forked from prometheus/prometheus
/
chunks.go
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/
chunks.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 chunks
import (
"bufio"
"bytes"
"encoding/binary"
"fmt"
"hash"
"hash/crc32"
"io"
"io/ioutil"
"os"
"path/filepath"
"strconv"
"github.com/pkg/errors"
"github.com/prometheus/prometheus/tsdb/chunkenc"
tsdb_errors "github.com/prometheus/prometheus/tsdb/errors"
"github.com/prometheus/prometheus/tsdb/fileutil"
)
// Segment header fields constants.
const (
// MagicChunks is 4 bytes at the head of a series file.
MagicChunks = 0x85BD40DD
// MagicChunksSize is the size in bytes of MagicChunks.
MagicChunksSize = 4
chunksFormatV1 = 1
ChunksFormatVersionSize = 1
segmentHeaderPaddingSize = 3
// SegmentHeaderSize defines the total size of the header part.
SegmentHeaderSize = MagicChunksSize + ChunksFormatVersionSize + segmentHeaderPaddingSize
)
// Chunk fields constants.
const (
// MaxChunkLengthFieldSize defines the maximum size of the data length part.
MaxChunkLengthFieldSize = binary.MaxVarintLen32
// ChunkEncodingSize defines the size of the chunk encoding part.
ChunkEncodingSize = 1
)
// Meta holds information about a chunk of data.
type Meta struct {
// Ref and Chunk hold either a reference that can be used to retrieve
// chunk data or the data itself.
// When it is a reference it is the segment offset at which the chunk bytes start.
// Generally, only one of them is set.
Ref uint64
Chunk chunkenc.Chunk
// Time range the data covers.
// When MaxTime == math.MaxInt64 the chunk is still open and being appended to.
MinTime, MaxTime int64
}
// Iterator iterates over the chunk of a time series.
type Iterator interface {
// At returns the current meta.
// It depends on implementation if the chunk is populated or not.
At() Meta
// Next advances the iterator by one.
Next() bool
// Err returns optional error if Next is false.
Err() error
}
// writeHash writes the chunk encoding and raw data into the provided hash.
func (cm *Meta) writeHash(h hash.Hash, buf []byte) error {
buf = append(buf[:0], byte(cm.Chunk.Encoding()))
if _, err := h.Write(buf[:1]); err != nil {
return err
}
if _, err := h.Write(cm.Chunk.Bytes()); err != nil {
return err
}
return nil
}
// OverlapsClosedInterval Returns true if the chunk overlaps [mint, maxt].
func (cm *Meta) OverlapsClosedInterval(mint, maxt int64) bool {
// The chunk itself is a closed interval [cm.MinTime, cm.MaxTime].
return cm.MinTime <= maxt && mint <= cm.MaxTime
}
var (
errInvalidSize = fmt.Errorf("invalid size")
)
var castagnoliTable *crc32.Table
func init() {
castagnoliTable = crc32.MakeTable(crc32.Castagnoli)
}
// newCRC32 initializes a CRC32 hash with a preconfigured polynomial, so the
// polynomial may be easily changed in one location at a later time, if necessary.
func newCRC32() hash.Hash32 {
return crc32.New(castagnoliTable)
}
// Writer implements the ChunkWriter interface for the standard
// serialization format.
type Writer struct {
dirFile *os.File
files []*os.File
wbuf *bufio.Writer
n int64
crc32 hash.Hash
buf [binary.MaxVarintLen32]byte
segmentSize int64
}
const (
// DefaultChunkSegmentSize is the default chunks segment size.
DefaultChunkSegmentSize = 512 * 1024 * 1024
)
// NewWriterWithSegSize returns a new writer against the given directory
// and allows setting a custom size for the segments.
func NewWriterWithSegSize(dir string, segmentSize int64) (*Writer, error) {
return newWriter(dir, segmentSize)
}
// NewWriter returns a new writer against the given directory
// using the default segment size.
