Fix Loki Chunks Dashboard (#1126)

This commit cleans up the Loki Chunks dashboard either by renaming incorrectly 
named series or adding needed metrics.

Added new metrics:

  - loki_ingester_memory_chunks
  - loki_ingester_memory_streams 
  - loki_ingester_chunk_utilization
  - loki_ingester_chunk_compression_ratio

The following metrics were already being published with a different name. 
Fixed in the dashboard:

  - cortex_chunk_store_index_entries_per_chunk
  - cortex_ingester_flush_queue_length
  - loki_ingester_chunk_entries

docs/operations/observability.md

@@ -24,22 +24,26 @@ The Loki Distributors expose the following metrics:
 
 The Loki Ingesters expose the following metrics:
 
-| Metric Name                               | Metric Type | Description                                                                                 |
-| ----------------------------------------- | ----------- | ------------------------------------------------------------------------------------------- |
-| `cortex_ingester_flush_queue_length`      | Gauge       | The total number of series pending in the flush queue.                                      |
-| `loki_ingester_chunk_age_seconds`         | Histogram   | Distribution of chunk ages when flushed.                                                    |
-| `loki_ingester_chunk_encode_time_seconds` | Histogram   | Distribution of chunk encode times.                                                         |
-| `loki_ingester_chunk_entries`             | Histogram   | Distribution of entires per-chunk when flushed.                                             |
-| `loki_ingester_chunk_size_bytes`          | Histogram   | Distribution of chunk sizes when flushed.                                                   |
-| `loki_ingester_chunk_stored_bytes_total`  | Counter     | Total bytes stored in chunks per tenant.                                                    |
-| `loki_ingester_chunks_created_total`      | Counter     | The total number of chunks created in the ingester.                                         |
-| `loki_ingester_chunks_flushed_total`      | Counter     | The total number of chunks flushed by the ingester.                                         |
-| `loki_ingester_chunks_stored_total`       | Counter     | Total stored chunks per tenant.                                                             |
-| `loki_ingester_received_chunks`           | Counter     | The total number of chunks sent by this ingester whilst joining during the handoff process. |
-| `loki_ingester_samples_per_chunk`         | Histogram   | The number of samples in a chunk.                                                           |
-| `loki_ingester_sent_chunks`               | Counter     | The total number of chunks sent by this ingester whilst leaving during the handoff process. |
-| `loki_ingester_streams_created_total`     | Counter     | The total number of streams created per tenant.                                             |
-| `loki_ingester_streams_removed_total`     | Counter     | The total number of streams removed per tenant.                                             |
+| Metric Name                                  | Metric Type | Description                                                                                 |
+| -------------------------------------------- | ----------- | ------------------------------------------------------------------------------------------- |
+| `cortex_ingester_flush_queue_length`         | Gauge       | The total number of series pending in the flush queue.                                      |
+| `cortex_chunk_store_index_entries_per_chunk` | Histogram   | Number of index entries written to storage per chunk.                                       |
+| `loki_ingester_memory_chunks`                | Gauge       | The total number of chunks in memory.                                                       |
+| `loki_ingester_memory_streams`               | Gauge       | The total number of streams in memory.                                                      |
+| `loki_ingester_chunk_age_seconds`            | Histogram   | Distribution of chunk ages when flushed.                                                    |
+| `loki_ingester_chunk_encode_time_seconds`    | Histogram   | Distribution of chunk encode times.                                                         |
+| `loki_ingester_chunk_entries`                | Histogram   | Distribution of lines per-chunk when flushed.                                               |
+| `loki_ingester_chunk_size_bytes`             | Histogram   | Distribution of chunk sizes when flushed.                                                   |
+| `loki_ingester_chunk_utilization`            | Histogram   | Distribution of chunk utilization (filled uncompressed bytes vs maximum uncompressed bytes) when flushed.                                             |
+| `loki_ingester_chunk_compression_ratio`      | Histogram   | Distribution of chunk compression ratio when flushed.                                       |
+| `loki_ingester_chunk_stored_bytes_total`     | Counter     | Total bytes stored in chunks per tenant.                                                    |
+| `loki_ingester_chunks_created_total`         | Counter     | The total number of chunks created in the ingester.                                         |
+| `loki_ingester_chunks_stored_total`          | Counter     | Total stored chunks per tenant.                                                             |
+| `loki_ingester_received_chunks`              | Counter     | The total number of chunks sent by this ingester whilst joining during the handoff process. |
+| `loki_ingester_samples_per_chunk`            | Histogram   | The number of samples in a chunk.                                                           |
+| `loki_ingester_sent_chunks`                  | Counter     | The total number of chunks sent by this ingester whilst leaving during the handoff process. |
+| `loki_ingester_streams_created_total`        | Counter     | The total number of streams created per tenant.                                             |
+| `loki_ingester_streams_removed_total`        | Counter     | The total number of streams removed per tenant.                                             |
 
