prometheus/tsdb/head_read.go

514 lines
14 KiB
Go

// Copyright 2021 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.
package tsdb
import (
"context"
"math"
"sort"
"github.com/go-kit/log/level"
"github.com/pkg/errors"
"github.com/prometheus/prometheus/pkg/labels"
"github.com/prometheus/prometheus/storage"
"github.com/prometheus/prometheus/tsdb/chunkenc"
"github.com/prometheus/prometheus/tsdb/chunks"
"github.com/prometheus/prometheus/tsdb/index"
)
func (h *Head) ExemplarQuerier(ctx context.Context) (storage.ExemplarQuerier, error) {
return h.exemplars.ExemplarQuerier(ctx)
}
// Index returns an IndexReader against the block.
func (h *Head) Index() (IndexReader, error) {
return h.indexRange(math.MinInt64, math.MaxInt64), nil
}
func (h *Head) indexRange(mint, maxt int64) *headIndexReader {
if hmin := h.MinTime(); hmin > mint {
mint = hmin
}
return &headIndexReader{head: h, mint: mint, maxt: maxt}
}
type headIndexReader struct {
head *Head
mint, maxt int64
}
func (h *headIndexReader) Close() error {
return nil
}
func (h *headIndexReader) Symbols() index.StringIter {
return h.head.postings.Symbols()
}
// SortedLabelValues returns label values present in the head for the
// specific label name that are within the time range mint to maxt.
// If matchers are specified the returned result set is reduced
// to label values of metrics matching the matchers.
func (h *headIndexReader) SortedLabelValues(name string, matchers ...*labels.Matcher) ([]string, error) {
values, err := h.LabelValues(name, matchers...)
if err == nil {
sort.Strings(values)
}
return values, err
}
// LabelValues returns label values present in the head for the
// specific label name that are within the time range mint to maxt.
// If matchers are specified the returned result set is reduced
// to label values of metrics matching the matchers.
func (h *headIndexReader) LabelValues(name string, matchers ...*labels.Matcher) ([]string, error) {
if h.maxt < h.head.MinTime() || h.mint > h.head.MaxTime() {
return []string{}, nil
}
if len(matchers) == 0 {
return h.head.postings.LabelValues(name), nil
}
return labelValuesWithMatchers(h, name, matchers...)
}
// LabelNames returns all the unique label names present in the head
// that are within the time range mint to maxt.
func (h *headIndexReader) LabelNames(matchers ...*labels.Matcher) ([]string, error) {
if h.maxt < h.head.MinTime() || h.mint > h.head.MaxTime() {
return []string{}, nil
}
if len(matchers) == 0 {
labelNames := h.head.postings.LabelNames()
sort.Strings(labelNames)
return labelNames, nil
}
return labelNamesWithMatchers(h, matchers...)
}
// Postings returns the postings list iterator for the label pairs.
func (h *headIndexReader) Postings(name string, values ...string) (index.Postings, error) {
res := make([]index.Postings, 0, len(values))
for _, value := range values {
res = append(res, h.head.postings.Get(name, value))
}
return index.Merge(res...), nil
}
func (h *headIndexReader) SortedPostings(p index.Postings) index.Postings {
series := make([]*memSeries, 0, 128)
// Fetch all the series only once.
for p.Next() {
s := h.head.series.getByID(p.At())
if s == nil {
level.Debug(h.head.logger).Log("msg", "Looked up series not found")
} else {
series = append(series, s)
}
}
if err := p.Err(); err != nil {
return index.ErrPostings(errors.Wrap(err, "expand postings"))
}
sort.Slice(series, func(i, j int) bool {
return labels.Compare(series[i].lset, series[j].lset) < 0
})
// Convert back to list.
ep := make([]uint64, 0, len(series))
for _, p := range series {
ep = append(ep, p.ref)
}
return index.NewListPostings(ep)
}
// Series returns the series for the given reference.
func (h *headIndexReader) Series(ref uint64, lbls *labels.Labels, chks *[]chunks.Meta) error {
s := h.head.series.getByID(ref)
if s == nil {
h.head.metrics.seriesNotFound.Inc()
return storage.ErrNotFound
}
*lbls = append((*lbls)[:0], s.lset...)
s.Lock()
defer s.Unlock()
*chks = (*chks)[:0]
for i, c := range s.mmappedChunks {
// Do not expose chunks that are outside of the specified range.
if !c.OverlapsClosedInterval(h.mint, h.maxt) {
continue
}
*chks = append(*chks, chunks.Meta{
MinTime: c.minTime,
MaxTime: c.maxTime,
Ref: packChunkID(s.ref, uint64(s.chunkID(i))),
})
}
if s.headChunk != nil && s.headChunk.OverlapsClosedInterval(h.mint, h.maxt) {
*chks = append(*chks, chunks.Meta{
MinTime: s.headChunk.minTime,
MaxTime: math.MaxInt64, // Set the head chunks as open (being appended to).
