mirror of https://github.com/prometheus/prometheus
511 lines
12 KiB
Go
511 lines
12 KiB
Go
// Copyright 2017 The Prometheus Authors
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
// The code in this file was largely written by Damian Gryski as part of
|
|
// https://github.com/dgryski/go-tsz and published under the license below.
|
|
// It was modified to accommodate reading from byte slices without modifying
|
|
// the underlying bytes, which would panic when reading from mmap'd
|
|
// read-only byte slices.
|
|
|
|
// Copyright (c) 2015,2016 Damian Gryski <damian@gryski.com>
|
|
// All rights reserved.
|
|
|
|
// Redistribution and use in source and binary forms, with or without
|
|
// modification, are permitted provided that the following conditions are met:
|
|
|
|
// * Redistributions of source code must retain the above copyright notice,
|
|
// this list of conditions and the following disclaimer.
|
|
//
|
|
// * Redistributions in binary form must reproduce the above copyright notice,
|
|
// this list of conditions and the following disclaimer in the documentation
|
|
// and/or other materials provided with the distribution.
|
|
//
|
|
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
|
|
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
|
|
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
|
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
|
|
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
|
|
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
|
|
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
|
|
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
|
|
package chunkenc
|
|
|
|
import (
|
|
"encoding/binary"
|
|
"math"
|
|
"math/bits"
|
|
|
|
"github.com/prometheus/prometheus/model/histogram"
|
|
)
|
|
|
|
const (
|
|
chunkCompactCapacityThreshold = 32
|
|
)
|
|
|
|
// XORChunk holds XOR encoded sample data.
|
|
type XORChunk struct {
|
|
b bstream
|
|
}
|
|
|
|
// NewXORChunk returns a new chunk with XOR encoding of the given size.
|
|
func NewXORChunk() *XORChunk {
|
|
b := make([]byte, 2, 128)
|
|
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
|
|
}
|
|
|
|
// Bytes returns the underlying byte slice of the chunk.
|
|
func (c *XORChunk) Bytes() []byte {
|
|
return c.b.bytes()
|
|
}
|
|
|
|
// NumSamples returns the number of samples in the chunk.
|
|
func (c *XORChunk) NumSamples() int {
|
|
return int(binary.BigEndian.Uint16(c.Bytes()))
|
|
}
|
|
|
|
// Compact implements the Chunk interface.
|
|
func (c *XORChunk) Compact() {
|
|
if l := len(c.b.stream); cap(c.b.stream) > l+chunkCompactCapacityThreshold {
|
|
buf := make([]byte, l)
|
|
copy(buf, c.b.stream)
|
|
c.b.stream = buf
|
|
}
|
|
}
|
|
|
|
// Appender implements the Chunk interface.
|
|
// It is not valid to call Appender() multiple times concurrently or to use multiple
|
|
// Appenders on the same chunk.
|
|
func (c *XORChunk) Appender() (Appender, error) {
|
|
it := c.iterator(nil)
|
|
|
|
// To get an appender we must know the state it would have if we had
|
|
// appended all existing data from scratch.
|
|
// We iterate through the end and populate via the iterator's state.
|
|
for it.Next() != ValNone {
|
|
}
|
|
if err := it.Err(); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
a := &xorAppender{
|
|
b: &c.b,
|
|
t: it.t,
|
|
v: it.val,
|
|
tDelta: it.tDelta,
|
|
leading: it.leading,
|
|
trailing: it.trailing,
|
|
}
|
|
if it.numTotal == 0 {
|
|
a.leading = 0xff
|
|
}
|
|
return a, nil
|
|
}
|
|
|
|
func (c *XORChunk) iterator(it Iterator) *xorIterator {
|
|
if xorIter, ok := it.(*xorIterator); ok {
|
|
xorIter.Reset(c.b.bytes())
|
|
return xorIter
|
|
}
|
|
return &xorIterator{
|
|
// The first 2 bytes contain chunk headers.
|
|
// We skip that for actual samples.
|
|
br: newBReader(c.b.bytes()[2:]),
|
|
numTotal: binary.BigEndian.Uint16(c.b.bytes()),
|
|
t: math.MinInt64,
|
|
}
|
|
}
|
|
|
|
// Iterator implements the Chunk interface.
