diff --git a/vendor/go.etcd.io/bbolt/db.go b/vendor/go.etcd.io/bbolt/db.go
new file mode 100644
index 0000000..622947d
--- /dev/null
+++ b/vendor/go.etcd.io/bbolt/db.go
@@ -0,0 +1,1398 @@
+package bbolt
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"runtime"
+	"sync"
+	"time"
+	"unsafe"
+
+	berrors "go.etcd.io/bbolt/errors"
+	"go.etcd.io/bbolt/internal/common"
+	fl "go.etcd.io/bbolt/internal/freelist"
+)
+
+// The time elapsed between consecutive file locking attempts.
+const flockRetryTimeout = 50 * time.Millisecond
+
+// FreelistType is the type of the freelist backend
+type FreelistType string
+
+// TODO(ahrtr): eventually we should (step by step)
+//  1. default to `FreelistMapType`;
+//  2. remove the `FreelistArrayType`, do not export `FreelistMapType`
+//     and remove field `FreelistType' from both `DB` and `Options`;
+const (
+	// FreelistArrayType indicates backend freelist type is array
+	FreelistArrayType = FreelistType("array")
+	// FreelistMapType indicates backend freelist type is hashmap
+	FreelistMapType = FreelistType("hashmap")
+)
+
+// DB represents a collection of buckets persisted to a file on disk.
+// All data access is performed through transactions which can be obtained through the DB.
+// All the functions on DB will return a ErrDatabaseNotOpen if accessed before Open() is called.
+type DB struct {
+	// Put `stats` at the first field to ensure it's 64-bit aligned. Note that
+	// the first word in an allocated struct can be relied upon to be 64-bit
+	// aligned. Refer to https://pkg.go.dev/sync/atomic#pkg-note-BUG. Also
+	// refer to discussion in https://github.com/etcd-io/bbolt/issues/577.
+	stats Stats
+
+	// When enabled, the database will perform a Check() after every commit.
+	// A panic is issued if the database is in an inconsistent state. This
+	// flag has a large performance impact so it should only be used for
+	// debugging purposes.
+	StrictMode bool
+
+	// Setting the NoSync flag will cause the database to skip fsync()
+	// calls after each commit. This can be useful when bulk loading data
+	// into a database and you can restart the bulk load in the event of
+	// a system failure or database corruption. Do not set this flag for
+	// normal use.
+	//
+	// If the package global IgnoreNoSync constant is true, this value is
+	// ignored.  See the comment on that constant for more details.
+	//
+	// THIS IS UNSAFE. PLEASE USE WITH CAUTION.
+	NoSync bool
+
+	// When true, skips syncing freelist to disk. This improves the database
+	// write performance under normal operation, but requires a full database
+	// re-sync during recovery.
+	NoFreelistSync bool
+
+	// FreelistType sets the backend freelist type. There are two options. Array which is simple but endures
+	// dramatic performance degradation if database is large and fragmentation in freelist is common.
+	// The alternative one is using hashmap, it is faster in almost all circumstances
+	// but it doesn't guarantee that it offers the smallest page id available. In normal case it is safe.
+	// The default type is array
+	FreelistType FreelistType
+
+	// When true, skips the truncate call when growing the database.
+	// Setting this to true is only safe on non-ext3/ext4 systems.
+	// Skipping truncation avoids preallocation of hard drive space and
+	// bypasses a truncate() and fsync() syscall on remapping.
+	//
+	// https://github.com/boltdb/bolt/issues/284
+	NoGrowSync bool
+
+	// When `true`, bbolt will always load the free pages when opening the DB.
+	// When opening db in write mode, this flag will always automatically
+	// set to `true`.
+	PreLoadFreelist bool
+
+	// If you want to read the entire database fast, you can set MmapFlag to
+	// syscall.MAP_POPULATE on Linux 2.6.23+ for sequential read-ahead.
+	MmapFlags int
+
+	// MaxBatchSize is the maximum size of a batch. Default value is
+	// copied from DefaultMaxBatchSize in Open.
+	//
+	// If <=0, disables batching.
+	//
+	// Do not change concurrently with calls to Batch.
+	MaxBatchSize int
+
+	// MaxBatchDelay is the maximum delay before a batch starts.
+	// Default value is copied from DefaultMaxBatchDelay in Open.
+	//
+	// If <=0, effectively disables batching.
+	//
+	// Do not change concurrently with calls to Batch.
+	MaxBatchDelay time.Duration
+
+	// AllocSize is the amount of space allocated when the database
+	// needs to create new pages. This is done to amortize the cost
+	// of truncate() and fsync() when growing the data file.
+	AllocSize int
+
+	// Mlock locks database file in memory when set to true.
+	// It prevents major page faults, however used memory can't be reclaimed.
+	//
+	// Supported only on Unix via mlock/munlock syscalls.
+	Mlock bool
+
+	logger Logger
+
+	path     string
+	openFile func(string, int, os.FileMode) (*os.File, error)
+	file     *os.File
+	// `dataref` isn't used at all on Windows, and the golangci-lint
+	// always fails on Windows platform.
+	//nolint
+	dataref  []byte // mmap'ed readonly, write throws SEGV
+	data     *[common.MaxMapSize]byte
+	datasz   int
+	meta0    *common.Meta
+	meta1    *common.Meta
+	pageSize int
+	opened   bool
+	rwtx     *Tx
+	txs      []*Tx
+
+	freelist     fl.Interface
+	freelistLoad sync.Once
+
+	pagePool sync.Pool
+
+	batchMu sync.Mutex
+	batch   *batch
+
+	rwlock   sync.Mutex   // Allows only one writer at a time.
+	metalock sync.Mutex   // Protects meta page access.
+	mmaplock sync.RWMutex // Protects mmap access during remapping.
+	statlock sync.RWMutex // Protects stats access.
+
+	ops struct {
+		writeAt func(b []byte, off int64) (n int, err error)
+	}
+
+	// Read only mode.
+	// When true, Update() and Begin(true) return ErrDatabaseReadOnly immediately.
+	readOnly bool
+}
+
+// Path returns the path to currently open database file.
