plugeth/core/rawdb/freezer_table.go

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// Copyright 2019 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package rawdb
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"os"
"path/filepath"
"sync"
"sync/atomic"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/metrics"
"github.com/golang/snappy"
)
var (
// errClosed is returned if an operation attempts to read from or write to the
// freezer table after it has already been closed.
errClosed = errors.New("closed")
// errOutOfBounds is returned if the item requested is not contained within the
// freezer table.
errOutOfBounds = errors.New("out of bounds")
// errNotSupported is returned if the database doesn't support the required operation.
errNotSupported = errors.New("this operation is not supported")
)
// indexEntry contains the number/id of the file that the data resides in, aswell as the
// offset within the file to the end of the data
// In serialized form, the filenum is stored as uint16.
type indexEntry struct {
filenum uint32 // stored as uint16 ( 2 bytes)
offset uint32 // stored as uint32 ( 4 bytes)
}
const indexEntrySize = 6
// unmarshalBinary deserializes binary b into the rawIndex entry.
func (i *indexEntry) unmarshalBinary(b []byte) error {
i.filenum = uint32(binary.BigEndian.Uint16(b[:2]))
i.offset = binary.BigEndian.Uint32(b[2:6])
return nil
}
// append adds the encoded entry to the end of b.
func (i *indexEntry) append(b []byte) []byte {
offset := len(b)
out := append(b, make([]byte, indexEntrySize)...)
binary.BigEndian.PutUint16(out[offset:], uint16(i.filenum))
binary.BigEndian.PutUint32(out[offset+2:], i.offset)
return out
}
// bounds returns the start- and end- offsets, and the file number of where to
// read there data item marked by the two index entries. The two entries are
// assumed to be sequential.
func (start *indexEntry) bounds(end *indexEntry) (startOffset, endOffset, fileId uint32) {
if start.filenum != end.filenum {
// If a piece of data 'crosses' a data-file,
// it's actually in one piece on the second data-file.
// We return a zero-indexEntry for the second file as start
return 0, end.offset, end.filenum
}
return start.offset, end.offset, end.filenum
}
// freezerTable represents a single chained data table within the freezer (e.g. blocks).
// It consists of a data file (snappy encoded arbitrary data blobs) and an indexEntry
// file (uncompressed 64 bit indices into the data file).
type freezerTable struct {
// WARNING: The `items` field is accessed atomically. On 32 bit platforms, only
// 64-bit aligned fields can be atomic. The struct is guaranteed to be so aligned,
// so take advantage of that (https://golang.org/pkg/sync/atomic/#pkg-note-BUG).
items uint64 // Number of items stored in the table (including items removed from tail)
noCompression bool // if true, disables snappy compression. Note: does not work retroactively
readonly bool
maxFileSize uint32 // Max file size for data-files
name string
path string
head *os.File // File descriptor for the data head of the table
files map[uint32]*os.File // open files
headId uint32 // number of the currently active head file
tailId uint32 // number of the earliest file
index *os.File // File descriptor for the indexEntry file of the table
// In the case that old items are deleted (from the tail), we use itemOffset
// to count how many historic items have gone missing.
itemOffset uint32 // Offset (number of discarded items)
headBytes int64 // Number of bytes written to the head file
readMeter metrics.Meter // Meter for measuring the effective amount of data read
writeMeter metrics.Meter // Meter for measuring the effective amount of data written
sizeGauge metrics.Gauge // Gauge for tracking the combined size of all freezer tables
logger log.Logger // Logger with database path and table name ambedded
lock sync.RWMutex // Mutex protecting the data file descriptors
}
// NewFreezerTable opens the given path as a freezer table.
