cmd/bitcask: add recovery tool for datafiles (#102)

* cmd/bitcask: refactor recovery index logic

* cmd/bitcask: first version of datafile recovery tool

* cmd/bitcask: finished recovery datafile tool

* cmd/bitcask: temporary script to test recovery tool

* cmd/bitcask: remove commited binary file

* cmd/bitcask: delete bash test

cmd/bitcask/recover.go

@@ -1,11 +1,15 @@
 package main
 
 import (
+	"fmt"
+	"io"
 	"os"
 	"path/filepath"
 
 	"github.com/prologic/bitcask"
+	"github.com/prologic/bitcask/internal"
 	"github.com/prologic/bitcask/internal/config"
+	"github.com/prologic/bitcask/internal/data/codec"
 	"github.com/prologic/bitcask/internal/index"
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
@@ -37,37 +41,101 @@ func init() {
 
 func recover(path string, dryRun bool) int {
 	maxKeySize := bitcask.DefaultMaxKeySize
+	maxValueSize := bitcask.DefaultMaxValueSize
 	if cfg, err := config.Load(filepath.Join(path, "config.json")); err == nil {
 		maxKeySize = cfg.MaxKeySize
+		maxValueSize = cfg.MaxValueSize
 	}
 
+	if err := recoverIndex(filepath.Join(path, "index"), maxKeySize, dryRun); err != nil {
+		log.WithError(err).Info("recovering index file")
+		return 1
+	}
+
+	datafiles, err := internal.GetDatafiles(path)
+	if err != nil {
+		log.WithError(err).Info("coudn't list existing datafiles")
+		return 1
+	}
+	for _, file := range datafiles {
+		if err := recoverDatafile(file, maxKeySize, maxValueSize, dryRun); err != nil {
+			log.WithError(err).Info("recovering data file")
+			return 1
+		}
+	}
+
+	return 0
+}
+
+func recoverIndex(path string, maxKeySize uint32, dryRun bool) error {
 	t, found, err := index.NewIndexer().Load(path, maxKeySize)
 	if err != nil && !index.IsIndexCorruption(err) {
-		log.WithError(err).Info("error while opening the index file")
+		log.WithError(err).Info("opening the index file")
 	}
 	if !found {
 		log.Info("index file doesn't exist, will be recreated on next run.")
-		return 0
+		return nil
 	}
 
 	if err == nil {
 		log.Debug("index file is not corrupted")
-		return 0
+		return nil
 	}
 	log.Debugf("index file is corrupted: %v", err)
 
 	if dryRun {
 		log.Debug("dry-run mode, not writing to a file")
-		return 0
+		return nil
 	}
 
 	// Leverage that t has the partiatially read tree even on corrupted files
 	err = index.NewIndexer().Save(t, "index.recovered")
 	if err != nil {
-		log.WithError(err).Info("error while writing the recovered index file")
-		return 1
+		return fmt.Errorf("writing the recovered index file: %w", err)
 	}
 	log.Debug("the index was recovered in the index.recovered new file")
 
-	return 0
+	return nil
+}
+
+func recoverDatafile(path string, maxKeySize uint32, maxValueSize uint64, dryRun bool) error {
+	f, err := os.Open(path)
+	if err != nil {
+		return fmt.Errorf("opening the datafile: %w", err)
+	}
+	defer f.Close()
+	_, file := filepath.Split(path)
+	fr, err := os.OpenFile(fmt.Sprintf("%s.recovered", file), os.O_CREATE|os.O_WRONLY, os.ModePerm)
+	if err != nil {
+		return fmt.Errorf("creating the recovered datafile: %w", err)
+	}
+	defer fr.Close()
+
+	dec := codec.NewDecoder(f, maxKeySize, maxValueSize)
+	enc := codec.NewEncoder(fr)
+	e := internal.Entry{}
+	for {
+		_, err = dec.Decode(&e)
+		if err == io.EOF {
+			break
+		}
+		if codec.IsCorruptedData(err) {
+			log.Debugf("%s is corrupted, a best-effort recovery was done", file)
+			return nil
+		}
+		if err != nil {
+			return fmt.Errorf("unexpected error while reading datafile: %w", err)
+		}
+		if dryRun {
+			continue
+		}
+		if _, err := enc.Encode(e); err != nil {
+			return fmt.Errorf("writing to recovered datafile: %w", err)
+		}
+	}
+	if err := os.Remove(fr.Name()); err != nil {
+		return fmt.Errorf("can't remove temporal recovered datafile: %w", err)
+	}
+	log.Debugf("%s is not corrupted", file)
+	return nil
 }