+func (db *DB) Path() string {
+	return db.path
+}
+
+// GoString returns the Go string representation of the database.
+func (db *DB) GoString() string {
+	return fmt.Sprintf("bolt.DB{path:%q}", db.path)
+}
+
+// String returns the string representation of the database.
+func (db *DB) String() string {
+	return fmt.Sprintf("DB<%q>", db.path)
+}
+
+// Open creates and opens a database at the given path with a given file mode.
+// If the file does not exist then it will be created automatically with a given file mode.
+// Passing in nil options will cause Bolt to open the database with the default options.
+// Note: For read/write transactions, ensure the owner has write permission on the created/opened database file, e.g. 0600
+func Open(path string, mode os.FileMode, options *Options) (db *DB, err error) {
+	db = &DB{
+		opened: true,
+	}
+
+	// Set default options if no options are provided.
+	if options == nil {
+		options = DefaultOptions
+	}
+	db.NoSync = options.NoSync
+	db.NoGrowSync = options.NoGrowSync
+	db.MmapFlags = options.MmapFlags
+	db.NoFreelistSync = options.NoFreelistSync
+	db.PreLoadFreelist = options.PreLoadFreelist
+	db.FreelistType = options.FreelistType
+	db.Mlock = options.Mlock
+
+	// Set default values for later DB operations.
+	db.MaxBatchSize = common.DefaultMaxBatchSize
+	db.MaxBatchDelay = common.DefaultMaxBatchDelay
+	db.AllocSize = common.DefaultAllocSize
+
+	if options.Logger == nil {
+		db.logger = getDiscardLogger()
+	} else {
+		db.logger = options.Logger
+	}
+
+	lg := db.Logger()
+	if lg != discardLogger {
+		lg.Infof("Opening db file (%s) with mode %s and with options: %s", path, mode, options)
+		defer func() {
+			if err != nil {
+				lg.Errorf("Opening bbolt db (%s) failed: %v", path, err)
+			} else {
+				lg.Infof("Opening bbolt db (%s) successfully", path)
+			}
+		}()
+	}
+
+	flag := os.O_RDWR
+	if options.ReadOnly {
+		flag = os.O_RDONLY
+		db.readOnly = true
+	} else {
+		// always load free pages in write mode
+		db.PreLoadFreelist = true
+		flag |= os.O_CREATE
+	}
+
+	db.openFile = options.OpenFile
+	if db.openFile == nil {
+		db.openFile = os.OpenFile
+	}
+
+	// Open data file and separate sync handler for metadata writes.
+	if db.file, err = db.openFile(path, flag, mode); err != nil {
+		_ = db.close()
+		lg.Errorf("failed to open db file (%s): %v", path, err)
+		return nil, err
+	}
+	db.path = db.file.Name()
+
+	// Lock file so that other processes using Bolt in read-write mode cannot
+	// use the database  at the same time. This would cause corruption since
+	// the two processes would write meta pages and free pages separately.
+	// The database file is locked exclusively (only one process can grab the lock)
+	// if !options.ReadOnly.
+	// The database file is locked using the shared lock (more than one process may
+	// hold a lock at the same time) otherwise (options.ReadOnly is set).
+	if err = flock(db, !db.readOnly, options.Timeout); err != nil {
+		_ = db.close()
+		lg.Errorf("failed to lock db file (%s), readonly: %t, error: %v", path, db.readOnly, err)
+		return nil, err
+	}
+
+	// Default values for test hooks
+	db.ops.writeAt = db.file.WriteAt
+
+	if db.pageSize = options.PageSize; db.pageSize == 0 {
+		// Set the default page size to the OS page size.
+		db.pageSize = common.DefaultPageSize
+	}
+
+	// Initialize the database if it doesn't exist.
+	if info, statErr := db.file.Stat(); statErr != nil {
+		_ = db.close()
+		lg.Errorf("failed to get db file's stats (%s): %v", path, err)
+		return nil, statErr
+	} else if info.Size() == 0 {
+		// Initialize new files with meta pages.
+		if err = db.init(); err != nil {
+			// clean up file descriptor on initialization fail
+			_ = db.close()
+			lg.Errorf("failed to initialize db file (%s): %v", path, err)
+			return nil, err
+		}
+	} else {
+		// try to get the page size from the metadata pages
+		if db.pageSize, err = db.getPageSize(); err != nil {
+			_ = db.close()
+			lg.Errorf("failed to get page size from db file (%s): %v", path, err)
+			return nil, err
+		}
+	}
+
+	// Initialize page pool.
+	db.pagePool = sync.Pool{
+		New: func() interface{} {
+			return make([]byte, db.pageSize)
+		},
+	}
+
+	// Memory map the data file.
+	if err = db.mmap(options.InitialMmapSize); err != nil {
+		_ = db.close()
+		lg.Errorf("failed to map db file (%s): %v", path, err)
+		return nil, err
+	}
+
+	if db.PreLoadFreelist {
+		db.loadFreelist()
+	}
+
+	if db.readOnly {
+		return db, nil
+	}
+
+	// Flush freelist when transitioning from no sync to sync so
+	// NoFreelistSync unaware boltdb can open the db later.
+	if !db.NoFreelistSync && !db.hasSyncedFreelist() {
+		tx, txErr := db.Begin(true)
+		if tx != nil {
+			txErr = tx.Commit()
+		}
+		if txErr != nil {
+			lg.Errorf("starting readwrite transaction failed: %v", txErr)
+			_ = db.close()
+			return nil, txErr
+		}
+	}
+
+	// Mark the database as opened and return.
+	return db, nil
+}
+
+// getPageSize reads the pageSize from the meta pages. It tries
+// to read the first meta page firstly. If the first page is invalid,
+// then it tries to read the second page using the default page size.
+func (db *DB) getPageSize() (int, error) {
+	var (
+		meta0CanRead, meta1CanRead bool
+	)
+
+	// Read the first meta page to determine the page size.
+	if pgSize, canRead, err := db.getPageSizeFromFirstMeta(); err != nil {
+		// We cannot read the page size from page 0, but can read page 0.