|
|
// Iterator() must not be called concurrently with any modifications to the chunk,
|
|
// but after it returns you can use an Iterator concurrently with an Appender or
|
|
// other Iterators.
|
|
func (c *XORChunk) Iterator(it Iterator) Iterator {
|
|
return c.iterator(it)
|
|
}
|
|
|
|
type xorAppender struct {
|
|
b *bstream
|
|
|
|
t int64
|
|
v float64
|
|
tDelta uint64
|
|
|
|
leading uint8
|
|
trailing uint8
|
|
}
|
|
|
|
func (a *xorAppender) Append(t int64, v float64) {
|
|
var tDelta uint64
|
|
num := binary.BigEndian.Uint16(a.b.bytes())
|
|
switch num {
|
|
case 0:
|
|
buf := make([]byte, binary.MaxVarintLen64)
|
|
for _, b := range buf[:binary.PutVarint(buf, t)] {
|
|
a.b.writeByte(b)
|
|
}
|
|
a.b.writeBits(math.Float64bits(v), 64)
|
|
case 1:
|
|
tDelta = uint64(t - a.t)
|
|
|
|
buf := make([]byte, binary.MaxVarintLen64)
|
|
for _, b := range buf[:binary.PutUvarint(buf, tDelta)] {
|
|
a.b.writeByte(b)
|
|
}
|
|
|
|
a.writeVDelta(v)
|
|
default:
|
|
tDelta = uint64(t - a.t)
|
|
dod := int64(tDelta - a.tDelta)
|
|
|
|
// Gorilla has a max resolution of seconds, Prometheus milliseconds.
|
|
// Thus we use higher value range steps with larger bit size.
|
|
//
|
|
// TODO(beorn7): This seems to needlessly jump to large bit
|
|
// sizes even for very small deviations from zero. Timestamp
|
|
// compression can probably benefit from some smaller bit
|
|
// buckets. See also what was done for histogram encoding in
|
|
// varbit.go.
|
|
switch {
|
|
case dod == 0:
|
|
a.b.writeBit(zero)
|
|
case bitRange(dod, 14):
|
|
a.b.writeBits(0b10, 2)
|
|
a.b.writeBits(uint64(dod), 14)
|
|
case bitRange(dod, 17):
|
|
a.b.writeBits(0b110, 3)
|
|
a.b.writeBits(uint64(dod), 17)
|
|
case bitRange(dod, 20):
|
|
a.b.writeBits(0b1110, 4)
|
|
a.b.writeBits(uint64(dod), 20)
|
|
default:
|
|
a.b.writeBits(0b1111, 4)
|
|
a.b.writeBits(uint64(dod), 64)
|
|
}
|
|
|
|
a.writeVDelta(v)
|
|
}
|
|
|
|
a.t = t
|
|
a.v = v
|
|
binary.BigEndian.PutUint16(a.b.bytes(), num+1)
|
|
a.tDelta = tDelta
|
|
}
|
|
|
|
// bitRange returns whether the given integer can be represented by nbits.
|
|
// See docs/bstream.md.
|
|
func bitRange(x int64, nbits uint8) bool {
|
|
return -((1<<(nbits-1))-1) <= x && x <= 1<<(nbits-1)
|
|
}
|
|
|
|
func (a *xorAppender) writeVDelta(v float64) {
|
|
xorWrite(a.b, v, a.v, &a.leading, &a.trailing)
|
|
}
|
|
|
|
func (a *xorAppender) AppendHistogram(*HistogramAppender, int64, *histogram.Histogram, bool) (Chunk, bool, Appender, error) {
|
|
panic("appended a histogram sample to a float chunk")
|
|
}
|
|
|
|
func (a *xorAppender) AppendFloatHistogram(*FloatHistogramAppender, int64, *histogram.FloatHistogram, bool) (Chunk, bool, Appender, error) {
|
|
panic("appended a float histogram sample to a float chunk")
|
|
}
|
|
|
|
type xorIterator struct {
|
|
br bstreamReader
|
|
numTotal uint16
|
|
numRead uint16
|
|
|
|
t int64
|
|
val float64
|
|
|
|
leading uint8
|
|
trailing uint8
|
|
|
|
tDelta uint64
|
|
err error
|
|
}
|
|
|
|
func (it *xorIterator) Seek(t int64) ValueType {
|
|
if it.err != nil {
|
|
return ValNone
|
|
}
|
|
|
|
for t > it.t || it.numRead == 0 {
|
|
if it.Next() == ValNone {
|
|
return ValNone
|
|
}
|
|
}
|
|
return ValFloat
|
|
}
|
|
|
|
func (it *xorIterator) At() (int64, float64) {
|
|
return it.t, it.val
|
|
}
|
|
|
|
func (it *xorIterator) AtHistogram(*histogram.Histogram) (int64, *histogram.Histogram) {
|
|
panic("cannot call xorIterator.AtHistogram")
|
|
}
|
|
|
|
func (it *xorIterator) AtFloatHistogram(*histogram.FloatHistogram) (int64, *histogram.FloatHistogram) {
|
|
panic("cannot call xorIterator.AtFloatHistogram")
|
|
}
|
|
|
|
func (it *xorIterator) AtT() int64 {
|
|
return it.t
|
|
}
|
|
|
|
func (it *xorIterator) Err() error {
|
|
return it.err
|
|
}
|
|
|
|
func (it *xorIterator) Reset(b []byte) {
|
|
// The first 2 bytes contain chunk headers.
