internal static async Task Catchup(
IReifiedProjection projection,
IEventStream stream,
CancellationToken cancel = default,
ILogAdapter log = null)
{
try
{
// Load project and discard events before that.
log?.Info("[ES init] loading projections.");
await projection.TryLoadAsync(cancel).ConfigureAwait(false);
var catchUp = projection.Sequence + 1;
log?.Info($"[ES init] advancing stream to seq {catchUp}.");
var streamSequence = await stream.DiscardUpTo(catchUp, cancel).ConfigureAwait(false);
if (cancel.IsCancellationRequested)
{
return;
}
if (streamSequence != projection.Sequence)
{
log?.Warning(
$"[ES init] projection seq {projection.Sequence} not found in stream (max seq is {streamSequence}: resetting everything.");
// Cache is apparently beyond the available sequence. Could happen in
// development environments with non-persistent events but persistent
// caches. Treat cache as invalid and start from the beginning.
stream.Reset();
projection.Reset();
}
}
catch (Exception e)
{
log?.Warning("[ES init] error while reading cache.", e);
// Something went wrong when reading the cache. Stop.
stream.Reset();
projection.Reset();
}
}