+		meta0CanRead = canRead
+	} else {
+		return pgSize, nil
+	}
+
+	// Read the second meta page to determine the page size.
+	if pgSize, canRead, err := db.getPageSizeFromSecondMeta(); err != nil {
+		// We cannot read the page size from page 1, but can read page 1.
+		meta1CanRead = canRead
+	} else {
+		return pgSize, nil
+	}
+
+	// If we can't read the page size from both pages, but can read
+	// either page, then we assume it's the same as the OS or the one
+	// given, since that's how the page size was chosen in the first place.
+	//
+	// If both pages are invalid, and (this OS uses a different page size
+	// from what the database was created with or the given page size is
+	// different from what the database was created with), then we are out
+	// of luck and cannot access the database.
+	if meta0CanRead || meta1CanRead {
+		return db.pageSize, nil
+	}
+
+	return 0, berrors.ErrInvalid
+}
+
+// getPageSizeFromFirstMeta reads the pageSize from the first meta page
+func (db *DB) getPageSizeFromFirstMeta() (int, bool, error) {
+	var buf [0x1000]byte
+	var metaCanRead bool
+	if bw, err := db.file.ReadAt(buf[:], 0); err == nil && bw == len(buf) {
+		metaCanRead = true
+		if m := db.pageInBuffer(buf[:], 0).Meta(); m.Validate() == nil {
+			return int(m.PageSize()), metaCanRead, nil
+		}
+	}
+	return 0, metaCanRead, berrors.ErrInvalid
+}
+
+// getPageSizeFromSecondMeta reads the pageSize from the second meta page
+func (db *DB) getPageSizeFromSecondMeta() (int, bool, error) {
+	var (
+		fileSize    int64
+		metaCanRead bool
+	)
+
+	// get the db file size
+	if info, err := db.file.Stat(); err != nil {
+		return 0, metaCanRead, err
+	} else {
+		fileSize = info.Size()
+	}
+
+	// We need to read the second meta page, so we should skip the first page;
+	// but we don't know the exact page size yet, it's chicken & egg problem.
+	// The solution is to try all the possible page sizes, which starts from 1KB
+	// and until 16MB (1024<<14) or the end of the db file
+	//
+	// TODO: should we support larger page size?
+	for i := 0; i <= 14; i++ {
+		var buf [0x1000]byte
+		var pos int64 = 1024 << uint(i)
+		if pos >= fileSize-1024 {
+			break
+		}
+		bw, err := db.file.ReadAt(buf[:], pos)
+		if (err == nil && bw == len(buf)) || (err == io.EOF && int64(bw) == (fileSize-pos)) {
+			metaCanRead = true
+			if m := db.pageInBuffer(buf[:], 0).Meta(); m.Validate() == nil {
+				return int(m.PageSize()), metaCanRead, nil
+			}
+		}
+	}
+
+	return 0, metaCanRead, berrors.ErrInvalid
+}
+
+// loadFreelist reads the freelist if it is synced, or reconstructs it
+// by scanning the DB if it is not synced. It assumes there are no
+// concurrent accesses being made to the freelist.
+func (db *DB) loadFreelist() {
+	db.freelistLoad.Do(func() {
+		db.freelist = newFreelist(db.FreelistType)
+		if !db.hasSyncedFreelist() {
+			// Reconstruct free list by scanning the DB.
+			db.freelist.Init(db.freepages())
+		} else {
+			// Read free list from freelist page.
+			db.freelist.Read(db.page(db.meta().Freelist()))
+		}
+		db.stats.FreePageN = db.freelist.FreeCount()
+	})
+}
+
+func (db *DB) hasSyncedFreelist() bool {
+	return db.meta().Freelist() != common.PgidNoFreelist
+}
+
+func (db *DB) fileSize() (int, error) {
+	info, err := db.file.Stat()
+	if err != nil {
+		return 0, fmt.Errorf("file stat error: %w", err)
+	}
+	sz := int(info.Size())
+	if sz < db.pageSize*2 {
+		return 0, fmt.Errorf("file size too small %d", sz)
+	}
+	return sz, nil
+}
+
+// mmap opens the underlying memory-mapped file and initializes the meta references.
+// minsz is the minimum size that the new mmap can be.
+func (db *DB) mmap(minsz int) (err error) {
+	db.mmaplock.Lock()
+	defer db.mmaplock.Unlock()
+
+	lg := db.Logger()
+
+	// Ensure the size is at least the minimum size.
+	var fileSize int
+	fileSize, err = db.fileSize()
+	if err != nil {
+		lg.Errorf("getting file size failed: %w", err)
+		return err
+	}
+	var size = fileSize
+	if size < minsz {
+		size = minsz
+	}
+	size, err = db.mmapSize(size)
+	if err != nil {
+		lg.Errorf("getting map size failed: %w", err)
+		return err
+	}
+
+	if db.Mlock {
+		// Unlock db memory
+		if err := db.munlock(fileSize); err != nil {
+			return err
+		}
+	}
+
+	// Dereference all mmap references before unmapping.
+	if db.rwtx != nil {
+		db.rwtx.root.dereference()
+	}
+
+	// Unmap existing data before continuing.
+	if err = db.munmap(); err != nil {
+		return err
+	}
+
+	// Memory-map the data file as a byte slice.
+	// gofail: var mapError string
+	// return errors.New(mapError)
+	if err = mmap(db, size); err != nil {
+		lg.Errorf("[GOOS: %s, GOARCH: %s] mmap failed, size: %d, error: %v", runtime.GOOS, runtime.GOARCH, size, err)
+		return err
+	}
+
+	// Perform unmmap on any error to reset all data fields:
+	// dataref, data, datasz, meta0 and meta1.
+	defer func() {
+		if err != nil {
+			if unmapErr := db.munmap(); unmapErr != nil {
+				err = fmt.Errorf("%w; rollback unmap also failed: %v", err, unmapErr)
+			}
+		}
+	}()
+
+	if db.Mlock {
+		// Don't allow swapping of data file
+		if err := db.mlock(fileSize); err != nil {
+			return err
+		}
+	}
+
+	// Save references to the meta pages.