|
|
// We skip that for actual samples.
|
|
it.br = newBReader(b[2:])
|
|
it.numTotal = binary.BigEndian.Uint16(b)
|
|
|
|
it.numRead = 0
|
|
it.t = 0
|
|
it.val = 0
|
|
it.leading = 0
|
|
it.trailing = 0
|
|
it.tDelta = 0
|
|
it.err = nil
|
|
}
|
|
|
|
func (it *xorIterator) Next() ValueType {
|
|
if it.err != nil || it.numRead == it.numTotal {
|
|
return ValNone
|
|
}
|
|
|
|
if it.numRead == 0 {
|
|
t, err := binary.ReadVarint(&it.br)
|
|
if err != nil {
|
|
it.err = err
|
|
return ValNone
|
|
}
|
|
v, err := it.br.readBits(64)
|
|
if err != nil {
|
|
it.err = err
|
|
return ValNone
|
|
}
|
|
it.t = t
|
|
it.val = math.Float64frombits(v)
|
|
|
|
it.numRead++
|
|
return ValFloat
|
|
}
|
|
if it.numRead == 1 {
|
|
tDelta, err := binary.ReadUvarint(&it.br)
|
|
if err != nil {
|
|
it.err = err
|
|
return ValNone
|
|
}
|
|
it.tDelta = tDelta
|
|
it.t += int64(it.tDelta)
|
|
|
|
return it.readValue()
|
|
}
|
|
|
|
var d byte
|
|
// read delta-of-delta
|
|
for i := 0; i < 4; i++ {
|
|
d <<= 1
|
|
bit, err := it.br.readBitFast()
|
|
if err != nil {
|
|
bit, err = it.br.readBit()
|
|
}
|
|
if err != nil {
|
|
it.err = err
|
|
return ValNone
|
|
}
|
|
if bit == zero {
|
|
break
|
|
}
|
|
d |= 1
|
|
}
|
|
var sz uint8
|
|
var dod int64
|
|
switch d {
|
|
case 0b0:
|
|
// dod == 0
|
|
case 0b10:
|
|
sz = 14
|
|
case 0b110:
|
|
sz = 17
|
|
case 0b1110:
|
|
sz = 20
|
|
case 0b1111:
|
|
// Do not use fast because it's very unlikely it will succeed.
|
|
bits, err := it.br.readBits(64)
|
|
if err != nil {
|
|
it.err = err
|
|
return ValNone
|
|
}
|
|
|
|
dod = int64(bits)
|
|
}
|
|
|
|
if sz != 0 {
|
|
bits, err := it.br.readBitsFast(sz)
|
|
if err != nil {
|
|
bits, err = it.br.readBits(sz)
|
|
}
|
|
if err != nil {
|
|
it.err = err
|
|
return ValNone
|
|
}
|
|
|
|
// Account for negative numbers, which come back as high unsigned numbers.
|
|
// See docs/bstream.md.
