internal void AddSpan(JsonMessagePullerSpan newSpan)
{
if (newSpan.StartMessageId > newSpan.EndMessageId)
{
throw new ArgumentException("Invalid span: startMessageId > endMessageId");
}
foreach (var span in Spans.ToArray())
{
// Are the spans overlapping (or adjacent)?
if (span.StartMessageId <= (newSpan.EndMessageId + 1) && (span.EndMessageId + 1) >= newSpan.StartMessageId)
{
// Expand newSpan to include span
if (span.EndMessageId > newSpan.EndMessageId)
{
newSpan.EndMessageId = span.EndMessageId;
}
if (span.StartMessageId < newSpan.StartMessageId)
{
newSpan.StartMessageId = span.StartMessageId;
newSpan.StartTimeUtc = span.StartTimeUtc;
}
// Discard the old span
Spans.Remove(span);
}
}
// Append newSpan
Spans.Add(newSpan);
Spans.Sort();
}
async Task ProcessSpanAsync(JsonSyncingFeed syncingFeed, bool forceCheckNew)
{
this.appContext.RequireForegroundThread();
long feedId = syncingFeed.FeedId;
DateTime queryUtc = DateTime.UtcNow;
bool checkNew = forceCheckNew ||
syncingFeed.Spans.Count < 1 ||
(syncingFeed.Spans.Count == 1 && syncingFeed.ReachedEmptyResult);
long?olderThan = null;
if (checkNew)
{
syncingFeed.SpanCyclesSinceCheckNew = 0;
syncingFeed.LastCheckNewUtc = queryUtc;
}
else
{
++syncingFeed.SpanCyclesSinceCheckNew;
// Work backwards from the most recent gap
var lastSpan = syncingFeed.Spans.Last();
olderThan = lastSpan.StartMessageId;
}
syncingFeed.LastUpdateUtc = queryUtc;
if (CallingService != null)
{
CallingService(this, new MessagePullerCallingServiceEventArgs(feedId, null));
}
JsonMessageEnvelope envelope;
try
{
// Perform a REST query like this:
// https://www.yammer.com/example.com/api/v1/messages/in_group/3.json?threaded=extended&older_than=129
envelope = await yamsterApi.GetMessagesInFeedAsync(feedId, olderThan);
this.appContext.RequireForegroundThread();
}
catch (RateLimitExceededException ex)
{
yamsterApi.NotifyRateLimitExceeded();
OnError(ex);
return;
}
catch (WebException ex)
{
var response = ex.Response as HttpWebResponse;
if (response != null)
{
if (response.StatusCode == HttpStatusCode.NotFound && syncingFeed.GroupState != null)
{
// The group does not exist; disable further syncing for it and report
// a more specific error
DbGroupState groupState = syncingFeed.GroupState;
groupState.ShouldSync = false;
yamsterCoreDb.GroupStates.InsertRecord(groupState, SQLiteConflictResolution.Replace);
OnError(new YamsterFailedSyncException(feedId, ex));
return;
}
}
// A general error has occurred
yamsterApi.BackOff();
OnError(ex);
return;
}
var newSpan = new JsonMessagePullerSpan();
newSpan.StartMessageId = long.MaxValue;
newSpan.StartTimeUtc = DateTime.MaxValue;
newSpan.EndMessageId = long.MinValue;
using (var transaction = yamsterArchiveDb.BeginTransaction())
{
WriteReferencesToDb(envelope.References, queryUtc);
foreach (var threadStarter in envelope.Messages)
{
// Clean up any corrupted data
if (yamsterCoreDb.SyncingThreads
.DeleteRecords("WHERE [ThreadId] = " + threadStarter.ThreadId) > 0)
{
Debug.WriteLine("MessagePuller: WARNING: Removed unexpected sync state for thread ID={0}",
threadStarter.ThreadId);
}
JsonMessage[] extendedMessages;
// Note that ThreadedExtended is indexed by thread ID, not message ID
if (!envelope.ThreadedExtended.TryGetValue(threadStarter.ThreadId, out extendedMessages))
{
extendedMessages = new JsonMessage[0];
}
// Update the span bounds
long latestMessageIdInThread;
DateTime latestMessageTimeInThread;
if (extendedMessages.Length > 0)
{
latestMessageIdInThread = extendedMessages.Max(x => x.Id);
latestMessageTimeInThread = extendedMessages.Max(x => x.Created);
}
else
{
latestMessageIdInThread = threadStarter.Id;
latestMessageTimeInThread = threadStarter.Created;
}
newSpan.StartMessageId = Math.Min(newSpan.StartMessageId, latestMessageIdInThread);
if (latestMessageTimeInThread < newSpan.StartTimeUtc)
{
newSpan.StartTimeUtc = latestMessageTimeInThread;
}
newSpan.EndMessageId = Math.Max(newSpan.EndMessageId, latestMessageIdInThread);
WriteMessageToDb(threadStarter, queryUtc);
// NOTE: The thread is presumed to be contiguous at this point.
