Adds a counter for total flushed chunks per reason. (#1819)

Signed-off-by: Cyril Tovena <cyril.tovena@gmail.com>

pkg/ingester/flush.go

@@ -76,6 +76,11 @@ var (
 		// 10ms to 10s.
 		Buckets: prometheus.ExponentialBuckets(0.01, 4, 6),
 	})
+	chunksFlushedPerReason = promauto.NewCounterVec(prometheus.CounterOpts{
+		Namespace: "loki",
+		Name:      "ingester_chunks_flushed_total",
+		Help:      "Total flushed chunks per reason.",
+	}, []string{"reason"})
 )
 
 const (
@@ -85,6 +90,12 @@ const (
 
 	nameLabel = "__name__"
 	logsValue = "logs"
+
+	flushReasonIdle   = "idle"
+	flushReasonMaxAge = "max_age"
+	flushReasonForced = "forced"
+	flushReasonFull   = "full"
+	flushReasonSynced = "synced"
 )
 
 // Flush triggers a flush of all the chunks and closes the flush queues.
@@ -147,7 +158,8 @@ func (i *Ingester) sweepStream(instance *instance, stream *stream, immediate boo
 	}
 
 	lastChunk := stream.chunks[len(stream.chunks)-1]
-	if len(stream.chunks) == 1 && !immediate && !i.shouldFlushChunk(&lastChunk) {
+	shouldFlush, _ := i.shouldFlushChunk(&lastChunk)
+	if len(stream.chunks) == 1 && !immediate && !shouldFlush {
 		return
 	}
 
@@ -226,35 +238,43 @@ func (i *Ingester) collectChunksToFlush(instance *instance, fp model.Fingerprint
 
 	var result []*chunkDesc
 	for j := range stream.chunks {
-		if immediate || i.shouldFlushChunk(&stream.chunks[j]) {
+		shouldFlush, reason := i.shouldFlushChunk(&stream.chunks[j])
+		if immediate || shouldFlush {
 			// Ensure no more writes happen to this chunk.
 			if !stream.chunks[j].closed {
 				stream.chunks[j].closed = true
 			}
 			// Flush this chunk if it hasn't already been successfully flushed.
 			if stream.chunks[j].flushed.IsZero() {
 				result = append(result, &stream.chunks[j])
+				if immediate {
+					reason = flushReasonForced
+				}
+				chunksFlushedPerReason.WithLabelValues(reason).Add(1)
 			}
 		}
 	}
 	return result, stream.labels
 }
 
-func (i *Ingester) shouldFlushChunk(chunk *chunkDesc) bool {
+func (i *Ingester) shouldFlushChunk(chunk *chunkDesc) (bool, string) {
 	// Append should close the chunk when the a new one is added.
 	if chunk.closed {
-		return true
+		if chunk.synced {
+			return true, flushReasonSynced
+		}
+		return true, flushReasonFull
 	}
 
 	if time.Since(chunk.lastUpdated) > i.cfg.MaxChunkIdle {
-		return true
+		return true, flushReasonIdle
 	}
 
 	if from, to := chunk.chunk.Bounds(); to.Sub(from) > i.cfg.MaxChunkAge {
-		return true
+		return true, flushReasonMaxAge
 	}
 
-	return false
+	return false, ""
 }
 
 func (i *Ingester) removeFlushedChunks(instance *instance, stream *stream) {

pkg/ingester/stream.go

@@ -73,6 +73,7 @@ type stream struct {
 type chunkDesc struct {
 	chunk   chunkenc.Chunk
 	closed  bool
+	synced  bool
 	flushed time.Time
 
 	lastUpdated time.Time
@@ -138,7 +139,7 @@ func (s *stream) Push(_ context.Context, entries []logproto.Entry, synchronizePe
 		}
 
 		chunk := &s.chunks[len(s.chunks)-1]
-		if chunk.closed || !chunk.chunk.SpaceFor(&entries[i]) || s.cutChunkForSynchronization(entries[i].Timestamp, lastChunkTimestamp, chunk.chunk, synchronizePeriod, minUtilization) {
+		if chunk.closed || !chunk.chunk.SpaceFor(&entries[i]) || s.cutChunkForSynchronization(entries[i].Timestamp, lastChunkTimestamp, chunk, synchronizePeriod, minUtilization) {
 			// If the chunk has no more space call Close to make sure anything in the head block is cut and compressed
 			err := chunk.chunk.Close()
 			if err != nil {
@@ -226,7 +227,7 @@ func (s *stream) Push(_ context.Context, entries []logproto.Entry, synchronizePe
 
 // Returns true, if chunk should be cut before adding new entry. This is done to make ingesters
 // cut the chunk for this stream at the same moment, so that new chunk will contain exactly the same entries.
-func (s *stream) cutChunkForSynchronization(entryTimestamp, prevEntryTimestamp time.Time, chunk chunkenc.Chunk, synchronizePeriod time.Duration, minUtilization float64) bool {
+func (s *stream) cutChunkForSynchronization(entryTimestamp, prevEntryTimestamp time.Time, c *chunkDesc, synchronizePeriod time.Duration, minUtilization float64) bool {
 	if synchronizePeriod <= 0 || prevEntryTimestamp.IsZero() {
 		return false
 	}
@@ -239,10 +240,12 @@ func (s *stream) cutChunkForSynchronization(entryTimestamp, prevEntryTimestamp t
 	// if current entry timestamp has rolled over synchronization period
 	if cts < pts {
 		if minUtilization <= 0 {
+			c.synced = true
 			return true
 		}
 
-		if chunk.Utilization() > minUtilization {
+		if c.chunk.Utilization() > minUtilization {
+			c.synced = true
 			return true
 		}
 	}