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RaftLog.java
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RaftLog.java
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/*
* 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 <http://www.gnu.org/licenses/>.
*/
package org.neo4j.coreedge.raft.log;
import org.neo4j.coreedge.raft.replication.ReplicatedContent;
/**
* Persists entries that are coordinated through RAFT, i.e. this is the log
* of user data.
* <p/>
* All write operations in this interface must be durably persisted before
* returning from the respective functions.
* <p/>
* Entries are appended during the RAFT replication phase, and when safely
* replicated they will be committed. The consumer of the raft entry log
* can then safely apply the committed entry, typically to a state machine
* with the entry representing a state transition to be performed.
*/
public interface RaftLog extends ReadableRaftLog
{
String APPEND_INDEX_TAG = "appendIndex";
String COMMIT_INDEX_TAG = "commitIndex";
void replay() throws Throwable;
void registerListener( Listener consumer );
interface Listener
{
void onAppended( ReplicatedContent content, long logIndex );
void onCommitted( ReplicatedContent content, long logIndex );
void onTruncated( long fromLogIndex );
}
/**
* Appends entry to the end of the log. The first log index is 0.
* <p/>
* The entries must be uniquely identifiable and already appended
* entries must not be re-appended (unless they have been removed
* through truncation).
*
* @param entry The log entry.
* @return Returns the index at which the entry was appended, or -1
* if the entry was not accepted.
*/
long append( RaftLogEntry entry ) throws RaftStorageException;
/**
* Truncates the log starting from the supplied index. Committed
* entries can never be truncated.
*
* @param fromIndex The start index (inclusive).
*/
void truncate( long fromIndex ) throws RaftStorageException;
/**
* Signals the safe replication of any entries previously appended up to and
* including the supplied commitIndex. These entries can now be applied.
* <p/>
* The implementation must remember which committed entries have already been
* applied so that they are not applied multiple times.
*
* @param commitIndex The end index (inclusive).
*/
void commit( long commitIndex ) throws RaftStorageException;
}