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FollowerTest.java
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FollowerTest.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.util.Iterator;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.runners.MockitoJUnitRunner;
import org.neo4j.coreedge.raft.RaftMessages;
import org.neo4j.coreedge.raft.RaftMessages.Message;
import org.neo4j.coreedge.raft.RaftMessages.Timeout.Election;
import org.neo4j.coreedge.raft.RaftMessages.Vote;
import org.neo4j.coreedge.raft.ReplicatedString;
import org.neo4j.coreedge.raft.log.InMemoryRaftLog;
import org.neo4j.coreedge.raft.log.RaftLog;
import org.neo4j.coreedge.raft.log.RaftLogEntry;
import org.neo4j.coreedge.raft.log.RaftStorageException;
import org.neo4j.coreedge.raft.net.Inbound;
import org.neo4j.coreedge.raft.outcome.CommitCommand;
import org.neo4j.coreedge.raft.outcome.LogCommand;
import org.neo4j.coreedge.raft.outcome.Outcome;
import org.neo4j.coreedge.raft.replication.ReplicatedContent;
import org.neo4j.coreedge.raft.state.RaftState;
import org.neo4j.coreedge.server.RaftTestMember;
import org.neo4j.logging.Log;
import org.neo4j.logging.LogProvider;
import org.neo4j.logging.NullLogProvider;
import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.Matchers.hasItem;
import static org.hamcrest.Matchers.instanceOf;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertThat;
import static org.junit.Assert.assertTrue;
import static org.neo4j.coreedge.raft.MessageUtils.messageFor;
import static org.neo4j.coreedge.raft.RaftMessages.AppendEntries;
import static org.neo4j.coreedge.raft.TestMessageBuilders.appendEntriesRequest;
import static org.neo4j.coreedge.raft.TestMessageBuilders.appendEntriesResponse;
import static org.neo4j.coreedge.raft.TestMessageBuilders.heartbeat;
import static org.neo4j.coreedge.raft.TestMessageBuilders.voteRequest;
import static org.neo4j.coreedge.raft.roles.Role.CANDIDATE;
import static org.neo4j.coreedge.raft.roles.Role.FOLLOWER;
import static org.neo4j.coreedge.raft.state.RaftStateBuilder.raftState;
import static org.neo4j.coreedge.server.RaftTestMember.member;
import static org.neo4j.helpers.collection.Iterables.single;
import static org.neo4j.helpers.collection.IteratorUtil.asSet;
@RunWith(MockitoJUnitRunner.class)
public class FollowerTest
{
private RaftTestMember myself = member( 0 );
/* A few members that we use at will in tests. */
private RaftTestMember member1 = member( 1 );
private RaftTestMember member2 = member( 2 );
private RaftTestMember leader = member( 3 );
@Mock
private Inbound inbound;
private LogProvider logProvider = NullLogProvider.getInstance();
private static final int HIGHEST_TERM = 99;
@Test
public void followerShouldUpdateTermToCurrentMessage() throws Exception
{
// Given
RaftState<RaftTestMember> state = raftState().build();
Follower follower = new Follower();
// When
Outcome<RaftTestMember> outcome = follower.handle( voteRequest().from( member1 ).term( HIGHEST_TERM )
.lastLogIndex( 0 ).lastLogTerm( -1 )
.build(), state, log() );
// Then
assertEquals( HIGHEST_TERM, outcome.getTerm() );
}
@Test
public void shouldVoteOnceOnlyPerTerm() throws Exception
{
// given
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.votingMembers( asSet( myself, member1, member2 ) )
.build();
Follower follower = new Follower();
// when
Outcome<RaftTestMember> outcome1 = follower.handle( voteRequest().from( member1 ).term( 1 ).build(), state,
log() );
state.update( outcome1 );
Outcome<RaftTestMember> outcome2 = follower.handle( voteRequest().from( member2 ).term( 1 ).build(), state,
log() );
// then
assertEquals( new Vote.Response<>( myself, 1, true ), messageFor( outcome1, member1 ) );
assertEquals( new Vote.Response<>( myself, 1, false ), messageFor( outcome2, member2 ) );
}
@Test
public void followersShouldRejectAnyMessageWithOldTermAndStayAFollower() throws Exception
{
// given
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.votingMembers( asSet( myself, member1, member2 ) )
.build();
