mirror of
https://github.com/prometheus/prometheus.git
synced 2024-11-10 15:44:05 -08:00
576 lines
16 KiB
Go
576 lines
16 KiB
Go
// Copyright 2014 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package local
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import (
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"encoding/binary"
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"fmt"
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"io"
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"math"
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"sort"
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"github.com/prometheus/common/model"
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"github.com/prometheus/prometheus/storage/metric"
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)
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// The 37-byte header of a delta-encoded chunk looks like:
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//
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// - used buf bytes: 2 bytes
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// - time double-delta bytes: 1 bytes
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// - value double-delta bytes: 1 bytes
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// - is integer: 1 byte
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// - base time: 8 bytes
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// - base value: 8 bytes
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// - base time delta: 8 bytes
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// - base value delta: 8 bytes
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const (
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doubleDeltaHeaderBytes = 37
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doubleDeltaHeaderBufLenOffset = 0
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doubleDeltaHeaderTimeBytesOffset = 2
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doubleDeltaHeaderValueBytesOffset = 3
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doubleDeltaHeaderIsIntOffset = 4
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doubleDeltaHeaderBaseTimeOffset = 5
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doubleDeltaHeaderBaseValueOffset = 13
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doubleDeltaHeaderBaseTimeDeltaOffset = 21
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doubleDeltaHeaderBaseValueDeltaOffset = 29
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)
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// A doubleDeltaEncodedChunk adaptively stores sample timestamps and values with
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// a double-delta encoding of various types (int, float) and bit widths. A base
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// value and timestamp and a base delta for each is saved in the header. The
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// payload consists of double-deltas, i.e. deviations from the values and
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// timestamps calculated by applying the base value and time and the base deltas.
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// However, once 8 bytes would be needed to encode a double-delta value, a
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// fall-back to the absolute numbers happens (so that timestamps are saved
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// directly as int64 and values as float64).
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// doubleDeltaEncodedChunk implements the chunk interface.
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type doubleDeltaEncodedChunk []byte
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// newDoubleDeltaEncodedChunk returns a newly allocated doubleDeltaEncodedChunk.
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func newDoubleDeltaEncodedChunk(tb, vb deltaBytes, isInt bool, length int) *doubleDeltaEncodedChunk {
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if tb < 1 {
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panic("need at least 1 time delta byte")
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}
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if length < doubleDeltaHeaderBytes+16 {
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panic(fmt.Errorf(
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"chunk length %d bytes is insufficient, need at least %d",
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length, doubleDeltaHeaderBytes+16,
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))
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}
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c := make(doubleDeltaEncodedChunk, doubleDeltaHeaderIsIntOffset+1, length)
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c[doubleDeltaHeaderTimeBytesOffset] = byte(tb)
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c[doubleDeltaHeaderValueBytesOffset] = byte(vb)
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if vb < d8 && isInt { // Only use int for fewer than 8 value double-delta bytes.
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c[doubleDeltaHeaderIsIntOffset] = 1
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} else {
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c[doubleDeltaHeaderIsIntOffset] = 0
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}
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return &c
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}
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// add implements chunk.
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func (c doubleDeltaEncodedChunk) add(s *model.SamplePair) []chunk {
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if c.len() == 0 {
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return c.addFirstSample(s)
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}
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tb := c.timeBytes()
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vb := c.valueBytes()
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if c.len() == 1 {
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return c.addSecondSample(s, tb, vb)
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}
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remainingBytes := cap(c) - len(c)
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sampleSize := c.sampleSize()
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// Do we generally have space for another sample in this chunk? If not,
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// overflow into a new one.
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if remainingBytes < sampleSize {
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overflowChunks := newChunk().add(s)
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return []chunk{&c, overflowChunks[0]}
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}
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projectedTime := c.baseTime() + model.Time(c.len())*c.baseTimeDelta()
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ddt := s.Timestamp - projectedTime
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projectedValue := c.baseValue() + model.SampleValue(c.len())*c.baseValueDelta()
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ddv := s.Value - projectedValue
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ntb, nvb, nInt := tb, vb, c.isInt()
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// If the new sample is incompatible with the current encoding, reencode the
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// existing chunk data into new chunk(s).
