syncer.go

   1 /*
   2 syncer -- stateful file/device data syncer.
   3 Copyright (C) 2015-2018 Sergey Matveev <stargrave@stargrave.org>
   4
   5 This program is free software: you can redistribute it and/or modify
   6 it under the terms of the GNU General Public License as published by
   7 the Free Software Foundation, either version 3 of the License, or
   8 (at your option) any later version.
   9
  10 This program is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 */
  18
  19 // Stateful file/device data syncer.
  20 package main
  21
  22 import (
  23         "bytes"
  24         "encoding/binary"
  25         "flag"
  26         "io"
  27         "io/ioutil"
  28         "log"
  29         "os"
  30         "runtime"
  31
  32         "github.com/dchest/blake2b"
  33 )
  34
  35 var (
  36         blkSize   = flag.Int64("blk", 2*1<<10, "Block size (KiB)")
  37         statePath = flag.String("state", "state.bin", "Path to statefile")
  38         dstPath   = flag.String("dst", "", "Path to destination disk")
  39         srcPath   = flag.String("src", "/dev/da0", "Path to source disk")
  40 )
  41
  42 type SyncEvent struct {
  43         i    int64
  44         buf  []byte
  45         data []byte
  46 }
  47
  48 func main() {
  49         flag.Parse()
  50         bs := *blkSize * int64(1<<10)
  51
  52         if *dstPath == "" {
  53                 log.Fatalln("Not destination is specified")
  54         }
  55
  56         // Open source, calculate number of blocks
  57         var size int64
  58         src, err := os.Open(*srcPath)
  59         if err != nil {
  60                 log.Fatalln("Unable to open src:", err)
  61         }
  62         defer src.Close()
  63         fi, err := src.Stat()
  64         if err != nil {
  65                 log.Fatalln("Unable to read src stat:", err)
  66         }
  67         if fi.Mode()&os.ModeDevice == os.ModeDevice {
  68                 size, err = src.Seek(0, 2)
  69                 if err != nil {
  70                         log.Fatalln("Unable to seek src:", err)
  71                 }
  72                 src.Seek(0, 0)
  73         } else {
  74                 size = fi.Size()
  75         }
  76         blocks := size / bs
  77         if size%bs != 0 {
  78                 blocks++
  79         }
  80         log.Println(blocks, bs, "byte blocks")
  81
  82         // Open destination
  83         dst, err := os.OpenFile(*dstPath, os.O_WRONLY|os.O_CREATE, 0600)
  84         if err != nil {
  85                 log.Fatalln("Unable to open dst:", err)
  86         }
  87         defer dst.Close()
  88
  89         // Check if we already have statefile and read the state
  90         state := make([]byte, blake2b.Size*blocks)
  91         var i int64
  92         var tmp []byte
  93         if _, err := os.Stat(*statePath); err == nil {
  94                 log.Println("State file found")
  95                 stateFile, err := os.Open(*statePath)
  96                 if err != nil {
  97                         log.Fatalln("Unable to read statefile:", err)
  98                 }
  99
 100                 // Check previously used size and block size
 101                 tmp = make([]byte, 8)
 102                 n, err := stateFile.Read(tmp)
 103                 if err != nil || n != 8 {
 104                         log.Fatalln("Invalid statefile")
 105                 }
 106                 prevSize := int64(binary.BigEndian.Uint64(tmp))
 107                 if size != prevSize {
 108                         log.Fatalln(
 109                                 "Size differs with state file:",
 110                                 prevSize, "instead of", size,
 111                         )
 112                 }
 113                 tmp = make([]byte, 8)
 114                 n, err = stateFile.Read(tmp)
 115                 if err != nil || n != 8 {
 116                         log.Fatalln("Invalid statefile")
 117                 }
 118                 prevBs := int64(binary.BigEndian.Uint64(tmp))
 119                 if bs != prevBs {
 120                         log.Fatalln(
 121                                 "Blocksize differs with state file:",
 122                                 prevBs, "instead of", bs,
 123                         )
 124                 }
 125
 126                 n, err = stateFile.Read(state)
 127                 if err != nil || n != len(state) {
 128                         log.Fatalln("Corrupted statefile")
 129                 }
 130                 stateFile.Close()
 131         }
 132         stateFile, err := ioutil.TempFile(".", "syncer")
 133         if err != nil {
 134                 log.Fatalln("Unable to create temporary file:", err)
 135         }
 136         tmp = make([]byte, 8)
 137         binary.BigEndian.PutUint64(tmp, uint64(size))
 138         stateFile.Write(tmp)
 139         tmp = make([]byte, 8)
 140         binary.BigEndian.PutUint64(tmp, uint64(bs))
 141         stateFile.Write(tmp)
 142
 143         // Create buffers and event channel
 144         workers := runtime.NumCPU()
 145         log.Println(workers, "workers")
 146         bufs := make(chan []byte, workers)
 147         for i := 0; i < workers; i++ {
 148                 bufs <- make([]byte, int(bs))
 149         }
 150         syncs := make(chan chan SyncEvent, workers)
 151
 152         // Writer
 153         prn := NewPrinter(blocks)
 154         finished := make(chan struct{})
 155         go func() {
 156                 var event SyncEvent
 157                 for sync := range syncs {
 158                         event = <-sync
 159                         if event.data != nil {
 160                                 dst.Seek(event.i*bs, 0)
 161                                 dst.Write(event.data)
 162                         }
 163                         bufs <- event.buf
 164                         <-sync
 165                 }
 166                 close(finished)
 167         }()
 168
 169         // Reader
 170         for i = 0; i < blocks; i++ {
 171                 buf := <-bufs
 172                 n, err := src.Read(buf)
 173                 if err != nil {
 174                         if err != io.EOF {
 175                                 log.Fatalln("Error during src read:", err)
 176                         }
 177                         break
 178                 }
 179                 sync := make(chan SyncEvent)
 180                 syncs <- sync
 181                 go func(i int64) {
 182                         sum := blake2b.Sum512(buf[:n])
 183                         sumState := state[i*blake2b.Size : i*blake2b.Size+blake2b.Size]
 184                         if bytes.Compare(sumState, sum[:]) != 0 {
 185                                 sync <- SyncEvent{i, buf, buf[:n]}
 186                                 prn.Changed()
 187                         } else {
 188                                 sync <- SyncEvent{i, buf, nil}
 189                                 prn.Unchanged()
 190                         }
 191                         copy(sumState, sum[:])
 192                         close(sync)
 193                 }(i)
 194         }
 195         close(syncs)
 196         <-finished
 197         prn.Output()
 198
 199         log.Println("Saving state")
 200         stateFile.Write(state)
 201         stateFile.Close()
 202         if err = os.Rename(stateFile.Name(), *statePath); err != nil {
 203                 log.Fatalln(
 204                         "Unable to overwrite statefile:", err,
 205                         "saved state is in:", stateFile.Name(),
 206                 )
 207         }
 208 }