private void Received(OrderedCommitNotification msg)
{
//if their previous matches our current, project
//if their previous is less than our current, ignore
//if their previous is > our current, catchup
var comparer = new CheckpointComparer();
var comparision = comparer.Compare(Checkpoint, msg.PreviousCheckpoint);
if (comparision == 0)
{
Project(msg.Commit); //order matched, project
}
else if (comparision > 0)
{
//we are ahead of this commit so no-op, this is a bit odd, so log it
Context.GetLogger().Debug("Received a commit notification (checkpoint {0}) behind our checkpoint ({1})", msg.Commit.CheckpointToken, Checkpoint.Get());
}
else
{
//we are behind the head, should catch up
var fromPoint = Checkpoint.Map(x => x.ToString()).GetOrElse("beginning of time");
Context.GetLogger().Info("Catchup started from checkpoint {0} after receiving out-of-sequence commit with checkpoint {1} and previous checkpoint {2}", fromPoint, msg.Commit.CheckpointToken, msg.PreviousCheckpoint);
Catchup();
Context.GetLogger().Info("Catchup finished from {0} to checkpoint {1} after receiving commit with checkpoint {2}", fromPoint, Checkpoint.Map(x => x.ToString()).GetOrElse("beginning of time"), msg.Commit.CheckpointToken);
}
}
/// <summary>
/// Catches-up the projector if it has fallen behind the head
/// </summary>
protected virtual void Catchup()
{
var comparer = new CheckpointComparer();
IEnumerable <ICommit> commits = _persistStreams.GetFrom(Checkpoint.GetOrElse(() => 0)); //load all commits after our current checkpoint from db
foreach (var commit in commits)
{
Project(commit);
if (comparer.Compare(Checkpoint, commit.CheckpointToken.ToSome()) != 0)
{
//something went wrong, we couldn't project
Context.GetLogger().Warning("Stopped catchup! was unable to project the commit at checkpoint {0}", commit.CheckpointToken);
break;
}
}
}