Ref: packChunkID(s.ref, uint64(s.chunkID(len(s.mmappedChunks)))),
})
}
return nil
}
func (s *memSeries) chunkID(pos int) int {
return pos + s.firstChunkID
}
// LabelValueFor returns label value for the given label name in the series referred to by ID.
func (h *headIndexReader) LabelValueFor(id uint64, label string) (string, error) {
memSeries := h.head.series.getByID(id)
if memSeries == nil {
return "", storage.ErrNotFound
}
value := memSeries.lset.Get(label)
if value == "" {
return "", storage.ErrNotFound
}
return value, nil
}
// LabelNamesFor returns all the label names for the series referred to by IDs.
// The names returned are sorted.
func (h *headIndexReader) LabelNamesFor(ids ...uint64) ([]string, error) {
namesMap := make(map[string]struct{})
for _, id := range ids {
memSeries := h.head.series.getByID(id)
if memSeries == nil {
return nil, storage.ErrNotFound
}
for _, lbl := range memSeries.lset {
namesMap[lbl.Name] = struct{}{}
}
}
names := make([]string, 0, len(namesMap))
for name := range namesMap {
names = append(names, name)
}
sort.Strings(names)
return names, nil
}
// Chunks returns a ChunkReader against the block.
func (h *Head) Chunks() (ChunkReader, error) {
return h.chunksRange(math.MinInt64, math.MaxInt64, h.iso.State(math.MinInt64, math.MaxInt64))
}
func (h *Head) chunksRange(mint, maxt int64, is *isolationState) (*headChunkReader, error) {
h.closedMtx.Lock()
defer h.closedMtx.Unlock()
if h.closed {
return nil, errors.New("can't read from a closed head")
}
if hmin := h.MinTime(); hmin > mint {
mint = hmin
}
return &headChunkReader{
head: h,
mint: mint,
maxt: maxt,
isoState: is,
}, nil
}
type headChunkReader struct {
head *Head
mint, maxt int64
isoState *isolationState
}
func (h *headChunkReader) Close() error {
h.isoState.Close()
return nil
}
// packChunkID packs a seriesID and a chunkID within it into a global 8 byte ID.
// It panicks if the seriesID exceeds 5 bytes or the chunk ID 3 bytes.
func packChunkID(seriesID, chunkID uint64) uint64 {
if seriesID > (1<<40)-1 {
panic("series ID exceeds 5 bytes")
}
if chunkID > (1<<24)-1 {
panic("chunk ID exceeds 3 bytes")
}
return (seriesID << 24) | chunkID
}
func unpackChunkID(id uint64) (seriesID, chunkID uint64) {
return id >> 24, (id << 40) >> 40
}
// Chunk returns the chunk for the reference number.
func (h *headChunkReader) Chunk(ref uint64) (chunkenc.Chunk, error) {
sid, cid := unpackChunkID(ref)
s := h.head.series.getByID(sid)
// This means that the series has been garbage collected.
if s == nil {
return nil, storage.ErrNotFound
}
s.Lock()
c, garbageCollect, err := s.chunk(int(cid), h.head.chunkDiskMapper)
if err != nil {
s.Unlock()
return nil, err
}
defer func() {
if garbageCollect {
// Set this to nil so that Go GC can collect it after it has been used.
c.chunk = nil
s.memChunkPool.Put(c)
}
}()
// This means that the chunk is outside the specified range.
if !c.OverlapsClosedInterval(h.mint, h.maxt) {
s.Unlock()
return nil, storage.ErrNotFound
}
s.Unlock()
return &safeChunk{
Chunk: c.chunk,
s: s,
cid: int(cid),
isoState: h.isoState,
chunkDiskMapper: h.head.chunkDiskMapper,
}, nil
}
// chunk returns the chunk for the chunk id from memory or by m-mapping it from the disk.
// If garbageCollect is true, it means that the returned *memChunk
// (and not the chunkenc.Chunk inside it) can be garbage collected after it's usage.
func (s *memSeries) chunk(id int, chunkDiskMapper *chunks.ChunkDiskMapper) (chunk *memChunk, garbageCollect bool, err error) {
// ix represents the index of chunk in the s.mmappedChunks slice. The chunk id's are
// incremented by 1 when new chunk is created, hence (id - firstChunkID) gives the slice index.
