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head.go
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head.go
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// 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.
package tsdb
import (
"fmt"
"math"
"math/rand"
"os"
"sort"
"sync"
"sync/atomic"
"time"
"github.com/go-kit/kit/log"
"github.com/oklog/ulid"
"github.com/pkg/errors"
"github.com/prometheus/tsdb/chunks"
"github.com/prometheus/tsdb/labels"
)
var (
// ErrNotFound is returned if a looked up resource was not found.
ErrNotFound = errors.Errorf("not found")
// ErrOutOfOrderSample is returned if an appended sample has a
// timestamp larger than the most recent sample.
ErrOutOfOrderSample = errors.New("out of order sample")
// ErrAmendSample is returned if an appended sample has the same timestamp
// as the most recent sample but a different value.
ErrAmendSample = errors.New("amending sample")
// ErrOutOfBounds is returned if an appended sample is out of the
// writable time range.
ErrOutOfBounds = errors.New("out of bounds")
)
// headBlock handles reads and writes of time series data within a time window.
type headBlock struct {
mtx sync.RWMutex
dir string
wal *WAL
activeWriters uint64
closed bool
// descs holds all chunk descs for the head block. Each chunk implicitly
// is assigned the index as its ID.
series []*memSeries
// hashes contains a collision map of label set hashes of chunks
// to their chunk descs.
hashes map[uint64][]*memSeries
values map[string]stringset // label names to possible values
postings *memPostings // postings lists for terms
meta BlockMeta
}
func createHeadBlock(dir string, seq int, l log.Logger, mint, maxt int64) (*headBlock, error) {
// Make head block creation appear atomic.
tmp := dir + ".tmp"
if err := os.MkdirAll(tmp, 0777); err != nil {
return nil, err
}
entropy := rand.New(rand.NewSource(time.Now().UnixNano()))
ulid, err := ulid.New(ulid.Now(), entropy)
if err != nil {
return nil, err
}
if err := writeMetaFile(tmp, &BlockMeta{
ULID: ulid,
Sequence: seq,
MinTime: mint,
MaxTime: maxt,
}); err != nil {
return nil, err
}
if err := renameFile(tmp, dir); err != nil {
return nil, err
}
return openHeadBlock(dir, l)
}
// openHeadBlock creates a new empty head block.
func openHeadBlock(dir string, l log.Logger) (*headBlock, error) {
wal, err := OpenWAL(dir, log.With(l, "component", "wal"), 5*time.Second)
if err != nil {
return nil, err
}
meta, err := readMetaFile(dir)
if err != nil {
return nil, err
}
h := &headBlock{
dir: dir,
wal: wal,
series: []*memSeries{},
hashes: map[uint64][]*memSeries{},
values: map[string]stringset{},
postings: &memPostings{m: make(map[term][]uint32)},
meta: *meta,
}
r := wal.Reader()
Outer:
for r.Next() {
series, samples := r.At()
for _, lset := range series {
h.create(lset.Hash(), lset)
h.meta.Stats.NumSeries++
}
for _, s := range samples {
if int(s.ref) >= len(h.series) {
l.Log("msg", "unknown series reference, abort WAL restore", "got", s.ref, "max", len(h.series)-1)
break Outer
}
h.series[s.ref].append(s.t, s.v)
if !h.inBounds(s.t) {
return nil, errors.Wrap(ErrOutOfBounds, "consume WAL")
}
h.meta.Stats.NumSamples++
}
}
if err := r.Err(); err != nil {
return nil, errors.Wrap(err, "consume WAL")
}
return h, nil
}
// inBounds returns true if the given timestamp is within the valid
// time bounds of the block.
func (h *headBlock) inBounds(t int64) bool {
return t >= h.meta.MinTime && t <= h.meta.MaxTime
}
func (h *headBlock) String() string {
return fmt.Sprintf("(%d, %s)", h.meta.Sequence, h.meta.ULID)
}
// Close syncs all data and closes underlying resources of the head block.
func (h *headBlock) Close() error {
h.mtx.Lock()
defer h.mtx.Unlock()
if err := h.wal.Close(); err != nil {
return errors.Wrapf(err, "close WAL for head %s", h.dir)
}
// Check whether the head block still exists in the underlying dir
// or has already been replaced with a compacted version or removed.
