285 lines
9.0 KiB
Go
285 lines
9.0 KiB
Go
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// Copyright 2018 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package rawdb
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"os"
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"path/filepath"
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"sync"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/log"
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"github.com/ethereum/go-ethereum/metrics"
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"github.com/golang/snappy"
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)
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var (
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// errClosed is returned if an operation attempts to read from or write to the
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// freezer table after it has already been closed.
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errClosed = errors.New("closed")
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// errOutOfBounds is returned if the item requested is not contained within the
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// freezer table.
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errOutOfBounds = errors.New("out of bounds")
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)
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// freezerTable represents a single chained data table within the freezer (e.g. blocks).
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// It consists of a data file (snappy encoded arbitrary data blobs) and an index
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// file (uncompressed 64 bit indices into the data file).
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type freezerTable struct {
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content *os.File // File descriptor for the data content of the table
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offsets *os.File // File descriptor for the index file of the table
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items uint64 // Number of items stored in the table
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bytes uint64 // Number of content bytes stored in the table
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readMeter metrics.Meter // Meter for measuring the effective amount of data read
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writeMeter metrics.Meter // Meter for measuring the effective amount of data written
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logger log.Logger // Logger with database path and table name ambedded
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lock sync.RWMutex // Mutex protecting the data file descriptors
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}
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// newTable opens a freezer table, creating the data and index files if they are
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// non existent. Both files are truncated to the shortest common length to ensure
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// they don't go out of sync.
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func newTable(path string, name string, readMeter metrics.Meter, writeMeter metrics.Meter) (*freezerTable, error) {
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// Ensure the containing directory exists and open the two data files
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if err := os.MkdirAll(path, 0755); err != nil {
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return nil, err
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}
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content, err := os.OpenFile(filepath.Join(path, name+".dat"), os.O_RDWR|os.O_CREATE|os.O_APPEND, 0644)
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if err != nil {
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return nil, err
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}
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offsets, err := os.OpenFile(filepath.Join(path, name+".idx"), os.O_RDWR|os.O_CREATE|os.O_APPEND, 0644)
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if err != nil {
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content.Close()
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return nil, err
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}
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// Create the table and repair any past inconsistency
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tab := &freezerTable{
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content: content,
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offsets: offsets,
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readMeter: readMeter,
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writeMeter: writeMeter,
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logger: log.New("database", path, "table", name),
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}
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if err := tab.repair(); err != nil {
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offsets.Close()
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content.Close()
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return nil, err
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}
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return tab, nil
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}
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// repair cross checks the content and the offsets file and truncates them to
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// be in sync with each other after a potential crash / data loss.
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func (t *freezerTable) repair() error {
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// Create a temporary offset buffer to init files with and read offsts into
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offset := make([]byte, 8)
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// If we've just created the files, initialize the offsets with the 0 index
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stat, err := t.offsets.Stat()
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if err != nil {
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return err
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}
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if stat.Size() == 0 {
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if _, err := t.offsets.Write(offset); err != nil {
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return err
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}
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}
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// Ensure the offsets are a multiple of 8 bytes
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if overflow := stat.Size() % 8; overflow != 0 {
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t.offsets.Truncate(stat.Size() - overflow) // New file can't trigger this path
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}
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// Retrieve the file sizes and prepare for truncation
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if stat, err = t.offsets.Stat(); err != nil {
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return err
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}
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offsetsSize := stat.Size()
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if stat, err = t.content.Stat(); err != nil {
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return err
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}
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contentSize := stat.Size()
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// Keep truncating both files until they come in sync
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t.offsets.ReadAt(offset, offsetsSize-8)
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contentExp := int64(binary.LittleEndian.Uint64(offset))
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for contentExp != contentSize {
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// Truncate the content file to the last offset pointer
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if contentExp < contentSize {
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t.logger.Warn("Truncating dangling content", "indexed", common.StorageSize(contentExp), "stored", common.StorageSize(contentSize))
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if err := t.content.Truncate(contentExp); err != nil {
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return err
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}
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contentSize = contentExp
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}
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// Truncate the offsets to point within the content file
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if contentExp > contentSize {
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t.logger.Warn("Truncating dangling offsets", "indexed", common.StorageSize(contentExp), "stored", common.StorageSize(contentSize))
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if err := t.offsets.Truncate(offsetsSize - 8); err != nil {
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return err
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}
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offsetsSize -= 8
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t.offsets.ReadAt(offset, offsetsSize-8)
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contentExp = int64(binary.LittleEndian.Uint64(offset))
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}
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}
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// Ensure all reparation changes have been written to disk
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if err := t.offsets.Sync(); err != nil {
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return err
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}
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if err := t.content.Sync(); err != nil {
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return err
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}
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// Update the item and byte counters and return
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t.items = uint64(offsetsSize/8 - 1) // last index points to the end of the data file
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t.bytes = uint64(contentSize)
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t.logger.Debug("Chain freezer table opened", "items", t.items, "size", common.StorageSize(t.bytes))
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return nil
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}
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// truncate discards any recent data above the provided threashold number.