Follower follower = new Follower();
// when
Outcome<RaftTestMember> outcome = follower.handle( voteRequest().from( member1 ).term( state.term() - 1 )
.lastLogIndex( 0 ).lastLogTerm( -1 ).build(), state, log() );
// then
assertEquals( new Vote.Response<>( myself, state.term(), false ), messageFor( outcome, member1 ) );
assertEquals( FOLLOWER, outcome.getNewRole() );
}
@Test
public void followerShouldTransitToCandidateAndInstigateAnElectionAfterTimeout() throws Exception
{
// given
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.votingMembers( asSet( myself, member1, member2 ) )
.build();
// when
Outcome<RaftTestMember> outcome = new Follower().handle( new Election<>( myself ), state,
log() );
state.update( outcome );
// then
assertEquals( CANDIDATE, outcome.getNewRole() );
assertNotNull( messageFor( outcome, member1 ) );
assertNotNull( messageFor( outcome, member2 ) );
}
@Test
public void followerShouldVoteForOnlyOneCandidatePerElection() throws Exception
{
// given
RaftState<RaftTestMember> state = raftState().build();
Follower follower = new Follower();
// when
final long startingTerm = state.term() + 1;
Outcome<RaftTestMember> outcome1 = follower.handle( voteRequest().from( member1 ).term( startingTerm )
.lastLogIndex( 0 )
.lastLogTerm( -1 ).build(), state, log() );
// This updates state.term() as a side-effect
state.update( outcome1 );
Outcome<RaftTestMember> outcome2 = follower.handle( voteRequest().from( member2 ).term( state.term() )
.lastLogIndex( 0 )
.lastLogTerm( -1 ).build(), state, log() );
// then
assertThat( messageFor( outcome1, member1 ), instanceOf( Vote.Response.class ) );
assertFalse( ((Vote.Response) messageFor( outcome2, member2 )).voteGranted() );
}
@Test
public void shouldBecomeCandidateOnReceivingElectionTimeoutMessage() throws Exception
{
// given
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.votingMembers( asSet( myself, member1, member2 ) )
.build();
Follower follower = new Follower();
// when
Outcome outcome = follower.handle( new Election<>( myself ), state, log() );
// then
assertEquals( CANDIDATE, outcome.getNewRole() );
}
@Test
public void followerShouldRejectEntriesForWhichItDoesNotHavePrecedentInItsLog() throws Exception
{
// given
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.votingMembers( asSet( myself, member1, member2 ) )
.build();
Follower follower = new Follower();
// when
Outcome<RaftTestMember> outcome = follower.handle( new RaftMessages.AppendEntries.Request<>( myself, 99,
99, 0, new RaftLogEntry[] { new RaftLogEntry( 99, ContentGenerator.content() ) }, 99 ), state, log() );
// then
Message<RaftTestMember> response = messageFor( outcome, myself );
assertThat( response, instanceOf( AppendEntries.Response.class ) );
assertFalse( ((AppendEntries.Response) response).success() );
}
@Test
public void followerShouldAcceptEntriesForWhichItHasPrecedentInItsLog() throws Exception
{
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.build();
Follower follower = new Follower();
state.update( follower.handle( new RaftMessages.AppendEntries.Request<>( myself, 0, -1, -1,
new RaftLogEntry[] { new RaftLogEntry( 0, ContentGenerator.content() ) }, 0 ), state, log() ) );
// when
Outcome<RaftTestMember> outcome = follower.handle( new RaftMessages.AppendEntries.Request<>( myself, 0,
0, 0, new RaftLogEntry[] { new RaftLogEntry( 0, ContentGenerator.content() ) }, 1 ), state, log() );
state.update( outcome );
// then
Message<RaftTestMember> response = messageFor( outcome, myself );
assertThat( response, instanceOf( AppendEntries.Response.class ) );
assertTrue( ((AppendEntries.Response) response).success() );
}
@Test
public void followerShouldOverwriteSomeAppendedEntriesOnReceiptOfConflictingCommittedEntries() throws Exception
{
// given
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.build();
Follower follower = new Follower();
appendSomeEntriesToLog( state, follower, 9, 0 );
// when
Outcome<RaftTestMember> outcome = follower.handle( new AppendEntries.Request<>( myself, 1, -1, -1,
