tsdb/chunkenc.Pool: Refactor Get and Put

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

tsdb/chunkenc/bstream.go

@@ -52,6 +52,12 @@ type bstream struct {
 	count  uint8  // How many right-most bits are available for writing in the current byte (the last byte of the stream).
 }
 
+// Reset resets b around stream.
+func (b *bstream) Reset(stream []byte) {
+	b.stream = stream
+	b.count = 0
+}
+
 func (b *bstream) bytes() []byte {
 	return b.stream
 }

tsdb/chunkenc/bstream_test.go

@@ -19,6 +19,19 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestBstream_Reset(t *testing.T) {
+	bs := bstream{
+		stream: []byte("test"),
+		count:  10,
+	}
+	bs.Reset([]byte("was reset"))
+
+	require.Equal(t, bstream{
+		stream: []byte("was reset"),
+		count:  0,
+	}, bs)
+}
+
 func TestBstreamReader(t *testing.T) {
 	// Write to the bit stream.
 	w := bstream{}

tsdb/chunkenc/chunk.go

@@ -87,6 +87,9 @@ type Chunk interface {
 	// There's no strong guarantee that no samples will be appended once
 	// Compact() is called. Implementing this function is optional.
 	Compact()
+
+	// Reset resets the chunk given stream.
+	Reset(stream []byte)
 }
 
 type Iterable interface {
@@ -303,64 +306,47 @@ func NewPool() Pool {
 }
 
 func (p *pool) Get(e Encoding, b []byte) (Chunk, error) {
+	var c Chunk
 	switch e {
 	case EncXOR:
-		c := p.xor.Get().(*XORChunk)
-		c.b.stream = b
-		c.b.count = 0
-		return c, nil
+		c = p.xor.Get().(*XORChunk)
 	case EncHistogram:
-		c := p.histogram.Get().(*HistogramChunk)
-		c.b.stream = b
-		c.b.count = 0
-		return c, nil
+		c = p.histogram.Get().(*HistogramChunk)
 	case EncFloatHistogram:
-		c := p.floatHistogram.Get().(*FloatHistogramChunk)
-		c.b.stream = b
-		c.b.count = 0
-		return c, nil
+		c = p.floatHistogram.Get().(*FloatHistogramChunk)
+	default:
+		return nil, fmt.Errorf("invalid chunk encoding %q", e)
 	}
-	return nil, fmt.Errorf("invalid chunk encoding %q", e)
+
+	c.Reset(b)
+	return c, nil
 }
 
 func (p *pool) Put(c Chunk) error {
+	var sp *sync.Pool
+	var ok bool
 	switch c.Encoding() {
 	case EncXOR:
-		xc, ok := c.(*XORChunk)
-		// This may happen often with wrapped chunks. Nothing we can really do about
-		// it but returning an error would cause a lot of allocations again. Thus,
-		// we just skip it.
-		if !ok {
-			return nil
-		}
-		xc.b.stream = nil
-		xc.b.count = 0
-		p.xor.Put(c)
+		_, ok = c.(*XORChunk)
+		sp = &p.xor
 	case EncHistogram:
-		sh, ok := c.(*HistogramChunk)
-		// This may happen often with wrapped chunks. Nothing we can really do about
-		// it but returning an error would cause a lot of allocations again. Thus,
-		// we just skip it.
-		if !ok {
-			return nil
-		}
-		sh.b.stream = nil
-		sh.b.count = 0
-		p.histogram.Put(c)
+		_, ok = c.(*HistogramChunk)
+		sp = &p.histogram
 	case EncFloatHistogram:
-		sh, ok := c.(*FloatHistogramChunk)
+		_, ok = c.(*FloatHistogramChunk)
+		sp = &p.floatHistogram
+	default:
+		return fmt.Errorf("invalid chunk encoding %q", c.Encoding())
+	}
+	if !ok {
 		// This may happen often with wrapped chunks. Nothing we can really do about
 		// it but returning an error would cause a lot of allocations again. Thus,
 		// we just skip it.
-		if !ok {
-			return nil
-		}
-		sh.b.stream = nil
-		sh.b.count = 0
-		p.floatHistogram.Put(c)
-	default:
-		return fmt.Errorf("invalid chunk encoding %q", c.Encoding())
+		return nil
 	}
+
+	c.Reset(nil)
+	sp.Put(c)
 	return nil
 }
 

tsdb/chunkenc/chunk_test.go

@@ -110,6 +110,96 @@ func testChunk(t *testing.T, c Chunk) {
 	require.Equal(t, ValNone, it3.Seek(exp[len(exp)-1].t+1))
 }
 
