowed()
{
return false;
}
},
/**
* Member now knows that a master is available, and is transitioning itself to become a slave to that master.
* It is performing the transition process here, and so is not yet available as a slave.
*/
TO_SLAVE
{
@Override
public HighAvailabilityMemberState masterIsElected( HighAvailabilityMemberContext context,
InstanceId masterId )
{
if ( masterId.equals( context.getElectedMasterId() ) )
{
// A member joined and we all got the same event
return this;
}
if ( masterId.equals( context.getMyId() ) )
{
return TO_MASTER;
}
// This may mean the master changed from the time we transitioned here
return PENDING;
}
@Override
public HighAvailabilityMemberState masterIsAvailable( HighAvailabilityMemberContext context,
InstanceId masterId,
URI masterHaURI )
{
if ( masterId.equals( context.getMyId() ) )
{
HighAvailabilityMemberState result = ILLEGAL;
result.setErrorMessage( "i (" + context.getMyId() + ") am trying to become a slave but " +
"someone said i am available as master" );
return result;
}
if ( masterId.equals( context.getElectedMasterId() ) )
{
// A member joined and we all got the same event
return this;
}
HighAvailabilityMemberState result = ILLEGAL;
result.setErrorMessage( "my (" + context.getMyId() + ") current master is " + context
.getAvailableHaMaster() + " (elected as " + context.getElectedMasterId() + " but i got a " +
"masterIsAvailable event for " + masterHaURI );
return result;
}
@Override
public HighAvailabilityMemberState slaveIsAvailable( HighAvailabilityMemberContext context,
InstanceId slaveId,
URI slaveUri )
{
if ( slaveId.equals( context.getMyId() ) )
{
return SLAVE;
}
return this;
}
@Override
public boolean isEligibleForElection()
{
return false;
}
@Override
public boolean isAccessAllowed()
{
return false;
}
},
/**
* The cluster member knows that it has been elected as master, and starts the transitioning process.
*/
TO_MASTER
{
@Override
public HighAvailabilityMemberState masterIsElected( HighAvailabilityMemberContext context,
InstanceId masterId )
{
assert context.getAvailableHaMaster() == null;
if ( masterId.equals( context.getMyId() ) )
{
return this;
}
return PENDING; // everything still goes
}
@Override
public HighAvailabilityMemberState masterIsAvailable( HighAvailabilityMemberContext context,
InstanceId masterId,
URI masterHaURI )
{
if ( masterId.equals( context.getMyId() ) )
{
return MASTER;
}
HighAvailabilityMemberState result = ILLEGAL;
result.setErrorMessage( "Received a MasterIsAvailable event for instance " + masterId
+ " while in TO_MASTER state" );
return result;
}
@Override
public HighAvailabilityMemberState slaveIsAvailable( HighAvailabilityMemberContext context,
InstanceId slaveId,
URI slaveUri )
{
if ( slaveId.equals( context.getMyId() ) )
{
HighAvailabilityMemberState result = ILLEGAL;
result.setErrorMessage( "Cannot be transitioning to master and slave at the same time" );
return result;
}
return this;
}
@Override
public boolean isEligibleForElection()
{
return true;
}
@Override
public boolean isAccessAllowed()
{
return false;
}
},
/**
* Cluster member is available as master for other cluster members to use.
*/
MASTER
{
@Override
public HighAvailabilityMemberState masterIsElected( HighAvailabilityMemberContext context,
InstanceId masterId )
{
if ( masterId.equals( context.getMyId() ) )
{
return this;
}
// This means we (probably) were disconnected and got back in the cluster
// and we find out that we are not the master anymore.
