minio/cmd/metacache-stream.go

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/*
* MinIO Cloud Storage, (C) 2020 MinIO, Inc.
*
* 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 cmd
import (
"bytes"
"context"
"errors"
"fmt"
"io"
"strings"
"sync"
jsoniter "github.com/json-iterator/go"
"github.com/klauspost/compress/s2"
"github.com/minio/minio/cmd/logger"
"github.com/tinylib/msgp/msgp"
)
// metadata stream format:
//
// The stream is s2 compressed.
// https://github.com/klauspost/compress/tree/master/s2#s2-compression
// This ensures integrity and reduces the size typically by at least 50%.
//
// All stream elements are msgpack encoded.
//
// 1 Integer, metacacheStreamVersion of the writer.
// This can be used for managing breaking changes.
//
// For each element:
// 1. Bool. If false at end of stream.
// 2. String. Name of object. Directories contains a trailing slash.
// 3. Binary. Blob of metadata. Length 0 on directories.
// ... Next element.
//
// Streams can be assumed to be sorted in ascending order.
// If the stream ends before a false boolean it can be assumed it was truncated.
const metacacheStreamVersion = 1
// metacacheWriter provides a serializer of metacache objects.
type metacacheWriter struct {
mw *msgp.Writer
creator func() error
closer func() error
blockSize int
streamErr error
streamWg sync.WaitGroup
}
// newMetacacheWriter will create a serializer that will write objects in given order to the output.
// Provide a block size that affects latency. If 0 a default of 128KiB will be used.
// Block size can be up to 4MiB.
func newMetacacheWriter(out io.Writer, blockSize int) *metacacheWriter {
if blockSize < 8<<10 {
blockSize = 128 << 10
}
w := metacacheWriter{
mw: nil,
blockSize: blockSize,
}
w.creator = func() error {
s2w := s2.NewWriter(out, s2.WriterBlockSize(blockSize))
w.mw = msgp.NewWriter(s2w)
w.creator = nil
if err := w.mw.WriteByte(metacacheStreamVersion); err != nil {
return err
}
w.closer = func() (err error) {
defer func() {
cerr := s2w.Close()
if err == nil && cerr != nil {
err = cerr
}
}()
if w.streamErr != nil {
return w.streamErr
}
if err = w.mw.WriteBool(false); err != nil {
return err
}
return w.mw.Flush()
}
return nil
}
return &w
}
// write one or more objects to the stream in order.
// It is favorable to send as many objects as possible in a single write,
// but no more than math.MaxUint32
func (w *metacacheWriter) write(objs ...metaCacheEntry) error {
if w == nil {
return errors.New("metacacheWriter: nil writer")
}
if len(objs) == 0 {
return nil
}
if w.creator != nil {
err := w.creator()
w.creator = nil
if err != nil {
return fmt.Errorf("metacacheWriter: unable to create writer: %w", err)
}
if w.mw == nil {
return errors.New("metacacheWriter: writer not initialized")
}
}
for _, o := range objs {
if len(o.name) == 0 {
return errors.New("metacacheWriter: no name provided")
}
// Indicate EOS
err := w.mw.WriteBool(true)
if err != nil {
return err
}
err = w.mw.WriteString(o.name)
if err != nil {
return err
}
err = w.mw.WriteBytes(o.metadata)
if err != nil {
return err
}
}
return nil
}
// stream entries to the output.
// The returned channel should be closed when done.
// Any error is reported when closing the metacacheWriter.
func (w *metacacheWriter) stream() (chan<- metaCacheEntry, error) {
if w.creator != nil {
err := w.creator()
w.creator = nil
if err != nil {
return nil, fmt.Errorf("metacacheWriter: unable to create writer: %w", err)
}
if w.mw == nil {
return nil, errors.New("metacacheWriter: writer not initialized")
}
}
var objs = make(chan metaCacheEntry, 100)
w.streamErr = nil
w.streamWg.Add(1)
go func() {
defer w.streamWg.Done()
for o := range objs {
if len(o.name) == 0 || w.streamErr != nil {
continue
}
// Indicate EOS
err := w.mw.WriteBool(true)
if err != nil {
w.streamErr = err
continue
}
err = w.mw.WriteString(o.name)
if err != nil {
w.streamErr = err
continue
}
err = w.mw.WriteBytes(o.metadata)
if err != nil {
w.streamErr = err
continue
}
}
}()
return objs, nil
}
// Close and release resources.
func (w *metacacheWriter) Close() error {
if w == nil || w.closer == nil {
return nil
}
w.streamWg.Wait()
err := w.closer()
w.closer = nil
return err
}
// Reset and start writing to new writer.
