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// Copyright 2018 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"
"io"
"io/ioutil"
"math"
"os"
"path/filepath"
"strconv"
"strings"
"github.com/pkg/errors"
"github.com/prometheus/tsdb/fileutil"
"github.com/prometheus/tsdb/wal"
)
// CheckpointStats returns stats about a created checkpoint.
type CheckpointStats struct {
DroppedSeries int
DroppedSamples int
DroppedTombstones int
TotalSeries int // Processed series including dropped ones.
TotalSamples int // Processed samples including dropped ones.
TotalTombstones int // Processed tombstones including dropped ones.
}
// LastCheckpoint returns the directory name and index of the most recent checkpoint.
// If dir does not contain any checkpoints, ErrNotFound is returned.
func LastCheckpoint(dir string) (string, int, error) {
files, err := ioutil.ReadDir(dir)
if err != nil {
return "", 0, err
}
// Traverse list backwards since there may be multiple checkpoints left.
for i := len(files) - 1; i >= 0; i-- {
fi := files[i]
if !strings.HasPrefix(fi.Name(), checkpointPrefix) {
continue
}
if !fi.IsDir() {
return "", 0, errors.Errorf("checkpoint %s is not a directory", fi.Name())
}
idx, err := strconv.Atoi(fi.Name()[len(checkpointPrefix):])
if err != nil {
continue
}
return filepath.Join(dir, fi.Name()), idx, nil
}
return "", 0, ErrNotFound
}
// DeleteCheckpoints deletes all checkpoints in a directory below a given index.
func DeleteCheckpoints(dir string, maxIndex int) error {
var errs MultiError
files, err := ioutil.ReadDir(dir)
if err != nil {
return err
}
for _, fi := range files {
if !strings.HasPrefix(fi.Name(), checkpointPrefix) {
continue
}
index, err := strconv.Atoi(fi.Name()[len(checkpointPrefix):])
if err != nil || index >= maxIndex {
continue
}
if err := os.RemoveAll(filepath.Join(dir, fi.Name())); err != nil {
errs.Add(err)
}
}
return errs.Err()
}
const checkpointPrefix = "checkpoint."
// Checkpoint creates a compacted checkpoint of segments in range [first, last] in the given WAL.
// It includes the most recent checkpoint if it exists.
// All series not satisfying keep and samples below mint are dropped.
//
// The checkpoint is stored in a directory named checkpoint.N in the same
// segmented format as the original WAL itself.
// This makes it easy to read it through the WAL package and concatenate
// it with the original WAL.
func Checkpoint(w *wal.WAL, from, to int, keep func(id uint64) bool, mint int64) (*CheckpointStats, error) {
stats := &CheckpointStats{}
var sgmReader io.ReadCloser
{
var sgmRange []wal.SegmentRange
dir, idx, err := LastCheckpoint(w.Dir())
if err != nil && err != ErrNotFound {
return nil, errors.Wrap(err, "find last checkpoint")
}
last := idx + 1
if err == nil {
if from > last {
return nil, fmt.Errorf("unexpected gap to last checkpoint. expected:%v, requested:%v", last, from)
}
// Ignore WAL files below the checkpoint. They shouldn't exist to begin with.
from = last
sgmRange = append(sgmRange, wal.SegmentRange{Dir: dir, Last: math.MaxInt32})
}
sgmRange = append(sgmRange, wal.SegmentRange{Dir: w.Dir(), First: from, Last: to})
sgmReader, err = wal.NewSegmentsRangeReader(sgmRange...)
if err != nil {
return nil, errors.Wrap(err, "create segment reader")
}
defer sgmReader.Close()
}
cpdir := filepath.Join(w.Dir(), fmt.Sprintf(checkpointPrefix+"%06d", to))
cpdirtmp := cpdir + ".tmp"
if err := os.MkdirAll(cpdirtmp, 0777); err != nil {
return nil, errors.Wrap(err, "create checkpoint dir")
}
cp, err := wal.New(nil, nil, cpdirtmp)
if err != nil {
return nil, errors.Wrap(err, "open checkpoint")
}
// Ensures that an early return caused by an error doesn't leave any tmp files.
defer func() {
cp.Close()
os.RemoveAll(cpdirtmp)
}()
r := wal.NewReader(sgmReader)
var (
series []RefSeries
samples []RefSample
tstones []Stone
dec RecordDecoder
enc RecordEncoder
buf []byte
recs [][]byte
)
for r.Next() {
series, samples, tstones = series[:0], samples[:0], tstones[:0]
// We don't reset the buffer since we batch up multiple records
// before writing them to the checkpoint.
// Remember where the record for this iteration starts.
start := len(buf)
rec := r.Record()
switch dec.Type(rec) {
case RecordSeries:
series, err = dec.Series(rec, series)
if err != nil {
return nil, errors.Wrap(err, "decode series")
}
// Drop irrelevant series in place.
repl := series[:0]
for _, s := range series {
if keep(s.Ref) {
repl = append(repl, s)
}
}
if len(repl) > 0 {
buf = enc.Series(repl, buf)
}
stats.TotalSeries += len(series)
stats.DroppedSeries += len(series) - len(repl)
case RecordSamples:
samples, err = dec.Samples(rec, samples)
if err != nil {
return nil, errors.Wrap(err, "decode samples")
}
// Drop irrelevant samples in place.
repl := samples[:0]
for _, s := range samples {
if s.T >= mint {
repl = append(repl, s)
}
}
if len(repl) > 0 {
buf = enc.Samples(repl, buf)
}
stats.TotalSamples += len(samples)
stats.DroppedSamples += len(samples) - len(repl)
case RecordTombstones:
tstones, err = dec.Tombstones(rec, tstones)
if err != nil {
return nil, errors.Wrap(err, "decode deletes")
}
// Drop irrelevant tombstones in place.
repl := tstones[:0]
for _, s := range tstones {
for _, iv := range s.intervals {
if iv.Maxt >= mint {
repl = append(repl, s)
break
}
}
}
if len(repl) > 0 {
buf = enc.Tombstones(repl, buf)
}
stats.TotalTombstones += len(tstones)
stats.DroppedTombstones += len(tstones) - len(repl)
default:
return nil, errors.New("invalid record type")
}
if len(buf[start:]) == 0 {
continue // All contents discarded.
}
recs = append(recs, buf[start:])
// Flush records in 1 MB increments.
if len(buf) > 1*1024*1024 {
if err := cp.Log(recs...); err != nil {
return nil, errors.Wrap(err, "flush records")
}
buf, recs = buf[:0], recs[:0]
}
}
// If we hit any corruption during checkpointing, repairing is not an option.
// The head won't know which series records are lost.
if r.Err() != nil {
return nil, errors.Wrap(r.Err(), "read segments")
}
// Flush remaining records.
if err := cp.Log(recs...); err != nil {
return nil, errors.Wrap(err, "flush records")
}
if err := cp.Close(); err != nil {
return nil, errors.Wrap(err, "close checkpoint")
}
if err := fileutil.Replace(cpdirtmp, cpdir); err != nil {
return nil, errors.Wrap(err, "rename checkpoint directory")
}
return stats, nil
}