+	db.meta0 = db.page(0).Meta()
+	db.meta1 = db.page(1).Meta()
+
+	// Validate the meta pages. We only return an error if both meta pages fail
+	// validation, since meta0 failing validation means that it wasn't saved
+	// properly -- but we can recover using meta1. And vice-versa.
+	err0 := db.meta0.Validate()
+	err1 := db.meta1.Validate()
+	if err0 != nil && err1 != nil {
+		lg.Errorf("both meta pages are invalid, meta0: %v, meta1: %v", err0, err1)
+		return err0
+	}
+
+	return nil
+}
+
+func (db *DB) invalidate() {
+	db.dataref = nil
+	db.data = nil
+	db.datasz = 0
+
+	db.meta0 = nil
+	db.meta1 = nil
+}
+
+// munmap unmaps the data file from memory.
+func (db *DB) munmap() error {
+	defer db.invalidate()
+
+	// gofail: var unmapError string
+	// return errors.New(unmapError)
+	if err := munmap(db); err != nil {
+		db.Logger().Errorf("[GOOS: %s, GOARCH: %s] munmap failed, db.datasz: %d, error: %v", runtime.GOOS, runtime.GOARCH, db.datasz, err)
+		return fmt.Errorf("unmap error: %v", err.Error())
+	}
+
+	return nil
+}
+
+// mmapSize determines the appropriate size for the mmap given the current size
+// of the database. The minimum size is 32KB and doubles until it reaches 1GB.
+// Returns an error if the new mmap size is greater than the max allowed.
+func (db *DB) mmapSize(size int) (int, error) {
+	// Double the size from 32KB until 1GB.
+	for i := uint(15); i <= 30; i++ {
+		if size <= 1<<i {
+			return 1 << i, nil
+		}
+	}
+
+	// Verify the requested size is not above the maximum allowed.
+	if size > common.MaxMapSize {
+		return 0, errors.New("mmap too large")
+	}
+
+	// If larger than 1GB then grow by 1GB at a time.
+	sz := int64(size)
+	if remainder := sz % int64(common.MaxMmapStep); remainder > 0 {
+		sz += int64(common.MaxMmapStep) - remainder
+	}
+
+	// Ensure that the mmap size is a multiple of the page size.
+	// This should always be true since we're incrementing in MBs.
+	pageSize := int64(db.pageSize)
+	if (sz % pageSize) != 0 {
+		sz = ((sz / pageSize) + 1) * pageSize
+	}
+
+	// If we've exceeded the max size then only grow up to the max size.
+	if sz > common.MaxMapSize {
+		sz = common.MaxMapSize
+	}
+
+	return int(sz), nil
+}
+
+func (db *DB) munlock(fileSize int) error {
+	// gofail: var munlockError string
+	// return errors.New(munlockError)
+	if err := munlock(db, fileSize); err != nil {
+		db.Logger().Errorf("[GOOS: %s, GOARCH: %s] munlock failed, fileSize: %d, db.datasz: %d, error: %v", runtime.GOOS, runtime.GOARCH, fileSize, db.datasz, err)
+		return fmt.Errorf("munlock error: %v", err.Error())
+	}
+	return nil
+}
+
+func (db *DB) mlock(fileSize int) error {
+	// gofail: var mlockError string
+	// return errors.New(mlockError)
+	if err := mlock(db, fileSize); err != nil {
+		db.Logger().Errorf("[GOOS: %s, GOARCH: %s] mlock failed, fileSize: %d, db.datasz: %d, error: %v", runtime.GOOS, runtime.GOARCH, fileSize, db.datasz, err)
+		return fmt.Errorf("mlock error: %v", err.Error())
+	}
+	return nil
+}
+
+func (db *DB) mrelock(fileSizeFrom, fileSizeTo int) error {
+	if err := db.munlock(fileSizeFrom); err != nil {
+		return err
+	}
+	if err := db.mlock(fileSizeTo); err != nil {
+		return err
+	}
+	return nil
+}
+
+// init creates a new database file and initializes its meta pages.
+func (db *DB) init() error {
+	// Create two meta pages on a buffer.
+	buf := make([]byte, db.pageSize*4)
+	for i := 0; i < 2; i++ {
+		p := db.pageInBuffer(buf, common.Pgid(i))
+		p.SetId(common.Pgid(i))
+		p.SetFlags(common.MetaPageFlag)
+
+		// Initialize the meta page.
+		m := p.Meta()
+		m.SetMagic(common.Magic)
+		m.SetVersion(common.Version)
+		m.SetPageSize(uint32(db.pageSize))
+		m.SetFreelist(2)
+		m.SetRootBucket(common.NewInBucket(3, 0))
+		m.SetPgid(4)
+		m.SetTxid(common.Txid(i))
+		m.SetChecksum(m.Sum64())
+	}
+
+	// Write an empty freelist at page 3.
+	p := db.pageInBuffer(buf, common.Pgid(2))
+	p.SetId(2)
+	p.SetFlags(common.FreelistPageFlag)
+	p.SetCount(0)
+
+	// Write an empty leaf page at page 4.
+	p = db.pageInBuffer(buf, common.Pgid(3))
+	p.SetId(3)
+	p.SetFlags(common.LeafPageFlag)
+	p.SetCount(0)
+
+	// Write the buffer to our data file.
+	if _, err := db.ops.writeAt(buf, 0); err != nil {
+		db.Logger().Errorf("writeAt failed: %w", err)
+		return err
+	}
+	if err := fdatasync(db); err != nil {
+		db.Logger().Errorf("[GOOS: %s, GOARCH: %s] fdatasync failed: %w", runtime.GOOS, runtime.GOARCH, err)
+		return err
+	}
+
+	return nil
+}
+
+// Close releases all database resources.
+// It will block waiting for any open transactions to finish
+// before closing the database and returning.
+func (db *DB) Close() error {
+	db.rwlock.Lock()
+	defer db.rwlock.Unlock()
+
+	db.metalock.Lock()
+	defer db.metalock.Unlock()
+
+	db.mmaplock.Lock()
+	defer db.mmaplock.Unlock()
+
+	return db.close()
+}
+
+func (db *DB) close() error {
+	if !db.opened {
+		return nil
+	}
+
+	db.opened = false
+
+	db.freelist = nil
+
+	// Clear ops.
