Package org.jgroups.blocks
Class VotingAdapter
- java.lang.Object
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- org.jgroups.blocks.VotingAdapter
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- All Implemented Interfaces:
VoteResponseProcessor
,MembershipListener
,MessageListener
public class VotingAdapter extends java.lang.Object implements MessageListener, MembershipListener, VoteResponseProcessor
Voting adapter provides a voting functionality for an application. There should be at most oneVotingAdapter
listening on oneChannel
instance. Each adapter can have zero or more registeredVotingListener
instances that will be called during voting process.Decree is an object that has some semantic meaning within the application. Each voting listener receives a decree and can respond with either
true
or false. If the decree has no meaning for the voting listener, it is required to throwVoteException
. In this case this specific listener will be excluded from the voting on the specified decree. After performing local voting, this voting adapter sends the request back to the originator of the voting process. Originator receives results from each node and decides if all voting process succeeded or not depending on the consensus type specified during voting.- Version:
- $Id: VotingAdapter.java,v 1.10 2006/09/27 12:42:53 belaban Exp $
- Author:
- Roman Rokytskyy (rrokytskyy@acm.org), Robert Schaffar-Taurok (robert@fusion.at)
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
VotingAdapter.FailureVoteResult
Class that represents a result of local voting on the failed node.static class
VotingAdapter.VoteResult
This class represents the result of local voting.
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Field Summary
Fields Modifier and Type Field Description protected org.apache.commons.logging.Log
log
static int
VOTE_ALL
This consensus type means that at least one positive vote and no negative votes are required for the voting to succeed.static int
VOTE_ANY
This consensus type means that at least one positive vote is required for the voting to succeed.static int
VOTE_MAJORITY
This consensus type means that number of positive votes should be greater than number of negative votes.
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Constructor Summary
Constructors Constructor Description VotingAdapter(PullPushAdapter adapter, java.io.Serializable id)
VotingAdapter(Channel channel)
Creates an instance of the VoteChannel that uses JGroups for communication between group members.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
addMembershipListener(MembershipListener l)
void
addVoteListener(VotingListener listener)
Adds voting listener.void
block()
Blocks the channel until the ViewAccepted is invoked.static java.lang.String
getConsensusStr(int consensusType)
Convert consensus type into string representation.java.util.Collection
getMembers()
byte[]
getState()
Get the channel state.VotingAdapter.VoteResult
localVote(java.lang.Object decree)
This method performs voting on the specific decree between all local voteListeners.boolean
processResponses(RspList responses, int consensusType, java.lang.Object decree)
Processes the response list and makes a decision according to the type of the consensus for current voting.void
receive(Message msg)
Receive the message.void
removeMembershipListener(MembershipListener l)
void
removeVoteListener(VotingListener listener)
Removes voting listener.void
setState(byte[] state)
Set the channel state.void
suspect(Address suspected)
Callback for notification that one node is suspectedvoid
viewAccepted(View newView)
Callback for notification about the new view of the group.boolean
vote(java.lang.Object decree, int consensusType, long timeout)
Performs actual voting on the VoteChannel using the JGroups facilities for communication.boolean
vote(java.lang.Object decree, int consensusType, long timeout, VoteResponseProcessor voteResponseProcessor)
Performs actual voting on the VoteChannel using the JGroups facilities for communication.boolean
vote(java.lang.Object decree, long timeout)
Vote on the specified decree requiring all nodes to vote.boolean
vote(java.lang.Object decree, long timeout, VoteResponseProcessor voteResponseProcessor)
Vote on the specified decree requiring all nodes to vote.