func NewFreezerTable(path, name string, disableSnappy, readonly bool) (*freezerTable, error) {
return newTable(path, name, metrics.NilMeter{}, metrics.NilMeter{}, metrics.NilGauge{}, freezerTableSize, disableSnappy, readonly)
}
// openFreezerFileForAppend opens a freezer table file and seeks to the end
func openFreezerFileForAppend(filename string) (*os.File, error) {
// Open the file without the O_APPEND flag
// because it has differing behaviour during Truncate operations
// on different OS's
file, err := os.OpenFile(filename, os.O_RDWR|os.O_CREATE, 0644)
if err != nil {
return nil, err
}
// Seek to end for append
if _, err = file.Seek(0, io.SeekEnd); err != nil {
return nil, err
}
return file, nil
}
// openFreezerFileForReadOnly opens a freezer table file for read only access
func openFreezerFileForReadOnly(filename string) (*os.File, error) {
return os.OpenFile(filename, os.O_RDONLY, 0644)
}
// openFreezerFileTruncated opens a freezer table making sure it is truncated
func openFreezerFileTruncated(filename string) (*os.File, error) {
return os.OpenFile(filename, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
}
// truncateFreezerFile resizes a freezer table file and seeks to the end
func truncateFreezerFile(file *os.File, size int64) error {
if err := file.Truncate(size); err != nil {
return err
}
// Seek to end for append
if _, err := file.Seek(0, io.SeekEnd); err != nil {
return err
}
return nil
}
// newTable opens a freezer table, creating the data and index files if they are
// non existent. Both files are truncated to the shortest common length to ensure
// they don't go out of sync.
func newTable(path string, name string, readMeter metrics.Meter, writeMeter metrics.Meter, sizeGauge metrics.Gauge, maxFilesize uint32, noCompression, readonly bool) (*freezerTable, error) {
// Ensure the containing directory exists and open the indexEntry file
if err := os.MkdirAll(path, 0755); err != nil {
return nil, err
}
var idxName string
if noCompression {
// Raw idx
idxName = fmt.Sprintf("%s.ridx", name)
} else {
// Compressed idx
idxName = fmt.Sprintf("%s.cidx", name)
}
var (
err error
offsets *os.File
)
if readonly {
// Will fail if table doesn't exist
offsets, err = openFreezerFileForReadOnly(filepath.Join(path, idxName))
} else {
offsets, err = openFreezerFileForAppend(filepath.Join(path, idxName))
}
if err != nil {
return nil, err
}
// Create the table and repair any past inconsistency
tab := &freezerTable{
index: offsets,
files: make(map[uint32]*os.File),
readMeter: readMeter,
writeMeter: writeMeter,
sizeGauge: sizeGauge,
name: name,
path: path,
logger: log.New("database", path, "table", name),
noCompression: noCompression,
readonly: readonly,
maxFileSize: maxFilesize,
}
if err := tab.repair(); err != nil {
tab.Close()
return nil, err
}
// Initialize the starting size counter
size, err := tab.sizeNolock()
if err != nil {
tab.Close()
return nil, err
}
tab.sizeGauge.Inc(int64(size))
return tab, nil
}
// repair cross checks the head and the index file and truncates them to
// be in sync with each other after a potential crash / data loss.