// This is guaranteed to return at least threadStarter.Id written above
long latestMessageInDb = yamsterArchiveDb.Mapper.QueryScalar <long>(
"SELECT MAX(Id) FROM [" + this.yamsterArchiveDb.ArchiveMessages.TableName
+ "] WHERE ThreadId = " + threadStarter.ThreadId.ToString());
// There are two scenarios where we can prove that there is no gap,
// i.e. that we already have all the messages for the thread.
// NOTE: Originally we assumed there was no gap if extendedMessages.Length<2,
// but a counterexample was found.
bool gapped = true;
// For debugging -- skip pulling most messages to accumulate threads faster
#if false
if ((threadStarter.ThreadId & 31) != 0)
{
gapped = false;
}
#endif
// Scenario 1: Does the envelope contain the complete thread?
var threadReference = envelope.References
.OfType <ThreadReferenceJson>()
.Where(x => x.Id == threadStarter.ThreadId)
.FirstOrDefault();
if (threadReference != null)
{
// (+1 for threadStarter)
if (extendedMessages.Length + 1 == threadReference.Stats.MessagesCount)
{
// This criteria should work, but I found cases where Yammer's counter is incorrect
#if false
// The envelope contains the complete thread
gapped = false;
#endif
}
}
else
{
// This should never happen, but if it does it's okay if we wrongly assume
// the thread is gapped
Debug.Assert(false);
}
// Scenario 2: Do the envelope messages overlap with the database's version of the thread?
if (gapped && extendedMessages.Length > 0)
{
long extendedStartId = extendedMessages.Min(x => x.Id);
if (latestMessageInDb >= extendedStartId)
{
// Yes, the messages overlap
gapped = false;
}
}
if (gapped)
{
var gappedThread = new DbSyncingThread();
gappedThread.FeedId = feedId;
gappedThread.ThreadId = threadStarter.ThreadId;
gappedThread.StopMessageId = latestMessageInDb;
// NOTE: In a static database, it would be most efficient to call
// WriteMessageToDb() for the extendedMessages that we already received
// and pick up with LastPulledMessageId=extendedStartId.
// However, if we assume people are actively posting in Yammer, it's
// better to begin processing a gapped thread by querying for the absolute
// latest stuff, since a fair amount of time may have elapsed by the
// time we get around to doing the query.
gappedThread.LastPulledMessageId = null;
gappedThread.RetryCount = 0;
// A key violation should be impossible here since if there was a conflicting
// record, we deleted it above.
yamsterCoreDb.SyncingThreads.InsertRecord(gappedThread);
}
else
{
foreach (var extendedMessage in extendedMessages)
{
WriteMessageToDb(extendedMessage, queryUtc);
}
}
}
if (envelope.Messages.Length > 0)
{
if (olderThan.HasValue)
{
// If the Yammer result includes messages newer than what we asked
// for with olderThan, this is most likely a bug.
// NOTE: Skip this check for the Inbox feed, which seems to have minor
// overlap about 50% of the time. This issue wasn't observed in the Yammer web page,
// but that may be due to the additional filtering there for seen/unarchived.
if (feedId != YamsterGroup.InboxFeedId)
{
Debug.Assert(newSpan.EndMessageId < olderThan);
}
// If olderThan was specified, then the span actually covers anything
// up to that point in the history
newSpan.EndMessageId = olderThan.Value - 1;
}
// Now create a span corresponding to the range of messages we just received.
syncingFeed.AddSpan(newSpan);
}
else
{
syncingFeed.ReachedEmptyResult = true;
}
yamsterCoreDb.UpdateJsonSyncingFeed(feedId, syncingFeed);
if (feedId == YamsterGroup.InboxFeedId)
{
// For each GroupId in the messages that we wrote, make sure ShowInYamster = 1
string showInYamsterSql = string.Format(
@"UPDATE [GroupStates] SET [ShowInYamster] = 1"
+ " WHERE [GroupId] in ({0}) AND [ShowInYamster] <> 1",
string.Join(
", ",
envelope.Messages.Where(x => x.GroupId != null).Select(x => x.GroupId).Distinct()
)
);
yamsterCoreDb.Mapper.ExecuteNonQuery(showInYamsterSql);
// For each ThreadId in the messages that we wrote, mark it as appearing in the inbox
string seenInInboxSql = string.Format(
@"UPDATE [ThreadStates] SET [SeenInInboxFeed] = 1"
+ " WHERE [ThreadId] in ({0}) AND [SeenInInboxFeed] <> 1",
string.Join(
", ",
envelope.Messages.Select(x => x.ThreadId).Distinct()
)
);
yamsterCoreDb.Mapper.ExecuteNonQuery(seenInInboxSql);
}
transaction.Commit();
if (UpdatedDatabase != null)
{
UpdatedDatabase(this, EventArgs.Empty);
}
}
}