new RaftLogEntry[] { new RaftLogEntry( 1, new ReplicatedString( "commit this!" ) ) }, 0 ), state, log() );
state.update( outcome );
// then
assertEquals( 0, state.entryLog().commitIndex() );
}
@Test
public void followerWithEmptyLogShouldCommitEntriesWithHigherTerm() throws Exception
{
// given
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.build();
Follower follower = new Follower();
// when
Outcome<RaftTestMember> outcome = follower.handle( new AppendEntries.Request<>( myself, 1, -1, -1,
new RaftLogEntry[] { new RaftLogEntry( 1, new ReplicatedString( "commit this!" ) ) }, 0 ), state, log() );
state.update( outcome );
// then
assertEquals( 0, state.entryLog().commitIndex() );
assertEquals( 1, state.term() );
}
@Test
public void followerWithNonEmptyLogShouldOverwriteAppendedEntriesOnReceiptOfCommittedEntryWithHigherTerm()
throws Exception
{
// given
int term = 1;
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.term( term )
.build();
Follower follower = new Follower();
appendSomeEntriesToLog( state, follower, 9, term );
// when leader says it agrees with some of the existing log
Outcome<RaftTestMember> outcome = follower.handle( new AppendEntries.Request<>( member1, 2, 3, 1,
new RaftLogEntry[] { new RaftLogEntry( 2, new ReplicatedString( "commit this!" ) ) }, 4 ), state, log() );
state.update( outcome );
// then
assertEquals( 4, state.entryLog().commitIndex() );
assertEquals( 2, state.term() );
}
@Test
public void followerReceivingHeartbeatIndicatingClusterIsAheadShouldElicitAppendResponse() throws Exception
{
// given
int term = 1;
int followerAppendIndex = 9;
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.term( term )
.build();
Follower follower = new Follower();
appendSomeEntriesToLog( state, follower, followerAppendIndex, term );
AppendEntries.Request<RaftTestMember> heartbeat = appendEntriesRequest().from( member1 )
.leader( member1 )
.leaderTerm( term )
.prevLogIndex( followerAppendIndex + 2 ) // leader has appended 2 ahead from this follower
.prevLogTerm( term ) // in the same term
.build(); // no entries, this is a heartbeat
Outcome<RaftTestMember> outcome = follower.handle( heartbeat, state, log() );
assertEquals( 1, outcome.getOutgoingMessages().size() );
Message<RaftTestMember> outgoing = outcome.getOutgoingMessages().iterator().next().message();
assertEquals( RaftMessages.Type.APPEND_ENTRIES_RESPONSE, outgoing.type() );
RaftMessages.AppendEntries.Response response = (AppendEntries.Response) outgoing;
assertFalse( response.success() );
}
@Test
public void heartbeatShouldNotResultInCommitIfReferringToFutureEntries() throws Exception
{
int term = 1;
int followerAppendIndex = 9;
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.term( term )
.build();
Follower follower = new Follower();
appendSomeEntriesToLog( state, follower, followerAppendIndex, term );
RaftMessages.Heartbeat<RaftTestMember> heartbeat = heartbeat().from( member1 )
.commitIndex( followerAppendIndex + 2 ) // The leader is talking about committing stuff we don't know about
.commitIndexTerm( term ) // And is in the same term
.leaderTerm( term + 2 )
.build();
Outcome<RaftTestMember> outcome = follower.handle( heartbeat, state, log() );
// Then there should be no actions taken against the log
assertFalse( outcome.getLogCommands().iterator().hasNext() );
}
@Test
public void heartbeatShouldNotResultInCommitIfHistoryMismatches() throws Exception
{
int term = 1;
int followerAppendIndex = 9;
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.term( term )
.build();
Follower follower = new Follower();
appendSomeEntriesToLog( state, follower, followerAppendIndex, term );
RaftMessages.Heartbeat<RaftTestMember> heartbeat = heartbeat().from( member1 )
.commitIndex( followerAppendIndex ) // The leader suggests that we commit stuff we have appended
.commitIndexTerm( term + 2 ) // but in a different term
.leaderTerm( term + 2 ) // And is in a term that is further in the future
.build();
Outcome<RaftTestMember> outcome = follower.handle( heartbeat, state, log() );