|
|
if bits > (1 << (sz - 1)) {
|
|
bits -= 1 << sz
|
|
}
|
|
dod = int64(bits)
|
|
}
|
|
|
|
it.tDelta = uint64(int64(it.tDelta) + dod)
|
|
it.t += int64(it.tDelta)
|
|
|
|
return it.readValue()
|
|
}
|
|
|
|
func (it *xorIterator) readValue() ValueType {
|
|
err := xorRead(&it.br, &it.val, &it.leading, &it.trailing)
|
|
if err != nil {
|
|
it.err = err
|
|
return ValNone
|
|
}
|
|
it.numRead++
|
|
return ValFloat
|
|
}
|
|
|
|
func xorWrite(b *bstream, newValue, currentValue float64, leading, trailing *uint8) {
|
|
delta := math.Float64bits(newValue) ^ math.Float64bits(currentValue)
|
|
|
|
if delta == 0 {
|
|
b.writeBit(zero)
|
|
return
|
|
}
|
|
b.writeBit(one)
|
|
|
|
newLeading := uint8(bits.LeadingZeros64(delta))
|
|
newTrailing := uint8(bits.TrailingZeros64(delta))
|
|
|
|
// Clamp number of leading zeros to avoid overflow when encoding.
|
|
if newLeading >= 32 {
|
|
newLeading = 31
|
|
}
|
|
|
|
if *leading != 0xff && newLeading >= *leading && newTrailing >= *trailing {
|
|
// In this case, we stick with the current leading/trailing.
|
|
b.writeBit(zero)
|
|
b.writeBits(delta>>*trailing, 64-int(*leading)-int(*trailing))
|
|
return
|
|
}
|
|
|
|
// Update leading/trailing for the caller.
|
|
*leading, *trailing = newLeading, newTrailing
|
|
|
|
b.writeBit(one)
|
|
b.writeBits(uint64(newLeading), 5)
|
|
|
|
// Note that if newLeading == newTrailing == 0, then sigbits == 64. But
|
|
// that value doesn't actually fit into the 6 bits we have. Luckily, we
|
|
// never need to encode 0 significant bits, since that would put us in
|
|
// the other case (vdelta == 0). So instead we write out a 0 and adjust
|
|
// it back to 64 on unpacking.
|
|
sigbits := 64 - newLeading - newTrailing
|
|
b.writeBits(uint64(sigbits), 6)
|
|
b.writeBits(delta>>newTrailing, int(sigbits))
|
|
}
|
|
|
|
func xorRead(br *bstreamReader, value *float64, leading, trailing *uint8) error {
|
|
bit, err := br.readBitFast()
|
|
if err != nil {
|
|
bit, err = br.readBit()
|
|
}
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if bit == zero {
|
|
return nil
|
|
}
|
|
bit, err = br.readBitFast()
|
|
if err != nil {
|
|
bit, err = br.readBit()
|
|
}
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
var (
|
|
bits uint64
|
|
newLeading, newTrailing, mbits uint8
|
|
)
|
|
|
|
if bit == zero {
|
|
// Reuse leading/trailing zero bits.
|
|
newLeading, newTrailing = *leading, *trailing
|
|
mbits = 64 - newLeading - newTrailing
|
|
} else {
|
|
bits, err = br.readBitsFast(5)
|
|
if err != nil {
|
|
bits, err = br.readBits(5)
|
|
}
|
|
if err != nil {
|
|
return err
|
|
}
|
|
newLeading = uint8(bits)
|
|
|
|
bits, err = br.readBitsFast(6)
|
|
if err != nil {
|
|
bits, err = br.readBits(6)
|
|
}
|
|
if err != nil {
|
|
return err
|
|
}
|
|
mbits = uint8(bits)
|
|
// 0 significant bits here means we overflowed and we actually
|
|
// need 64; see comment in xrWrite.
|
|
if mbits == 0 {
|
|
mbits = 64
|
|
}
|
|
newTrailing = 64 - newLeading - mbits
|
|
// Update leading/trailing zero bits for the caller.
|
|
*leading, *trailing = newLeading, newTrailing
|
|
}
|
|
bits, err = br.readBitsFast(mbits)
|
|
if err != nil {
|
|
bits, err = br.readBits(mbits)
|
|
}
|
|
if err != nil {
|
|
return err
|
|
}
|
|
vbits := math.Float64bits(*value)
|
|
vbits ^= bits << newTrailing
|
|
*value = math.Float64frombits(vbits)
|
|
return nil
|
|
}
|