func NewWriter(dir string) (*Writer, error) {
return newWriter(dir, DefaultChunkSegmentSize)
}
func newWriter(dir string, segmentSize int64) (*Writer, error) {
if segmentSize <= 0 {
segmentSize = DefaultChunkSegmentSize
}
if err := os.MkdirAll(dir, 0777); err != nil {
return nil, err
}
dirFile, err := fileutil.OpenDir(dir)
if err != nil {
return nil, err
}
return &Writer{
dirFile: dirFile,
n: 0,
crc32: newCRC32(),
segmentSize: segmentSize,
}, nil
}
func (w *Writer) tail() *os.File {
if len(w.files) == 0 {
return nil
}
return w.files[len(w.files)-1]
}
// finalizeTail writes all pending data to the current tail file,
// truncates its size, and closes it.
func (w *Writer) finalizeTail() error {
tf := w.tail()
if tf == nil {
return nil
}
if err := w.wbuf.Flush(); err != nil {
return err
}
if err := tf.Sync(); err != nil {
return err
}
// As the file was pre-allocated, we truncate any superfluous zero bytes.
off, err := tf.Seek(0, io.SeekCurrent)
if err != nil {
return err
}
if err := tf.Truncate(off); err != nil {
return err
}
return tf.Close()
}
func (w *Writer) cut() error {
// Sync current tail to disk and close.
if err := w.finalizeTail(); err != nil {
return err
}
n, f, _, err := cutSegmentFile(w.dirFile, MagicChunks, chunksFormatV1, w.segmentSize)
if err != nil {
return err
}
w.n = int64(n)
w.files = append(w.files, f)
if w.wbuf != nil {
w.wbuf.Reset(f)
} else {
w.wbuf = bufio.NewWriterSize(f, 8*1024*1024)
}
return nil
}
func cutSegmentFile(dirFile *os.File, magicNumber uint32, chunksFormat byte, allocSize int64) (headerSize int, newFile *os.File, seq int, returnErr error) {
p, seq, err := nextSequenceFile(dirFile.Name())
if err != nil {
return 0, nil, 0, errors.Wrap(err, "next sequence file")
}
ptmp := p + ".tmp"
f, err := os.OpenFile(ptmp, os.O_WRONLY|os.O_CREATE, 0666)
if err != nil {
return 0, nil, 0, errors.Wrap(err, "open temp file")
}
defer func() {
if returnErr != nil {
errs := tsdb_errors.NewMulti(returnErr)
if f != nil {
errs.Add(f.Close())
}
// Calling RemoveAll on a non-existent file does not return error.
errs.Add(os.RemoveAll(ptmp))
returnErr = errs.Err()
}
}()
if allocSize > 0 {
if err = fileutil.Preallocate(f, allocSize, true); err != nil {
return 0, nil, 0, errors.Wrap(err, "preallocate")
}
}
if err = dirFile.Sync(); err != nil {
return 0, nil, 0, errors.Wrap(err, "sync directory")
}
// Write header metadata for new file.
metab := make([]byte, SegmentHeaderSize)
binary.BigEndian.PutUint32(metab[:MagicChunksSize], magicNumber)
metab[4] = chunksFormat
n, err := f.Write(metab)
if err != nil {
return 0, nil, 0, errors.Wrap(err, "write header")
}
if err := f.Close(); err != nil {
return 0, nil, 0, errors.Wrap(err, "close temp file")
}
f = nil
if err := fileutil.Rename(ptmp, p); err != nil {
return 0, nil, 0, errors.Wrap(err, "replace file")
}
f, err = os.OpenFile(p, os.O_WRONLY, 0666)
if err != nil {
return 0, nil, 0, errors.Wrap(err, "open final file")
}
// Skip header for further writes.
if _, err := f.Seek(int64(n), 0); err != nil {
return 0, nil, 0, errors.Wrap(err, "seek in final file")
}
return n, f, seq, nil
}
func (w *Writer) write(b []byte) error {
n, err := w.wbuf.Write(b)
w.n += int64(n)
return err
}
// WriteChunks writes as many chunks as possible to the current segment,
// cuts a new segment when the current segment is full and
// writes the rest of the chunks in the new segment.
func (w *Writer) WriteChunks(chks ...Meta) error {
var (
batchSize = int64(0)
batchStart = 0
batches = make([][]Meta, 1)
batchID = 0
firstBatch = true
)
for i, chk := range chks {
// Each chunk contains: data length + encoding + the data itself + crc32
chkSize := int64(MaxChunkLengthFieldSize) // The data length is a variable length field so use the maximum possible value.
chkSize += ChunkEncodingSize // The chunk encoding.