meta, err := readMetaFile(h.dir)
if os.IsNotExist(err) {
return nil
}
if err != nil {
return err
}
if meta.ULID == h.meta.ULID {
return writeMetaFile(h.dir, &h.meta)
}
h.closed = true
return nil
}
func (h *headBlock) Meta() BlockMeta {
m := BlockMeta{
ULID: h.meta.ULID,
Sequence: h.meta.Sequence,
MinTime: h.meta.MinTime,
MaxTime: h.meta.MaxTime,
Compaction: h.meta.Compaction,
}
m.Stats.NumChunks = atomic.LoadUint64(&h.meta.Stats.NumChunks)
m.Stats.NumSeries = atomic.LoadUint64(&h.meta.Stats.NumSeries)
m.Stats.NumSamples = atomic.LoadUint64(&h.meta.Stats.NumSamples)
return m
}
func (h *headBlock) Dir() string { return h.dir }
func (h *headBlock) Persisted() bool { return false }
func (h *headBlock) Index() IndexReader { return &headIndexReader{h} }
func (h *headBlock) Chunks() ChunkReader { return &headChunkReader{h} }
func (h *headBlock) Querier(mint, maxt int64) Querier {
h.mtx.RLock()
defer h.mtx.RUnlock()
if h.closed {
panic(fmt.Sprintf("block %s already closed", h.dir))
}
// Reference on the original slice to use for postings mapping.
series := h.series[:]
return &blockQuerier{
mint: mint,
maxt: maxt,
index: h.Index(),
chunks: h.Chunks(),
postingsMapper: func(p Postings) Postings {
ep := make([]uint32, 0, 64)
for p.Next() {
// Skip posting entries that include series added after we
// instantiated the querier.
if int(p.At()) >= len(series) {
break
}
ep = append(ep, p.At())
}
if err := p.Err(); err != nil {
return errPostings{err: errors.Wrap(err, "expand postings")}
}
sort.Slice(ep, func(i, j int) bool {
return labels.Compare(series[ep[i]].lset, series[ep[j]].lset) < 0
})
return newListPostings(ep)
},
}
}
func (h *headBlock) Appender() Appender {
atomic.AddUint64(&h.activeWriters, 1)
h.mtx.RLock()
if h.closed {
panic(fmt.Sprintf("block %s already closed", h.dir))
}
return &headAppender{headBlock: h, samples: getHeadAppendBuffer()}
}
func (h *headBlock) Busy() bool {
return atomic.LoadUint64(&h.activeWriters) > 0
}
var headPool = sync.Pool{}
func getHeadAppendBuffer() []refdSample {
b := headPool.Get()
if b == nil {
return make([]refdSample, 0, 512)
}
return b.([]refdSample)
}
func putHeadAppendBuffer(b []refdSample) {
headPool.Put(b[:0])
}
type headAppender struct {
*headBlock
newSeries map[uint64]hashedLabels
newHashes map[uint64]uint64
refmap map[uint64]uint64
newLabels []labels.Labels
samples []refdSample
}
type hashedLabels struct {
hash uint64
labels labels.Labels
}
type refdSample struct {
ref uint64
t int64
v float64
}
func (a *headAppender) Add(lset labels.Labels, t int64, v float64) (uint64, error) {
hash := lset.Hash()
if ms := a.get(hash, lset); ms != nil {
return uint64(ms.ref), a.AddFast(uint64(ms.ref), t, v)
}
if ref, ok := a.newHashes[hash]; ok {
return uint64(ref), a.AddFast(uint64(ref), t, v)
}
// We only know the actual reference after committing. We generate an
// intermediate reference only valid for this batch.
// It is indicated by the the LSB of the 4th byte being set to 1.
// We use a random ID to avoid collisions when new series are created
// in two subsequent batches.
// TODO(fabxc): Provide method for client to determine whether a ref
// is valid beyond the current transaction.
ref := uint64(rand.Int31()) | (1 << 32)
if a.newSeries == nil {
a.newSeries = map[uint64]hashedLabels{}
a.newHashes = map[uint64]uint64{}
a.refmap = map[uint64]uint64{}
}
a.newSeries[ref] = hashedLabels{hash: hash, labels: lset}
a.newHashes[hash] = ref
return ref, a.AddFast(ref, t, v)
}
func (a *headAppender) AddFast(ref uint64, t int64, v float64) error {
// We only own the last 5 bytes of the reference. Anything before is
// used by higher-order appenders. We erase it to avoid issues.
ref = (ref << 24) >> 24
// Distinguish between existing series and series created in
// this transaction.
if ref&(1<<32) != 0 {
if _, ok := a.newSeries[ref]; !ok {
return ErrNotFound
}
// TODO(fabxc): we also have to validate here that the
// sample sequence is valid.