+	db.ops.writeAt = nil
+
+	var errs []error
+	// Close the mmap.
+	if err := db.munmap(); err != nil {
+		errs = append(errs, err)
+	}
+
+	// Close file handles.
+	if db.file != nil {
+		// No need to unlock read-only file.
+		if !db.readOnly {
+			// Unlock the file.
+			if err := funlock(db); err != nil {
+				errs = append(errs, fmt.Errorf("bolt.Close(): funlock error: %w", err))
+			}
+		}
+
+		// Close the file descriptor.
+		if err := db.file.Close(); err != nil {
+			errs = append(errs, fmt.Errorf("db file close: %w", err))
+		}
+		db.file = nil
+	}
+
+	db.path = ""
+
+	if len(errs) > 0 {
+		return errs[0]
+	}
+	return nil
+}
+
+// Begin starts a new transaction.
+// Multiple read-only transactions can be used concurrently but only one
+// write transaction can be used at a time. Starting multiple write transactions
+// will cause the calls to block and be serialized until the current write
+// transaction finishes.
+//
+// Transactions should not be dependent on one another. Opening a read
+// transaction and a write transaction in the same goroutine can cause the
+// writer to deadlock because the database periodically needs to re-mmap itself
+// as it grows and it cannot do that while a read transaction is open.
+//
+// If a long running read transaction (for example, a snapshot transaction) is
+// needed, you might want to set DB.InitialMmapSize to a large enough value
+// to avoid potential blocking of write transaction.
+//
+// IMPORTANT: You must close read-only transactions after you are finished or
+// else the database will not reclaim old pages.
+func (db *DB) Begin(writable bool) (t *Tx, err error) {
+	if lg := db.Logger(); lg != discardLogger {
+		lg.Debugf("Starting a new transaction [writable: %t]", writable)
+		defer func() {
+			if err != nil {
+				lg.Errorf("Starting a new transaction [writable: %t] failed: %v", writable, err)
+			} else {
+				lg.Debugf("Starting a new transaction [writable: %t] successfully", writable)
+			}
+		}()
+	}
+
+	if writable {
+		return db.beginRWTx()
+	}
+	return db.beginTx()
+}
+
+func (db *DB) Logger() Logger {
+	if db == nil || db.logger == nil {
+		return getDiscardLogger()
+	}
+	return db.logger
+}
+
+func (db *DB) beginTx() (*Tx, error) {
+	// Lock the meta pages while we initialize the transaction. We obtain
+	// the meta lock before the mmap lock because that's the order that the
+	// write transaction will obtain them.
+	db.metalock.Lock()
+
+	// Obtain a read-only lock on the mmap. When the mmap is remapped it will
+	// obtain a write lock so all transactions must finish before it can be
+	// remapped.
+	db.mmaplock.RLock()
+
+	// Exit if the database is not open yet.
+	if !db.opened {
+		db.mmaplock.RUnlock()
+		db.metalock.Unlock()
+		return nil, berrors.ErrDatabaseNotOpen
+	}
+
+	// Exit if the database is not correctly mapped.
+	if db.data == nil {
+		db.mmaplock.RUnlock()
+		db.metalock.Unlock()
+		return nil, berrors.ErrInvalidMapping
+	}
+
+	// Create a transaction associated with the database.
+	t := &Tx{}
+	t.init(db)
+
+	// Keep track of transaction until it closes.
+	db.txs = append(db.txs, t)
+	n := len(db.txs)
+	if db.freelist != nil {
+		db.freelist.AddReadonlyTXID(t.meta.Txid())
+	}
+
+	// Unlock the meta pages.
+	db.metalock.Unlock()
+
+	// Update the transaction stats.
+	db.statlock.Lock()
+	db.stats.TxN++
+	db.stats.OpenTxN = n
+	db.statlock.Unlock()
+
+	return t, nil
+}
+
+func (db *DB) beginRWTx() (*Tx, error) {
+	// If the database was opened with Options.ReadOnly, return an error.
+	if db.readOnly {
+		return nil, berrors.ErrDatabaseReadOnly
+	}
+
+	// Obtain writer lock. This is released by the transaction when it closes.
+	// This enforces only one writer transaction at a time.
+	db.rwlock.Lock()
+
+	// Once we have the writer lock then we can lock the meta pages so that
+	// we can set up the transaction.
+	db.metalock.Lock()
+	defer db.metalock.Unlock()
+
+	// Exit if the database is not open yet.
+	if !db.opened {
+		db.rwlock.Unlock()
+		return nil, berrors.ErrDatabaseNotOpen
+	}
+
+	// Exit if the database is not correctly mapped.
+	if db.data == nil {
+		db.rwlock.Unlock()
+		return nil, berrors.ErrInvalidMapping
+	}
+
+	// Create a transaction associated with the database.
+	t := &Tx{writable: true}
+	t.init(db)
+	db.rwtx = t
+	db.freelist.ReleasePendingPages()
+	return t, nil
+}
+
+// removeTx removes a transaction from the database.
+func (db *DB) removeTx(tx *Tx) {
+	// Release the read lock on the mmap.
+	db.mmaplock.RUnlock()
+
+	// Use the meta lock to restrict access to the DB object.
+	db.metalock.Lock()
+
+	// Remove the transaction.
+	for i, t := range db.txs {
+		if t == tx {
+			last := len(db.txs) - 1
+			db.txs[i] = db.txs[last]
+			db.txs[last] = nil
+			db.txs = db.txs[:last]
+			break
+		}
+	}
+	n := len(db.txs)
+	if db.freelist != nil {
+		db.freelist.RemoveReadonlyTXID(tx.meta.Txid())
+	}
+
+	// Unlock the meta pages.
+	db.metalock.Unlock()
+
+	// Merge statistics.
+	db.statlock.Lock()
+	db.stats.OpenTxN = n
+	db.stats.TxStats.add(&tx.stats)
+	db.statlock.Unlock()
+}
+
+// Update executes a function within the context of a read-write managed transaction.