func (t *freezerTable) repair() error {
// Create a temporary offset buffer to init files with and read indexEntry into
buffer := make([]byte, indexEntrySize)
// If we've just created the files, initialize the index with the 0 indexEntry
stat, err := t.index.Stat()
if err != nil {
return err
}
if stat.Size() == 0 {
if _, err := t.index.Write(buffer); err != nil {
return err
}
}
// Ensure the index is a multiple of indexEntrySize bytes
if overflow := stat.Size() % indexEntrySize; overflow != 0 {
truncateFreezerFile(t.index, stat.Size()-overflow) // New file can't trigger this path
}
// Retrieve the file sizes and prepare for truncation
if stat, err = t.index.Stat(); err != nil {
return err
}
offsetsSize := stat.Size()
// Open the head file
var (
firstIndex indexEntry
lastIndex indexEntry
contentSize int64
contentExp int64
)
// Read index zero, determine what file is the earliest
// and what item offset to use
t.index.ReadAt(buffer, 0)
firstIndex.unmarshalBinary(buffer)
t.tailId = firstIndex.filenum
t.itemOffset = firstIndex.offset
t.index.ReadAt(buffer, offsetsSize-indexEntrySize)
lastIndex.unmarshalBinary(buffer)
if t.readonly {
t.head, err = t.openFile(lastIndex.filenum, openFreezerFileForReadOnly)
} else {
t.head, err = t.openFile(lastIndex.filenum, openFreezerFileForAppend)
}
if err != nil {
return err
}
if stat, err = t.head.Stat(); err != nil {
return err
}
contentSize = stat.Size()
// Keep truncating both files until they come in sync
contentExp = int64(lastIndex.offset)
for contentExp != contentSize {
// Truncate the head file to the last offset pointer
if contentExp < contentSize {
t.logger.Warn("Truncating dangling head", "indexed", common.StorageSize(contentExp), "stored", common.StorageSize(contentSize))
if err := truncateFreezerFile(t.head, contentExp); err != nil {
return err
}
contentSize = contentExp
}
// Truncate the index to point within the head file
if contentExp > contentSize {
t.logger.Warn("Truncating dangling indexes", "indexed", common.StorageSize(contentExp), "stored", common.StorageSize(contentSize))
if err := truncateFreezerFile(t.index, offsetsSize-indexEntrySize); err != nil {
return err
}
offsetsSize -= indexEntrySize
t.index.ReadAt(buffer, offsetsSize-indexEntrySize)
var newLastIndex indexEntry
newLastIndex.unmarshalBinary(buffer)
// We might have slipped back into an earlier head-file here
if newLastIndex.filenum != lastIndex.filenum {
// Release earlier opened file
t.releaseFile(lastIndex.filenum)
if t.head, err = t.openFile(newLastIndex.filenum, openFreezerFileForAppend); err != nil {
return err
}
if stat, err = t.head.Stat(); err != nil {
// TODO, anything more we can do here?
// A data file has gone missing...
return err
}
contentSize = stat.Size()
}
lastIndex = newLastIndex
contentExp = int64(lastIndex.offset)
}
}
// Sync() fails for read-only files on windows.
if !t.readonly {
// Ensure all reparation changes have been written to disk
if err := t.index.Sync(); err != nil {
return err
}
if err := t.head.Sync(); err != nil {
return err
}
}
// Update the item and byte counters and return
t.items = uint64(t.itemOffset) + uint64(offsetsSize/indexEntrySize-1) // last indexEntry points to the end of the data file
t.headBytes = contentSize
t.headId = lastIndex.filenum
// Close opened files and preopen all files
if err := t.preopen(); err != nil {
return err
}
t.logger.Debug("Chain freezer table opened", "items", t.items, "size", common.StorageSize(t.headBytes))
return nil
}
// preopen opens all files that the freezer will need. This method should be called from an init-context,
// since it assumes that it doesn't have to bother with locking
// The rationale for doing preopen is to not have to do it from within Retrieve, thus not needing to ever
// obtain a write-lock within Retrieve.
func (t *freezerTable) preopen() (err error) {
// The repair might have already opened (some) files
t.releaseFilesAfter(0, false)
// Open all except head in RDONLY
for i := t.tailId; i < t.headId; i++ {
if _, err = t.openFile(i, openFreezerFileForReadOnly); err != nil {
return err
}
}
if t.readonly {
t.head, err = t.openFile(t.headId, openFreezerFileForReadOnly)
} else {
// Open head in read/write
t.head, err = t.openFile(t.headId, openFreezerFileForAppend)
}
return err
}
// truncate discards any recent data above the provided threshold number.