 Promtail exposes these metrics:
 

pkg/chunkenc/dumb_chunk.go

@@ -50,6 +50,16 @@ func (c *dumbChunk) Size() int {
 	return len(c.entries)
 }
 
+// UncompressedSize implements Chunk.
+func (c *dumbChunk) UncompressedSize() int {
+	return c.Size()
+}
+
+// Utilization implements Chunk
+func (c *dumbChunk) Utilization() float64 {
+	return float64(len(c.entries)) / float64(tmpNumEntries)
+}
+
 // Returns an iterator that goes from _most_ recent to _least_ recent (ie,
 // backwards).
 func (c *dumbChunk) Iterator(from, through time.Time, direction logproto.Direction, _ logql.Filter) (iter.EntryIterator, error) {

pkg/chunkenc/facade.go

@@ -52,7 +52,23 @@ func (Facade) Encoding() encoding.Encoding {
 	return GzipLogChunk
 }
 
+// Utilization implements encoding.Chunk.
+func (f Facade) Utilization() float64 {
+	return f.c.Utilization()
+}
+
 // LokiChunk returns the chunkenc.Chunk.
 func (f Facade) LokiChunk() Chunk {
 	return f.c
 }
+
+// UncompressedSize is a helper function to hide the type assertion kludge when wanting the uncompressed size of the Cortex interface encoding.Chunk.
+func UncompressedSize(c encoding.Chunk) (int, bool) {
+	f, ok := c.(*Facade)
+
+	if !ok {
+		return 0, false
+	}
+
+	return f.c.UncompressedSize(), true
+}

pkg/chunkenc/gzip.go

@@ -61,7 +61,8 @@ type block struct {
 
 	mint, maxt int64
 
-	offset int // The offset of the block in the chunk.
+	offset           int // The offset of the block in the chunk.
+	uncompressedSize int // Total uncompressed size in bytes when the chunk is cut.
 }
 
 // This block holds the un-compressed entries. Once it has enough data, this is
@@ -313,6 +314,28 @@ func (c *MemChunk) SpaceFor(*logproto.Entry) bool {
 	return len(c.blocks) < blocksPerChunk
 }
 
+// UncompressedSize implements Chunk.
+func (c *MemChunk) UncompressedSize() int {
+	size := 0
+
+	if !c.head.isEmpty() {
+		size += c.head.size
+	}
+
+	for _, b := range c.blocks {
+		size += b.uncompressedSize
+	}
+
+	return size
+}
+
+// Utilization implements Chunk.  It is the bytes used as a percentage of the
+func (c *MemChunk) Utilization() float64 {
+	size := c.UncompressedSize()
+
+	return float64(size) / float64(blocksPerChunk*c.blockSize)
+}
+
 // Append implements Chunk.
 func (c *MemChunk) Append(entry *logproto.Entry) error {
 	entryTimestamp := entry.Timestamp.UnixNano()
@@ -352,10 +375,11 @@ func (c *MemChunk) cut() error {
 	}
 
 	c.blocks = append(c.blocks, block{
-		b:          b,
-		numEntries: len(c.head.entries),
-		mint:       c.head.mint,
-		maxt:       c.head.maxt,
+		b:                b,
+		numEntries:       len(c.head.entries),
+		mint:             c.head.mint,
+		maxt:             c.head.maxt,
+		uncompressedSize: c.head.size,
 	})
 
 	c.head.entries = c.head.entries[:0]

pkg/chunkenc/interface.go

@@ -50,6 +50,8 @@ type Chunk interface {
 	Iterator(from, through time.Time, direction logproto.Direction, filter logql.Filter) (iter.EntryIterator, error)
 	Size() int
 	Bytes() ([]byte, error)
+	Utilization() float64
+	UncompressedSize() int
 }
 
 // CompressionWriter is the writer that compresses the data passed to it.

