//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 <LogEntry> GetEntryAsync <LogEntry>(this IAuditTrail <LogEntry> auditTrail, long index)
where LogEntry : class, IMessage
{
var entries = await auditTrail.GetEntriesAsync(index, index).ConfigureAwait(false);
return(entries.Count > 0 ? entries[0] : null);
}
private static async void OnCommitted(IAuditTrail <ILogEntry> sender, long startIndex, long count)
{
foreach (var entry in await sender.GetEntriesAsync(startIndex, startIndex + count).ConfigureAwait(false))
{
var content = await entry.ReadAsTextAsync().ConfigureAwait(false);
Console.WriteLine($"Message '{content}' is committed at term {entry.Term}");
}
}
