Auto recovery (#153)

* implement autorepair

Signed-off-by: Ignacio Hagopian <jsign.uy@gmail.com>

* fix misspell

Signed-off-by: Ignacio Hagopian <jsign.uy@gmail.com>

* Update internal/data/recover.go

Co-authored-by: James Mills <prologic@shortcircuit.net.au>

* Update internal/utils.go

Co-authored-by: James Mills <prologic@shortcircuit.net.au>

* Update internal/data/recover.go

Co-authored-by: James Mills <prologic@shortcircuit.net.au>

* skip failing test on windows

Signed-off-by: Ignacio Hagopian <jsign.uy@gmail.com>

Co-authored-by: James Mills <prologic@shortcircuit.net.au>

bitcask_test.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
+	"path"
 	"path/filepath"
 	"reflect"
 	"runtime"
@@ -15,6 +16,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"github.com/prologic/bitcask/internal"
 	"github.com/prologic/bitcask/internal/config"
@@ -334,6 +336,85 @@ func TestConfigErrors(t *testing.T) {
 	})
 }
 
+func TestAutoRecovery(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.SkipNow()
+	}
+	withAutoRecovery := []bool{false, true}
+
+	for _, autoRecovery := range withAutoRecovery {
+		t.Run(fmt.Sprintf("%v", autoRecovery), func(t *testing.T) {
+			require := require.New(t)
+			testdir, err := ioutil.TempDir("", "bitcask")
+			require.NoError(err)
+			db, err := Open(testdir)
+			require.NoError(err)
+
+			// Insert 10 key-value pairs and verify all is ok.
+			makeKeyVal := func(i int) ([]byte, []byte) {
+				return []byte(fmt.Sprintf("foo%d", i)), []byte(fmt.Sprintf("bar%d", i))
+			}
+			n := 10
+			for i := 0; i < n; i++ {
+				key, val := makeKeyVal(i)
+				err = db.Put(key, val)
+				require.NoError(err)
+			}
+			for i := 0; i < n; i++ {
+				key, val := makeKeyVal(i)
+				rval, err := db.Get(key)
+				require.NoError(err)
+				require.Equal(val, rval)
+			}
+			err = db.Close()
+			require.NoError(err)
+
+			// Corrupt the last inserted key
+			f, err := os.OpenFile(path.Join(testdir, "000000000.data"), os.O_RDWR, 0755)
+			require.NoError(err)
+			fi, err := f.Stat()
+			require.NoError(err)
+			err = f.Truncate(fi.Size() - 1)
+			require.NoError(err)
+			err = f.Close()
+			require.NoError(err)
+
+			db, err = Open(testdir, WithAutoRecovery(autoRecovery))
+			require.NoError(err)
+			defer db.Close()
+			// Check that all values but the last are still intact.
+			for i := 0; i < 9; i++ {
+				key, val := makeKeyVal(i)
+				rval, err := db.Get(key)
+				require.NoError(err)
+				require.Equal(val, rval)
+			}
+			// Check the index has no more keys than non-corrupted ones.
+			// i.e: all but the last one.
+			numKeys := 0
+			for range db.Keys() {
+				numKeys++
+			}
+			if !autoRecovery {
+				// We are opening without autorepair, and thus are
+				// in a corrupted state. The index isn't coherent with
+				// the datafile.
+				require.Equal(n, numKeys)
+				return
+			}
+
+			require.Equal(n-1, numKeys, "The index should have n-1 keys")
+
+			// Double-check explicitly the corrupted one isn't here.
+			// This check is redundant considering the last two checks,
+			// but doesn't hurt.
+			corrKey, _ := makeKeyVal(9)
+			_, err = db.Get(corrKey)
+			require.Equal(ErrKeyNotFound, err)
+		})
+	}
+}
+
 func TestReIndex(t *testing.T) {
 	assert := assert.New(t)