mirror of
https://github.com/prometheus/prometheus.git
synced 2024-12-27 14:39:40 -08:00
445 lines
12 KiB
Go
445 lines
12 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 21-byte header of a delta-encoded chunk looks like:
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//
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// - time delta bytes: 1 bytes
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// - value 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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// - used buf bytes: 2 bytes
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const (
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deltaHeaderBytes = 21
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deltaHeaderTimeBytesOffset = 0
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deltaHeaderValueBytesOffset = 1
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deltaHeaderIsIntOffset = 2
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deltaHeaderBaseTimeOffset = 3
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deltaHeaderBaseValueOffset = 11
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deltaHeaderBufLenOffset = 19
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)
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// A deltaEncodedChunk adaptively stores sample timestamps and values with a
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// delta encoding of various types (int, float) and bit widths. However, once 8
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// bytes would be needed to encode a delta value, a fall-back to the absolute
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// numbers happens (so that timestamps are saved directly as int64 and values as
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// float64). It implements the chunk interface.
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type deltaEncodedChunk []byte
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// newDeltaEncodedChunk returns a newly allocated deltaEncodedChunk.
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func newDeltaEncodedChunk(tb, vb deltaBytes, isInt bool, length int) *deltaEncodedChunk {
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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 < deltaHeaderBytes+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, deltaHeaderBytes+16,
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))
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}
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c := make(deltaEncodedChunk, deltaHeaderIsIntOffset+1, length)
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c[deltaHeaderTimeBytesOffset] = byte(tb)
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c[deltaHeaderValueBytesOffset] = byte(vb)
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if vb < d8 && isInt { // Only use int for fewer than 8 value delta bytes.
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c[deltaHeaderIsIntOffset] = 1
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} else {
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c[deltaHeaderIsIntOffset] = 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 deltaEncodedChunk) add(s *model.SamplePair) []chunk {
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if c.len() == 0 {
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c = c[:deltaHeaderBytes]
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binary.LittleEndian.PutUint64(c[deltaHeaderBaseTimeOffset:], uint64(s.Timestamp))
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binary.LittleEndian.PutUint64(c[deltaHeaderBaseValueOffset:], math.Float64bits(float64(s.Value)))
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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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baseValue := c.baseValue()
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dt := s.Timestamp - c.baseTime()
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if dt < 0 {
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panic("time delta is less than zero")
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}
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dv := s.Value - baseValue
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tb := c.timeBytes()
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vb := c.valueBytes()
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isInt := 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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ntb, nvb, nInt := tb, vb, isInt
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if isInt && !isInt64(dv) {
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// int->float.
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nvb = d4
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nInt = false
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} else if !isInt && vb == d4 && baseValue+model.SampleValue(float32(dv)) != 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, bytesNeededForUnsignedTimestampDelta(dt))
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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(dv))
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}
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}
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if tb != ntb || vb != nvb || isInt != nInt {
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if len(c)*2 < cap(c) {
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return transcodeAndAdd(newDeltaEncodedChunk(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(dt)
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case d2:
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binary.LittleEndian.PutUint16(c[offset:], uint16(dt))
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case d4:
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binary.LittleEndian.PutUint32(c[offset:], uint32(dt))
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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 value is stored as base value.
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case d1:
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c[offset] = byte(int8(dv))
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case d2:
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binary.LittleEndian.PutUint16(c[offset:], uint16(int16(dv)))
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case d4:
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binary.LittleEndian.PutUint32(c[offset:], uint32(int32(dv)))
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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(dv)))
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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 deltaEncodedChunk) clone() chunk {
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clone := make(deltaEncodedChunk, 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 deltaEncodedChunk) 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 *deltaEncodedChunk) newIterator() chunkIterator {
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return &deltaEncodedChunkIterator{
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c: *c,
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len: c.len(),
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baseT: c.baseTime(),
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baseV: c.baseValue(),
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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 deltaEncodedChunk) 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[deltaHeaderBufLenOffset:], 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", cap(c), n)
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}
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return nil
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}
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// marshalToBuf implements chunk.