// Close must have been called before this.
func (w *metacacheWriter) Reset(out io.Writer) {
w.streamErr = nil
w.creator = func() error {
s2w := s2.NewWriter(out, s2.WriterBlockSize(w.blockSize))
w.mw = msgp.NewWriter(s2w)
w.creator = nil
if err := w.mw.WriteByte(metacacheStreamVersion); err != nil {
return err
}
w.closer = func() error {
if w.streamErr != nil {
return w.streamErr
}
if err := w.mw.WriteBool(false); err != nil {
return err
}
if err := w.mw.Flush(); err != nil {
return err
}
return s2w.Close()
}
return nil
}
}
var s2DecPool = sync.Pool{New: func() interface{} {
return s2.NewReader(nil)
}}
// metacacheReader allows reading a cache stream.
type metacacheReader struct {
mr *msgp.Reader
current metaCacheEntry
err error // stateful error
closer func()
creator func() error
}
// newMetacacheReader creates a new cache reader.
// Nothing will be read from the stream yet.
func newMetacacheReader(r io.Reader) (*metacacheReader, error) {
dec := s2DecPool.Get().(*s2.Reader)
dec.Reset(r)
mr := msgp.NewReader(dec)
m := metacacheReader{
mr: mr,
closer: func() {
dec.Reset(nil)
s2DecPool.Put(dec)
},
creator: func() error {
v, err := mr.ReadByte()
if err != nil {
return err
}
switch v {
case metacacheStreamVersion:
default:
return fmt.Errorf("metacacheReader: Unknown version: %d", v)
}
return nil
},
}
return &m, nil
}
func (r *metacacheReader) checkInit() {
if r.creator == nil || r.err != nil {
return
}
r.err = r.creator()
r.creator = nil
}
// peek will return the name of the next object.
// Will return io.EOF if there are no more objects.
// Should be used sparingly.
func (r *metacacheReader) peek() (metaCacheEntry, error) {
r.checkInit()
if r.err != nil {
return metaCacheEntry{}, r.err
}
if r.current.name != "" {
return r.current, nil
}
if more, err := r.mr.ReadBool(); !more {
switch err {
case nil:
r.err = io.EOF
return metaCacheEntry{}, io.EOF
case io.EOF:
r.err = io.ErrUnexpectedEOF
return metaCacheEntry{}, io.ErrUnexpectedEOF
}
r.err = err
return metaCacheEntry{}, err
}
var err error
if r.current.name, err = r.mr.ReadString(); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return metaCacheEntry{}, err
}
r.current.metadata, err = r.mr.ReadBytes(r.current.metadata[:0])
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return r.current, err
}
// next will read one entry from the stream.
// Generally not recommended for fast operation.
func (r *metacacheReader) next() (metaCacheEntry, error) {
r.checkInit()
if r.err != nil {
return metaCacheEntry{}, r.err
}
var m metaCacheEntry
var err error
if r.current.name != "" {
m.name = r.current.name
m.metadata = r.current.metadata
r.current.name = ""
r.current.metadata = nil
return m, nil
}
if more, err := r.mr.ReadBool(); !more {
switch err {
case nil:
r.err = io.EOF
return m, io.EOF
case io.EOF:
r.err = io.ErrUnexpectedEOF
return m, io.ErrUnexpectedEOF
}
r.err = err
return m, err
}
if m.name, err = r.mr.ReadString(); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return m, err
}
m.metadata, err = r.mr.ReadBytes(nil)
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return m, err
}
// next will read one entry from the stream.
// Generally not recommended for fast operation.
func (r *metacacheReader) nextEOF() bool {
r.checkInit()
if r.err != nil {
return r.err == io.EOF
}
if r.current.name != "" {
return false
}
_, err := r.peek()
if err != nil {
r.err = err
return r.err == io.EOF
}
return false
}
// forwardTo will forward to the first entry that is >= s.
// Will return io.EOF if end of stream is reached without finding any.
func (r *metacacheReader) forwardTo(s string) error {
r.checkInit()
if r.err != nil {
return r.err
}
if s == "" {
return nil
}
if r.current.name != "" {
if r.current.name >= s {
return nil
}
r.current.name = ""
r.current.metadata = nil
}
// temporary name buffer.
var tmp = make([]byte, 0, 256)
for {
if more, err := r.mr.ReadBool(); !more {
switch err {
case nil:
r.err = io.EOF
return io.EOF
case io.EOF:
r.err = io.ErrUnexpectedEOF
return io.ErrUnexpectedEOF
}
r.err = err
return err
}
// Read name without allocating more than 1 buffer.
sz, err := r.mr.ReadStringHeader()
if err != nil {
r.err = err
return err
}
if cap(tmp) < int(sz) {
tmp = make([]byte, 0, sz+256)
}
tmp = tmp[:sz]
_, err = r.mr.R.ReadFull(tmp)
if err != nil {
r.err = err
return err
}
if string(tmp) >= s {
r.current.name = string(tmp)
r.current.metadata, err = r.mr.ReadBytes(nil)
return err
}
// Skip metadata
err = r.mr.Skip()
if err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return err
}
}
}
// readN will return all the requested number of entries in order
// or all if n < 0.