return PENDING;
}
@Override
public HighAvailabilityMemberState masterIsAvailable( HighAvailabilityMemberContext context,
InstanceId masterId,
URI masterHaURI )
{
if ( masterId.equals( context.getMyId() ) )
{
return this;
}
HighAvailabilityMemberState result = ILLEGAL;
result.setErrorMessage( "I, " + context.getMyId() + " got a masterIsAvailable for " +
masterHaURI + " (id is " + masterId + " ) while in MASTER state. Probably missed a " +
"MasterIsElected event." );
return result;
}
@Override
public HighAvailabilityMemberState slaveIsAvailable( HighAvailabilityMemberContext context,
InstanceId slaveId,
URI slaveUri )
{
if ( slaveId.equals( context.getMyId() ) )
{
HighAvailabilityMemberState result = ILLEGAL;
result.setErrorMessage( "Cannot be master and transition to slave at the same time" );
return result;
}
return this;
}
@Override
public boolean isEligibleForElection()
{
return true;
}
@Override
public boolean isAccessAllowed()
{
return true;
}
},
/**
* Cluster member is ready as a slave
*/
SLAVE
{
@Override
public HighAvailabilityMemberState masterIsElected( HighAvailabilityMemberContext context,
InstanceId masterId )
{
if ( masterId.equals( context.getMyId() ) )
{
return TO_MASTER;
}
if ( masterId.equals( context.getElectedMasterId() ) )
{
return this;
}
return PENDING;
}
@Override
public HighAvailabilityMemberState masterIsAvailable( HighAvailabilityMemberContext context,
InstanceId masterId,
URI masterHaURI )
{
if ( masterId.equals( context.getMyId() ) )
{
HighAvailabilityMemberState returnValue = ILLEGAL;
returnValue.setErrorMessage( "Cannot transition to MASTER directly from SLAVE state" );
return returnValue;
}
else if ( masterId.equals( context.getElectedMasterId() ) )
{
// this is just someone else that joined the cluster
return this;
}
HighAvailabilityMemberState returnValue = ILLEGAL;
returnValue.setErrorMessage( "Received a MasterIsAvailable event for " + masterId +
" which is different from the current master (" + context.getElectedMasterId() +
") while in the SLAVE state (probably missed a MasterIsElected event)" );
return returnValue;
}
@Override
public HighAvailabilityMemberState slaveIsAvailable( HighAvailabilityMemberContext context, InstanceId slaveId, URI slaveUri )
{
return this;
}
@Override
public boolean isEligibleForElection()
{
return true;
}
@Override
public boolean isAccessAllowed()
{
return true;
}
},
ILLEGAL
{
@Override
public HighAvailabilityMemberState masterIsElected( HighAvailabilityMemberContext context, InstanceId masterId )
{
throw new IllegalStateException("The ILLEGAL state is not meant to be used as a state, merely as an indicator that" +
" something went wrong while handling a message and the state should be set to PENDING");
}
@Override
public HighAvailabilityMemberState masterIsAvailable( HighAvailabilityMemberContext context, InstanceId masterId, URI masterHaURI )
{
throw new IllegalStateException("The ILLEGAL state is not meant to be used as a state, merely as an indicator that" +
" something went wrong while handling a message and the state should be set to PENDING");
}
@Override
public HighAvailabilityMemberState slaveIsAvailable( HighAvailabilityMemberContext context,
InstanceId slaveId, URI slaveUri )
{
throw new IllegalStateException("The ILLEGAL state is not meant to be used as a state, merely as an indicator that" +
" something went wrong while handling a message and the state should be set to PENDING");
}
@Override
public boolean isEligibleForElection()
{
throw new IllegalStateException("The ILLEGAL state is not meant to be used as a state, merely as an indicator that" +
" something went wrong while handling a message and the state should be set to PENDING");
}
@Override
public boolean isAccessAllowed()
{
throw new IllegalStateException("The ILLEGAL state is not meant to be used as a state, merely as an indicator that" +
" something went wrong while handling a message and the state should be set to PENDING");
}
};
private String errorMessage = "";
public abstract HighAvailabilityMemberState masterIsElected( HighAvailabilityMemberContext context, InstanceId masterId );
public abstract HighAvailabilityMemberState masterIsAvailable( HighAvailabilityMemberContext context, InstanceId masterId,
URI masterHaURI );
public abstract HighAvailabilityMemberState slaveIsAvailable( HighAvailabilityMemberContext context, InstanceId slaveId, URI slaveUri );
/**
* The purpose of this is that an instance cannot vote in an election while becoming a slave,
* as it is copying stores.
*
* @return whether the instance is eligible or not
*/
public abstract boolean isEligibleForElection();
public abstract boolean isAccessAllowed();
public String errorMessage()
{
return errorMessage;
}
private void setErrorMessage( String message )
{
errorMessage = message;
}
}