tests: introduce powerfailure case

Signed-off-by: Wei Fu <fuweid89@gmail.com>

go.mod

@@ -3,6 +3,7 @@ module go.etcd.io/bbolt
 go 1.21
 
 require (
+	github.com/fuweid/go-dmflakey v0.0.0-20231120170452-3fb3c5f05920
 	github.com/spf13/cobra v1.8.0
 	github.com/spf13/pflag v1.0.5
 	github.com/stretchr/testify v1.8.4

go.sum

@@ -1,6 +1,8 @@
 github.com/cpuguy83/go-md2man/v2 v2.0.3/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/fuweid/go-dmflakey v0.0.0-20231120170452-3fb3c5f05920 h1:htgd4chS+39MRDlQIY3/sjiQiYk/30Zr2j5yPSSAga4=
+github.com/fuweid/go-dmflakey v0.0.0-20231120170452-3fb3c5f05920/go.mod h1:LyUyUu5fLT6AhjTmoztxGdgvFOTyA+3hU2kM92drr9M=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=

tests/failpoint/db_failpoint_test.go

@@ -1,12 +1,19 @@
 package failpoint
 
 import (
+	"bytes"
 	"fmt"
+	"os"
+	"os/exec"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 
+	"github.com/fuweid/go-dmflakey"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"golang.org/x/sys/unix"
 
 	bolt "go.etcd.io/bbolt"
 	"go.etcd.io/bbolt/errors"
@@ -155,3 +162,115 @@ func TestFailpoint_LackOfDiskSpace(t *testing.T) {
 	require.Error(t, err)
 	require.ErrorIs(t, err, errors.ErrTxClosed)
 }
+
+// TestRestartFromPowerFailure is to test data after unexpected power failure.
+func TestRestartFromPowerFailure(t *testing.T) {
+	flakey := initFlakeyDevice(t, "")
+	root := flakey.rootfs()
+
+	dbPath := filepath.Join(root, "boltdb")
+
+	args := []string{"bbolt", "bench",
+		"-work", // keep the database
+		"-path", dbPath,
+		"-count=1000000000",
+		"-batch-size=5", // separate total count into multiple truncation
+	}
+	cmd := exec.Command(args[0], args[1:]...)
+	logger := &bytes.Buffer{}
+	cmd.Stdout = logger
+	cmd.Stderr = logger
+
+	t.Logf("start %s", strings.Join(args, " "))
+	require.NoError(t, cmd.Start(), "args: %v", args)
+	time.Sleep(3 * time.Second)
+
+	t.Logf("simulate power failure")
+	cmd.Process.Kill()
+	require.Error(t, cmd.Wait())
+	require.NoError(t, flakey.powerFailure(""))
+	t.Logf("dump log:\n: %s", logger.String())
+
+	st, err := os.Stat(dbPath)
+	require.NoError(t, err)
+	t.Logf("db size: %d", st.Size())
+
+	t.Logf("verify data")
+	output, err := exec.Command("bbolt", "check", dbPath).CombinedOutput()
+	require.NoError(t, err, "bbolt check output: %s", string(output))
+}
+
+// initFlakeyDevice inits flakey device with ext4 filesystem.
+func initFlakeyDevice(t *testing.T, mntOpt string) *flakeyDevice {
+	imgDir := t.TempDir()
+	rootDir := t.TempDir()
+	fsType := dmflakey.FSTypeEXT4
+
+	flakey, err := dmflakey.InitFlakey("bbolt-failpoint", imgDir, fsType)
+	require.NoError(t, err, "init flakey device")
+	t.Cleanup(func() {
+		assert.NoError(t, flakey.Teardown())
+	})
+
+	err = unix.Mount(flakey.DevicePath(), rootDir, string(fsType), 0, mntOpt)
+	require.NoError(t, err, "init rootfs with flakey device")
+	t.Cleanup(func() {
+		assert.NoError(t, unmount(rootDir))
+	})
+
+	return &flakeyDevice{
+		fsType: fsType,
+		flakey: flakey,
+
+		rootDir: rootDir,
+	}
+}
+
+type flakeyDevice struct {
+	fsType dmflakey.FSType
+	flakey dmflakey.Flakey
+
+	rootDir string
+}
+
+// rootfs returns the rootfs where flakey device mounts.
+func (f *flakeyDevice) rootfs() string {
+	return f.rootDir
+}
+
+// powerFailure drops all the pending writes and remount the rootfs.
+func (f *flakeyDevice) powerFailure(mntOpt string) error {
+	if err := f.flakey.DropWrites(); err != nil {
+		return fmt.Errorf("failed to drop_writes: %w", err)
+	}
+
+	if err := unmount(f.rootDir); err != nil {
+		return fmt.Errorf("failed to unmount rootfs %s: %w", f.rootDir, err)
+	}
+
+	if err := f.flakey.AllowWrites(); err != nil {
+		return fmt.Errorf("failed to allow_writes: %w", err)
+	}
+
+	if err := unix.Mount(f.flakey.DevicePath(), f.rootDir, string(f.fsType), 0, mntOpt); err != nil {
+		return fmt.Errorf("failed to mount rootfs %s: %w", f.rootDir, err)
+	}
+	return nil
+}
+
+func unmount(target string) error {
+	for i := 0; i < 50; i++ {
+		if err := unix.Unmount(target, 0); err != nil {
+			switch err {
+			case unix.EBUSY:
+				time.Sleep(500 * time.Millisecond)
+				continue
+			case unix.EINVAL:
+			default:
+				return fmt.Errorf("failed to umount %s: %w", target, err)
+			}
+		}
+		return nil
+	}
+	return unix.EBUSY
+}