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func (c deltaEncodedChunk) marshalToBuf(buf []byte) 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[deltaHeaderBufLenOffset:], uint16(len(c)))
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n := copy(buf, c)
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if n != len(c) {
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return fmt.Errorf("wanted to copy %d bytes to buffer, copied %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 *deltaEncodedChunk) 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)[deltaHeaderBufLenOffset:])]
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return nil
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}
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// unmarshalFromBuf implements chunk.
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func (c *deltaEncodedChunk) 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)[deltaHeaderBufLenOffset:])]
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}
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// encoding implements chunk.
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func (c deltaEncodedChunk) encoding() chunkEncoding { return delta }
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func (c deltaEncodedChunk) timeBytes() deltaBytes {
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return deltaBytes(c[deltaHeaderTimeBytesOffset])
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}
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func (c deltaEncodedChunk) valueBytes() deltaBytes {
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return deltaBytes(c[deltaHeaderValueBytesOffset])
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}
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func (c deltaEncodedChunk) isInt() bool {
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return c[deltaHeaderIsIntOffset] == 1
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}
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func (c deltaEncodedChunk) baseTime() model.Time {
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return model.Time(binary.LittleEndian.Uint64(c[deltaHeaderBaseTimeOffset:]))
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}
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func (c deltaEncodedChunk) baseValue() model.SampleValue {
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return model.SampleValue(math.Float64frombits(binary.LittleEndian.Uint64(c[deltaHeaderBaseValueOffset:])))
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}
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func (c deltaEncodedChunk) sampleSize() int {
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return int(c.timeBytes() + c.valueBytes())
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}
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func (c deltaEncodedChunk) len() int {
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if len(c) < deltaHeaderBytes {
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return 0
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}
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return (len(c) - deltaHeaderBytes) / c.sampleSize()
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}
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// deltaEncodedChunkIterator implements chunkIterator.
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type deltaEncodedChunkIterator struct {
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c deltaEncodedChunk
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len int
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baseT model.Time
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baseV 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 *deltaEncodedChunkIterator) length() int { return it.len }
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// valueAtTime implements chunkIterator.
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func (it *deltaEncodedChunkIterator) 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 *deltaEncodedChunkIterator) 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 *deltaEncodedChunkIterator) 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 *deltaEncodedChunkIterator) 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 *deltaEncodedChunkIterator) timestampAtIndex(idx int) model.Time {
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offset := deltaHeaderBytes + idx*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 + model.Time(uint8(it.c[offset]))
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case d2:
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return it.baseT + model.Time(binary.LittleEndian.Uint16(it.c[offset:]))
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case d4:
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return it.baseT + model.Time(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 *deltaEncodedChunkIterator) 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 *deltaEncodedChunkIterator) sampleValueAtIndex(idx int) model.SampleValue {
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offset := deltaHeaderBytes + idx*int(it.tBytes+it.vBytes) + int(it.tBytes)
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if it.isInt {
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switch it.vBytes {
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case d0:
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return it.baseV
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case d1:
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return it.baseV + model.SampleValue(int8(it.c[offset]))
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case d2:
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return it.baseV + model.SampleValue(int16(binary.LittleEndian.Uint16(it.c[offset:])))
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case d4:
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return it.baseV + model.SampleValue(int32(binary.LittleEndian.Uint32(it.c[offset:])))
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// No d8 for ints.
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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 it.vBytes {
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case d4:
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return it.baseV + model.SampleValue(math.Float32frombits(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.SampleValue(math.Float64frombits(binary.LittleEndian.Uint64(it.c[offset:])))
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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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}
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// lastSampleValue implements chunkIterator.
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func (it *deltaEncodedChunkIterator) lastSampleValue() model.SampleValue {
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return it.sampleValueAtIndex(it.len - 1)
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}
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