Adds WAL support (experimental)

.gitignore

@@ -5,6 +5,7 @@
 *.output
 *.tgz
 *.exe
+__debug_bin
 requirements.lock
 mixin/vendor/
 cmd/loki/loki

cmd/loki/loki-local-config.yaml

@@ -4,6 +4,10 @@ server:
   http_listen_port: 3100
 
 ingester:
+  wal:
+    enabled: true
+    dir: /tmp/wal
+    recover: true
   lifecycler:
     address: 127.0.0.1
     ring:

docs/sources/api/_index.md

@@ -37,6 +37,7 @@ The HTTP API includes the following endpoints:
     - [Examples](#examples-8)
   - [`GET /ready`](#get-ready)
   - [`POST /flush`](#post-flush)
+  - [`POST /ingester/shutdown`](#post-shutdown)
   - [`GET /metrics`](#get-metrics)
   - [Series](#series)
     - [Examples](#examples-9)
@@ -107,6 +108,7 @@ While these endpoints are exposed by just the distributor:
 And these endpoints are exposed by just the ingester:
 
 - [`POST /flush`](#post-flush)
+- [`POST /ingester/shutdown`](#post-shutdown)
 
 The API endpoints starting with `/loki/` are [Prometheus API-compatible](https://prometheus.io/docs/prometheus/latest/querying/api/) and the result formats can be used interchangeably.
 
@@ -844,6 +846,14 @@ backing store. Mainly used for local testing.
 
 In microservices mode, the `/flush` endpoint is exposed by the ingester.
 
+## `POST /ingester/shutdown`
+
+`/ingester/shutdown` triggers a shutdown of the ingester and notably will _always_ flush any in memory chunks it holds.
+This is helpful for scaling down WAL-enabled ingesters where we want to ensure old WAL directories are not orphaned,
+but instead flushed to our chunk backend.
+
+In microservices mode, the `/ingester/shutdown` endpoint is exposed by the ingester.
+
 ## `GET /metrics`
 
 `/metrics` exposes Prometheus metrics. See

pkg/chunkenc/encoding_helpers.go

@@ -119,4 +119,17 @@ func (d *decbuf) byte() byte {
 	return x
 }
 
+func (d *decbuf) bytes(n int) []byte {
+	if d.e != nil {
+		return nil
+	}
+	if len(d.b) < n {
+		d.e = ErrInvalidSize
+		return nil
+	}
+	x := d.b[:n]
+	d.b = d.b[n:]
+	return x
+}
+
 func (d *decbuf) err() error { return d.e }

pkg/chunkenc/memchunk.go

@@ -152,6 +152,94 @@ func (hb *headBlock) serialise(pool WriterPool) ([]byte, error) {
 	return outBuf.Bytes(), nil
 }
 
+// CheckpointBytes serializes a headblock to []byte. This is used by the WAL checkpointing,
+// which does not want to mutate a chunk by cutting it (otherwise risking content address changes), but
+// needs to serialize/deserialize the data to disk to ensure data durability.
+func (hb *headBlock) CheckpointBytes(version byte) ([]byte, error) {
+	encB := BytesBufferPool.Get(1 << 10).([]byte)
+
+	defer func() {
+		BytesBufferPool.Put(encB[:0])
+	}()
+
+	buf := bytes.NewBuffer(make([]byte, 0, 1<<10))
+	eb := encbuf{b: encB}
+
+	eb.putByte(version)
+	_, err := buf.Write(eb.get())
+	if err != nil {
+		return nil, errors.Wrap(err, "write headBlock version")
+	}
+	eb.reset()
+
+	eb.putUvarint(len(hb.entries))
+	eb.putUvarint(hb.size)
+	eb.putVarint64(hb.mint)
+	eb.putVarint64(hb.maxt)
+
+	_, err = buf.Write(eb.get())
+	if err != nil {
+		return nil, errors.Wrap(err, "write headBlock metas")
+	}
+	eb.reset()
+
+	for _, entry := range hb.entries {
+		eb.putVarint64(entry.t)
+		eb.putUvarint(len(entry.s))
+		_, err = buf.Write(eb.get())
+		if err != nil {
+			return nil, errors.Wrap(err, "write headBlock entry ts")
+		}
+		eb.reset()
+
+		_, err := buf.WriteString(entry.s)
+		if err != nil {
+			return nil, errors.Wrap(err, "write headblock entry line")
+		}
+	}
+	return buf.Bytes(), nil
+}
+
+func (hb *headBlock) FromCheckpoint(b []byte) error {
+	if len(b) < 1 {
+		return nil
+	}
+
+	db := decbuf{b: b}
+
+	version := db.byte()
+	if db.err() != nil {
+		return errors.Wrap(db.err(), "verifying headblock header")
+	}
+	if version != chunkFormatV3 {
+		return errors.New("incompatible headBlock version, only V3 is currently supported")
+	}
+
+	ln := db.uvarint()
+	hb.size = db.uvarint()
+	hb.mint = db.varint64()
+	hb.maxt = db.varint64()
+
+	if err := db.err(); err != nil {
+		return errors.Wrap(err, "verifying headblock metadata")
+	}
+
+	hb.entries = make([]entry, ln)
+	for i := 0; i < ln && db.err() == nil; i++ {
+		var entry entry
+		entry.t = db.varint64()
+		lineLn := db.uvarint()
+		entry.s = string(db.bytes(lineLn))
+		hb.entries[i] = entry
+	}
+
+	if err := db.err(); err != nil {
+		return errors.Wrap(err, "decoding entries")
+	}
+
+	return nil
+}
+
 type entry struct {
 	t int64
 	s string
@@ -256,6 +344,7 @@ func NewByteChunk(b []byte, blockSize, targetSize int) (*MemChunk, error) {
 }
 