// Will return io.EOF if end of stream is reached.
// If requesting 0 objects nil error will always be returned regardless of at end of stream.
// Use peek to determine if at end of stream.
func (r *metacacheReader) readN(n int, inclDeleted, inclDirs bool, prefix string) (metaCacheEntriesSorted, error) {
r.checkInit()
if n == 0 {
return metaCacheEntriesSorted{}, nil
}
if r.err != nil {
return metaCacheEntriesSorted{}, r.err
}
var res metaCacheEntries
if n > 0 {
res = make(metaCacheEntries, 0, n)
}
if prefix != "" {
if err := r.forwardTo(prefix); err != nil {
return metaCacheEntriesSorted{}, err
}
}
next, err := r.peek()
if err != nil {
return metaCacheEntriesSorted{}, err
}
if !next.hasPrefix(prefix) {
return metaCacheEntriesSorted{}, io.EOF
}
if r.current.name != "" {
if (inclDeleted || !r.current.isLatestDeletemarker()) && r.current.hasPrefix(prefix) && (inclDirs || r.current.isObject()) {
res = append(res, r.current)
}
r.current.name = ""
r.current.metadata = nil
}
for n < 0 || len(res) < n {
if more, err := r.mr.ReadBool(); !more {
switch err {
case nil:
r.err = io.EOF
return metaCacheEntriesSorted{o: res}, io.EOF
case io.EOF:
r.err = io.ErrUnexpectedEOF
return metaCacheEntriesSorted{o: res}, io.ErrUnexpectedEOF
}
r.err = err
return metaCacheEntriesSorted{o: res}, err
}
var err error
var meta metaCacheEntry
if meta.name, err = r.mr.ReadString(); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return metaCacheEntriesSorted{o: res}, err
}
if !meta.hasPrefix(prefix) {
r.mr.R.Skip(1)
return metaCacheEntriesSorted{o: res}, io.EOF
}
if meta.metadata, err = r.mr.ReadBytes(nil); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return metaCacheEntriesSorted{o: res}, err
}
if !inclDirs && meta.isDir() {
continue
}
if meta.isDir() && !inclDeleted && meta.isLatestDeletemarker() {
continue
}
res = append(res, meta)
}
return metaCacheEntriesSorted{o: res}, nil
}
// readAll will return all remaining objects on the dst channel and close it when done.
// The context allows the operation to be canceled.
func (r *metacacheReader) readAll(ctx context.Context, dst chan<- metaCacheEntry) error {
r.checkInit()
if r.err != nil {
return r.err
}
defer close(dst)
if r.current.name != "" {
select {
case <-ctx.Done():
r.err = ctx.Err()
return ctx.Err()
case dst <- r.current:
}
r.current.name = ""
r.current.metadata = nil
}
for {
if more, err := r.mr.ReadBool(); !more {
switch err {
case io.EOF:
err = io.ErrUnexpectedEOF
}
r.err = err
return err
}
var err error
var meta metaCacheEntry
if meta.name, err = r.mr.ReadString(); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return err
}
if meta.metadata, err = r.mr.ReadBytes(nil); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return err
}
select {
case <-ctx.Done():
r.err = ctx.Err()
return ctx.Err()
case dst <- meta:
}
}
}
// readFn will return all remaining objects
// and provide a callback for each entry read in order
// as long as true is returned on the callback.
func (r *metacacheReader) readFn(fn func(entry metaCacheEntry) bool) error {
r.checkInit()
if r.err != nil {
return r.err
}
if r.current.name != "" {
fn(r.current)
r.current.name = ""
r.current.metadata = nil
}
for {
if more, err := r.mr.ReadBool(); !more {
switch err {
case io.EOF:
r.err = io.ErrUnexpectedEOF
return io.ErrUnexpectedEOF
case nil:
r.err = io.EOF
return io.EOF
}
return err
}
var err error
var meta metaCacheEntry
if meta.name, err = r.mr.ReadString(); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return err
}
if meta.metadata, err = r.mr.ReadBytes(nil); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return err
}
// Send it!
if !fn(meta) {
return nil
}
}
}
// readNames will return all the requested number of names in order
// or all if n < 0.
