private void Run()
{
var ambassadorsToRemove = new List <CandidateAmbassador>();
try
{
try
{
// Operation may fail, that's why we don't RaiseOrDie
_running.Raise();
ElectionTerm = _engine.CurrentTerm;
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info($"Candidate {_engine.Tag}: Starting elections");
}
ClusterTopology clusterTopology;
using (_engine.ContextPool.AllocateOperationContext(out ClusterOperationContext context))
using (context.OpenReadTransaction())
{
clusterTopology = _engine.GetTopology(context);
}
if (clusterTopology.Members.Count == 1)
{
CastVoteForSelf(ElectionTerm + 1, "Single member cluster, natural leader");
_engine.SwitchToLeaderState(ElectionTerm, ClusterCommandsVersionManager.CurrentClusterMinimalVersion,
"I'm the only one in the cluster, so no need for elections, I rule.");
return;
}
if (_engine.RequestSnapshot)
{
// we aren't allowed to be elected for leadership if we requested a snapshot
if (_engine.Log.IsOperationsEnabled)
{
_engine.Log.Operations("we aren't allowed to be elected for leadership if we requested a snapshot");
}
return;
}
if (IsForcedElection)
{
CastVoteForSelf(ElectionTerm + 1, "Voting for self in forced elections");
}
else
{
ElectionTerm = ElectionTerm + 1;
}
foreach (var voter in clusterTopology.Members)
{
if (voter.Key == _engine.Tag)
{
continue; // we already voted for ourselves
}
var candidateAmbassador = new CandidateAmbassador(_engine, this, voter.Key, voter.Value);
_voters = new List <CandidateAmbassador>(_voters)
{
candidateAmbassador
};
_engine.AppendStateDisposable(this, candidateAmbassador); // concurrency exception here will dispose the current candidate and it ambassadors
candidateAmbassador.Start();
}
while (_running && _engine.CurrentState == RachisState.Candidate)
{
if (_peersWaiting.WaitOne(_engine.Timeout.TimeoutPeriod) == false)
{
ElectionTerm = _engine.CurrentTerm + 1;
_engine.RandomizeTimeout(extend: true);
StateChange(); // will wake ambassadors and make them ping peers again
continue;
}
if (_running == false)
{
return;
}
_peersWaiting.Reset();
var trialElectionsCount = 1;
var realElectionsCount = 1;
foreach (var ambassador in _voters)
{
if (ambassador.NotInTopology)
{
MoveCandidateToPassive("A leader node has indicated that I'm not in their topology, I was probably kicked out.");
return;
}
if (ambassador.TopologyMismatch)
{
ambassadorsToRemove.Add(ambassador);
continue;
}
if (ambassador.RealElectionWonAtTerm == ElectionTerm)
{
realElectionsCount++;
}
if (ambassador.TrialElectionWonAtTerm == ElectionTerm)
{
trialElectionsCount++;
}
}
if (StillHavePeers(ambassadorsToRemove) == false)
{
MoveCandidateToPassive("I'm left alone in the cluster.");
return;
}
var majority = ((_voters.Count + 1) / 2) + 1;
if (realElectionsCount >= majority)
{
ElectionResult = ElectionResult.Won;
_running.Lower();
var connections = new Dictionary <string, RemoteConnection>();
var versions = new List <int>
{
ClusterCommandsVersionManager.MyCommandsVersion
};
foreach (var candidateAmbassador in _voters)
{
if (candidateAmbassador.ClusterCommandsVersion > 0)
{
versions.Add(candidateAmbassador.ClusterCommandsVersion);
}
if (candidateAmbassador.TryGetPublishedConnection(out var connection))
{
connections[candidateAmbassador.Tag] = connection;
}
}
StateChange();
var minimalVersion = ClusterCommandsVersionManager.GetClusterMinimalVersion(versions, _engine.MaximalVersion);
string msg = $"Was elected by {realElectionsCount} nodes for leadership in term {ElectionTerm} with cluster version of {minimalVersion}";
_engine.SwitchToLeaderState(ElectionTerm, minimalVersion, msg, connections);
break;
}
if (RunRealElectionAtTerm != ElectionTerm &&
trialElectionsCount >= majority)
{
CastVoteForSelf(ElectionTerm, "Won in the trial elections");
}
}
}
catch (Exception e)
{
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info($"Candidate {_engine.Tag}: Failure during candidacy run with current state of {_engine.CurrentState}", e);
}
if (_engine.CurrentState == RachisState.Candidate)
{
// if we are still a candidate, start the candidacy again.