func (t *freezerTable) truncate(items uint64) error {
t.lock.Lock()
defer t.lock.Unlock()
// If our item count is correct, don't do anything
existing := atomic.LoadUint64(&t.items)
if existing <= items {
return nil
}
// We need to truncate, save the old size for metrics tracking
oldSize, err := t.sizeNolock()
if err != nil {
return err
}
// Something's out of sync, truncate the table's offset index
log := t.logger.Debug
if existing > items+1 {
log = t.logger.Warn // Only loud warn if we delete multiple items
}
log("Truncating freezer table", "items", existing, "limit", items)
if err := truncateFreezerFile(t.index, int64(items+1)*indexEntrySize); err != nil {
return err
}
// Calculate the new expected size of the data file and truncate it
buffer := make([]byte, indexEntrySize)
if _, err := t.index.ReadAt(buffer, int64(items*indexEntrySize)); err != nil {
return err
}
var expected indexEntry
expected.unmarshalBinary(buffer)
// We might need to truncate back to older files
if expected.filenum != t.headId {
// If already open for reading, force-reopen for writing
t.releaseFile(expected.filenum)
newHead, err := t.openFile(expected.filenum, openFreezerFileForAppend)
if err != nil {
return err
}
// Release any files _after the current head -- both the previous head
// and any files which may have been opened for reading
t.releaseFilesAfter(expected.filenum, true)
// Set back the historic head
t.head = newHead
t.headId = expected.filenum
}
if err := truncateFreezerFile(t.head, int64(expected.offset)); err != nil {
return err
}
// All data files truncated, set internal counters and return
t.headBytes = int64(expected.offset)
atomic.StoreUint64(&t.items, items)
// Retrieve the new size and update the total size counter
newSize, err := t.sizeNolock()
if err != nil {
return err
}
t.sizeGauge.Dec(int64(oldSize - newSize))
return nil
}
// Close closes all opened files.
func (t *freezerTable) Close() error {
t.lock.Lock()
defer t.lock.Unlock()
var errs []error
if err := t.index.Close(); err != nil {
errs = append(errs, err)
}
t.index = nil
for _, f := range t.files {
if err := f.Close(); err != nil {
errs = append(errs, err)
}
}
t.head = nil
if errs != nil {
return fmt.Errorf("%v", errs)
}
return nil
}
// openFile assumes that the write-lock is held by the caller
func (t *freezerTable) openFile(num uint32, opener func(string) (*os.File, error)) (f *os.File, err error) {
var exist bool
if f, exist = t.files[num]; !exist {
var name string
if t.noCompression {
name = fmt.Sprintf("%s.%04d.rdat", t.name, num)
} else {
name = fmt.Sprintf("%s.%04d.cdat", t.name, num)
}
f, err = opener(filepath.Join(t.path, name))
if err != nil {
return nil, err
}
t.files[num] = f
}
return f, err
}
// releaseFile closes a file, and removes it from the open file cache.
// Assumes that the caller holds the write lock
func (t *freezerTable) releaseFile(num uint32) {
if f, exist := t.files[num]; exist {
delete(t.files, num)
f.Close()
}
}
// releaseFilesAfter closes all open files with a higher number, and optionally also deletes the files
func (t *freezerTable) releaseFilesAfter(num uint32, remove bool) {
for fnum, f := range t.files {
if fnum > num {
delete(t.files, fnum)
f.Close()
if remove {
os.Remove(f.Name())
}
}
}
}
// getIndices returns the index entries for the given from-item, covering 'count' items.
// N.B: The actual number of returned indices for N items will always be N+1 (unless an
// error is returned).
// OBS: This method assumes that the caller has already verified (and/or trimmed) the range
// so that the items are within bounds. If this method is used to read out of bounds,
// it will return error.
func (t *freezerTable) getIndices(from, count uint64) ([]*indexEntry, error) {
// Apply the table-offset
from = from - uint64(t.itemOffset)
// For reading N items, we need N+1 indices.
buffer := make([]byte, (count+1)*indexEntrySize)
if _, err := t.index.ReadAt(buffer, int64(from*indexEntrySize)); err != nil {
return nil, err
}
var (
indices []*indexEntry
offset int
)
for i := from; i <= from+count; i++ {
index := new(indexEntry)
index.unmarshalBinary(buffer[offset:])
offset += indexEntrySize
indices = append(indices, index)
}
if from == 0 {
// Special case if we're reading the first item in the freezer. We assume that
// the first item always start from zero(regarding the deletion, we
// only support deletion by files, so that the assumption is held).
