public AppendEntryResponse AppendEntryRPCHandler(AppendEntry entry)
{
//Check the log check to prevent a intermittent term increase with no back tracking, TODO check whether this causes potentially concurrency issues
if (entry.Term < _nodeStorage.CurrentTerm && entry.LeaderCommit <= NodeStateService.CommitIndex)
{
Logger.LogDebug(NodeStateService.GetNodeLogId() + "Rejected RPC from " + entry.LeaderId + " due to lower term " + entry.Term + "<" + _nodeStorage.CurrentTerm);
return(new AppendEntryResponse()
{
ConflictName = AppendEntriesExceptionNames.OldTermException,
NodeId = _nodeStorage.Id,
IsSuccessful = false
});
}
//Reset the timer if the append is from a valid term
ResetTimer(_electionTimeoutTimer, ClusterOptions.ElectionTimeoutMs, ClusterOptions.ElectionTimeoutMs);
//If you are a leader or candidate, swap to a follower
if (NodeStateService.Role == NodeState.Candidate || NodeStateService.Role == NodeState.Leader)
{
Logger.LogDebug(NodeStateService.GetNodeLogId() + " detected node " + entry.LeaderId + " is further ahead. Changing to follower");
SetNodeRole(NodeState.Follower);
}
if (NodeStateService.CurrentLeader != entry.LeaderId)
{
Logger.LogDebug(NodeStateService.GetNodeLogId() + "Detected uncontacted leader, discovering leader now.");
//Reset the current leader
NodeStateService.CurrentLeader = entry.LeaderId;
}
if (entry.LeaderCommit > NodeStateService.LatestLeaderCommit)
{
Logger.LogDebug(NodeStateService.GetNodeLogId() + "Detected leader commit of " + entry.LeaderCommit + " commiting data on node.");
NodeStateService.LatestLeaderCommit = entry.LeaderCommit;
}
// If your log entry is not within the last snapshot, then check the validity of the previous log index
if (_nodeStorage.LastSnapshotIncludedIndex < entry.PrevLogIndex)
{
var previousEntry = _nodeStorage.GetLogAtIndex(entry.PrevLogIndex);
if (previousEntry == null && entry.PrevLogIndex != 0)
{
Logger.LogDebug(NodeStateService.GetNodeLogId() + "Missing previous entry at index " + entry.PrevLogIndex + " from term " + entry.PrevLogTerm + " does not exist.");
return(new AppendEntryResponse()
{
IsSuccessful = false,
ConflictingTerm = null,
ConflictName = AppendEntriesExceptionNames.MissingLogEntryException,
FirstTermIndex = null,
NodeId = _nodeStorage.Id,
LastLogEntryIndex = _nodeStorage.GetTotalLogCount()
});
}
}
else
{
if (_nodeStorage.LastSnapshotIncludedTerm != entry.PrevLogTerm)
{
Logger.LogDebug(NodeStateService.GetNodeLogId() + "Inconsistency found in the node snapshot and leaders logs, log " + entry.PrevLogIndex + " from term " + entry.PrevLogTerm + " does not exist.");
return(new AppendEntryResponse()
{
ConflictName = AppendEntriesExceptionNames.ConflictingLogEntryException,
IsSuccessful = false,
ConflictingTerm = entry.PrevLogTerm,
NodeId = _nodeStorage.Id,
FirstTermIndex = 0 //always set to 0 as snapshots are assumed to be from 0 > n
});
}
}
_nodeStorage.SetCurrentTerm(entry.Term);
foreach (var log in entry.Entries)
{
var existingEnty = _nodeStorage.GetLogAtIndex(log.Index);
if (existingEnty != null && existingEnty.Term != log.Term)
{
Logger.LogDebug(NodeStateService.GetNodeLogId() + "Found inconsistent logs in state, deleting logs from index " + log.Index);
_nodeStorage.DeleteLogsFromIndex(log.Index);
break;
}
}
NodeStateService.InCluster = true;
DateTime time = DateTime.Now;
if (entry.Entries != null && _nodeStorage.GetLogAtIndex(entry.PrevLogIndex) != null && entry.Entries.Count() > 0 && entry.Entries.First().Index > 1 && _nodeStorage.GetLogAtIndex(entry.Entries.First().Index - 1).Term != entry.PrevLogTerm)
{
Logger.LogInformation(NodeStateService.GetNodeLogId() + "Last term does not match, log " + entry.PrevLogIndex + " from term " + entry.PrevLogTerm + " does not exist.");
return(new AppendEntryResponse()
{
ConflictName = AppendEntriesExceptionNames.ConflictingLogEntryException,
IsSuccessful = false,
ConflictingTerm = entry.PrevLogTerm,
NodeId = _nodeStorage.Id,
FirstTermIndex = 0//always set to 0 as snapshots are assumed to be from 0 > n
});
}
foreach (var log in entry.Entries)
{
try
{
if (!_nodeStorage.LogExists(log.Index))
{
Logger.LogDebug(NodeStateService.GetNodeLogId() + " adding to node storage " + log);
_nodeStorage.AddLog(log);
}
}
catch (MissingLogEntryException e)
{
Logger.LogError(NodeStateService.GetNodeLogId() + " failed to add log " + log.Index + " with exception " + e.Message + Environment.NewLine + e.StackTrace);
return(new AppendEntryResponse()
{
IsSuccessful = false,
ConflictingTerm = null,
ConflictName = AppendEntriesExceptionNames.MissingLogEntryException,
FirstTermIndex = null,
NodeId = _nodeStorage.Id,
LastLogEntryIndex = _nodeStorage.GetTotalLogCount()
});
}
catch (Exception e)
{
Logger.LogError(NodeStateService.GetNodeLogId() + " failed to add log " + log.Index + " with exception " + e.Message + Environment.NewLine + e.StackTrace);
return(new AppendEntryResponse()
{
IsSuccessful = false,
ConflictingTerm = null,
ConflictName = AppendEntriesExceptionNames.LogAppendingException,
FirstTermIndex = null,
NodeId = _nodeStorage.Id,
LastLogEntryIndex = _nodeStorage.GetTotalLogCount()
});
}
}
return(new AppendEntryResponse()
{
IsSuccessful = true,
NodeId = _nodeStorage.Id,
});
}