pkg/ingester/flush.go

@@ -22,16 +22,30 @@ import (
 )
 
 var (
+	chunkUtilization = promauto.NewHistogram(prometheus.HistogramOpts{
+		Name:    "loki_ingester_chunk_utilization",
+		Help:    "Distribution of stored chunk utilization (when stored).",
+		Buckets: prometheus.LinearBuckets(0, 0.2, 6),
+	})
+	memoryChunks = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "loki_ingester_memory_chunks",
+		Help: "The total number of chunks in memory.",
+	})
 	chunkEntries = promauto.NewHistogram(prometheus.HistogramOpts{
 		Name:    "loki_ingester_chunk_entries",
-		Help:    "Distribution of stored chunk entries (when stored).",
+		Help:    "Distribution of stored lines per chunk (when stored).",
 		Buckets: prometheus.ExponentialBuckets(200, 2, 9), // biggest bucket is 200*2^(9-1) = 51200
 	})
 	chunkSize = promauto.NewHistogram(prometheus.HistogramOpts{
 		Name:    "loki_ingester_chunk_size_bytes",
 		Help:    "Distribution of stored chunk sizes (when stored).",
 		Buckets: prometheus.ExponentialBuckets(10000, 2, 7), // biggest bucket is 10000*2^(7-1) = 640000 (~640KB)
 	})
+	chunkCompressionRatio = promauto.NewHistogram(prometheus.HistogramOpts{
+		Name:    "loki_ingester_chunk_compression_ratio",
+		Help:    "Compression ratio of chunks (when stored).",
+		Buckets: prometheus.LinearBuckets(1, 1.5, 6),
+	})
 	chunksPerTenant = promauto.NewCounterVec(prometheus.CounterOpts{
 		Name: "loki_ingester_chunks_stored_total",
 		Help: "Total stored chunks per tenant.",
@@ -234,6 +248,7 @@ func (i *Ingester) shouldFlushChunk(chunk *chunkDesc) bool {
 func (i *Ingester) removeFlushedChunks(instance *instance, stream *stream) {
 	now := time.Now()
 
+	prevNumChunks := len(stream.chunks)
 	for len(stream.chunks) > 0 {
 		if stream.chunks[0].flushed.IsZero() || now.Sub(stream.chunks[0].flushed) < i.cfg.RetainPeriod {
 			break
@@ -242,11 +257,13 @@ func (i *Ingester) removeFlushedChunks(instance *instance, stream *stream) {
 		stream.chunks[0].chunk = nil // erase reference so the chunk can be garbage-collected
 		stream.chunks = stream.chunks[1:]
 	}
+	memoryChunks.Sub(float64(prevNumChunks - len(stream.chunks)))
 
 	if len(stream.chunks) == 0 {
 		delete(instance.streams, stream.fp)
 		instance.index.Delete(client.FromLabelAdaptersToLabels(stream.labels), stream.fp)
 		instance.streamsRemovedTotal.Inc()
+		memoryStreams.Dec()
 	}
 }
 
@@ -292,9 +309,17 @@ func (i *Ingester) flushChunks(ctx context.Context, fp model.Fingerprint, labelP
 			continue
 		}
 
+		compressedSize := float64(len(byt))
+		uncompressedSize, ok := chunkenc.UncompressedSize(wc.Data)
+
+		if ok {
+			chunkCompressionRatio.Observe(float64(uncompressedSize) / compressedSize)
+		}
+
+		chunkUtilization.Observe(wc.Data.Utilization())
 		chunkEntries.Observe(float64(numEntries))
-		chunkSize.Observe(float64(len(byt)))
-		sizePerTenant.Add(float64(len(byt)))
+		chunkSize.Observe(compressedSize)
+		sizePerTenant.Add(compressedSize)
 		countPerTenant.Inc()
 		firstTime, _ := cs[i].chunk.Bounds()
 		chunkAge.Observe(time.Since(firstTime).Seconds())

pkg/ingester/instance.go

@@ -32,6 +32,10 @@ var (
 )
 
 var (
+	memoryStreams = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "loki_ingester_memory_streams",
+		Help: "The total number of streams in memory.",
+	})
 	streamsCreatedTotal = promauto.NewCounterVec(prometheus.CounterOpts{
 		Namespace: "loki",
 		Name:      "ingester_streams_created_total",
@@ -89,10 +93,16 @@ func (i *instance) consumeChunk(ctx context.Context, labels []client.LabelAdapte
 		i.index.Add(labels, fp)
 		i.streams[fp] = stream
 		i.streamsCreatedTotal.Inc()
+		memoryStreams.Inc()
 		i.addTailersToNewStream(stream)
 	}
 