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if c.isInt() && !isInt64(ddv) {
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// int->float.
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nvb = d4
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nInt = false
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} else if !c.isInt() && vb == d4 && projectedValue+model.SampleValue(float32(ddv)) != s.Value {
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// float32->float64.
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nvb = d8
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} else {
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if tb < d8 {
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// Maybe more bytes for timestamp.
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ntb = max(tb, bytesNeededForSignedTimestampDelta(ddt))
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}
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if c.isInt() && vb < d8 {
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// Maybe more bytes for sample value.
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nvb = max(vb, bytesNeededForIntegerSampleValueDelta(ddv))
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}
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}
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if tb != ntb || vb != nvb || c.isInt() != nInt {
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if len(c)*2 < cap(c) {
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return transcodeAndAdd(newDoubleDeltaEncodedChunk(ntb, nvb, nInt, cap(c)), &c, s)
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}
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// Chunk is already half full. Better create a new one and save the transcoding efforts.
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overflowChunks := newChunk().add(s)
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return []chunk{&c, overflowChunks[0]}
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}
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offset := len(c)
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c = c[:offset+sampleSize]
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switch tb {
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case d1:
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c[offset] = byte(ddt)
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case d2:
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binary.LittleEndian.PutUint16(c[offset:], uint16(ddt))
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case d4:
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binary.LittleEndian.PutUint32(c[offset:], uint32(ddt))
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case d8:
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// Store the absolute value (no delta) in case of d8.
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binary.LittleEndian.PutUint64(c[offset:], uint64(s.Timestamp))
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default:
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panic("invalid number of bytes for time delta")
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}
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offset += int(tb)
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if c.isInt() {
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switch vb {
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case d0:
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// No-op. Constant delta is stored as base value.
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case d1:
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c[offset] = byte(int8(ddv))
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case d2:
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binary.LittleEndian.PutUint16(c[offset:], uint16(int16(ddv)))
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case d4:
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binary.LittleEndian.PutUint32(c[offset:], uint32(int32(ddv)))
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// d8 must not happen. Those samples are encoded as float64.
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default:
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panic("invalid number of bytes for integer delta")
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}
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} else {
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switch vb {
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case d4:
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binary.LittleEndian.PutUint32(c[offset:], math.Float32bits(float32(ddv)))
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case d8:
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// Store the absolute value (no delta) in case of d8.
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binary.LittleEndian.PutUint64(c[offset:], math.Float64bits(float64(s.Value)))
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default:
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panic("invalid number of bytes for floating point delta")
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}
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}
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return []chunk{&c}
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}
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// clone implements chunk.
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func (c doubleDeltaEncodedChunk) clone() chunk {
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clone := make(doubleDeltaEncodedChunk, len(c), cap(c))
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copy(clone, c)
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return &clone
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}
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// firstTime implements chunk.
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func (c doubleDeltaEncodedChunk) firstTime() model.Time {
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return c.baseTime()
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}
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// newIterator implements chunk.
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func (c *doubleDeltaEncodedChunk) newIterator() chunkIterator {
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return &doubleDeltaEncodedChunkIterator{
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c: *c,
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len: c.len(),
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baseT: c.baseTime(),
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baseΔT: c.baseTimeDelta(),
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baseV: c.baseValue(),
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baseΔV: c.baseValueDelta(),
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tBytes: c.timeBytes(),
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vBytes: c.valueBytes(),
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isInt: c.isInt(),
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}
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}
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// marshal implements chunk.
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func (c doubleDeltaEncodedChunk) marshal(w io.Writer) error {
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if len(c) > math.MaxUint16 {
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panic("chunk buffer length would overflow a 16 bit uint.")
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}
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binary.LittleEndian.PutUint16(c[doubleDeltaHeaderBufLenOffset:], uint16(len(c)))
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n, err := w.Write(c[:cap(c)])
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if err != nil {
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return err
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}
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if n != cap(c) {
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return fmt.Errorf("wanted to write %d bytes, wrote %d", len(c), n)
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}
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return nil
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}
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// unmarshal implements chunk.