// This means we can use the first item metadata to carry information about
// the 'global' offset, for the deletion-case
indices[0].offset = 0
indices[0].filenum = indices[1].filenum
}
return indices, nil
}
// Retrieve looks up the data offset of an item with the given number and retrieves
// the raw binary blob from the data file.
func (t *freezerTable) Retrieve(item uint64) ([]byte, error) {
items, err := t.RetrieveItems(item, 1, 0)
if err != nil {
return nil, err
}
return items[0], nil
}
// RetrieveItems returns multiple items in sequence, starting from the index 'start'.
// It will return at most 'max' items, but will abort earlier to respect the
// 'maxBytes' argument. However, if the 'maxBytes' is smaller than the size of one
// item, it _will_ return one element and possibly overflow the maxBytes.
func (t *freezerTable) RetrieveItems(start, count, maxBytes uint64) ([][]byte, error) {
// First we read the 'raw' data, which might be compressed.
diskData, sizes, err := t.retrieveItems(start, count, maxBytes)
if err != nil {
return nil, err
}
var (
output = make([][]byte, 0, count)
offset int // offset for reading
outputSize int // size of uncompressed data
)
// Now slice up the data and decompress.
for i, diskSize := range sizes {
item := diskData[offset : offset+diskSize]
offset += diskSize
decompressedSize := diskSize
if !t.noCompression {
decompressedSize, _ = snappy.DecodedLen(item)
}
if i > 0 && uint64(outputSize+decompressedSize) > maxBytes {
break
}
if !t.noCompression {
data, err := snappy.Decode(nil, item)
if err != nil {
return nil, err
}
output = append(output, data)
} else {
output = append(output, item)
}
outputSize += decompressedSize
}
return output, nil
}
// retrieveItems reads up to 'count' items from the table. It reads at least
// one item, but otherwise avoids reading more than maxBytes bytes.
// It returns the (potentially compressed) data, and the sizes.
func (t *freezerTable) retrieveItems(start, count, maxBytes uint64) ([]byte, []int, error) {
t.lock.RLock()
defer t.lock.RUnlock()
// Ensure the table and the item is accessible
if t.index == nil || t.head == nil {
return nil, nil, errClosed
}
itemCount := atomic.LoadUint64(&t.items) // max number
// Ensure the start is written, not deleted from the tail, and that the
// caller actually wants something
if itemCount <= start || uint64(t.itemOffset) > start || count == 0 {
return nil, nil, errOutOfBounds
}
if start+count > itemCount {
count = itemCount - start
}
var (
output = make([]byte, maxBytes) // Buffer to read data into
outputSize int // Used size of that buffer
)
// readData is a helper method to read a single data item from disk.
readData := func(fileId, start uint32, length int) error {
// In case a small limit is used, and the elements are large, may need to
// realloc the read-buffer when reading the first (and only) item.
if len(output) < length {
output = make([]byte, length)
}
dataFile, exist := t.files[fileId]
if !exist {
return fmt.Errorf("missing data file %d", fileId)
}
if _, err := dataFile.ReadAt(output[outputSize:outputSize+length], int64(start)); err != nil {
return err
}
outputSize += length
return nil
}
// Read all the indexes in one go
indices, err := t.getIndices(start, count)
if err != nil {
return nil, nil, err
}
var (
sizes []int // The sizes for each element
totalSize = 0 // The total size of all data read so far
readStart = indices[0].offset // Where, in the file, to start reading
unreadSize = 0 // The size of the as-yet-unread data
)
for i, firstIndex := range indices[:len(indices)-1] {
secondIndex := indices[i+1]
// Determine the size of the item.