// We also have to revalidate it as we switch locks an create
// the new series.
} else if ref > uint64(len(a.series)) {
return ErrNotFound
} else {
ms := a.series[int(ref)]
if ms == nil {
return ErrNotFound
}
// TODO(fabxc): memory series should be locked here already.
// Only problem is release of locks in case of a rollback.
c := ms.head()
if !a.inBounds(t) {
return ErrOutOfBounds
}
if t < c.maxTime {
return ErrOutOfOrderSample
}
if c.maxTime == t && ms.lastValue != v {
return ErrAmendSample
}
}
a.samples = append(a.samples, refdSample{
ref: ref,
t: t,
v: v,
})
return nil
}
func (a *headAppender) createSeries() {
if len(a.newSeries) == 0 {
return
}
a.newLabels = make([]labels.Labels, 0, len(a.newSeries))
base0 := len(a.series)
a.mtx.RUnlock()
a.mtx.Lock()
base1 := len(a.series)
for ref, l := range a.newSeries {
// We switched locks and have to re-validate that the series were not
// created by another goroutine in the meantime.
if base1 > base0 {
if ms := a.get(l.hash, l.labels); ms != nil {
a.refmap[ref] = uint64(ms.ref)
continue
}
}
// Series is still new.
a.newLabels = append(a.newLabels, l.labels)
a.refmap[ref] = uint64(len(a.series))
a.create(l.hash, l.labels)
}
a.mtx.Unlock()
a.mtx.RLock()
}
func (a *headAppender) Commit() error {
defer atomic.AddUint64(&a.activeWriters, ^uint64(0))
defer putHeadAppendBuffer(a.samples)
a.createSeries()
for i := range a.samples {
s := &a.samples[i]
if s.ref&(1<<32) > 0 {
s.ref = a.refmap[s.ref]
}
}
// Write all new series and samples to the WAL and add it to the
// in-mem database on success.
if err := a.wal.Log(a.newLabels, a.samples); err != nil {
a.mtx.RUnlock()
return err
}
var (
total = uint64(len(a.samples))
mint = int64(math.MaxInt64)
maxt = int64(math.MinInt64)
)
for _, s := range a.samples {
if !a.series[s.ref].append(s.t, s.v) {
total--
}
if s.t < mint {
mint = s.t
}
if s.t > maxt {
maxt = s.t
}
}
a.mtx.RUnlock()
atomic.AddUint64(&a.meta.Stats.NumSamples, total)
atomic.AddUint64(&a.meta.Stats.NumSeries, uint64(len(a.newSeries)))
return nil
}
func (a *headAppender) Rollback() error {
a.mtx.RUnlock()
atomic.AddUint64(&a.activeWriters, ^uint64(0))
putHeadAppendBuffer(a.samples)
return nil
}
type headChunkReader struct {
*headBlock
}
// Chunk returns the chunk for the reference number.
func (h *headChunkReader) Chunk(ref uint64) (chunks.Chunk, error) {
h.mtx.RLock()
defer h.mtx.RUnlock()
si := ref >> 32
ci := (ref << 32) >> 32
c := &safeChunk{
Chunk: h.series[si].chunks[ci].chunk,
s: h.series[si],
i: int(ci),
}
return c, nil
}
type safeChunk struct {
chunks.Chunk
s *memSeries
i int
}
func (c *safeChunk) Iterator() chunks.Iterator {
c.s.mtx.RLock()
defer c.s.mtx.RUnlock()
return c.s.iterator(c.i)
}
// func (c *safeChunk) Appender() (chunks.Appender, error) { panic("illegal") }
// func (c *safeChunk) Bytes() []byte { panic("illegal") }
// func (c *safeChunk) Encoding() chunks.Encoding { panic("illegal") }
type headIndexReader struct {
*headBlock
}
// LabelValues returns the possible label values
func (h *headIndexReader) LabelValues(names ...string) (StringTuples, error) {
h.mtx.RLock()
defer h.mtx.RUnlock()
if len(names) != 1 {
return nil, errInvalidSize
}
var sl []string
for s := range h.values[names[0]] {
sl = append(sl, s)
}
sort.Strings(sl)
return &stringTuples{l: len(names), s: sl}, nil
}
// Postings returns the postings list iterator for the label pair.