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func (c *doubleDeltaEncodedChunk) unmarshal(r io.Reader) error {
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*c = (*c)[:cap(*c)]
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if _, err := io.ReadFull(r, *c); err != nil {
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return err
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}
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*c = (*c)[:binary.LittleEndian.Uint16((*c)[doubleDeltaHeaderBufLenOffset:])]
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return nil
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}
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// unmarshalFromBuf implements chunk.
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func (c *doubleDeltaEncodedChunk) unmarshalFromBuf(buf []byte) {
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*c = (*c)[:cap(*c)]
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copy(*c, buf)
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*c = (*c)[:binary.LittleEndian.Uint16((*c)[doubleDeltaHeaderBufLenOffset:])]
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}
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// encoding implements chunk.
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func (c doubleDeltaEncodedChunk) encoding() chunkEncoding { return doubleDelta }
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func (c doubleDeltaEncodedChunk) baseTime() model.Time {
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return model.Time(
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binary.LittleEndian.Uint64(
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c[doubleDeltaHeaderBaseTimeOffset:],
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),
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)
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}
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func (c doubleDeltaEncodedChunk) baseValue() model.SampleValue {
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return model.SampleValue(
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math.Float64frombits(
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binary.LittleEndian.Uint64(
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c[doubleDeltaHeaderBaseValueOffset:],
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),
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),
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)
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}
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func (c doubleDeltaEncodedChunk) baseTimeDelta() model.Time {
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if len(c) < doubleDeltaHeaderBaseTimeDeltaOffset+8 {
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return 0
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}
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return model.Time(
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binary.LittleEndian.Uint64(
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c[doubleDeltaHeaderBaseTimeDeltaOffset:],
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),
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)
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}
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func (c doubleDeltaEncodedChunk) baseValueDelta() model.SampleValue {
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if len(c) < doubleDeltaHeaderBaseValueDeltaOffset+8 {
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return 0
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}
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return model.SampleValue(
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math.Float64frombits(
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binary.LittleEndian.Uint64(
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c[doubleDeltaHeaderBaseValueDeltaOffset:],
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),
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),
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)
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}
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func (c doubleDeltaEncodedChunk) timeBytes() deltaBytes {
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return deltaBytes(c[doubleDeltaHeaderTimeBytesOffset])
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}
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func (c doubleDeltaEncodedChunk) valueBytes() deltaBytes {
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return deltaBytes(c[doubleDeltaHeaderValueBytesOffset])
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}
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func (c doubleDeltaEncodedChunk) sampleSize() int {
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return int(c.timeBytes() + c.valueBytes())
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}
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func (c doubleDeltaEncodedChunk) len() int {
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if len(c) <= doubleDeltaHeaderIsIntOffset+1 {
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return 0
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}
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if len(c) <= doubleDeltaHeaderBaseValueOffset+8 {
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return 1
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}
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return (len(c)-doubleDeltaHeaderBytes)/c.sampleSize() + 2
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}
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func (c doubleDeltaEncodedChunk) isInt() bool {
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return c[doubleDeltaHeaderIsIntOffset] == 1
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}
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// addFirstSample is a helper method only used by c.add(). It adds timestamp and
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// value as base time and value.
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func (c doubleDeltaEncodedChunk) addFirstSample(s *model.SamplePair) []chunk {
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c = c[:doubleDeltaHeaderBaseValueOffset+8]
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binary.LittleEndian.PutUint64(
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c[doubleDeltaHeaderBaseTimeOffset:],
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uint64(s.Timestamp),
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)
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binary.LittleEndian.PutUint64(
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c[doubleDeltaHeaderBaseValueOffset:],
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math.Float64bits(float64(s.Value)),
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)
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return []chunk{&c}
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}
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// addSecondSample is a helper method only used by c.add(). It calculates the
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// base delta from the provided sample and adds it to the chunk.
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func (c doubleDeltaEncodedChunk) addSecondSample(s *model.SamplePair, tb, vb deltaBytes) []chunk {
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baseTimeDelta := s.Timestamp - c.baseTime()
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if baseTimeDelta < 0 {
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panic("base time delta is less than zero")
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}
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c = c[:doubleDeltaHeaderBytes]
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if tb >= d8 || bytesNeededForUnsignedTimestampDelta(baseTimeDelta) >= d8 {
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// If already the base delta needs d8 (or we are at d8
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// already, anyway), we better encode this timestamp
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// directly rather than as a delta and switch everything
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// to d8.