offset1, offset2, _ := firstIndex.bounds(secondIndex)
size := int(offset2 - offset1)
// Crossing a file boundary?
if secondIndex.filenum != firstIndex.filenum {
// If we have unread data in the first file, we need to do that read now.
if unreadSize > 0 {
if err := readData(firstIndex.filenum, readStart, unreadSize); err != nil {
return nil, nil, err
}
unreadSize = 0
}
readStart = 0
}
if i > 0 && uint64(totalSize+size) > maxBytes {
// About to break out due to byte limit being exceeded. We don't
// read this last item, but we need to do the deferred reads now.
if unreadSize > 0 {
if err := readData(secondIndex.filenum, readStart, unreadSize); err != nil {
return nil, nil, err
}
}
break
}
// Defer the read for later
unreadSize += size
totalSize += size
sizes = append(sizes, size)
if i == len(indices)-2 || uint64(totalSize) > maxBytes {
// Last item, need to do the read now
if err := readData(secondIndex.filenum, readStart, unreadSize); err != nil {
return nil, nil, err
}
break
}
}
return output[:outputSize], sizes, nil
}
// has returns an indicator whether the specified number data
// exists in the freezer table.
func (t *freezerTable) has(number uint64) bool {
return atomic.LoadUint64(&t.items) > number
}
// size returns the total data size in the freezer table.
func (t *freezerTable) size() (uint64, error) {
t.lock.RLock()
defer t.lock.RUnlock()
return t.sizeNolock()
}
// sizeNolock returns the total data size in the freezer table without obtaining
// the mutex first.
func (t *freezerTable) sizeNolock() (uint64, error) {
stat, err := t.index.Stat()
if err != nil {
return 0, err
}
total := uint64(t.maxFileSize)*uint64(t.headId-t.tailId) + uint64(t.headBytes) + uint64(stat.Size())
return total, nil
}
// advanceHead should be called when the current head file would outgrow the file limits,
// and a new file must be opened. The caller of this method must hold the write-lock
// before calling this method.
func (t *freezerTable) advanceHead() error {
t.lock.Lock()
defer t.lock.Unlock()
// We open the next file in truncated mode -- if this file already
// exists, we need to start over from scratch on it.
nextID := t.headId + 1
newHead, err := t.openFile(nextID, openFreezerFileTruncated)
if err != nil {
return err
}
// Close old file, and reopen in RDONLY mode.
t.releaseFile(t.headId)
t.openFile(t.headId, openFreezerFileForReadOnly)
// Swap out the current head.
t.head = newHead
t.headBytes = 0
t.headId = nextID
return nil
}
// Sync pushes any pending data from memory out to disk. This is an expensive
// operation, so use it with care.
func (t *freezerTable) Sync() error {
if err := t.index.Sync(); err != nil {
return err
}
return t.head.Sync()
}
// DumpIndex is a debug print utility function, mainly for testing. It can also
// be used to analyse a live freezer table index.
func (t *freezerTable) DumpIndex(start, stop int64) {
t.dumpIndex(os.Stdout, start, stop)
}
func (t *freezerTable) dumpIndexString(start, stop int64) string {
var out bytes.Buffer
out.WriteString("\n")
t.dumpIndex(&out, start, stop)
return out.String()
}
func (t *freezerTable) dumpIndex(w io.Writer, start, stop int64) {
buf := make([]byte, indexEntrySize)
fmt.Fprintf(w, "| number | fileno | offset |\n")
fmt.Fprintf(w, "|--------|--------|--------|\n")
for i := uint64(start); ; i++ {
if _, err := t.index.ReadAt(buf, int64(i*indexEntrySize)); err != nil {
break
}
var entry indexEntry
entry.unmarshalBinary(buf)
fmt.Fprintf(w, "| %03d | %03d | %03d | \n", i, entry.filenum, entry.offset)
if stop > 0 && i >= uint64(stop) {
break
}
}
fmt.Fprintf(w, "|--------------------------|\n")
}