// 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 (
"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
// unmarshallBinary 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
}
// marshallBinary serializes the rawIndex entry into binary.
func (i *indexEntry) marshallBinary() []byte {
b := make([]byte, indexEntrySize)
binary.BigEndian.PutUint16(b[:2], uint16(i.filenum))
binary.BigEndian.PutUint32(b[2:6], i.offset)
return b
}
// 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
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 uint32 // 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
}
// newTable opens a freezer table with default settings - 2G files
func newTable(path string, name string, readMeter metrics.Meter, writeMeter metrics.Meter, sizeGauge metrics.Gauge, disableSnappy bool) (*freezerTable, error) {
return newCustomTable(path, name, readMeter, writeMeter, sizeGauge, 2*1000*1000*1000, disableSnappy)
}
// 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
}
// newCustomTable 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 newCustomTable(path string, name string, readMeter metrics.Meter, writeMeter metrics.Meter, sizeGauge metrics.Gauge, maxFilesize uint32, noCompression 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)
}
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,
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.offset
t.itemOffset = firstIndex.filenum
t.index.ReadAt(buffer, offsetsSize-indexEntrySize)
lastIndex.unmarshalBinary(buffer)
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)
}
}
// 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 = uint32(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
}
}
// 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
if atomic.LoadUint64(&t.items) <= 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
t.logger.Warn("Truncating freezer table", "items", t.items, "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
atomic.StoreUint32(&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
atomic.StoreUint64(&t.items, items)
atomic.StoreUint32(&t.headBytes, expected.offset)
// 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())
}
}
}
}
// Append injects a binary blob at the end of the freezer table. The item number
// is a precautionary parameter to ensure data correctness, but the table will
// reject already existing data.
//
// Note, this method will *not* flush any data to disk so be sure to explicitly
// fsync before irreversibly deleting data from the database.
func (t *freezerTable) Append(item uint64, blob []byte) error {
// Read lock prevents competition with truncate
t.lock.RLock()
// Ensure the table is still accessible
if t.index == nil || t.head == nil {
t.lock.RUnlock()
return errClosed
}
// Ensure only the next item can be written, nothing else
if atomic.LoadUint64(&t.items) != item {
t.lock.RUnlock()
return fmt.Errorf("appending unexpected item: want %d, have %d", t.items, item)
}
// Encode the blob and write it into the data file
if !t.noCompression {
blob = snappy.Encode(nil, blob)
}
bLen := uint32(len(blob))
if t.headBytes+bLen < bLen ||
t.headBytes+bLen > t.maxFileSize {
// we need a new file, writing would overflow
t.lock.RUnlock()
t.lock.Lock()
nextID := atomic.LoadUint32(&t.headId) + 1
// We open the next file in truncated mode -- if this file already
// exists, we need to start over from scratch on it
newHead, err := t.openFile(nextID, openFreezerFileTruncated)
if err != nil {
t.lock.Unlock()
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
atomic.StoreUint32(&t.headBytes, 0)
atomic.StoreUint32(&t.headId, nextID)
t.lock.Unlock()
t.lock.RLock()
}
defer t.lock.RUnlock()
if _, err := t.head.Write(blob); err != nil {
return err
}
newOffset := atomic.AddUint32(&t.headBytes, bLen)
idx := indexEntry{
filenum: atomic.LoadUint32(&t.headId),
offset: newOffset,
}
// Write indexEntry
t.index.Write(idx.marshallBinary())
t.writeMeter.Mark(int64(bLen + indexEntrySize))
t.sizeGauge.Inc(int64(bLen + indexEntrySize))
atomic.AddUint64(&t.items, 1)
return nil
}
// getBounds returns the indexes for the item
// returns start, end, filenumber and error
func (t *freezerTable) getBounds(item uint64) (uint32, uint32, uint32, error) {
var startIdx, endIdx indexEntry
buffer := make([]byte, indexEntrySize)
if _, err := t.index.ReadAt(buffer, int64(item*indexEntrySize)); err != nil {
return 0, 0, 0, err
}
startIdx.unmarshalBinary(buffer)
if _, err := t.index.ReadAt(buffer, int64((item+1)*indexEntrySize)); err != nil {
return 0, 0, 0, err
}
endIdx.unmarshalBinary(buffer)
if startIdx.filenum != endIdx.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, endIdx.offset, endIdx.filenum, nil
}
return startIdx.offset, endIdx.offset, endIdx.filenum, 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) {
// Ensure the table and the item is accessible
if t.index == nil || t.head == nil {
return nil, errClosed
}
if atomic.LoadUint64(&t.items) <= item {
return nil, errOutOfBounds
}
// Ensure the item was not deleted from the tail either
offset := atomic.LoadUint32(&t.itemOffset)
if uint64(offset) > item {
return nil, errOutOfBounds
}
t.lock.RLock()
startOffset, endOffset, filenum, err := t.getBounds(item - uint64(offset))
if err != nil {
t.lock.RUnlock()
return nil, err
}
dataFile, exist := t.files[filenum]
if !exist {
t.lock.RUnlock()
return nil, fmt.Errorf("missing data file %d", filenum)
}
// Retrieve the data itself, decompress and return
blob := make([]byte, endOffset-startOffset)
if _, err := dataFile.ReadAt(blob, int64(startOffset)); err != nil {
t.lock.RUnlock()
return nil, err
}
t.lock.RUnlock()
t.readMeter.Mark(int64(len(blob) + 2*indexEntrySize))
if t.noCompression {
return blob, nil
}
return snappy.Decode(nil, blob)
}
// 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
}
// 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()
}
// printIndex is a debug print utility function for testing
func (t *freezerTable) printIndex() {
buf := make([]byte, indexEntrySize)
fmt.Printf("|-----------------|\n")
fmt.Printf("| fileno | offset |\n")
fmt.Printf("|--------+--------|\n")
for i := uint64(0); ; i++ {
if _, err := t.index.ReadAt(buf, int64(i*indexEntrySize)); err != nil {
break
}
var entry indexEntry
entry.unmarshalBinary(buf)
fmt.Printf("| %03d | %03d | \n", entry.filenum, entry.offset)
if i > 100 {
fmt.Printf(" ... \n")
break
}
}
fmt.Printf("|-----------------|\n")
}
