sync: GU retry with less explicit TimeTicks logic

sync/sessions/nudge_tracker.cc

Index: sync/sessions/nudge_tracker.cc
diff --git a/sync/sessions/nudge_tracker.cc b/sync/sessions/nudge_tracker.cc
index f96d3464826e86653fb04d515c7d9575d891f2be..13186c7a678008c1f5f740384472298a59d25d4c 100644
--- a/sync/sessions/nudge_tracker.cc
+++ b/sync/sessions/nudge_tracker.cc
@@ -18,7 +18,8 @@ size_t NudgeTracker::kDefaultMaxPayloadsPerType = 10;
 NudgeTracker::NudgeTracker()
     : updates_source_(sync_pb::GetUpdatesCallerInfo::UNKNOWN),
       invalidations_enabled_(false),
-      invalidations_out_of_sync_(true) {
+      invalidations_out_of_sync_(true),
+      is_retry_required_(false) {
   ModelTypeSet protocol_types = ProtocolTypes();
   // Default initialize all the type trackers.
   for (ModelTypeSet::Iterator it = protocol_types.First(); it.Good();
@@ -44,11 +45,11 @@ bool NudgeTracker::IsSyncRequired() const {
   return false;
 }
 
-bool NudgeTracker::IsGetUpdatesRequired(base::TimeTicks now) const {
+bool NudgeTracker::IsGetUpdatesRequired() const {
   if (invalidations_out_of_sync_)
     return true;
 
-  if (IsRetryRequired(now))
+  if (IsRetryRequired())
     return true;
 
   for (TypeTrackerMap::const_iterator it = type_trackers_.begin();
@@ -60,16 +61,18 @@ bool NudgeTracker::IsGetUpdatesRequired(base::TimeTicks now) const {
   return false;
 }
 
-bool NudgeTracker::IsRetryRequired(base::TimeTicks now) const {
-  return !next_retry_time_.is_null() && next_retry_time_ < now;
+bool NudgeTracker::IsRetryRequired() const {
+  return is_retry_required_;
 }
 
-void NudgeTracker::RecordSuccessfulSyncCycle(base::TimeTicks now) {
+void NudgeTracker::RecordSuccessfulSyncCycle() {
   updates_source_ = sync_pb::GetUpdatesCallerInfo::UNKNOWN;
-  last_successful_sync_time_ = now;
 
-  if (next_retry_time_ < now)
-    next_retry_time_ = base::TimeTicks();
+  // If a retry was required, we've just serviced it.  Unset the flag.
+  is_retry_required_ = false;
+
+  // We don't unset the next_retry_time_ flag here, since it may have been
+  // updated during the sync cycle that just completed.
 
   // A successful cycle while invalidations are enabled puts us back into sync.
   invalidations_out_of_sync_ = !invalidations_enabled_;
@@ -239,6 +242,20 @@ void NudgeTracker::FillProtoMessage(
   type_trackers_.find(type)->second.FillGetUpdatesTriggersMessage(msg);
 }
 
+void NudgeTracker::ToggleRetryFlagIfRequired(base::TimeTicks now) {
+  // Assume we have nothing to do.
+  is_retry_required_ = false;
+
+  // Nothing to do if no retries are scheduled.
+  if (next_retry_time_.is_null())
+    return;
+
+  if (next_retry_time_ < now) {

[haitaol1, 2014/01/28 20:09:20]

where is next_retry_time nulled? Seems nudge tracker is stuck in retry without
that.

I feel storing start time is easy and may be useful in the future, too.

[rlarocque, 2014/01/28 22:24:38]

Thanks!

I had a nagging feeling that this code was wrong somehow, since I had concluded
on Friday that it was impossible to write this code correctly with so little
state.  But my unit tests passed and seemed to cover all the cases, so I figured
it must be correct...  Looks like I *was* missing something obvious.

I've updated the tests to catch this.

+    // The time has come.  We should perform a GU retry as soon as possible.
+    is_retry_required_ = true;
+  }
+}
+
 void NudgeTracker::SetHintBufferSize(size_t size) {
   for (TypeTrackerMap::iterator it = type_trackers_.begin();
        it != type_trackers_.end(); ++it) {
@@ -246,5 +263,9 @@ void NudgeTracker::SetHintBufferSize(size_t size) {
   }
 }
 
+void NudgeTracker::SetNextRetryTime(base::TimeTicks retry_time) {
+  next_retry_time_ = retry_time;
+}
+
 }  // namespace sessions
 }  // namespace syncer