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Follower.java
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Follower.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.roles;
import java.io.IOException;
import org.neo4j.coreedge.raft.RaftMessageHandler;
import org.neo4j.coreedge.raft.RaftMessages;
import org.neo4j.coreedge.raft.RaftMessages.AppendEntries;
import org.neo4j.coreedge.raft.RaftMessages.Heartbeat;
import org.neo4j.coreedge.raft.outcome.Outcome;
import org.neo4j.coreedge.raft.state.ReadableRaftState;
import org.neo4j.logging.Log;
import static java.lang.Long.min;
import static org.neo4j.coreedge.raft.roles.Role.CANDIDATE;
import static org.neo4j.coreedge.raft.roles.Role.FOLLOWER;
class Follower implements RaftMessageHandler
{
static boolean logHistoryMatches( ReadableRaftState ctx, long prevLogIndex, long prevLogTerm, Log log )
throws IOException
{
// NOTE: A prevLogIndex before or at our log's prevIndex means that we
// already have all history (in a compacted form), so we report that history matches
// NOTE: The entry term for a non existing log index is defined as -1,
// so the history for a non existing log entry never matches.
long logPrevIndex = ctx.entryLog().prevIndex();
long logPrevTerm = ctx.entryLog().readEntryTerm( prevLogIndex );
boolean logHistoryMatches = prevLogIndex <= logPrevIndex || logPrevTerm == prevLogTerm;
if ( !logHistoryMatches )
{
log.info( "Log history mismatch: index:[%s, %s], term:[%s, %s]",
logPrevIndex, prevLogIndex, logPrevTerm, prevLogTerm );
}
return logHistoryMatches;
}
static void commitToLogOnUpdate( ReadableRaftState ctx, long indexOfLastNewEntry, long leaderCommit, Outcome outcome )
{
long newCommitIndex = min( leaderCommit, indexOfLastNewEntry );
if ( newCommitIndex > ctx.commitIndex() )
{
outcome.setCommitIndex( newCommitIndex );
}
}
private static void handleLeaderLogCompaction( ReadableRaftState ctx, Outcome outcome, RaftMessages.LogCompactionInfo compactionInfo )
{
if ( compactionInfo.leaderTerm() < ctx.term() )
{
return;
}
if ( compactionInfo.prevIndex() > ctx.entryLog().appendIndex() )
{
outcome.markNeedForFreshSnapshot();
}
}
@Override
public Outcome handle( RaftMessages.RaftMessage message, ReadableRaftState ctx, Log log ) throws IOException
{
Outcome outcome = new Outcome( FOLLOWER, ctx );
switch ( message.type() )
{
case HEARTBEAT:
{
Heart.beat( ctx, outcome, (Heartbeat) message, log );
break;
}
case APPEND_ENTRIES_REQUEST:
{
Appending.handleAppendEntriesRequest( ctx, outcome, (AppendEntries.Request) message, log );
break;
}
case VOTE_REQUEST:
{
Voting.handleVoteRequest( ctx, outcome, (RaftMessages.Vote.Request) message );
break;
}
case LOG_COMPACTION_INFO:
{
handleLeaderLogCompaction( ctx, outcome, (RaftMessages.LogCompactionInfo) message );
break;
}
case ELECTION_TIMEOUT:
{
if ( Election.start( ctx, outcome, log ) )
{
outcome.setNextRole( CANDIDATE );
log.info( "Moving to CANDIDATE state after successfully starting election" );
}
break;
}
}
return outcome;
}
}