assertFalse( outcome.getLogCommands().iterator().hasNext() );
}
@Test
public void historyShouldResultInCommitIfHistoryMatches() throws Exception
{
int term = 1;
int followerAppendIndex = 9;
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.term( term )
.build();
Follower follower = new Follower();
appendSomeEntriesToLog( state, follower, followerAppendIndex, term );
RaftMessages.Heartbeat<RaftTestMember> heartbeat = heartbeat().from( member1 )
.commitIndex( followerAppendIndex - 1) // The leader suggests that we commit stuff we have appended
.commitIndexTerm( term ) // in the same term
.leaderTerm( term + 2 ) // with the leader in the future
.build();
Outcome<RaftTestMember> outcome = follower.handle( heartbeat, state, log() );
Iterator<LogCommand> iterator = outcome.getLogCommands().iterator();
assertTrue( iterator.hasNext() );
LogCommand logCommand = iterator.next();
assertFalse( iterator.hasNext() );
assertThat( logCommand, instanceOf( CommitCommand.class ) );
CommitCommand commit = (CommitCommand) logCommand;
CapturingRaftLog capture = new CapturingRaftLog();
commit.applyTo( capture );
assertEquals( followerAppendIndex - 1, capture.commitIndex() );
}
@Test
public void shouldAppendMultipleEntries() throws Exception
{
// given
int term = 1;
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.term( term )
.build();
Follower follower = new Follower();
RaftLogEntry[] entries = {
new RaftLogEntry( 1, new ReplicatedString( "commit this!" ) ),
new RaftLogEntry( 1, new ReplicatedString( "commit this as well!" ) ),
new RaftLogEntry( 1, new ReplicatedString( "commit this too!" ) )
};
Outcome<RaftTestMember> outcome = follower.handle(
new AppendEntries.Request<>( member1, 1, -1, -1, entries, -1 ), state, log() );
state.update( outcome );
// then
assertEquals( 2, state.entryLog().appendIndex() );
}
@Test
public void shouldTruncateIfTermDoesNotMatch() throws Exception
{
// given
int term = 1;
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.term( term )
.build();
Follower follower = new Follower();
state.update( follower.handle( new AppendEntries.Request<>( member1, 1, -1, -1,
new RaftLogEntry[] {
new RaftLogEntry( 2, ContentGenerator.content() ),
},
-1 ), state, log() ) );
RaftLogEntry[] entries = {
new RaftLogEntry( 1, new ReplicatedString( "commit this!" ) ),
};
Outcome<RaftTestMember> outcome = follower.handle(
new AppendEntries.Request<>( member1, 1, -1, -1, entries, -1 ), state, log() );
state.update( outcome );
// then
assertEquals( 0, state.entryLog().appendIndex() );
assertEquals( 1, state.entryLog().readEntryTerm( 0 ) );
}
@Test
public void followerLearningAboutHigherCommitCausesValuesTobeAppliedToItsLog() throws Exception
{
// given
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.build();
Follower follower = new Follower();
appendSomeEntriesToLog( state, follower, 3, 0 );
// when receiving AppEntries with high leader commit (3)
Outcome<RaftTestMember> outcome = follower.handle( new AppendEntries.Request<>( myself, 0, 2, 0,
new RaftLogEntry[] { new RaftLogEntry( 0, ContentGenerator.content() ) }, 3 ), state, log() );
state.update( outcome );
// then
assertEquals( 3, state.entryLog().commitIndex() );
}
@Test
public void shouldRenewElectionTimeoutOnReceiptOfHeartbeatInCurrentOrHigherTerm() throws Exception
{
// given
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.term(0)
.build();
Follower follower = new Follower();
Outcome<RaftTestMember> outcome = follower.handle( new RaftMessages.Heartbeat<>( myself, 1, 1, 1 ),
state, log() );
// then
assertTrue( outcome.electionTimeoutRenewed() );
}
@Test
public void shouldNotRenewElectionTimeoutOnReceiptOfHeartbeatInLowerTerm() throws Exception
{
// given
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.term( 2 )
.build();
Follower follower = new Follower();
Outcome<RaftTestMember> outcome = follower.handle( new RaftMessages.Heartbeat<>( myself, 1, 1, 1 ),
state, log() );
// then
assertFalse( outcome.electionTimeoutRenewed() );
}
@Test
public void shouldNotCommitAheadOfMatchingHistory() throws Exception