func (h *headIndexReader) Postings(name, value string) (Postings, error) {
h.mtx.RLock()
defer h.mtx.RUnlock()
return h.postings.get(term{name: name, value: value}), nil
}
// Series returns the series for the given reference.
func (h *headIndexReader) Series(ref uint32) (labels.Labels, []*ChunkMeta, error) {
h.mtx.RLock()
defer h.mtx.RUnlock()
if int(ref) >= len(h.series) {
return nil, nil, ErrNotFound
}
s := h.series[ref]
metas := make([]*ChunkMeta, 0, len(s.chunks))
s.mtx.RLock()
defer s.mtx.RUnlock()
for i, c := range s.chunks {
metas = append(metas, &ChunkMeta{
MinTime: c.minTime,
MaxTime: c.maxTime,
Ref: (uint64(ref) << 32) | uint64(i),
})
}
return s.lset, metas, nil
}
func (h *headIndexReader) LabelIndices() ([][]string, error) {
h.mtx.RLock()
defer h.mtx.RUnlock()
res := [][]string{}
for s := range h.values {
res = append(res, []string{s})
}
return res, nil
}
// get retrieves the chunk with the hash and label set and creates
// a new one if it doesn't exist yet.
func (h *headBlock) get(hash uint64, lset labels.Labels) *memSeries {
series := h.hashes[hash]
for _, s := range series {
if s.lset.Equals(lset) {
return s
}
}
return nil
}
func (h *headBlock) create(hash uint64, lset labels.Labels) *memSeries {
s := &memSeries{
lset: lset,
ref: uint32(len(h.series)),
}
// Allocate empty space until we can insert at the given index.
h.series = append(h.series, s)
h.hashes[hash] = append(h.hashes[hash], s)
for _, l := range lset {
valset, ok := h.values[l.Name]
if !ok {
valset = stringset{}
h.values[l.Name] = valset
}
valset.set(l.Value)
h.postings.add(s.ref, term{name: l.Name, value: l.Value})
}
h.postings.add(s.ref, term{})
return s
}
type sample struct {
t int64
v float64
}
type memSeries struct {
mtx sync.RWMutex
ref uint32
lset labels.Labels
chunks []*memChunk
lastValue float64
sampleBuf [4]sample
app chunks.Appender // Current appender for the chunk.
}
func (s *memSeries) cut() *memChunk {
c := &memChunk{
chunk: chunks.NewXORChunk(),
maxTime: math.MinInt64,
}
s.chunks = append(s.chunks, c)
app, err := c.chunk.Appender()
if err != nil {
panic(err)
}
s.app = app
return c
}
func (s *memSeries) append(t int64, v float64) bool {
s.mtx.Lock()
defer s.mtx.Unlock()
var c *memChunk
if s.app == nil || s.head().samples > 130 {
c = s.cut()
c.minTime = t
} else {
c = s.head()
// Skip duplicate samples.
if c.maxTime == t && s.lastValue != v {
return false
}
}
s.app.Append(t, v)
c.maxTime = t
c.samples++
s.lastValue = v
s.sampleBuf[0] = s.sampleBuf[1]
s.sampleBuf[1] = s.sampleBuf[2]
s.sampleBuf[2] = s.sampleBuf[3]
s.sampleBuf[3] = sample{t: t, v: v}
return true
}
func (s *memSeries) iterator(i int) chunks.Iterator {
c := s.chunks[i]
if i < len(s.chunks)-1 {
return c.chunk.Iterator()
}
it := &memSafeIterator{
Iterator: c.chunk.Iterator(),
i: -1,
total: c.samples,
buf: s.sampleBuf,
}
return it
}
func (s *memSeries) head() *memChunk {
return s.chunks[len(s.chunks)-1]
}
type memChunk struct {
chunk chunks.Chunk
minTime, maxTime int64
samples int
}
type memSafeIterator struct {
chunks.Iterator
i int
total int
buf [4]sample
}
func (it *memSafeIterator) Next() bool {
if it.i+1 >= it.total {
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
}