prometheus/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 tsdb
import (
"bufio"
"encoding/binary"
"fmt"
"hash"
"hash/crc32"
"io"
"os"
"github.com/coreos/etcd/pkg/fileutil"
"github.com/pkg/errors"
"github.com/prometheus/tsdb/chunks"
)
const (
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// MagicChunks is 4 bytes at the head of series file.
MagicChunks = 0x85BD40DD
)
// ChunkMeta holds information about a chunk of data.
type ChunkMeta struct {
// Ref and Chunk hold either a reference that can be used to retrieve
// chunk data or the data itself.
// Generally, only one of them is set.
Ref uint64
Chunk chunks.Chunk
MinTime, MaxTime int64 // time range the data covers
}
// ChunkWriter serializes a time block of chunked series data.
type ChunkWriter interface {
// WriteChunks writes several chunks. The data field of the ChunkMetas
// must be populated.
// After returning successfully, the Ref fields in the ChunkMetas
// is set and can be used to retrieve the chunks from the written data.
WriteChunks(chunks ...*ChunkMeta) error
// Close writes any required finalization and closes the resources
// associated with the underlying writer.
Close() error
}
// chunkWriter implements the ChunkWriter interface for the standard
// serialization format.
type chunkWriter struct {
dirFile *os.File
files []*os.File
wbuf *bufio.Writer
n int64
crc32 hash.Hash
segmentSize int64
}
const (
defaultChunkSegmentSize = 512 * 1024 * 1024
chunksFormatV1 = 1
)
func newChunkWriter(dir string) (*chunkWriter, error) {
if err := os.MkdirAll(dir, 0777); err != nil {
return nil, err
}
dirFile, err := fileutil.OpenDir(dir)
if err != nil {
return nil, err
}
cw := &chunkWriter{
dirFile: dirFile,
n: 0,
crc32: crc32.New(crc32.MakeTable(crc32.Castagnoli)),
segmentSize: defaultChunkSegmentSize,
}
return cw, nil
}
func (w *chunkWriter) 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 *chunkWriter) finalizeTail() error {
tf := w.tail()
if tf == nil {
return nil
}
if err := w.wbuf.Flush(); err != nil {
return err
}
if err := fileutil.Fsync(tf); err != nil {
return err
}
// As the file was pre-allocated, we truncate any superfluous zero bytes.
off, err := tf.Seek(0, os.SEEK_CUR)
if err != nil {
return err
}
if err := tf.Truncate(off); err != nil {
return err
}
return tf.Close()
}
func (w *chunkWriter) cut() error {
// Sync current tail to disk and close.
w.finalizeTail()
p, _, err := nextSequenceFile(w.dirFile.Name(), "")
if err != nil {
return err
}
f, err := os.OpenFile(p, os.O_WRONLY|os.O_CREATE, 0666)
if err != nil {
return err
}
if err = fileutil.Preallocate(f, w.segmentSize, true); err != nil {
return err
}
if err = w.dirFile.Sync(); err != nil {
return err
}
// Write header metadata for new file.
metab := make([]byte, 8)
binary.BigEndian.PutUint32(metab[:4], MagicChunks)
metab[4] = chunksFormatV1
if _, err := f.Write(metab); err != nil {
return err
}
w.files = append(w.files, f)
if w.wbuf != nil {
w.wbuf.Reset(f)
} else {
w.wbuf = bufio.NewWriterSize(f, 8*1024*1024)
}
w.n = 8
return nil
}
func (w *chunkWriter) write(wr io.Writer, b []byte) error {
n, err := wr.Write(b)
w.n += int64(n)
return err
}
func (w *chunkWriter) WriteChunks(chks ...*ChunkMeta) error {
// Calculate maximum space we need and cut a new segment in case
// we don't fit into the current one.
maxLen := int64(binary.MaxVarintLen32)
for _, c := range chks {
maxLen += binary.MaxVarintLen32 + 1
maxLen += int64(len(c.Chunk.Bytes()))
}
newsz := w.n + maxLen
if w.wbuf == nil || w.n > w.segmentSize || newsz > w.segmentSize && maxLen <= w.segmentSize {
if err := w.cut(); err != nil {
return err
}
}
// Write chunks sequentially and set the reference field in the ChunkMeta.
w.crc32.Reset()
wr := io.MultiWriter(w.crc32, w.wbuf)
b := make([]byte, binary.MaxVarintLen32)
n := binary.PutUvarint(b, uint64(len(chks)))
if err := w.write(wr, b[:n]); err != nil {
return err
}
seq := uint64(w.seq()) << 32
for _, chk := range chks {
chk.Ref = seq | uint64(w.n)
n = binary.PutUvarint(b, uint64(len(chk.Chunk.Bytes())))
if err := w.write(wr, b[:n]); err != nil {
return err
}
if err := w.write(wr, []byte{byte(chk.Chunk.Encoding())}); err != nil {
return err
}
if err := w.write(wr, chk.Chunk.Bytes()); err != nil {
return err
}
chk.Chunk = nil
}
if err := w.write(w.wbuf, w.crc32.Sum(nil)); err != nil {
return err
}
return nil
}
func (w *chunkWriter) seq() int {
return len(w.files) - 1
}
func (w *chunkWriter) Close() error {
return w.finalizeTail()
}
// ChunkReader provides reading access of serialized time series data.
type ChunkReader interface {
// Chunk returns the series data chunk with the given reference.
Chunk(ref uint64) (chunks.Chunk, error)
// Close releases all underlying resources of the reader.
Close() error
}
// chunkReader implements a SeriesReader for a serialized byte stream
// of series data.
type chunkReader struct {
// The underlying bytes holding the encoded series data.
bs [][]byte
// Closers for resources behind the byte slices.
cs []io.Closer
}
// newChunkReader returns a new chunkReader based on mmaped files found in dir.
func newChunkReader(dir string) (*chunkReader, error) {
files, err := sequenceFiles(dir, "")
if err != nil {
return nil, err
}
var cr chunkReader
for _, fn := range files {
f, err := openMmapFile(fn)
if err != nil {
return nil, errors.Wrapf(err, "mmap files")
}
cr.cs = append(cr.cs, f)
cr.bs = append(cr.bs, f.b)
}
for i, b := range cr.bs {
if len(b) < 4 {
return nil, errors.Wrapf(errInvalidSize, "validate magic in segment %d", i)
}
// Verify magic number.
if m := binary.BigEndian.Uint32(b[:4]); m != MagicChunks {
return nil, fmt.Errorf("invalid magic number %x", m)
}
}
return &cr, nil
}
func (s *chunkReader) Close() error {
return closeAll(s.cs...)
}
func (s *chunkReader) Chunk(ref uint64) (chunks.Chunk, error) {
var (
seq = int(ref >> 32)
off = int((ref << 32) >> 32)
)
if seq >= len(s.bs) {
return nil, errors.Errorf("reference sequence %d out of range", seq)
}
b := s.bs[seq]
if int(off) >= len(b) {
return nil, errors.Errorf("offset %d beyond data size %d", off, len(b))
}
b = b[off:]
l, n := binary.Uvarint(b)
if n < 0 {
return nil, fmt.Errorf("reading chunk length failed")
}
b = b[n:]
enc := chunks.Encoding(b[0])
c, err := chunks.FromData(enc, b[1:1+l])
if err != nil {
return nil, err
}
return c, nil
}