+// If no error is returned from the function then the transaction is committed.
+// If an error is returned then the entire transaction is rolled back.
+// Any error that is returned from the function or returned from the commit is
+// returned from the Update() method.
+//
+// Attempting to manually commit or rollback within the function will cause a panic.
+func (db *DB) Update(fn func(*Tx) error) error {
+	t, err := db.Begin(true)
+	if err != nil {
+		return err
+	}
+
+	// Make sure the transaction rolls back in the event of a panic.
+	defer func() {
+		if t.db != nil {
+			t.rollback()
+		}
+	}()
+
+	// Mark as a managed tx so that the inner function cannot manually commit.
+	t.managed = true
+
+	// If an error is returned from the function then rollback and return error.
+	err = fn(t)
+	t.managed = false
+	if err != nil {
+		_ = t.Rollback()
+		return err
+	}
+
+	return t.Commit()
+}
+
+// View executes a function within the context of a managed read-only transaction.
+// Any error that is returned from the function is returned from the View() method.
+//
+// Attempting to manually rollback within the function will cause a panic.
+func (db *DB) View(fn func(*Tx) error) error {
+	t, err := db.Begin(false)
+	if err != nil {
+		return err
+	}
+
+	// Make sure the transaction rolls back in the event of a panic.
+	defer func() {
+		if t.db != nil {
+			t.rollback()
+		}
+	}()
+
+	// Mark as a managed tx so that the inner function cannot manually rollback.
+	t.managed = true
+
+	// If an error is returned from the function then pass it through.
+	err = fn(t)
+	t.managed = false
+	if err != nil {
+		_ = t.Rollback()
+		return err
+	}
+
+	return t.Rollback()
+}
+
+// Batch calls fn as part of a batch. It behaves similar to Update,
+// except:
+//
+// 1. concurrent Batch calls can be combined into a single Bolt
+// transaction.
+//
+// 2. the function passed to Batch may be called multiple times,
+// regardless of whether it returns error or not.
+//
+// This means that Batch function side effects must be idempotent and
+// take permanent effect only after a successful return is seen in
+// caller.
+//
+// The maximum batch size and delay can be adjusted with DB.MaxBatchSize
+// and DB.MaxBatchDelay, respectively.
+//
+// Batch is only useful when there are multiple goroutines calling it.
+func (db *DB) Batch(fn func(*Tx) error) error {
+	errCh := make(chan error, 1)
+
+	db.batchMu.Lock()
+	if (db.batch == nil) || (db.batch != nil && len(db.batch.calls) >= db.MaxBatchSize) {
+		// There is no existing batch, or the existing batch is full; start a new one.
+		db.batch = &batch{
+			db: db,
+		}
+		db.batch.timer = time.AfterFunc(db.MaxBatchDelay, db.batch.trigger)
+	}
+	db.batch.calls = append(db.batch.calls, call{fn: fn, err: errCh})
+	if len(db.batch.calls) >= db.MaxBatchSize {
+		// wake up batch, it's ready to run
+		go db.batch.trigger()
+	}
+	db.batchMu.Unlock()
+
+	err := <-errCh
+	if err == trySolo {
+		err = db.Update(fn)
+	}
+	return err
+}
+
+type call struct {
+	fn  func(*Tx) error
+	err chan<- error
+}
+
+type batch struct {
+	db    *DB
+	timer *time.Timer
+	start sync.Once
+	calls []call
+}
+
+// trigger runs the batch if it hasn't already been run.
+func (b *batch) trigger() {
+	b.start.Do(b.run)
+}
+
+// run performs the transactions in the batch and communicates results
+// back to DB.Batch.
+func (b *batch) run() {
+	b.db.batchMu.Lock()
+	b.timer.Stop()
+	// Make sure no new work is added to this batch, but don't break
+	// other batches.
+	if b.db.batch == b {
+		b.db.batch = nil
+	}
+	b.db.batchMu.Unlock()
+
+retry:
+	for len(b.calls) > 0 {
+		var failIdx = -1
+		err := b.db.Update(func(tx *Tx) error {
+			for i, c := range b.calls {
+				if err := safelyCall(c.fn, tx); err != nil {
+					failIdx = i
+					return err
+				}
+			}
+			return nil
+		})
+
+		if failIdx >= 0 {
+			// take the failing transaction out of the batch. it's
+			// safe to shorten b.calls here because db.batch no longer
+			// points to us, and we hold the mutex anyway.
+			c := b.calls[failIdx]
+			b.calls[failIdx], b.calls = b.calls[len(b.calls)-1], b.calls[:len(b.calls)-1]
+			// tell the submitter re-run it solo, continue with the rest of the batch
+			c.err <- trySolo
+			continue retry
+		}
+
+		// pass success, or bolt internal errors, to all callers
+		for _, c := range b.calls {
+			c.err <- err
+		}
+		break retry
+	}
+}
+
+// trySolo is a special sentinel error value used for signaling that a
+// transaction function should be re-run. It should never be seen by
+// callers.
+var trySolo = errors.New("batch function returned an error and should be re-run solo")
+
+type panicked struct {
+	reason interface{}
+}
+
+func (p panicked) Error() string {
+	if err, ok := p.reason.(error); ok {
+		return err.Error()
+	}
+	return fmt.Sprintf("panic: %v", p.reason)
+}
+
+func safelyCall(fn func(*Tx) error, tx *Tx) (err error) {
+	defer func() {
+		if p := recover(); p != nil {
+			err = panicked{p}
+		}
+	}()
+	return fn(tx)
+}
+
+// Sync executes fdatasync() against the database file handle.
+//
+// This is not necessary under normal operation, however, if you use NoSync
+// then it allows you to force the database file to sync against the disk.
+func (db *DB) Sync() (err error) {
+	if lg := db.Logger(); lg != discardLogger {
+		lg.Debugf("Syncing bbolt db (%s)", db.path)
+		defer func() {
+			if err != nil {
+				lg.Errorf("[GOOS: %s, GOARCH: %s] syncing bbolt db (%s) failed: %v", runtime.GOOS, runtime.GOARCH, db.path, err)
+			} else {
+				lg.Debugf("Syncing bbolt db (%s) successfully", db.path)
+			}
+		}()
+	}
+
+	return fdatasync(db)
+}
+
+// Stats retrieves ongoing performance stats for the database.