+func TestPool(t *testing.T) {
+	p := NewPool()
+	for _, tc := range []struct {
+		name     string
+		encoding Encoding
+		expErr   error
+	}{
+		{
+			name:     "xor",
+			encoding: EncXOR,
+		},
+		{
+			name:     "histogram",
+			encoding: EncHistogram,
+		},
+		{
+			name:     "float histogram",
+			encoding: EncFloatHistogram,
+		},
+		{
+			name:     "invalid encoding",
+			encoding: EncNone,
+			expErr:   fmt.Errorf(`invalid chunk encoding "none"`),
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			c, err := p.Get(tc.encoding, []byte("test"))
+			if tc.expErr != nil {
+				require.EqualError(t, err, tc.expErr.Error())
+				return
+			}
+
+			require.NoError(t, err)
+
+			var b *bstream
+			switch tc.encoding {
+			case EncHistogram:
+				b = &c.(*HistogramChunk).b
+			case EncFloatHistogram:
+				b = &c.(*FloatHistogramChunk).b
+			default:
+				b = &c.(*XORChunk).b
+			}
+
+			require.Equal(t, &bstream{
+				stream: []byte("test"),
+				count:  0,
+			}, b)
+
+			b.count = 1
+			require.NoError(t, p.Put(c))
+			require.Equal(t, &bstream{
+				stream: nil,
+				count:  0,
+			}, b)
+		})
+	}
+
+	t.Run("put bad chunk wrapper", func(t *testing.T) {
+		// When a wrapping chunk poses as an encoding it can't be converted to, Put should skip it.
+		c := fakeChunk{
+			encoding: EncXOR,
+			t:        t,
+		}
+		require.NoError(t, p.Put(c))
+	})
+	t.Run("put invalid encoding", func(t *testing.T) {
+		c := fakeChunk{
+			encoding: EncNone,
+			t:        t,
+		}
+		require.EqualError(t, p.Put(c), `invalid chunk encoding "none"`)
+	})
+}
+
+type fakeChunk struct {
+	Chunk
+
+	encoding Encoding
+	t        *testing.T
+}
+
+func (c fakeChunk) Encoding() Encoding {
+	return c.encoding
+}
+
+func (c fakeChunk) Reset([]byte) {
+	c.t.Fatal("Reset should not be called")
+}
+
 func benchmarkIterator(b *testing.B, newChunk func() Chunk) {
 	const samplesPerChunk = 250
 	var (

tsdb/chunkenc/float_histogram.go

@@ -44,6 +44,10 @@ func NewFloatHistogramChunk() *FloatHistogramChunk {
 	return &FloatHistogramChunk{b: bstream{stream: b, count: 0}}
 }
 
+func (c *FloatHistogramChunk) Reset(stream []byte) {
+	c.b.Reset(stream)
+}
+
 // xorValue holds all the necessary information to encode
 // and decode XOR encoded float64 values.
 type xorValue struct {

tsdb/chunkenc/histogram.go

@@ -45,6 +45,10 @@ func NewHistogramChunk() *HistogramChunk {
 	return &HistogramChunk{b: bstream{stream: b, count: 0}}
 }
 
+func (c *HistogramChunk) Reset(stream []byte) {
+	c.b.Reset(stream)
+}
+
 // Encoding returns the encoding type.
 func (c *HistogramChunk) Encoding() Encoding {
 	return EncHistogram

tsdb/chunkenc/xor.go

@@ -66,6 +66,10 @@ func NewXORChunk() *XORChunk {
 	return &XORChunk{b: bstream{stream: b, count: 0}}
 }
 
+func (c *XORChunk) Reset(stream []byte) {
+	c.b.Reset(stream)
+}
+
 // Encoding returns the encoding type.
 func (c *XORChunk) Encoding() Encoding {
 	return EncXOR
@@ -171,7 +175,6 @@ func (a *xorAppender) Append(t int64, v float64) {
 		}
 
 		a.writeVDelta(v)
-
 	default:
 		tDelta = uint64(t - a.t)
 		dod := int64(tDelta - a.tDelta)