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c[doubleDeltaHeaderTimeBytesOffset] = byte(d8)
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binary.LittleEndian.PutUint64(
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c[doubleDeltaHeaderBaseTimeDeltaOffset:],
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uint64(s.Timestamp),
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)
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} else {
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binary.LittleEndian.PutUint64(
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c[doubleDeltaHeaderBaseTimeDeltaOffset:],
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uint64(baseTimeDelta),
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)
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}
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baseValue := c.baseValue()
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baseValueDelta := s.Value - baseValue
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if vb >= d8 || baseValue+baseValueDelta != s.Value {
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// If we can't reproduce the original sample value (or
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// if we are at d8 already, anyway), we better encode
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// this value directly rather than as a delta and switch
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// everything to d8.
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c[doubleDeltaHeaderValueBytesOffset] = byte(d8)
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c[doubleDeltaHeaderIsIntOffset] = 0
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binary.LittleEndian.PutUint64(
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c[doubleDeltaHeaderBaseValueDeltaOffset:],
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math.Float64bits(float64(s.Value)),
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)
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} else {
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binary.LittleEndian.PutUint64(
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c[doubleDeltaHeaderBaseValueDeltaOffset:],
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math.Float64bits(float64(baseValueDelta)),
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)
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}
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return []chunk{&c}
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}
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// doubleDeltaEncodedChunkIterator implements chunkIterator.
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type doubleDeltaEncodedChunkIterator struct {
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c doubleDeltaEncodedChunk
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len int
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baseT, baseΔT model.Time
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baseV, baseΔV model.SampleValue
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tBytes, vBytes deltaBytes
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isInt bool
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}
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// length implements chunkIterator.
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func (it *doubleDeltaEncodedChunkIterator) length() int { return it.len }
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// valueAtTime implements chunkIterator.
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func (it *doubleDeltaEncodedChunkIterator) valueAtTime(t model.Time) []model.SamplePair {
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i := sort.Search(it.len, func(i int) bool {
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return !it.timestampAtIndex(i).Before(t)
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})
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switch i {
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case 0:
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return []model.SamplePair{{
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Timestamp: it.timestampAtIndex(0),
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Value: it.sampleValueAtIndex(0),
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}}
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case it.len:
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return []model.SamplePair{{
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Timestamp: it.timestampAtIndex(it.len - 1),
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Value: it.sampleValueAtIndex(it.len - 1),
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}}
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default:
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ts := it.timestampAtIndex(i)
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if ts.Equal(t) {
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return []model.SamplePair{{
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Timestamp: ts,
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Value: it.sampleValueAtIndex(i),
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}}
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}
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return []model.SamplePair{
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{
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Timestamp: it.timestampAtIndex(i - 1),
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Value: it.sampleValueAtIndex(i - 1),
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},
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{
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Timestamp: ts,
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Value: it.sampleValueAtIndex(i),
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},
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}
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}
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}
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// rangeValues implements chunkIterator.
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func (it *doubleDeltaEncodedChunkIterator) rangeValues(in metric.Interval) []model.SamplePair {
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oldest := sort.Search(it.len, func(i int) bool {
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return !it.timestampAtIndex(i).Before(in.OldestInclusive)
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})
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newest := sort.Search(it.len, func(i int) bool {
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return it.timestampAtIndex(i).After(in.NewestInclusive)
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})
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if oldest == it.len {
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return nil
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}
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result := make([]model.SamplePair, 0, newest-oldest)
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for i := oldest; i < newest; i++ {
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result = append(result, model.SamplePair{
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Timestamp: it.timestampAtIndex(i),
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Value: it.sampleValueAtIndex(i),
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})
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}
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return result
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}
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// contains implements chunkIterator.
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func (it *doubleDeltaEncodedChunkIterator) contains(t model.Time) bool {
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return !t.Before(it.baseT) && !t.After(it.timestampAtIndex(it.len-1))
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}
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// values implements chunkIterator.
