prometheus/storage/local/delta.go

400 lines
10 KiB
Go

package storage_ng
import (
"encoding/binary"
"fmt"
"io"
"math"
"sort"
clientmodel "github.com/prometheus/client_golang/model"
"github.com/prometheus/prometheus/storage/metric"
)
type deltaBytes int
const (
d0 deltaBytes = 0
d1 = 1
d2 = 2
d4 = 4
d8 = 8
)
// The 21-byte header of a delta-encoded chunk looks like:
//
// - time delta bytes: 1 bytes
// - value delta bytes: 1 bytes
// - is integer: 1 byte
// - base time: 8 bytes
// - base value: 8 bytes
// - used buf bytes: 2 bytes
const (
deltaHeaderBytes = 21
deltaHeaderTimeBytesOffset = 0
deltaHeaderValueBytesOffset = 1
deltaHeaderIsIntOffset = 2
deltaHeaderBaseTimeOffset = 3
deltaHeaderBaseValueOffset = 11
deltaHeaderBufLenOffset = 19
)
type deltaEncodedChunk struct {
buf []byte
}
func newDeltaEncodedChunk(tb, vb deltaBytes, isInt bool) *deltaEncodedChunk {
buf := chunkBufs.Get()
buf = buf[:deltaHeaderIsIntOffset+1]
buf[deltaHeaderTimeBytesOffset] = byte(tb)
buf[deltaHeaderValueBytesOffset] = byte(vb)
if isInt {
buf[deltaHeaderIsIntOffset] = 1
} else {
buf[deltaHeaderIsIntOffset] = 0
}
return &deltaEncodedChunk{
buf: buf,
}
}
func (c *deltaEncodedChunk) newFollowupChunk() chunk {
return newDeltaEncodedChunk(d1, d1, true)
//return newDeltaEncodedChunk(c.timeBytes(), c.valueBytes(), c.isInt())
}
func (c *deltaEncodedChunk) clone() chunk {
buf := chunkBufs.Get()
buf = buf[:len(c.buf)]
copy(buf, c.buf)
return &deltaEncodedChunk{
buf: buf,
}
}
func neededDeltaBytes(deltaT clientmodel.Timestamp, deltaV clientmodel.SampleValue, isInt bool) (dtb, dvb deltaBytes) {
dtb = 1
if deltaT >= 256 {
dtb = 2
}
if deltaT >= 256*256 {
dtb = 4
}
if deltaT >= 256*256*256*256 {
dtb = 8
}
if isInt {
dvb = 0
if deltaV != 0 {
dvb = 1
}
if deltaV < -(256/2) || deltaV > (256/2)-1 {
dvb = 2
}
if deltaV < -(256*256/2) || deltaV > (256*256/2)-1 {
dvb = 4
}
if deltaV < -(256*256*256*256/2) || deltaV > (256*256*256*256/2)-1 {
dvb = 8
}
} else {
dvb = 4
if clientmodel.SampleValue(float32(deltaV)) != deltaV {
dvb = 8
}
}
return dtb, dvb
}
func max(a, b deltaBytes) deltaBytes {
if a > b {
return a
}
return b
}
func (c *deltaEncodedChunk) timeBytes() deltaBytes {
return deltaBytes(c.buf[deltaHeaderTimeBytesOffset])
}
func (c *deltaEncodedChunk) valueBytes() deltaBytes {
return deltaBytes(c.buf[deltaHeaderValueBytesOffset])
}
func (c *deltaEncodedChunk) isInt() bool {
return c.buf[deltaHeaderIsIntOffset] == 1
}
func (c *deltaEncodedChunk) baseTime() clientmodel.Timestamp {
return clientmodel.Timestamp(binary.LittleEndian.Uint64(c.buf[deltaHeaderBaseTimeOffset:]))
}
func (c *deltaEncodedChunk) baseValue() clientmodel.SampleValue {
return clientmodel.SampleValue(math.Float64frombits(binary.LittleEndian.Uint64(c.buf[deltaHeaderBaseValueOffset:])))
}
func (c *deltaEncodedChunk) add(s *metric.SamplePair) chunks {
if len(c.buf) < deltaHeaderBytes {
c.buf = c.buf[:deltaHeaderBytes]
binary.LittleEndian.PutUint64(c.buf[deltaHeaderBaseTimeOffset:], uint64(s.Timestamp))
binary.LittleEndian.PutUint64(c.buf[deltaHeaderBaseValueOffset:], math.Float64bits(float64(s.Value)))
}
remainingBytes := cap(c.buf) - len(c.buf)
sampleSize := c.sampleSize()
// Do we generally have space for another sample in this chunk? If not,
// overflow into a new one. We assume that if we have seen floating point
// values once, the series will most likely contain floats in the future.
if remainingBytes < sampleSize {
//fmt.Println("overflow")
overflowChunks := c.newFollowupChunk().add(s)
return chunks{c, overflowChunks[0]}
}
dt := s.Timestamp - c.baseTime()
dv := s.Value - c.baseValue()
// If the new sample is incompatible with the current encoding, reencode the
// existing chunk data into new chunk(s).