chkSize += int64(len(chk.Chunk.Bytes())) // The data itself.
chkSize += crc32.Size // The 4 bytes of crc32.
batchSize += chkSize
// Cut a new batch when it is not the first chunk(to avoid empty segments) and
// the batch is too large to fit in the current segment.
cutNewBatch := (i != 0) && (batchSize+SegmentHeaderSize > w.segmentSize)
// When the segment already has some data than
// the first batch size calculation should account for that.
if firstBatch && w.n > SegmentHeaderSize {
cutNewBatch = batchSize+w.n > w.segmentSize
if cutNewBatch {
firstBatch = false
}
}
if cutNewBatch {
batchStart = i
batches = append(batches, []Meta{})
batchID++
batchSize = chkSize
}
batches[batchID] = chks[batchStart : i+1]
}
// Create a new segment when one doesn't already exist.
if w.n == 0 {
if err := w.cut(); err != nil {
return err
}
}
for i, chks := range batches {
if err := w.writeChunks(chks); err != nil {
return err
}
// Cut a new segment only when there are more chunks to write.
// Avoid creating a new empty segment at the end of the write.
if i < len(batches)-1 {
if err := w.cut(); err != nil {
return err
}
}
}
return nil
}
// writeChunks writes the chunks into the current segment irrespective
// of the configured segment size limit. A segment should have been already
// started before calling this.
func (w *Writer) writeChunks(chks []Meta) error {
if len(chks) == 0 {
return nil
}
var seq = uint64(w.seq()) << 32
for i := range chks {
chk := &chks[i]
// The reference is set to the segment index and the offset where
// the data starts for this chunk.
//
// The upper 4 bytes are for the segment index and
// the lower 4 bytes are for the segment offset where to start reading this chunk.
chk.Ref = seq | uint64(w.n)
n := binary.PutUvarint(w.buf[:], uint64(len(chk.Chunk.Bytes())))
if err := w.write(w.buf[:n]); err != nil {
return err
}
w.buf[0] = byte(chk.Chunk.Encoding())
if err := w.write(w.buf[:1]); err != nil {
return err
}
if err := w.write(chk.Chunk.Bytes()); err != nil {
return err
}
w.crc32.Reset()
if err := chk.writeHash(w.crc32, w.buf[:]); err != nil {
return err
}
if err := w.write(w.crc32.Sum(w.buf[:0])); err != nil {
return err
}
}
return nil
}
func (w *Writer) seq() int {
return len(w.files) - 1
}
func (w *Writer) Close() error {
if err := w.finalizeTail(); err != nil {
return err
}
// close dir file (if not windows platform will fail on rename)
return w.dirFile.Close()
}
// ByteSlice abstracts a byte slice.
type ByteSlice interface {
Len() int
Range(start, end int) []byte
}
type realByteSlice []byte
func (b realByteSlice) Len() int {
return len(b)
}
func (b realByteSlice) Range(start, end int) []byte {
return b[start:end]
}
// Reader implements a ChunkReader for a serialized byte stream
// of series data.
type Reader struct {
// The underlying bytes holding the encoded series data.
// Each slice holds the data for a different segment.
bs []ByteSlice
cs []io.Closer // Closers for resources behind the byte slices.
size int64 // The total size of bytes in the reader.
pool chunkenc.Pool
}
func newReader(bs []ByteSlice, cs []io.Closer, pool chunkenc.Pool) (*Reader, error) {
cr := Reader{pool: pool, bs: bs, cs: cs}
for i, b := range cr.bs {
if b.Len() < SegmentHeaderSize {
return nil, errors.Wrapf(errInvalidSize, "invalid segment header in segment %d", i)
}
// Verify magic number.
if m := binary.BigEndian.Uint32(b.Range(0, MagicChunksSize)); m != MagicChunks {
return nil, errors.Errorf("invalid magic number %x", m)
}
// Verify chunk format version.
if v := int(b.Range(MagicChunksSize, MagicChunksSize+ChunksFormatVersionSize)[0]); v != chunksFormatV1 {
return nil, errors.Errorf("invalid chunk format version %d", v)
}
cr.size += int64(b.Len())
}
return &cr, nil
}
// NewDirReader returns a new Reader against sequentially numbered files in the
// given directory.
