mirror of https://github.com/prometheus/prometheus
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
390 lines
9.2 KiB
390 lines
9.2 KiB
// 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 accomodate reading from byte slices without modifying
|
|
// the underlying bytes, which would panic when reading from mmaped
|
|
// 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 chunks
|
|
|
|
import (
|
|
"encoding/binary"
|
|
"math"
|
|
|
|
bits "github.com/dgryski/go-bits"
|
|
)
|
|
|
|
// 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}}
|
|
}
|
|
|
|
// 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()))
|
|
}
|
|
|
|
// Appender implements the Chunk interface.
|
|
func (c *XORChunk) Appender() (Appender, error) {
|
|
it := c.iterator()
|
|
|
|
// 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() {
|
|
}
|
|
if err := it.Err(); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
a := &xorAppender{
|
|
c: c,
|
|
b: c.b,
|
|
t: it.t,
|
|
v: it.val,
|
|
tDelta: it.tDelta,
|
|
leading: it.leading,
|
|
trailing: it.trailing,
|
|
}
|
|
if binary.BigEndian.Uint16(a.b.bytes()) == 0 {
|
|
a.leading = 0xff
|
|
}
|
|
return a, nil
|
|
}
|
|
|
|
func (c *XORChunk) iterator() *xorIterator {
|
|
// Should iterators guarantee to act on a copy of the data so it doesn't lock append?
|
|
// When using striped locks to guard access to chunks, probably yes.
|
|
// Could only copy data if the chunk is not completed yet.
|
|
return &xorIterator{
|
|
br: newBReader(c.b.bytes()[2:]),
|
|
numTotal: binary.BigEndian.Uint16(c.b.bytes()),
|
|
}
|
|
}
|
|
|
|
// Iterator implements the Chunk interface.
|
|
func (c *XORChunk) Iterator() Iterator {
|
|
return c.iterator()
|
|
}
|
|
|
|
type xorAppender struct {
|
|
c *XORChunk
|
|
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())
|
|
|
|
if num == 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)
|
|
|
|
} else if num == 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)
|
|
|
|
} else {
|
|
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.
|
|
switch {
|
|
case dod == 0:
|
|
a.b.writeBit(zero)
|
|
case bitRange(dod, 14):
|
|
a.b.writeBits(0x02, 2) // '10'
|
|
a.b.writeBits(uint64(dod), 14)
|
|
case bitRange(dod, 17):
|
|
a.b.writeBits(0x06, 3) // '110'
|
|
a.b.writeBits(uint64(dod), 17)
|
|
case bitRange(dod, 20):
|
|
a.b.writeBits(0x0e, 4) // '1110'
|
|
a.b.writeBits(uint64(dod), 20)
|
|
default:
|
|
a.b.writeBits(0x0f, 4) // '1111'
|
|
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
|
|
}
|
|
|
|
func bitRange(x int64, nbits uint8) bool {
|
|
return -((1<<(nbits-1))-1) <= x && x <= 1<<(nbits-1)
|
|
}
|
|
|
|
func (a *xorAppender) writeVDelta(v float64) {
|
|
vDelta := math.Float64bits(v) ^ math.Float64bits(a.v)
|
|
|
|
if vDelta == 0 {
|
|
a.b.writeBit(zero)
|
|
return
|
|
}
|
|
a.b.writeBit(one)
|
|
|
|
leading := uint8(bits.Clz(vDelta))
|
|
trailing := uint8(bits.Ctz(vDelta))
|
|
|
|
// Clamp number of leading zeros to avoid overflow when encoding.