//
// int->float.
// TODO: compare speed with Math.Modf.
if c.isInt() && clientmodel.SampleValue(int64(dv)) != dv {
//fmt.Println("int->float", len(c.buf), cap(c.buf))
return transcodeAndAdd(newDeltaEncodedChunk(c.timeBytes(), d4, false), c, s)
}
// float32->float64.
if !c.isInt() && c.valueBytes() == d4 && clientmodel.SampleValue(float32(dv)) != dv {
//fmt.Println("float32->float64", float32(dv), dv, len(c.buf), cap(c.buf))
return transcodeAndAdd(newDeltaEncodedChunk(c.timeBytes(), d8, false), c, s)
}
// More bytes per sample.
if dtb, dvb := neededDeltaBytes(dt, dv, c.isInt()); dtb > c.timeBytes() || dvb > c.valueBytes() {
//fmt.Printf("transcoding T: %v->%v, V: %v->%v, I: %v; len %v, cap %v\n", c.timeBytes(), dtb, c.valueBytes(), dvb, c.isInt(), len(c.buf), cap(c.buf))
dtb = max(dtb, c.timeBytes())
dvb = max(dvb, c.valueBytes())
return transcodeAndAdd(newDeltaEncodedChunk(dtb, dvb, c.isInt()), c, s)
}
offset := len(c.buf)
c.buf = c.buf[:offset+sampleSize]
switch c.timeBytes() {
case 1:
c.buf[offset] = byte(dt)
case 2:
binary.LittleEndian.PutUint16(c.buf[offset:], uint16(dt))
case 4:
binary.LittleEndian.PutUint32(c.buf[offset:], uint32(dt))
case 8:
binary.LittleEndian.PutUint64(c.buf[offset:], uint64(dt))
}
offset += int(c.timeBytes())
if c.isInt() {
switch c.valueBytes() {
case 0:
// No-op. Constant value is stored as base value.
case 1:
c.buf[offset] = byte(dv)
case 2:
binary.LittleEndian.PutUint16(c.buf[offset:], uint16(dv))
case 4:
binary.LittleEndian.PutUint32(c.buf[offset:], uint32(dv))
case 8:
binary.LittleEndian.PutUint64(c.buf[offset:], uint64(dv))
default:
panic("Invalid number of bytes for integer delta")
}
} else {
switch c.valueBytes() {
case 4:
binary.LittleEndian.PutUint32(c.buf[offset:], math.Float32bits(float32(dv)))
case 8:
binary.LittleEndian.PutUint64(c.buf[offset:], math.Float64bits(float64(dv)))
default:
panic("Invalid number of bytes for floating point delta")
}
}
return chunks{c}
}
func (c *deltaEncodedChunk) close() {
//fmt.Println("returning chunk")
chunkBufs.Give(c.buf)
}
func (c *deltaEncodedChunk) sampleSize() int {
return int(c.timeBytes() + c.valueBytes())
}
func (c *deltaEncodedChunk) len() int {
if len(c.buf) < deltaHeaderBytes {
return 0
}
return (len(c.buf) - deltaHeaderBytes) / c.sampleSize()
}
// TODO: remove?