// The max index for the s.mmappedChunks slice can be len(s.mmappedChunks)-1, hence if the ix
// is len(s.mmappedChunks), it represents the next chunk, which is the head chunk.
ix := id - s.firstChunkID
if ix < 0 || ix > len(s.mmappedChunks) {
return nil, false, storage.ErrNotFound
}
if ix == len(s.mmappedChunks) {
if s.headChunk == nil {
return nil, false, errors.New("invalid head chunk")
}
return s.headChunk, false, nil
}
chk, err := chunkDiskMapper.Chunk(s.mmappedChunks[ix].ref)
if err != nil {
if _, ok := err.(*chunks.CorruptionErr); ok {
panic(err)
}
return nil, false, err
}
mc := s.memChunkPool.Get().(*memChunk)
mc.chunk = chk
mc.minTime = s.mmappedChunks[ix].minTime
mc.maxTime = s.mmappedChunks[ix].maxTime
return mc, true, nil
}
type safeChunk struct {
chunkenc.Chunk
s *memSeries
cid int
isoState *isolationState
chunkDiskMapper *chunks.ChunkDiskMapper
}
func (c *safeChunk) Iterator(reuseIter chunkenc.Iterator) chunkenc.Iterator {
c.s.Lock()
it := c.s.iterator(c.cid, c.isoState, c.chunkDiskMapper, reuseIter)
c.s.Unlock()
return it
}
// iterator returns a chunk iterator.
// It is unsafe to call this concurrently with s.append(...) without holding the series lock.
func (s *memSeries) iterator(id int, isoState *isolationState, chunkDiskMapper *chunks.ChunkDiskMapper, it chunkenc.Iterator) chunkenc.Iterator {
c, garbageCollect, err := s.chunk(id, chunkDiskMapper)
// TODO(fabxc): Work around! An error will be returns when a querier have retrieved a pointer to a
// series's chunk, which got then garbage collected before it got
// accessed. We must ensure to not garbage collect as long as any
// readers still hold a reference.
if err != nil {
return chunkenc.NewNopIterator()
}
defer func() {
if garbageCollect {
// Set this to nil so that Go GC can collect it after it has been used.
// This should be done always at the end.
c.chunk = nil
s.memChunkPool.Put(c)
}
}()
ix := id - s.firstChunkID
numSamples := c.chunk.NumSamples()
stopAfter := numSamples
if isoState != nil {
totalSamples := 0 // Total samples in this series.
previousSamples := 0 // Samples before this chunk.
for j, d := range s.mmappedChunks {
totalSamples += int(d.numSamples)
if j < ix {
previousSamples += int(d.numSamples)
}
}
if s.headChunk != nil {
totalSamples += s.headChunk.chunk.NumSamples()
}
// Removing the extra transactionIDs that are relevant for samples that
// come after this chunk, from the total transactionIDs.
appendIDsToConsider := s.txs.txIDCount - (totalSamples - (previousSamples + numSamples))
// Iterate over the appendIDs, find the first one that the isolation state says not
// to return.
it := s.txs.iterator()
for index := 0; index < appendIDsToConsider; index++ {
appendID := it.At()
if appendID <= isoState.maxAppendID { // Easy check first.
if _, ok := isoState.incompleteAppends[appendID]; !ok {
it.Next()
continue
}
}
stopAfter = numSamples - (appendIDsToConsider - index)
if stopAfter < 0 {
stopAfter = 0 // Stopped in a previous chunk.
}
break
}
}
if stopAfter == 0 {
return chunkenc.NewNopIterator()
}
if id-s.firstChunkID < len(s.mmappedChunks) {
if stopAfter == numSamples {
return c.chunk.Iterator(it)
}
if msIter, ok := it.(*stopIterator); ok {
msIter.Iterator = c.chunk.Iterator(msIter.Iterator)
msIter.i = -1
msIter.stopAfter = stopAfter
return msIter
}
return &stopIterator{
Iterator: c.chunk.Iterator(it),
i: -1,
stopAfter: stopAfter,
}
}
// Serve the last 4 samples for the last chunk from the sample buffer
// as their compressed bytes may be mutated by added samples.
if msIter, ok := it.(*memSafeIterator); ok {
msIter.Iterator = c.chunk.Iterator(msIter.Iterator)
msIter.i = -1
msIter.total = numSamples
msIter.stopAfter = stopAfter
msIter.buf = s.sampleBuf
return msIter
}
return &memSafeIterator{
stopIterator: stopIterator{
Iterator: c.chunk.Iterator(it),
i: -1,
stopAfter: stopAfter,
},
total: numSamples,
buf: s.sampleBuf,
}
}
type memSafeIterator struct {
stopIterator
total int
buf [4]sample
}
func (it *memSafeIterator) Seek(t int64) bool {
if it.Err() != nil {
return false
}
ts, _ := it.At()
for t > ts || it.i == -1 {
if !it.Next() {
return false
}
ts, _ = it.At()
}
return true
}
func (it *memSafeIterator) Next() bool {
if it.i+1 >= it.stopAfter {
return false
}
it.i++
if it.total-it.i > 4 {
return it.Iterator.Next()
}
return true
}
func (it *memSafeIterator) At() (int64, float64) {
if it.total-it.i > 4 {
return it.Iterator.At()
}
s := it.buf[4-(it.total-it.i)]
return s.t, s.v
}
type stopIterator struct {
chunkenc.Iterator
i, stopAfter int
}
func (it *stopIterator) Next() bool {
if it.i+1 >= it.stopAfter {
return false
}
it.i++
return it.Iterator.Next()
}