// Will return io.EOF if end of stream is reached.
func (r *metacacheReader) readNames(n int) ([]string, error) {
r.checkInit()
if r.err != nil {
return nil, r.err
}
if n == 0 {
return nil, nil
}
var res []string
if n > 0 {
res = make([]string, 0, n)
}
if r.current.name != "" {
res = append(res, r.current.name)
r.current.name = ""
r.current.metadata = nil
}
for n < 0 || len(res) < n {
if more, err := r.mr.ReadBool(); !more {
switch err {
case nil:
r.err = io.EOF
return res, io.EOF
case io.EOF:
r.err = io.ErrUnexpectedEOF
return res, io.ErrUnexpectedEOF
}
return res, err
}
var err error
var name string
if name, err = r.mr.ReadString(); err != nil {
r.err = err
return res, err
}
if err = r.mr.Skip(); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return res, err
}
res = append(res, name)
}
return res, nil
}
// skip n entries on the input stream.
// If there are less entries left io.EOF is returned.
func (r *metacacheReader) skip(n int) error {
r.checkInit()
if r.err != nil {
return r.err
}
if n <= 0 {
return nil
}
if r.current.name != "" {
n--
r.current.name = ""
r.current.metadata = nil
}
for n > 0 {
if more, err := r.mr.ReadBool(); !more {
switch err {
case nil:
r.err = io.EOF
return io.EOF
case io.EOF:
r.err = io.ErrUnexpectedEOF
return io.ErrUnexpectedEOF
}
return err
}
if err := r.mr.Skip(); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return err
}
if err := r.mr.Skip(); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
r.err = err
return err
}
n--
}
return nil
}
// Close and release resources.
func (r *metacacheReader) Close() error {
if r == nil || r.closer == nil {
return nil
}
r.closer()
r.closer = nil
r.creator = nil
return nil
}
// metacacheBlockWriter collects blocks and provides a callaback to store them.
type metacacheBlockWriter struct {
wg sync.WaitGroup
streamErr error
blockEntries int
}
// newMetacacheBlockWriter provides a streaming block writer.
// Each block is the size of the capacity of the input channel.
// The caller should close to indicate the stream has ended.
func newMetacacheBlockWriter(in <-chan metaCacheEntry, nextBlock func(b *metacacheBlock) error) *metacacheBlockWriter {
w := metacacheBlockWriter{blockEntries: cap(in)}
w.wg.Add(1)
go func() {
defer w.wg.Done()
var current metacacheBlock
var n int
var buf bytes.Buffer
block := newMetacacheWriter(&buf, 1<<20)
finishBlock := func() {
err := block.Close()
if err != nil {
w.streamErr = err
return
}
current.data = buf.Bytes()
w.streamErr = nextBlock(&current)
// Prepare for next
current.n++
buf.Reset()
block.Reset(&buf)
current.First = ""
}
for o := range in {
if len(o.name) == 0 || w.streamErr != nil {
continue
}
if current.First == "" {
current.First = o.name
}
if n >= w.blockEntries-1 {
finishBlock()
n = 0
}
n++
w.streamErr = block.write(o)
if w.streamErr != nil {
continue
}
current.Last = o.name
}
if n > 0 || current.n == 0 {
current.EOS = true
finishBlock()
}
}()
return &w
}
// Close the stream.
// The incoming channel must be closed before calling this.
// Returns the first error the occurred during the writing if any.
func (w *metacacheBlockWriter) Close() error {
w.wg.Wait()
return w.streamErr
}
type metacacheBlock struct {
data []byte
n int
First string `json:"f"`
Last string `json:"l"`
EOS bool `json:"eos,omitempty"`
}
func (b metacacheBlock) headerKV() map[string]string {
var json = jsoniter.ConfigCompatibleWithStandardLibrary
v, err := json.Marshal(b)
if err != nil {
logger.LogIf(context.Background(), err) // Unlikely
return nil
}
return map[string]string{fmt.Sprintf("%s-metacache-part-%d", ReservedMetadataPrefixLower, b.n): string(v)}
}
// pastPrefix returns true if the given prefix is before start of the block.
func (b metacacheBlock) pastPrefix(prefix string) bool {
if prefix == "" || strings.HasPrefix(b.First, prefix) {
return false
}
// We have checked if prefix matches, so we can do direct compare.
return b.First > prefix
}
// endedPrefix returns true if the given prefix ends within the block.
func (b metacacheBlock) endedPrefix(prefix string) bool {
if prefix == "" || strings.HasPrefix(b.Last, prefix) {
return false
}
// We have checked if prefix matches, so we can do direct compare.
return b.Last > prefix
}