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func (it *doubleDeltaEncodedChunkIterator) values() <-chan *model.SamplePair {
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valuesChan := make(chan *model.SamplePair)
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go func() {
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for i := 0; i < it.len; i++ {
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valuesChan <- &model.SamplePair{
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Timestamp: it.timestampAtIndex(i),
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Value: it.sampleValueAtIndex(i),
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}
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}
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close(valuesChan)
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}()
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return valuesChan
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}
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// timestampAtIndex implements chunkIterator.
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func (it *doubleDeltaEncodedChunkIterator) timestampAtIndex(idx int) model.Time {
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if idx == 0 {
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return it.baseT
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}
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if idx == 1 {
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// If time bytes are at d8, the time is saved directly rather
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// than as a difference.
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if it.tBytes == d8 {
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return it.baseΔT
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}
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return it.baseT + it.baseΔT
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}
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offset := doubleDeltaHeaderBytes + (idx-2)*int(it.tBytes+it.vBytes)
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switch it.tBytes {
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case d1:
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return it.baseT +
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model.Time(idx)*it.baseΔT +
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model.Time(int8(it.c[offset]))
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case d2:
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return it.baseT +
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model.Time(idx)*it.baseΔT +
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model.Time(int16(binary.LittleEndian.Uint16(it.c[offset:])))
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case d4:
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return it.baseT +
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model.Time(idx)*it.baseΔT +
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model.Time(int32(binary.LittleEndian.Uint32(it.c[offset:])))
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case d8:
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// Take absolute value for d8.
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return model.Time(binary.LittleEndian.Uint64(it.c[offset:]))
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default:
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panic("invalid number of bytes for time delta")
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}
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}
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// lastTimestamp implements chunkIterator.
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func (it *doubleDeltaEncodedChunkIterator) lastTimestamp() model.Time {
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return it.timestampAtIndex(it.len - 1)
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}
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// sampleValueAtIndex implements chunkIterator.
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func (it *doubleDeltaEncodedChunkIterator) sampleValueAtIndex(idx int) model.SampleValue {
|
|
if idx == 0 {
|
|
return it.baseV
|
|
}
|
|
if idx == 1 {
|
|
// If value bytes are at d8, the value is saved directly rather
|
|
// than as a difference.
|
|
if it.vBytes == d8 {
|
|
return it.baseΔV
|
|
}
|
|
return it.baseV + it.baseΔV
|
|
}
|
|
|
|
offset := doubleDeltaHeaderBytes + (idx-2)*int(it.tBytes+it.vBytes) + int(it.tBytes)
|
|
|
|
if it.isInt {
|
|
switch it.vBytes {
|
|
case d0:
|
|
return it.baseV +
|
|
model.SampleValue(idx)*it.baseΔV
|
|
case d1:
|
|
return it.baseV +
|
|
model.SampleValue(idx)*it.baseΔV +
|
|
model.SampleValue(int8(it.c[offset]))
|
|
case d2:
|
|
return it.baseV +
|
|
model.SampleValue(idx)*it.baseΔV +
|
|
model.SampleValue(int16(binary.LittleEndian.Uint16(it.c[offset:])))
|
|
case d4:
|
|
return it.baseV +
|
|
model.SampleValue(idx)*it.baseΔV +
|
|
model.SampleValue(int32(binary.LittleEndian.Uint32(it.c[offset:])))
|
|
// No d8 for ints.
|
|
default:
|
|
panic("invalid number of bytes for integer delta")
|
|
}
|
|
} else {
|
|
switch it.vBytes {
|
|
case d4:
|
|
return it.baseV +
|
|
model.SampleValue(idx)*it.baseΔV +
|
|
model.SampleValue(math.Float32frombits(binary.LittleEndian.Uint32(it.c[offset:])))
|
|
case d8:
|
|
// Take absolute value for d8.
|
|
return model.SampleValue(math.Float64frombits(binary.LittleEndian.Uint64(it.c[offset:])))
|
|
default:
|
|
panic("invalid number of bytes for floating point delta")
|
|
}
|
|
}
|
|
}
|
|
|
|
// lastSampleValue implements chunkIterator.
|
|
func (it *doubleDeltaEncodedChunkIterator) lastSampleValue() model.SampleValue {
|
|
return it.sampleValueAtIndex(it.len - 1)
|
|
}
|