+// This is only updated when a transaction closes.
+func (db *DB) Stats() Stats {
+	db.statlock.RLock()
+	defer db.statlock.RUnlock()
+	return db.stats
+}
+
+// This is for internal access to the raw data bytes from the C cursor, use
+// carefully, or not at all.
+func (db *DB) Info() *Info {
+	common.Assert(db.data != nil, "database file isn't correctly mapped")
+	return &Info{uintptr(unsafe.Pointer(&db.data[0])), db.pageSize}
+}
+
+// page retrieves a page reference from the mmap based on the current page size.
+func (db *DB) page(id common.Pgid) *common.Page {
+	pos := id * common.Pgid(db.pageSize)
+	return (*common.Page)(unsafe.Pointer(&db.data[pos]))
+}
+
+// pageInBuffer retrieves a page reference from a given byte array based on the current page size.
+func (db *DB) pageInBuffer(b []byte, id common.Pgid) *common.Page {
+	return (*common.Page)(unsafe.Pointer(&b[id*common.Pgid(db.pageSize)]))
+}
+
+// meta retrieves the current meta page reference.
+func (db *DB) meta() *common.Meta {
+	// We have to return the meta with the highest txid which doesn't fail
+	// validation. Otherwise, we can cause errors when in fact the database is
+	// in a consistent state. metaA is the one with the higher txid.
+	metaA := db.meta0
+	metaB := db.meta1
+	if db.meta1.Txid() > db.meta0.Txid() {
+		metaA = db.meta1
+		metaB = db.meta0
+	}
+
+	// Use higher meta page if valid. Otherwise, fallback to previous, if valid.
+	if err := metaA.Validate(); err == nil {
+		return metaA
+	} else if err := metaB.Validate(); err == nil {
+		return metaB
+	}
+
+	// This should never be reached, because both meta1 and meta0 were validated
+	// on mmap() and we do fsync() on every write.
+	panic("bolt.DB.meta(): invalid meta pages")
+}
+
+// allocate returns a contiguous block of memory starting at a given page.
+func (db *DB) allocate(txid common.Txid, count int) (*common.Page, error) {
+	// Allocate a temporary buffer for the page.
+	var buf []byte
+	if count == 1 {
+		buf = db.pagePool.Get().([]byte)
+	} else {
+		buf = make([]byte, count*db.pageSize)
+	}
+	p := (*common.Page)(unsafe.Pointer(&buf[0]))
+	p.SetOverflow(uint32(count - 1))
+
+	// Use pages from the freelist if they are available.
+	p.SetId(db.freelist.Allocate(txid, count))
+	if p.Id() != 0 {
+		return p, nil
+	}
+
+	// Resize mmap() if we're at the end.
+	p.SetId(db.rwtx.meta.Pgid())
+	var minsz = int((p.Id()+common.Pgid(count))+1) * db.pageSize
+	if minsz >= db.datasz {
+		if err := db.mmap(minsz); err != nil {
+			return nil, fmt.Errorf("mmap allocate error: %s", err)
+		}
+	}
+
+	// Move the page id high water mark.
+	curPgid := db.rwtx.meta.Pgid()
+	db.rwtx.meta.SetPgid(curPgid + common.Pgid(count))
+
+	return p, nil
+}
+
+// grow grows the size of the database to the given sz.
+func (db *DB) grow(sz int) error {
+	// Ignore if the new size is less than available file size.
+	lg := db.Logger()
+	fileSize, err := db.fileSize()
+	if err != nil {
+		lg.Errorf("getting file size failed: %w", err)
+		return err
+	}
+	if sz <= fileSize {
+		return nil
+	}
+
+	// If the data is smaller than the alloc size then only allocate what's needed.
+	// Once it goes over the allocation size then allocate in chunks.
+	if db.datasz <= db.AllocSize {
+		sz = db.datasz
+	} else {
+		sz += db.AllocSize
+	}
+
+	// Truncate and fsync to ensure file size metadata is flushed.
+	// https://github.com/boltdb/bolt/issues/284
+	if !db.NoGrowSync && !db.readOnly {
+		if runtime.GOOS != "windows" {
+			// gofail: var resizeFileError string
+			// return errors.New(resizeFileError)
+			if err := db.file.Truncate(int64(sz)); err != nil {
+				lg.Errorf("[GOOS: %s, GOARCH: %s] truncating file failed, size: %d, db.datasz: %d, error: %v", runtime.GOOS, runtime.GOARCH, sz, db.datasz, err)
+				return fmt.Errorf("file resize error: %s", err)
+			}
+		}
+		if err := db.file.Sync(); err != nil {
+			lg.Errorf("[GOOS: %s, GOARCH: %s] syncing file failed, db.datasz: %d, error: %v", runtime.GOOS, runtime.GOARCH, db.datasz, err)
+			return fmt.Errorf("file sync error: %s", err)
+		}
+		if db.Mlock {
+			// unlock old file and lock new one
+			if err := db.mrelock(fileSize, sz); err != nil {
+				return fmt.Errorf("mlock/munlock error: %s", err)
+			}
+		}
+	}
+
+	return nil
+}
+
+func (db *DB) IsReadOnly() bool {
+	return db.readOnly
+}
+
+func (db *DB) freepages() []common.Pgid {
+	tx, err := db.beginTx()
+	defer func() {
+		err = tx.Rollback()
+		if err != nil {
+			panic("freepages: failed to rollback tx")
+		}
+	}()
+	if err != nil {
+		panic("freepages: failed to open read only tx")
+	}
+
+	reachable := make(map[common.Pgid]*common.Page)
+	nofreed := make(map[common.Pgid]bool)
+	ech := make(chan error)
+	go func() {
+		for e := range ech {
+			panic(fmt.Sprintf("freepages: failed to get all reachable pages (%v)", e))
+		}
+	}()
+	tx.recursivelyCheckBucket(&tx.root, reachable, nofreed, HexKVStringer(), ech)
+	close(ech)
+
+	// TODO: If check bucket reported any corruptions (ech) we shouldn't proceed to freeing the pages.
