CBG-4220 [3.2.0 backport] Pending unused sequences shouldn't update high cache sequence (#7102)

If unused sequences ranges are pushed to pendingLogs, they shouldn't increment the channel cache's highSequenceCached until they are processed.

Author: adamcfraser

db/change_cache.go

@@ -576,7 +576,6 @@ func (c *changeCache) releaseUnusedSequence(ctx context.Context, sequence uint64
 	} else {
 		changedChannels.Add(unusedSeq)
 	}
-	c.channelCache.AddUnusedSequence(change)
 	if c.notifyChange != nil && len(changedChannels) > 0 {
 		c.notifyChange(ctx, changedChannels)
 	}
@@ -599,7 +598,6 @@ func (c *changeCache) releaseUnusedSequenceRange(ctx context.Context, fromSequen
 		}
 		changedChannels := c.processEntry(ctx, change)
 		allChangedChannels = allChangedChannels.Update(changedChannels)
-		c.channelCache.AddUnusedSequence(change)
 		if c.notifyChange != nil {
 			c.notifyChange(ctx, allChangedChannels)
 		}
@@ -609,9 +607,6 @@ func (c *changeCache) releaseUnusedSequenceRange(ctx context.Context, fromSequen
 	// push unused range to either pending or skipped lists based on current state of the change cache
 	allChangedChannels = c.processUnusedRange(ctx, fromSequence, toSequence, allChangedChannels, timeReceived)
 
-	// update high seq cached
-	c.channelCache.AddUnusedSequence(&LogEntry{Sequence: toSequence})
-
 	if c.notifyChange != nil {
 		c.notifyChange(ctx, allChangedChannels)
 	}
@@ -804,8 +799,9 @@ func (c *changeCache) _addToCache(ctx context.Context, change *LogEntry) []chann
 	}
 	delete(c.receivedSeqs, change.Sequence)
 
-	// If unused sequence or principal, we're done after updating sequence
+	// If unused sequence, notify the cache and return
 	if change.DocID == "" {
+		c.channelCache.AddUnusedSequence(change)
 		return nil
 	}
 

db/change_cache_test.go

@@ -2430,7 +2430,7 @@ func TestReleasedSequenceRangeHandlingEverythingPending(t *testing.T) {
 		assert.Equal(c, int64(1), dbContext.DbStats.CacheStats.PendingSeqLen.Value())
 		assert.Equal(c, uint64(2), testChangeCache.nextSequence)
 		dbContext.UpdateCalculatedStats(ctx)
-		assert.Equal(c, int64(25), dbContext.DbStats.CacheStats.HighSeqCached.Value())
+		assert.Equal(c, int64(1), dbContext.DbStats.CacheStats.HighSeqCached.Value())
 	}, time.Second*10, time.Millisecond*100)
 }
 
@@ -2536,7 +2536,7 @@ func TestReleasedSequenceRangeHandlingEverythingPendingLowPendingCapacity(t *tes
 	defer testChangeCache.Stop(ctx)
 	require.NoError(t, err)
 
-	// process unused sequence range
+	// process unused sequence range, will be sent to pending.  Triggers seq 1 being sent to skipped
 	testChangeCache.releaseUnusedSequenceRange(ctx, 2, 25, time.Now())
 
 	require.EventuallyWithT(t, func(c *assert.CollectT) {
@@ -2647,7 +2647,7 @@ func TestReleasedSequenceRangeHandlingSingleSequence(t *testing.T) {
 		assert.Equal(c, int64(1), dbContext.DbStats.CacheStats.PendingSeqLen.Value())
 		assert.Equal(c, uint64(1), testChangeCache.nextSequence)
 		dbContext.UpdateCalculatedStats(ctx)
-		assert.Equal(c, int64(2), dbContext.DbStats.CacheStats.HighSeqCached.Value())
+		assert.Equal(c, int64(0), dbContext.DbStats.CacheStats.HighSeqCached.Value())
 	}, time.Second*10, time.Millisecond*100)
 
 	// process change that should overload pending and push sequence 1 to skipped

db/channel_cache.go

@@ -188,7 +188,11 @@ func (c *channelCacheImpl) AddPrincipal(change *LogEntry) {
 
 // Add unused Sequence notifies the cache of an unused sequence update. Updates the cache's high sequence
 func (c *channelCacheImpl) AddUnusedSequence(change *LogEntry) {
-	c.updateHighCacheSequence(change.Sequence)
+	if change.EndSequence > 0 {
+		c.updateHighCacheSequence(change.EndSequence)
+	} else {
+		c.updateHighCacheSequence(change.Sequence)
+	}
 }
 
 // Adds an entry to the appropriate channels' caches, returning the affected channels.  lateSequence