 // BytesWith uses a provided []byte for buffer instantiation
+// NOTE: This does not cut the head block nor include any head block data.
 func (c *MemChunk) BytesWith(b []byte) ([]byte, error) {
 	buf := bytes.NewBuffer(b[:0])
 	if _, err := c.WriteTo(buf); err != nil {
@@ -265,18 +354,18 @@ func (c *MemChunk) BytesWith(b []byte) ([]byte, error) {
 }
 
 // Bytes implements Chunk.
+// NOTE: Does not cut head block or include any head block data.
 func (c *MemChunk) Bytes() ([]byte, error) {
 	return c.BytesWith(nil)
 }
 
 // WriteTo Implements io.WriterTo
+// NOTE: Does not cut head block or include any head block data.
+// For this to be the case you must call Close() first.
+// This decision notably enables WAL checkpointing, which would otherwise
+// result in different content addressable chunks in storage based on the timing of when
+// they were checkpointed (which would cause new blocks to be cut early).
 func (c *MemChunk) WriteTo(w io.Writer) (int64, error) {
-	if c.head != nil {
-		// When generating the bytes, we need to flush the data held in-buffer.
-		if err := c.cut(); err != nil {
-			return 0, err
-		}
-	}
 	crc32Hash := newCRC32()
 
 	offset := int64(0)
@@ -348,6 +437,35 @@ func (c *MemChunk) WriteTo(w io.Writer) (int64, error) {
 	return offset, nil
 }
 
+// SerializeForCheckpoint returns []bytes representing the chunk & head. This is to ensure eventually
+// flushed chunks don't have different substructures depending on when they were checkpointed.
+// In turn this allows us to maintain a more effective dedupe ratio in storage.
+func (c *MemChunk) SerializeForCheckpoint(b []byte) (chk, head []byte, err error) {
+	chk, err = c.BytesWith(b)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if c.head.isEmpty() {
+		return chk, nil, nil
+	}
+
+	head, err = c.head.CheckpointBytes(c.format)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return chk, head, nil
+}
+
+func MemchunkFromCheckpoint(chk, head []byte, blockSize int, targetSize int) (*MemChunk, error) {
+	mc, err := NewByteChunk(chk, blockSize, targetSize)
+	if err != nil {
+		return nil, err
+	}
+	return mc, mc.head.FromCheckpoint(head)
+}
+
 // Encoding implements Chunk.
 func (c *MemChunk) Encoding() Encoding {
 	return c.encoding

pkg/chunkenc/memchunk_test.go

@@ -294,6 +294,7 @@ func TestSerialization(t *testing.T) {
 			for i := 0; i < numSamples; i++ {
 				require.NoError(t, chk.Append(logprotoEntry(int64(i), strconv.Itoa(i))))
 			}
+			require.NoError(t, chk.Close())
 
 			byt, err := chk.Bytes()
 			require.NoError(t, err)
@@ -840,6 +841,68 @@ func TestBytesWith(t *testing.T) {
 	require.Equal(t, exp, out)
 }
 
+func TestHeadBlockCheckpointing(t *testing.T) {
+	c := NewMemChunk(EncSnappy, 256*1024, 1500*1024)
+
+	// add a few entries
+	for i := 0; i < 5; i++ {
+		entry := &logproto.Entry{
+			Timestamp: time.Unix(int64(i), 0),
+			Line:      fmt.Sprintf("hi there - %d", i),
+		}
+		require.Equal(t, true, c.SpaceFor(entry))
+		require.Nil(t, c.Append(entry))
+	}
+
+	// ensure blocks are not cut
+	require.Equal(t, 0, len(c.blocks))
+
+	b, err := c.head.CheckpointBytes(c.format)
+	require.Nil(t, err)
+
+	hb := &headBlock{}
+	require.Nil(t, hb.FromCheckpoint(b))
+	require.Equal(t, c.head, hb)
+}
+
+func TestCheckpointEncoding(t *testing.T) {
+	blockSize, targetSize := 256*1024, 1500*1024
+	c := NewMemChunk(EncSnappy, blockSize, targetSize)
+
+	// add a few entries
+	for i := 0; i < 5; i++ {
+		entry := &logproto.Entry{
+			Timestamp: time.Unix(int64(i), 0),
+			Line:      fmt.Sprintf("hi there - %d", i),
+		}
+		require.Equal(t, true, c.SpaceFor(entry))
+		require.Nil(t, c.Append(entry))
+	}
+
+	// cut it
+	require.Nil(t, c.cut())
+
+	// add a few more to head
+	for i := 5; i < 10; i++ {
+		entry := &logproto.Entry{
+			Timestamp: time.Unix(int64(i), 0),
+			Line:      fmt.Sprintf("hi there - %d", i),
+		}
+		require.Equal(t, true, c.SpaceFor(entry))
+		require.Nil(t, c.Append(entry))
+	}
+
+	// ensure new blocks are not cut
+	require.Equal(t, 1, len(c.blocks))
+
+	chk, head, err := c.SerializeForCheckpoint(nil)
+	require.Nil(t, err)
+
+	cpy, err := MemchunkFromCheckpoint(chk, head, blockSize, targetSize)
+	require.Nil(t, err)
+	require.Equal(t, c, cpy)
+}
+
 var streams = []logproto.Stream{}
 var series = []logproto.Series{}
 

pkg/chunkenc/util_test.go

@@ -52,5 +52,6 @@ func fillChunk(c Chunk) int64 {
 		entry.Line = testdata.LogString(i)
 
 	}
+	_ = c.Close()
 	return inserted
 }