|
|
if leading >= 32 {
|
|
leading = 31
|
|
}
|
|
|
|
if a.leading != 0xff && leading >= a.leading && trailing >= a.trailing {
|
|
a.b.writeBit(zero)
|
|
a.b.writeBits(vDelta>>a.trailing, 64-int(a.leading)-int(a.trailing))
|
|
} else {
|
|
a.leading, a.trailing = leading, trailing
|
|
|
|
a.b.writeBit(one)
|
|
a.b.writeBits(uint64(leading), 5)
|
|
|
|
// Note that if leading == trailing == 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 - leading - trailing
|
|
a.b.writeBits(uint64(sigbits), 6)
|
|
a.b.writeBits(vDelta>>trailing, int(sigbits))
|
|
}
|
|
}
|
|
|
|
type xorIterator struct {
|
|
br *bstream
|
|
numTotal uint16
|
|
numRead uint16
|
|
|
|
t int64
|
|
val float64
|
|
|
|
leading uint8
|
|
trailing uint8
|
|
|
|
tDelta uint64
|
|
err error
|
|
}
|
|
|
|
func (it *xorIterator) At() (int64, float64) {
|
|
return it.t, it.val
|
|
}
|
|
|
|
func (it *xorIterator) Err() error {
|
|
return it.err
|
|
}
|
|
|
|
func (it *xorIterator) Next() bool {
|
|
if it.err != nil || it.numRead == it.numTotal {
|
|
return false
|
|
}
|
|
|
|
if it.numRead == 0 {
|
|
t, err := binary.ReadVarint(it.br)
|
|
if err != nil {
|
|
it.err = err
|
|
return false
|
|
}
|
|
v, err := it.br.readBits(64)
|
|
if err != nil {
|
|
it.err = err
|
|
return false
|
|
}
|
|
it.t = int64(t)
|
|
it.val = math.Float64frombits(v)
|
|
|
|
it.numRead++
|
|
return true
|
|
}
|
|
if it.numRead == 1 {
|
|
tDelta, err := binary.ReadUvarint(it.br)
|
|
if err != nil {
|
|
it.err = err
|
|
return false
|
|
}
|
|
it.tDelta = tDelta
|
|
it.t = 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.readBit()
|
|
if err != nil {
|
|
it.err = err
|
|
return false
|
|
}
|
|
if bit == zero {
|
|
break
|
|
}
|
|
d |= 1
|
|
}
|
|
var sz uint8
|
|
var dod int64
|
|
switch d {
|
|
case 0x00:
|
|
// dod == 0
|
|
case 0x02:
|
|
sz = 14
|
|
case 0x06:
|
|
sz = 17
|
|
case 0x0e:
|
|
sz = 20
|
|
case 0x0f:
|
|
bits, err := it.br.readBits(64)
|
|
if err != nil {
|
|
it.err = err
|
|
return false
|
|
}
|
|
|
|
dod = int64(bits)
|
|
}
|
|
|
|
if sz != 0 {
|
|
bits, err := it.br.readBits(int(sz))
|
|
if err != nil {
|
|
it.err = err
|
|
return false
|
|
}
|
|
if bits > (1 << (sz - 1)) {
|
|
// or something
|
|
bits = bits - (1 << sz)
|
|
}
|
|
dod = int64(bits)
|
|
}
|
|
|
|
it.tDelta = uint64(int64(it.tDelta) + dod)
|
|
it.t = it.t + int64(it.tDelta)
|
|
|
|
return it.readValue()
|
|
}
|
|
|
|
func (it *xorIterator) readValue() bool {
|
|
bit, err := it.br.readBit()
|
|
if err != nil {
|
|
it.err = err
|
|
return false
|
|
}
|
|
|
|
if bit == zero {
|
|
// it.val = it.val
|
|
} else {
|
|
bit, err := it.br.readBit()
|
|
if err != nil {
|
|
it.err = err
|
|
return false
|
|
}
|
|
if bit == zero {
|
|
// reuse leading/trailing zero bits
|
|
// it.leading, it.trailing = it.leading, it.trailing
|
|
} else {
|
|
bits, err := it.br.readBits(5)
|
|
if err != nil {
|
|
it.err = err
|
|
return false
|
|
}
|
|
it.leading = uint8(bits)
|
|
|
|
bits, err = it.br.readBits(6)
|
|
if err != nil {
|
|
it.err = err
|
|
return false
|
|
}
|
|
mbits := uint8(bits)
|
|
// 0 significant bits here means we overflowed and we actually need 64; see comment in encoder
|
|
if mbits == 0 {
|
|
mbits = 64
|
|
}
|
|
it.trailing = 64 - it.leading - mbits
|
|
}
|
|
|
|
mbits := int(64 - it.leading - it.trailing)
|
|
bits, err := it.br.readBits(mbits)
|
|
if err != nil {
|
|
it.err = err
|
|
return false
|
|
}
|
|
vbits := math.Float64bits(it.val)
|
|
vbits ^= (bits << it.trailing)
|
|
it.val = math.Float64frombits(vbits)
|
|
}
|
|
|
|
it.numRead++
|
|
return true
|
|
}
|