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Field Detail
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VOTE_ANY
public static final int VOTE_ANY
This consensus type means that at least one positive vote is required for the voting to succeed.- See Also:
- Constant Field Values
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VOTE_ALL
public static final int VOTE_ALL
This consensus type means that at least one positive vote and no negative votes are required for the voting to succeed.- See Also:
- Constant Field Values
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VOTE_MAJORITY
public static final int VOTE_MAJORITY
This consensus type means that number of positive votes should be greater than number of negative votes.- See Also:
- Constant Field Values
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log
protected final org.apache.commons.logging.Log log
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Constructor Detail
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VotingAdapter
public VotingAdapter(Channel channel)
Creates an instance of the VoteChannel that uses JGroups for communication between group members.- Parameters:
channel
- JGroups channel.
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VotingAdapter
public VotingAdapter(PullPushAdapter adapter, java.io.Serializable id)
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Method Detail
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getMembers
public java.util.Collection getMembers()
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addMembershipListener
public void addMembershipListener(MembershipListener l)
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removeMembershipListener
public void removeMembershipListener(MembershipListener l)
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vote
public boolean vote(java.lang.Object decree, int consensusType, long timeout) throws ChannelException
Performs actual voting on the VoteChannel using the JGroups facilities for communication.- Throws:
ChannelException
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vote
public boolean vote(java.lang.Object decree, int consensusType, long timeout, VoteResponseProcessor voteResponseProcessor) throws ChannelException
Performs actual voting on the VoteChannel using the JGroups facilities for communication.- Throws:
ChannelException
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processResponses
public boolean processResponses(RspList responses, int consensusType, java.lang.Object decree) throws ChannelException
Processes the response list and makes a decision according to the type of the consensus for current voting.Note: we do not support voting in case of Byzantine failures, i.e. when the node responds with the fault message.
- Specified by:
processResponses
in interfaceVoteResponseProcessor
- Parameters:
responses
- The responsesconsensusType
- The consensusType of the votedecree
- The vote decree- Returns:
- boolean
- Throws:
ChannelException
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viewAccepted
public void viewAccepted(View newView)
Callback for notification about the new view of the group.- Specified by:
viewAccepted
in interfaceMembershipListener
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suspect
public void suspect(Address suspected)
Callback for notification that one node is suspected- Specified by:
suspect
in interfaceMembershipListener
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block
public void block()
Blocks the channel until the ViewAccepted is invoked.- Specified by:
block
in interfaceMembershipListener
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getState
public byte[] getState()
Get the channel state.- Specified by:
getState
in interfaceMessageListener
- Returns:
- always
null
, we do not have any group-shared state.
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receive
public void receive(Message msg)
Receive the message. All messages are ignored.- Specified by:
receive
in interfaceMessageListener
- Parameters:
msg
- message to check.
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setState
public void setState(byte[] state)
Set the channel state. We do nothing here.- Specified by:
setState
in interfaceMessageListener
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vote
public boolean vote(java.lang.Object decree, long timeout) throws ChannelException
Vote on the specified decree requiring all nodes to vote.- Parameters:
decree
- decree on which nodes should vote.timeout
- time during which nodes can vote.- Returns:
true
if nodes agreed on a decree, otherwisefalse
- Throws:
ChannelException
- if something went wrong.
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vote
public boolean vote(java.lang.Object decree, long timeout, VoteResponseProcessor voteResponseProcessor) throws ChannelException
Vote on the specified decree requiring all nodes to vote.- Parameters:
decree
- decree on which nodes should vote.timeout
- time during which nodes can vote.voteResponseProcessor
- processor which will be called for every response that is received.- Returns:
true
if nodes agreed on a decree, otherwisefalse
- Throws:
ChannelException
- if something went wrong.
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addVoteListener
public void addVoteListener(VotingListener listener)
Adds voting listener.
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removeVoteListener
public void removeVoteListener(VotingListener listener)
Removes voting listener.
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localVote
public VotingAdapter.VoteResult localVote(java.lang.Object decree)
This method performs voting on the specific decree between all local voteListeners.
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getConsensusStr
public static java.lang.String getConsensusStr(int consensusType)
Convert consensus type into string representation. This method is useful for debugginf.- Parameters:
consensusType
- type of the consensus.- Returns:
- string representation of the consensus type.
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