//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 static async ValueTask <bool> IsUpToDateAsync(this IAuditTrail <ILogEntry> auditTrail, long index, long term)
{
var localIndex = auditTrail.GetLastIndex(false);
var localTerm = (await auditTrail.GetEntryAsync(localIndex).ConfigureAwait(false) ?? auditTrail.First)
.Term;
return(index >= localIndex && term >= localTerm);
}
private static async Task <Result <VotingResult> > VoteAsync(IRaftClusterMember voter, long term, IAuditTrail <ILogEntry> auditTrail, CancellationToken token)
{
var lastIndex = auditTrail.GetLastIndex(false);
var lastTerm = (await auditTrail.GetEntryAsync(lastIndex).ConfigureAwait(false) ?? auditTrail.First)
.Term;
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;
}
return(new Result <VotingResult>(term, result));
}
internal static async ValueTask <bool> ContainsAsync(this IAuditTrail <ILogEntry> auditTrail, long index,
long term)
=> term == (await auditTrail.GetEntryAsync(index).ConfigureAwait(false) ?? auditTrail.First).Term;