_engine.SwitchToCandidateState("An error occurred during the last candidacy: " + e);
}
else if (_engine.CurrentState != RachisState.Passive)
{
_engine.Timeout.Start(_engine.SwitchToCandidateStateOnTimeout);
}
}
}
finally
{
try
{
Dispose();
}
catch (Exception)
{
// nothing to be done here
}
}
}
private void FollowerSteadyState()
{
var entries = new List <RachisEntry>();
long lastCommit = 0, lastTruncate = 0, lastAcknowledgedIndex = 0;
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info($"{ToString()}: Entering steady state");
}
while (true)
{
entries.Clear();
using (_engine.ContextPool.AllocateOperationContext(out ClusterOperationContext context))
{
using (context.OpenReadTransaction())
{
if (_engine.RequestSnapshot)
{
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info($"{ToString()}: Snapshot was requested, so we close this follower.");
}
return;
}
}
_debugRecorder.Record("Wait for entries");
var appendEntries = _connection.Read <AppendEntries>(context);
var sp = Stopwatch.StartNew();
if (appendEntries.Term != _engine.CurrentTerm)
{
_connection.Send(context, new AppendEntriesResponse
{
CurrentTerm = _engine.CurrentTerm,
Message = "The current term that I have " + _engine.CurrentTerm + " doesn't match " + appendEntries.Term,
Success = false
});
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info($"{ToString()}: Got invalid term {appendEntries.Term} while the current term is {_engine.CurrentTerm}, aborting connection...");
}
return;
}
ClusterCommandsVersionManager.SetClusterVersion(appendEntries.MinCommandVersion);
_debugRecorder.Record("Got entries");
_engine.Timeout.Defer(_connection.Source);
if (appendEntries.EntriesCount != 0)
{
using (var cts = new CancellationTokenSource())
{
var task = Concurrent_SendAppendEntriesPendingToLeaderAsync(cts, _term, appendEntries.PrevLogIndex);
try
{
for (int i = 0; i < appendEntries.EntriesCount; i++)
{
entries.Add(_connection.ReadRachisEntry(context));
}
}
finally
{
cts.Cancel();
task.Wait(CancellationToken.None);
}
_engine.Timeout.Defer(_connection.Source);
}
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info($"{ToString()}: Got non empty append entries request with {entries.Count} entries. Last: ({entries[entries.Count - 1].Index} - {entries[entries.Count - 1].Flags})"
#if DEBUG
+ $"[{string.Join(" ,", entries.Select(x => x.ToString()))}]"
#endif
);
}
}
// don't start write transaction for noop
if (lastCommit != appendEntries.LeaderCommit ||
lastTruncate != appendEntries.TruncateLogBefore ||
entries.Count != 0)
{
using (var cts = new CancellationTokenSource())
{
// applying the leader state may take a while, we need to ping
// the server and let us know that we are still there
var task = Concurrent_SendAppendEntriesPendingToLeaderAsync(cts, _term, appendEntries.PrevLogIndex);
try
{
bool hasRemovedFromTopology;
(hasRemovedFromTopology, lastAcknowledgedIndex, lastTruncate, lastCommit) = ApplyLeaderStateToLocalState(sp,
context,
entries,
appendEntries);
if (hasRemovedFromTopology)
{
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info("Was notified that I was removed from the node topology, will be moving to passive mode now.");
}
_engine.SetNewState(RachisState.Passive, null, appendEntries.Term,
"I was kicked out of the cluster and moved to passive mode");
return;
}
}
catch (RachisInvalidOperationException)
{
// on raft protocol violation propagate the error and close this follower.
throw;
}
catch (ConcurrencyException)
{
// the term was changed
throw;
}
catch (Exception e)
{
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info($"Failed to apply leader state to local state with {entries.Count:#,#;;0} entries with leader commit: {appendEntries.LeaderCommit}, term: {appendEntries.Term}. Prev log index: {appendEntries.PrevLogIndex}", e);
}
}
finally
{
// here we need to wait until the concurrent send pending to leader
// is completed to avoid concurrent writes to the leader
cts.Cancel();
task.Wait(CancellationToken.None);
}
}
}
if (appendEntries.ForceElections)
{
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info($"{ToString()}: Got a request to become candidate from the leader.");
}
_engine.SwitchToCandidateState("Was asked to do so by my leader", forced: true);
return;
}
_debugRecorder.Record("Processing entries is completed");
_connection.Send(context, new AppendEntriesResponse
{
CurrentTerm = _term,
LastLogIndex = lastAcknowledgedIndex,
Success = true
});
if (sp.Elapsed > _engine.ElectionTimeout / 2)
{
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info($"{ToString()}: Took a long time to complete the cycle with {entries.Count} entries: {sp.Elapsed}");