func (c *deltaEncodedChunk) values() <-chan *metric.SamplePair {
n := c.len()
valuesChan := make(chan *metric.SamplePair)
go func() {
for i := 0; i < n; i++ {
valuesChan <- c.valueAtIndex(i)
}
close(valuesChan)
}()
return valuesChan
}
func (c *deltaEncodedChunk) valueAtIndex(idx int) *metric.SamplePair {
offset := deltaHeaderBytes + idx*c.sampleSize()
var dt uint64
switch c.timeBytes() {
case 1:
dt = uint64(uint8(c.buf[offset]))
case 2:
dt = uint64(binary.LittleEndian.Uint16(c.buf[offset:]))
case 4:
dt = uint64(binary.LittleEndian.Uint32(c.buf[offset:]))
case 8:
dt = uint64(binary.LittleEndian.Uint64(c.buf[offset:]))
}
offset += int(c.timeBytes())
var dv clientmodel.SampleValue
if c.isInt() {
switch c.valueBytes() {
case 0:
dv = clientmodel.SampleValue(0)
case 1:
dv = clientmodel.SampleValue(int8(c.buf[offset]))
case 2:
dv = clientmodel.SampleValue(int16(binary.LittleEndian.Uint16(c.buf[offset:])))
case 4:
dv = clientmodel.SampleValue(int32(binary.LittleEndian.Uint32(c.buf[offset:])))
case 8:
dv = clientmodel.SampleValue(int64(binary.LittleEndian.Uint64(c.buf[offset:])))
default:
panic("Invalid number of bytes for integer delta")
}
} else {
switch c.valueBytes() {
case 4:
dv = clientmodel.SampleValue(math.Float32frombits(binary.LittleEndian.Uint32(c.buf[offset:])))
case 8:
dv = clientmodel.SampleValue(math.Float64frombits(binary.LittleEndian.Uint64(c.buf[offset:])))
default:
panic("Invalid number of bytes for floating point delta")
}
}
return &metric.SamplePair{
Timestamp: c.baseTime() + clientmodel.Timestamp(dt),
Value: c.baseValue() + dv,
}
}
func (c *deltaEncodedChunk) firstTime() clientmodel.Timestamp {
return c.valueAtIndex(0).Timestamp
}
func (c *deltaEncodedChunk) lastTime() clientmodel.Timestamp {
return c.valueAtIndex(c.len() - 1).Timestamp
}
func (c *deltaEncodedChunk) marshal(w io.Writer) error {
// TODO: check somewhere that configured buf len cannot overflow 16 bit.
binary.LittleEndian.PutUint16(c.buf[deltaHeaderBufLenOffset:], uint16(len(c.buf)))
n, err := w.Write(c.buf[:cap(c.buf)])
if err != nil {
return err
}
if n != cap(c.buf) {
return fmt.Errorf("wanted to write %d bytes, wrote %d", len(c.buf), n)
}
return nil
}
func (c *deltaEncodedChunk) unmarshal(r io.Reader) error {
c.buf = c.buf[:cap(c.buf)]
readBytes := 0
for readBytes < len(c.buf) {
n, err := r.Read(c.buf[readBytes:])
if err != nil {
return err
}
readBytes += n
}
c.buf = c.buf[:binary.LittleEndian.Uint16(c.buf[deltaHeaderBufLenOffset:])]
return nil
}
type deltaEncodedChunkIterator struct {
chunk *deltaEncodedChunk
// TODO: add more fields here to keep track of last position.
}
func (c *deltaEncodedChunk) newIterator() chunkIterator {
return &deltaEncodedChunkIterator{
chunk: c,
}
}
func (it *deltaEncodedChunkIterator) getValueAtTime(t clientmodel.Timestamp) metric.Values {
i := sort.Search(it.chunk.len(), func(i int) bool {
return !it.chunk.valueAtIndex(i).Timestamp.Before(t)
})
switch i {
case 0:
return metric.Values{*it.chunk.valueAtIndex(0)}
case it.chunk.len():
return metric.Values{*it.chunk.valueAtIndex(it.chunk.len() - 1)}
default:
v := it.chunk.valueAtIndex(i)
if v.Timestamp.Equal(t) {
return metric.Values{*v}
}
return metric.Values{*it.chunk.valueAtIndex(i - 1), *v}
}
}
func (it *deltaEncodedChunkIterator) getBoundaryValues(in metric.Interval) metric.Values {
return nil
}
func (it *deltaEncodedChunkIterator) getRangeValues(in metric.Interval) metric.Values {
oldest := sort.Search(it.chunk.len(), func(i int) bool {
return !it.chunk.valueAtIndex(i).Timestamp.Before(in.OldestInclusive)
})
newest := sort.Search(it.chunk.len(), func(i int) bool {
return it.chunk.valueAtIndex(i).Timestamp.After(in.NewestInclusive)
})
if oldest == it.chunk.len() {
return nil
}
result := make(metric.Values, 0, newest-oldest)
for i := oldest; i < newest; i++ {
result = append(result, *it.chunk.valueAtIndex(i))
}
return result
}
func (it *deltaEncodedChunkIterator) contains(t clientmodel.Timestamp) bool {
return !t.Before(it.chunk.firstTime()) && !t.After(it.chunk.lastTime())
}