-	return stream.consumeChunk(ctx, chunk)
+	err := stream.consumeChunk(ctx, chunk)
+	if err == nil {
+		memoryChunks.Inc()
+	}
+
+	return err
 }
 
 func (i *instance) Push(ctx context.Context, req *logproto.PushRequest) error {
@@ -113,10 +123,13 @@ func (i *instance) Push(ctx context.Context, req *logproto.PushRequest) error {
 			continue
 		}
 
+		prevNumChunks := len(stream.chunks)
 		if err := stream.Push(ctx, s.Entries); err != nil {
 			appendErr = err
 			continue
 		}
+
+		memoryChunks.Add(float64(len(stream.chunks) - prevNumChunks))
 	}
 
 	return appendErr
@@ -136,6 +149,7 @@ func (i *instance) getOrCreateStream(labels []client.LabelAdapter) (*stream, err
 	stream = newStream(fp, labels, i.blockSize)
 	i.index.Add(labels, fp)
 	i.streams[fp] = stream
+	memoryStreams.Inc()
 	i.streamsCreatedTotal.Inc()
 	i.addTailersToNewStream(stream)
 

pkg/ingester/stream.go

@@ -25,11 +25,6 @@ var (
 		Name:      "ingester_chunks_created_total",
 		Help:      "The total number of chunks created in the ingester.",
 	})
-	chunksFlushedTotal = prometheus.NewCounter(prometheus.CounterOpts{
-		Namespace: "loki",
-		Name:      "ingester_chunks_flushed_total",
-		Help:      "The total number of chunks flushed by the ingester.",
-	})
 	samplesPerChunk = prometheus.NewHistogram(prometheus.HistogramOpts{
 		Namespace: "loki",
 		Subsystem: "ingester",
@@ -42,7 +37,6 @@ var (
 
 func init() {
 	prometheus.MustRegister(chunksCreatedTotal)
-	prometheus.MustRegister(chunksFlushedTotal)
 	prometheus.MustRegister(samplesPerChunk)
 }
 

production/loki-mixin/dashboards.libsonnet

@@ -92,7 +92,7 @@ local utils = import "mixin-utils/utils.libsonnet";
         )
         .addPanel(
           g.panel('Chunks per series') +
-          g.queryPanel('sum(loki_ingester_memory_chunks{cluster="$cluster", job="$namespace/ingester"}) / sum(loki_ingester_memory_series{job="$namespace/ingester"})', 'chunks'),
+          g.queryPanel('sum(loki_ingester_memory_chunks{cluster="$cluster", job="$namespace/ingester"}) / sum(loki_ingester_memory_streams{job="$namespace/ingester"})', 'chunks'),
         )
       )
       .addRow(
@@ -111,19 +111,19 @@ local utils = import "mixin-utils/utils.libsonnet";
         g.row('Flush Stats')
         .addPanel(
           g.panel('Size') +
-          g.latencyPanel('loki_ingester_chunk_length', '{cluster="$cluster", job="$namespace/ingester"}', multiplier='1') +
+          g.latencyPanel('loki_ingester_chunk_entries', '{cluster="$cluster", job="$namespace/ingester"}', multiplier='1') +
           { yaxes: g.yaxes('short') },
         )
         .addPanel(
           g.panel('Entries') +
-          g.queryPanel('sum(rate(loki_chunk_store_index_entries_per_chunk_sum{cluster="$cluster", job="$namespace/ingester"}[5m])) / sum(rate(loki_chunk_store_index_entries_per_chunk_count{cluster="$cluster", job="$namespace/ingester"}[5m]))', 'entries'),
+          g.queryPanel('sum(rate(cortex_chunk_store_index_entries_per_chunk_sum{cluster="$cluster", job="$namespace/ingester"}[5m])) / sum(rate(cortex_chunk_store_index_entries_per_chunk_count{cluster="$cluster", job="$namespace/ingester"}[5m]))', 'entries'),
         ),
       )
       .addRow(
         g.row('Flush Stats')
         .addPanel(
           g.panel('Queue Length') +
-          g.queryPanel('loki_ingester_flush_queue_length{cluster="$cluster", job="$namespace/ingester"}', '{{instance}}'),
+          g.queryPanel('cortex_ingester_flush_queue_length{cluster="$cluster", job="$namespace/ingester"}', '{{instance}}'),
         )
         .addPanel(
           g.panel('Flush Rate') +