func NewDirReader(dir string, pool chunkenc.Pool) (*Reader, error) {
files, err := sequenceFiles(dir)
if err != nil {
return nil, err
}
if pool == nil {
pool = chunkenc.NewPool()
}
var (
bs []ByteSlice
cs []io.Closer
)
for _, fn := range files {
f, err := fileutil.OpenMmapFile(fn)
if err != nil {
return nil, tsdb_errors.NewMulti(
errors.Wrap(err, "mmap files"),
tsdb_errors.CloseAll(cs),
).Err()
}
cs = append(cs, f)
bs = append(bs, realByteSlice(f.Bytes()))
}
reader, err := newReader(bs, cs, pool)
if err != nil {
return nil, tsdb_errors.NewMulti(
err,
tsdb_errors.CloseAll(cs),
).Err()
}
return reader, nil
}
func (s *Reader) Close() error {
return tsdb_errors.CloseAll(s.cs)
}
// Size returns the size of the chunks.
func (s *Reader) Size() int64 {
return s.size
}
// Chunk returns a chunk from a given reference.
func (s *Reader) Chunk(ref uint64) (chunkenc.Chunk, error) {
var (
// Get the upper 4 bytes.
// These contain the segment index.
sgmIndex = int(ref >> 32)
// Get the lower 4 bytes.
// These contain the segment offset where the data for this chunk starts.
chkStart = int((ref << 32) >> 32)
chkCRC32 = newCRC32()
)
if sgmIndex >= len(s.bs) {
return nil, errors.Errorf("segment index %d out of range", sgmIndex)
}
sgmBytes := s.bs[sgmIndex]
if chkStart+MaxChunkLengthFieldSize > sgmBytes.Len() {
return nil, errors.Errorf("segment doesn't include enough bytes to read the chunk size data field - required:%v, available:%v", chkStart+MaxChunkLengthFieldSize, sgmBytes.Len())
}
// With the minimum chunk length this should never cause us reading
// over the end of the slice.
c := sgmBytes.Range(chkStart, chkStart+MaxChunkLengthFieldSize)
chkDataLen, n := binary.Uvarint(c)
if n <= 0 {
return nil, errors.Errorf("reading chunk length failed with %d", n)
}
chkEncStart := chkStart + n
chkEnd := chkEncStart + ChunkEncodingSize + int(chkDataLen) + crc32.Size
chkDataStart := chkEncStart + ChunkEncodingSize
chkDataEnd := chkEnd - crc32.Size
if chkEnd > sgmBytes.Len() {
return nil, errors.Errorf("segment doesn't include enough bytes to read the chunk - required:%v, available:%v", chkEnd, sgmBytes.Len())
}
sum := sgmBytes.Range(chkDataEnd, chkEnd)
if _, err := chkCRC32.Write(sgmBytes.Range(chkEncStart, chkDataEnd)); err != nil {
return nil, err
}
if act := chkCRC32.Sum(nil); !bytes.Equal(act, sum) {
return nil, errors.Errorf("checksum mismatch expected:%x, actual:%x", sum, act)
}
chkData := sgmBytes.Range(chkDataStart, chkDataEnd)
chkEnc := sgmBytes.Range(chkEncStart, chkEncStart+ChunkEncodingSize)[0]
return s.pool.Get(chunkenc.Encoding(chkEnc), chkData)
}
func nextSequenceFile(dir string) (string, int, error) {
files, err := ioutil.ReadDir(dir)
if err != nil {
return "", 0, err
}
i := uint64(0)
for _, f := range files {
j, err := strconv.ParseUint(f.Name(), 10, 64)
if err != nil {
continue
}
// It is not necessary that we find the files in number order,
// for example with '1000000' and '200000', '1000000' would come first.
// Though this is a very very race case, we check anyway for the max id.
if j > i {
i = j
}
}
return segmentFile(dir, int(i+1)), int(i + 1), nil
}
func segmentFile(baseDir string, index int) string {
return filepath.Join(baseDir, fmt.Sprintf("%0.6d", index))
}
func sequenceFiles(dir string) ([]string, error) {
files, err := ioutil.ReadDir(dir)
if err != nil {
return nil, err
}
var res []string
for _, fi := range files {
if _, err := strconv.ParseUint(fi.Name(), 10, 64); err != nil {
continue
}
res = append(res, filepath.Join(dir, fi.Name()))
}
return res, nil
}