+
+	var fids []common.Pgid
+	for i := common.Pgid(2); i < db.meta().Pgid(); i++ {
+		if _, ok := reachable[i]; !ok {
+			fids = append(fids, i)
+		}
+	}
+	return fids
+}
+
+func newFreelist(freelistType FreelistType) fl.Interface {
+	if freelistType == FreelistMapType {
+		return fl.NewHashMapFreelist()
+	}
+	return fl.NewArrayFreelist()
+}
+
+// Options represents the options that can be set when opening a database.
+type Options struct {
+	// Timeout is the amount of time to wait to obtain a file lock.
+	// When set to zero it will wait indefinitely.
+	Timeout time.Duration
+
+	// Sets the DB.NoGrowSync flag before memory mapping the file.
+	NoGrowSync bool
+
+	// Do not sync freelist to disk. This improves the database write performance
+	// under normal operation, but requires a full database re-sync during recovery.
+	NoFreelistSync bool
+
+	// PreLoadFreelist sets whether to load the free pages when opening
+	// the db file. Note when opening db in write mode, bbolt will always
+	// load the free pages.
+	PreLoadFreelist bool
+
+	// FreelistType sets the backend freelist type. There are two options. Array which is simple but endures
+	// dramatic performance degradation if database is large and fragmentation in freelist is common.
+	// The alternative one is using hashmap, it is faster in almost all circumstances
+	// but it doesn't guarantee that it offers the smallest page id available. In normal case it is safe.
+	// The default type is array
+	FreelistType FreelistType
+
+	// Open database in read-only mode. Uses flock(..., LOCK_SH |LOCK_NB) to
+	// grab a shared lock (UNIX).
+	ReadOnly bool
+
+	// Sets the DB.MmapFlags flag before memory mapping the file.
+	MmapFlags int
+
+	// InitialMmapSize is the initial mmap size of the database
+	// in bytes. Read transactions won't block write transaction
+	// if the InitialMmapSize is large enough to hold database mmap
+	// size. (See DB.Begin for more information)
+	//
+	// If <=0, the initial map size is 0.
+	// If initialMmapSize is smaller than the previous database size,
+	// it takes no effect.
+	//
+	// Note: On Windows, due to platform limitations, the database file size
+	// will be immediately resized to match `InitialMmapSize` (aligned to page size)
+	// when the DB is opened. On non-Windows platforms, the file size will grow
+	// dynamically based on the actual amount of written data, regardless of `InitialMmapSize`.
+	// Refer to https://github.com/etcd-io/bbolt/issues/378#issuecomment-1378121966.
+	InitialMmapSize int
+
+	// PageSize overrides the default OS page size.
+	PageSize int
+
+	// NoSync sets the initial value of DB.NoSync. Normally this can just be
+	// set directly on the DB itself when returned from Open(), but this option
+	// is useful in APIs which expose Options but not the underlying DB.
+	NoSync bool
+
+	// OpenFile is used to open files. It defaults to os.OpenFile. This option
+	// is useful for writing hermetic tests.
+	OpenFile func(string, int, os.FileMode) (*os.File, error)
+
+	// Mlock locks database file in memory when set to true.
+	// It prevents potential page faults, however
+	// used memory can't be reclaimed. (UNIX only)
+	Mlock bool
+
+	// Logger is the logger used for bbolt.
+	Logger Logger
+}
+
+func (o *Options) String() string {
+	if o == nil {
+		return "{}"
+	}
+
+	return fmt.Sprintf("{Timeout: %s, NoGrowSync: %t, NoFreelistSync: %t, PreLoadFreelist: %t, FreelistType: %s, ReadOnly: %t, MmapFlags: %x, InitialMmapSize: %d, PageSize: %d, NoSync: %t, OpenFile: %p, Mlock: %t, Logger: %p}",
+		o.Timeout, o.NoGrowSync, o.NoFreelistSync, o.PreLoadFreelist, o.FreelistType, o.ReadOnly, o.MmapFlags, o.InitialMmapSize, o.PageSize, o.NoSync, o.OpenFile, o.Mlock, o.Logger)
+
+}
+
+// DefaultOptions represent the options used if nil options are passed into Open().
+// No timeout is used which will cause Bolt to wait indefinitely for a lock.
+var DefaultOptions = &Options{
+	Timeout:      0,
+	NoGrowSync:   false,
+	FreelistType: FreelistArrayType,
+}
+
+// Stats represents statistics about the database.
+type Stats struct {
+	// Put `TxStats` at the first field to ensure it's 64-bit aligned. Note
+	// that the first word in an allocated struct can be relied upon to be
+	// 64-bit aligned. Refer to https://pkg.go.dev/sync/atomic#pkg-note-BUG.
+	// Also refer to discussion in https://github.com/etcd-io/bbolt/issues/577.
+	TxStats TxStats // global, ongoing stats.
+
+	// Freelist stats
+	FreePageN     int // total number of free pages on the freelist
+	PendingPageN  int // total number of pending pages on the freelist
+	FreeAlloc     int // total bytes allocated in free pages
+	FreelistInuse int // total bytes used by the freelist
+
+	// Transaction stats
+	TxN     int // total number of started read transactions
+	OpenTxN int // number of currently open read transactions
+}
+
+// Sub calculates and returns the difference between two sets of database stats.
+// This is useful when obtaining stats at two different points and time and
+// you need the performance counters that occurred within that time span.
+func (s *Stats) Sub(other *Stats) Stats {
+	if other == nil {
+		return *s
+	}
+	var diff Stats
+	diff.FreePageN = s.FreePageN
+	diff.PendingPageN = s.PendingPageN
+	diff.FreeAlloc = s.FreeAlloc
+	diff.FreelistInuse = s.FreelistInuse
+	diff.TxN = s.TxN - other.TxN
+	diff.TxStats = s.TxStats.Sub(&other.TxStats)
+	return diff
+}
+
+type Info struct {
+	Data     uintptr
+	PageSize int
+}