{
// given
int LEADER_COMMIT = 10;
int LEADER1_TERM = 1;
int LEADER2_TERM = 2;
InMemoryRaftLog raftLog = new InMemoryRaftLog();
raftLog.append( new RaftLogEntry( LEADER1_TERM, ReplicatedString.valueOf( "gryffindor" ) ) ); // (0) we committed this far already
raftLog.commit( 0 );
raftLog.append( new RaftLogEntry( LEADER1_TERM, ReplicatedString.valueOf( "hufflepuff" ) ) ); // (1) we should only commit up to this, because this is how far we match
raftLog.append( new RaftLogEntry( LEADER1_TERM, ReplicatedString.valueOf( "ravenclaw" ) ) ); // (2) leader will have committed including this and more
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.entryLog( raftLog )
.term( 1 )
.build();
Follower follower = new Follower();
Outcome<RaftTestMember> outcome;
// when - append request matching history and truncating
RaftLogEntry[] newEntries = {
new RaftLogEntry( LEADER2_TERM, new ReplicatedString( "slytherin" ) ), // (1 - overwrite and truncate)
};
outcome = follower.handle( new RaftMessages.AppendEntries.Request<>( myself, LEADER2_TERM, 0, LEADER1_TERM, newEntries, LEADER_COMMIT ), state, log() );
// then
assertThat( outcome.getLogCommands(), hasItem( new CommitCommand( 1 ) ) );
}
@Test
public void shouldIncludeLatestAppendedInResponse() throws Exception
{
// given: just a single appended entry at follower
RaftLogEntry entryA = new RaftLogEntry( 1, ReplicatedString.valueOf( "b" ) );
InMemoryRaftLog raftLog = new InMemoryRaftLog();
raftLog.append( entryA );
RaftState<RaftTestMember> state = raftState()
.myself( myself )
.entryLog( raftLog )
.term( 1 )
.build();
Follower follower = new Follower();
RaftLogEntry entryB = new RaftLogEntry( 1, ReplicatedString.valueOf( "b" ) );
// when: append request for item way forward (index=10, term=2)
Outcome<RaftTestMember> outcome = follower.handle(
new RaftMessages.AppendEntries.Request<>( leader, 2, 10, 2,
new RaftLogEntry[]{entryB}, 10 ), state, log() );
// then: respond with false and how far ahead we are
assertThat( single( outcome.getOutgoingMessages()).message(), equalTo(
appendEntriesResponse().from( myself ).term( 2 ).appendIndex( 0 ).matchIndex( -1 ).failure()
.build() ) );
}
private void appendSomeEntriesToLog( RaftState<RaftTestMember> raft, Follower follower, int numberOfEntriesToAppend, int
term ) throws RaftStorageException
{
for ( int i = 0; i < numberOfEntriesToAppend; i++ )
{
if ( i == 0 )
{
raft.update( follower.handle( new AppendEntries.Request<>( myself, term, i - 1, -1,
new RaftLogEntry[] { new RaftLogEntry( term, ContentGenerator.content() ) }, -1 ), raft, log() ) );
}
else
{
raft.update( follower.handle( new AppendEntries.Request<>( myself, term, i - 1, term,
new RaftLogEntry[]{new RaftLogEntry( term, ContentGenerator.content() )}, -1 ), raft, log() ) );
}
}
}
private static class ContentGenerator
{
private static int count = 0;
public static ReplicatedString content()
{
return new ReplicatedString( String.format( "content#%d", count++ ) );
}
}
private Log log()
{
return logProvider.getLog( getClass() );
}
private static final class CapturingRaftLog implements RaftLog
{
private long commitIndex;
@Override
public void replay() throws Throwable
{
}
@Override
public void registerListener( Listener consumer )
{
}
@Override
public long append( RaftLogEntry entry ) throws RaftStorageException
{
return 0;
}
@Override
public void truncate( long fromIndex ) throws RaftStorageException
{
}
@Override
public void commit( long commitIndex ) throws RaftStorageException
{
this.commitIndex = commitIndex;
}
@Override
public long appendIndex()
{
return 0;
}
@Override
public long commitIndex()
{
return commitIndex;
}
@Override
public RaftLogEntry readLogEntry( long logIndex ) throws RaftStorageException
{
return null;
}
@Override
public ReplicatedContent readEntryContent( long logIndex ) throws RaftStorageException
{
return null;
}
@Override
public long readEntryTerm( long logIndex ) throws RaftStorageException
{
return 0;
}
@Override
public boolean entryExists( long logIndex )
{
return false;
}
}
}