}
}
_engine.Timeout.Defer(_connection.Source);
_engine.ReportLeaderTime(appendEntries.TimeAsLeader);
_debugRecorder.Record("Cycle done");
_debugRecorder.Start();
}
}
}
private void Run()
{
try
{
try
{
// Operation may fail, that's why we don't RaiseOrDie
_running.Raise();
ElectionTerm = _engine.CurrentTerm;
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info($"Candidate {_engine.Tag}: Starting elections");
}
ClusterTopology clusterTopology;
using (_engine.ContextPool.AllocateOperationContext(out TransactionOperationContext context))
using (context.OpenReadTransaction())
{
clusterTopology = _engine.GetTopology(context);
}
if (clusterTopology.Members.Count == 1)
{
CastVoteForSelf(ElectionTerm + 1, "Single member cluster, natural leader");
_engine.SwitchToLeaderState(ElectionTerm, ClusterCommandsVersionManager.CurrentClusterMinimalVersion,
"I'm the only one in the cluster, so no need for elections, I rule.");
return;
}
if (IsForcedElection)
{
CastVoteForSelf(ElectionTerm + 1, "Voting for self in forced elections");
}
else
{
ElectionTerm = ElectionTerm + 1;
}
foreach (var voter in clusterTopology.Members)
{
if (voter.Key == _engine.Tag)
{
continue; // we already voted for ourselves
}
var candidateAmbassador = new CandidateAmbassador(_engine, this, voter.Key, voter.Value,
_engine.ClusterCertificate);
_voters.Add(candidateAmbassador);
try
{
_engine.AppendStateDisposable(this, candidateAmbassador);
}
catch (ConcurrencyException)
{
foreach (var ambassador in _voters)
{
ambassador.Dispose();
}
return; // we lost the election, because someone else changed our state to follower
}
candidateAmbassador.Start();
}
while (_running && _engine.CurrentState == RachisState.Candidate)
{
if (_peersWaiting.WaitOne(_engine.Timeout.TimeoutPeriod) == false)
{
ElectionTerm = _engine.CurrentTerm;
// timeout?
if (IsForcedElection)
{
CastVoteForSelf(ElectionTerm + 1, "Timeout during forced elections");
}
else
{
ElectionTerm = ElectionTerm + 1;
}
_engine.RandomizeTimeout(extend: true);
StateChange(); // will wake ambassadors and make them ping peers again
continue;
}
if (_running == false)
{
return;
}
_peersWaiting.Reset();
bool removedFromTopology = false;
var trialElectionsCount = 1;
var realElectionsCount = 1;
foreach (var ambassador in _voters)
{
if (ambassador.NotInTopology)
{
removedFromTopology = true;
break;
}
if (ambassador.RealElectionWonAtTerm == ElectionTerm)
{
realElectionsCount++;
}
if (ambassador.TrialElectionWonAtTerm == ElectionTerm)
{
trialElectionsCount++;
}
}
var majority = ((_voters.Count + 1) / 2) + 1;
if (removedFromTopology)
{
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info(
$"Candidate {_engine.Tag}: A leader node has indicated that I'm not in their topology, I was probably kicked out. Moving to passive mode");
}
_engine.SetNewState(RachisState.Passive, this, _engine.CurrentTerm,
"I just learned from the leader that I'm not in their topology, moving to passive state");
break;
}
if (realElectionsCount >= majority)
{
ElectionResult = ElectionResult.Won;
_running.Lower();
StateChange();
var connections = new Dictionary <string, RemoteConnection>();
var versions = new List <int>
{
ClusterCommandsVersionManager.MyCommandsVersion
};
foreach (var candidateAmbassador in _voters)
{
connections[candidateAmbassador.Tag] = candidateAmbassador.Connection;
if (candidateAmbassador.ClusterCommandsVersion > 0)
{
versions.Add(candidateAmbassador.ClusterCommandsVersion);
}
}
var minimalVersion = ClusterCommandsVersionManager.GetClusterMinimalVersion(versions, _engine.MaximalVersion);
_engine.SwitchToLeaderState(ElectionTerm, minimalVersion,
$"Was elected by {realElectionsCount} nodes to leadership in {ElectionTerm} with cluster version of {minimalVersion}",
connections);
break;
}
if (RunRealElectionAtTerm != ElectionTerm &&
trialElectionsCount >= majority)
{
CastVoteForSelf(ElectionTerm, "Won in the trial elections");
}
}
}
catch (Exception e)
{
if (_engine.Log.IsInfoEnabled)
{
_engine.Log.Info($"Candidate {_engine.Tag}: Failure during candidacy run with current state of {_engine.CurrentState}", e);
}
if (_engine.CurrentState == RachisState.Candidate)
{
// if we are still a candidate, start the candidacy again.
_engine.SwitchToCandidateState("An error occured during the last candidacy: " + e);
}
else if (_engine.CurrentState != RachisState.Passive)
{
_engine.Timeout.Start(_engine.SwitchToCandidateStateOnTimeout);
}
}
}
finally
{
try
{
Dispose();
}
catch (Exception)
{
// nothing to be done here
}
}
}
