public async Task WriteCheckpoint(Flow flow)
{
var result = await _context.Connection.AppendToStreamAsync(
flow.Context.Key.GetCheckpointStream(),
ExpectedVersion.Any,
_context.GetCheckpointEventData(flow));
if (flow is Query query)
{
try
{
var checkpoint = new TimelinePosition(result.NextExpectedVersion);
var etag = QueryETag.From(query.Context.Key, checkpoint).ToString();
await _context.Connection.AppendToStreamAsync(
TimelineStreams.ChangedQueries,
ExpectedVersion.Any,
_context.GetQueryChangedEventData(new QueryChanged(etag)));
}
catch (Exception error)
{
Log.Error(error, "Failed to write QueryChanged for {Query} - subscribers will not be aware of the change until the query observes another event.", query);
}
}
}
internal async Task <TQuery> Get <TQuery>(Id id) where TQuery : Query
{
var key = GetKey <TQuery>(id);
var state = await _queryDb.ReadState(QueryETag.From(key));
return((TQuery)Deserialize(key.Type, state.ReadContent()));
}
QueryETag ReadETag(Type type, Id id)
{
if (TryGetIfNoneMatch(out var ifNoneMatch))
{
return(QueryETag.From(ifNoneMatch, _area));
}
var key = FlowKey.From(_area.Queries.Get(type), id);
return(QueryETag.From(key, TimelinePosition.None));
}
async Task TryWriteQueryStopped(Flow flow)
{
try
{
var etag = QueryETag.From(flow.Context.Key, flow.Context.CheckpointPosition).ToString();
await _context.AppendToClient(new QueryStopped(etag, flow.Context.ErrorMessage));
}
catch (Exception error)
{
Log.Error(error, "Failed to write stoppage of query {Query} to the client stream. Subscribers will not be aware of the failure", flow);
}
}
async Task TryWriteQueryChanged(Flow query)
{
try
{
var etag = QueryETag.From(query.Context.Key, query.Context.CheckpointPosition).ToString();
await _context.AppendToClient(new QueryChanged(etag));
}
catch (Exception error)
{
Log.Error(error, "Failed to write update of query {Query} to the client stream. Subscribers will not be aware of the change until the query observes another event.", query);
}
}
async Task <Stream> AppendAndWaitUntilChanged(FlowKey key, Event e, TestTimeline timeline)
{
var connectionId = Id.FromGuid();
await _queryDb.SubscribeToChanged(connectionId, QueryETag.From(key));
var position = await timeline.Append(e);
var newETag = QueryETag.From(key, position);
await _notifier.WaitUntilChanged(connectionId, newETag);
_queryDb.UnsubscribeFromChanged(connectionId);
return(await _queryDb.ReadContent(newETag));
}
public Task SubscribeToChanged(string etag) => _db.SubscribeToChanged(ConnectionId, QueryETag.From(etag, _area));
QueryETag ETagFrom(string etag) => QueryETag.From(etag, _context.Area);
void OnChanged(ResolvedEvent e) =>
_db.OnChanged(QueryETag.From(
_context.Json.FromJsonUtf8 <QueryChanged>(e.Event.Data).ETag,
_context.Area));