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func (t *freezerTable) truncate(items uint64) error {
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// If out item count is corrent, don't do anything
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if t.items <= items {
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return nil
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}
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// Something's out of sync, truncate the table's offset index
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t.logger.Warn("Truncating freezer table", "items", t.items, "limit", items)
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if err := t.offsets.Truncate(int64(items+1) * 8); err != nil {
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return err
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}
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// Calculate the new expected size of the data file and truncate it
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offset := make([]byte, 8)
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t.offsets.ReadAt(offset, int64(items)*8)
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expected := binary.LittleEndian.Uint64(offset)
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if err := t.content.Truncate(int64(expected)); err != nil {
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return err
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}
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// All data files truncated, set internal counters and return
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t.items, t.bytes = items, expected
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return nil
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}
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// Close unmaps all active memory mapped regions.
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func (t *freezerTable) Close() error {
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t.lock.Lock()
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defer t.lock.Unlock()
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var errs []error
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if err := t.offsets.Close(); err != nil {
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errs = append(errs, err)
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}
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t.offsets = nil
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if err := t.content.Close(); err != nil {
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errs = append(errs, err)
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}
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t.content = nil
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if errs != nil {
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return fmt.Errorf("%v", errs)
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}
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return nil
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}
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// Append injects a binary blob at the end of the freezer table. The item index
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// is a precautionary parameter to ensure data correctness, but the table will
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// reject already existing data.
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//
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// Note, this method will *not* flush any data to disk so be sure to explicitly
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// fsync before irreversibly deleting data from the database.
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func (t *freezerTable) Append(item uint64, blob []byte) error {
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// Ensure the table is still accessible
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if t.offsets == nil || t.content == nil {
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return errClosed
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}
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// Ensure only the next item can be written, nothing else
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if t.items != item {
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panic(fmt.Sprintf("appending unexpected item: want %d, have %d", t.items, item))
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}
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// Encode the blob and write it into the data file
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blob = snappy.Encode(nil, blob)
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if _, err := t.content.Write(blob); err != nil {
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return err
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}
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t.bytes += uint64(len(blob))
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offset := make([]byte, 8)
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binary.LittleEndian.PutUint64(offset, t.bytes)
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if _, err := t.offsets.Write(offset); err != nil {
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return err
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}
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t.items++
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t.writeMeter.Mark(int64(len(blob) + 8)) // 8 = 1 x 8 byte offset
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return nil
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}
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// Retrieve looks up the data offset of an item with the given index and retrieves
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// the raw binary blob from the data file.
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func (t *freezerTable) Retrieve(item uint64) ([]byte, error) {
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t.lock.RLock()
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defer t.lock.RUnlock()
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// Ensure the table and the item is accessible
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if t.offsets == nil || t.content == nil {
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return nil, errClosed
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}
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if t.items <= item {
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return nil, errOutOfBounds
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}
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// Item reachable, retrieve the data content boundaries
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offset := make([]byte, 8)
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if _, err := t.offsets.ReadAt(offset, int64(item*8)); err != nil {
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return nil, err
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}
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start := binary.LittleEndian.Uint64(offset)
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if _, err := t.offsets.ReadAt(offset, int64((item+1)*8)); err != nil {
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return nil, err
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}
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end := binary.LittleEndian.Uint64(offset)
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// Retrieve the data itself, decompress and return
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blob := make([]byte, end-start)
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if _, err := t.content.ReadAt(blob, int64(start)); err != nil {
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return nil, err
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}
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t.readMeter.Mark(int64(len(blob) + 16)) // 16 = 2 x 8 byte offset
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return snappy.Decode(nil, blob)
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}
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// Sync pushes any pending data from memory out to disk. This is an expensive
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// operation, so use it with care.
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func (t *freezerTable) Sync() error {
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if err := t.offsets.Sync(); err != nil {
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return err
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}
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return t.content.Sync()
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}
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