private static async Task <Result <VotingResult> > VoteAsync(IRaftClusterMember voter, long term, IAuditTrail <IRaftLogEntry> auditTrail, CancellationToken token)
{
var lastIndex = auditTrail.GetLastIndex(false);
var lastTerm = await auditTrail.GetTermAsync(lastIndex, token).ConfigureAwait(false);
VotingResult result;
try
{
var response = await voter.VoteAsync(term, lastIndex, lastTerm, token).ConfigureAwait(false);
term = response.Term;
result = response.Value ? VotingResult.Granted : VotingResult.Rejected;
}
catch (OperationCanceledException)
{
result = VotingResult.Canceled;
}
catch (MemberUnavailableException)
{
result = VotingResult.NotAvailable;
term = -1L;
}
return(new Result <VotingResult>(term, result));
}
//true if at least one entry from current term is stored on this node; otherwise, false
private static async Task <Result <bool> > AppendEntriesAsync(IRaftClusterMember member, long commitIndex,
long term,
IAuditTrail <ILogEntry> transactionLog, ILogger logger, CancellationToken token)
{
var currentIndex = transactionLog.GetLastIndex(false);
logger.ReplicationStarted(member.Endpoint, currentIndex);
var precedingIndex = Math.Max(0, member.NextIndex - 1);
var precedingTerm = (await transactionLog.GetEntryAsync(precedingIndex).ConfigureAwait(false) ??
transactionLog.First).Term;
var entries = currentIndex >= member.NextIndex
? await transactionLog.GetEntriesAsync(member.NextIndex).ConfigureAwait(false)
: Array.Empty <ILogEntry>();
logger.ReplicaSize(member.Endpoint, entries.Count, precedingIndex, precedingTerm);
//trying to replicate
var result = await member
.AppendEntriesAsync(term, entries, precedingIndex, precedingTerm, commitIndex, token)
.ConfigureAwait(false);
if (result.Value)
{
logger.ReplicationSuccessful(member.Endpoint, member.NextIndex);
member.NextIndex.VolatileWrite(currentIndex + 1);
//checks whether the at least one entry from current term is stored on this node
result = result.SetValue(entries.Any(entry => entry.Term == term));
}
else
{
logger.ReplicationFailed(member.Endpoint, member.NextIndex.DecrementAndGet());
}
return(result);
}
internal VotingState(IRaftClusterMember voter, long term, IAuditTrail <IRaftLogEntry> auditTrail, CancellationToken token)
{
Voter = voter;
// ensure parallel requesting of votes
Task = System.Threading.Tasks.Task.Run(() => VoteAsync(voter, term, auditTrail, token));
}
internal Replicator(IRaftClusterMember member,
long commitIndex,
long term,
long precedingIndex,
long precedingTerm,
ILogger logger,
CancellationToken token)
{
this.member = member;
this.precedingIndex = precedingIndex;
this.precedingTerm = precedingTerm;
this.commitIndex = commitIndex;
this.term = term;
this.logger = logger;
this.token = token;
}
// TODO: Replace with required init properties in the next version of C#
internal Replicator(
IAuditTrail <IRaftLogEntry> auditTrail,
IRaftClusterMember member,
long commitIndex,
long currentIndex,
long term,
long precedingIndex,
long precedingTerm,
ILogger logger,
CancellationToken token)
{
this.auditTrail = auditTrail;
this.member = member;
this.precedingIndex = precedingIndex;
this.precedingTerm = precedingTerm;
this.commitIndex = commitIndex;
this.currentIndex = currentIndex;
this.term = term;
this.logger = logger;
this.token = token;
}
internal VotingState(IRaftClusterMember voter, long term, IAuditTrail <IRaftLogEntry> auditTrail, CancellationToken token)
{
Voter = voter;
Task = VoteAsync(voter, term, auditTrail, token);
}
bool ILocalMember.IsLeader(IRaftClusterMember member) => ReferenceEquals(Leader, member);
bool IHostingContext.IsLeader(IRaftClusterMember member) => ReferenceEquals(Leader, member);
bool ILocalMember.IsLeader(IRaftClusterMember member) => throw new NotImplementedException();
ValueTask IPersistentState.UpdateVotedForAsync(IRaftClusterMember member)
{
votedFor = member;
return(new ValueTask());
}
bool IPersistentState.IsVotedFor(IRaftClusterMember member)
{
var lastVote = votedFor;
return(lastVote is null || ReferenceEquals(lastVote, member));
}
