rclone/cmd/bisync/march.go
nielash 4025f42bd9 bisync: Graceful Shutdown, --recover from interruptions without --resync - fixes #7470
Before this change, bisync had no mechanism to gracefully cancel a sync early
and exit in a clean state. Additionally, there was no way to recover on the
next run -- any interruption at all would cause bisync to require a --resync,
which made  bisync more difficult to use as a scheduled background process.

This change introduces a "Graceful Shutdown" mode and --recover flag to
robustly recover from even un-graceful shutdowns.

If --recover is set, in the event of a sudden interruption or other un-graceful
shutdown, bisync will attempt to automatically recover on the next run, instead
of requiring --resync. Bisync is able to recover robustly by keeping one
"backup" listing at all times, representing the state of both paths after the
last known successful sync. Bisync can then compare the current state with this
snapshot to determine which changes it needs to retry. Changes that were synced
after this snapshot (during the run that was later interrupted) will appear to
bisync as if they are "new or changed on both sides", but in most cases this is
not a problem, as bisync will simply do its usual "equality check" and learn
that no action needs to be taken on these files, since they are already
identical on both sides.

In the rare event that a file is synced successfully during a run that later
aborts, and then that same file changes AGAIN before the next run, bisync will
think it is a sync conflict, and handle it accordingly. (From bisync's
perspective, the file has changed on both sides since the last trusted sync,
and the files on either side are not currently identical.) Therefore, --recover
carries with it a slightly increased chance of having conflicts -- though in
practice this is pretty rare, as the conditions required to cause it are quite
specific. This risk can be reduced by using bisync's "Graceful Shutdown" mode
(triggered by sending SIGINT or Ctrl+C), when you have the choice, instead of
forcing a sudden termination.

--recover and --resilient are similar, but distinct -- the main difference is
that --resilient is about _retrying_, while --recover is about _recovering_.
Most users will probably want both. --resilient allows retrying when bisync has
chosen to abort itself due to safety features such as failing --check-access or
detecting a filter change. --resilient does not cover external interruptions
such as a user shutting down their computer in the middle of a sync -- that is
what --recover is for.

"Graceful Shutdown" mode is activated by sending SIGINT or pressing Ctrl+C
during a run. Once triggered, bisync will use best efforts to exit cleanly
before the timer runs out. If bisync is in the middle of transferring files, it
will attempt to cleanly empty its queue by finishing what it has started but
not taking more. If it cannot do so within 30 seconds, it will cancel the
in-progress transfers at that point and then give itself a maximum of 60
seconds to wrap up, save its state for next time, and exit. With the -vP flags
you will see constant status updates and a final confirmation of whether or not
the graceful shutdown was successful.

At any point during the "Graceful Shutdown" sequence, a second SIGINT or Ctrl+C
will trigger an immediate, un-graceful exit, which will leave things in a
messier state. Usually a robust recovery will still be possible if using
--recover mode, otherwise you will need to do a --resync.

If you plan to use Graceful Shutdown mode, it is recommended to use --resilient
and --recover, and it is important to NOT use --inplace, otherwise you risk
leaving partially-written files on one side, which may be confused for real
files on the next run. Note also that in the event of an abrupt interruption, a
lock file will be left behind to block concurrent runs. You will need to delete
it before you can proceed with the next run (or wait for it to expire on its
own, if using --max-lock.)
2024-01-20 16:31:28 -05:00

248 lines
6.0 KiB
Go

package bisync
import (
"context"
"sync"
"time"
"github.com/rclone/rclone/fs"
"github.com/rclone/rclone/fs/accounting"
"github.com/rclone/rclone/fs/filter"
"github.com/rclone/rclone/fs/hash"
"github.com/rclone/rclone/fs/march"
)
var ls1 = newFileList()
var ls2 = newFileList()
var err error
var firstErr error
var marchAliasLock sync.Mutex
var marchLsLock sync.Mutex
var marchErrLock sync.Mutex
var marchCtx context.Context
func (b *bisyncRun) makeMarchListing(ctx context.Context) (*fileList, *fileList, error) {
ci := fs.GetConfig(ctx)
marchCtx = ctx
b.setupListing()
fs.Debugf(b, "starting to march!")
// set up a march over fdst (Path2) and fsrc (Path1)
m := &march.March{
Ctx: ctx,
Fdst: b.fs2,
Fsrc: b.fs1,
Dir: "",
NoTraverse: false,
Callback: b,
DstIncludeAll: false,
NoCheckDest: false,
NoUnicodeNormalization: ci.NoUnicodeNormalization,
}
err = m.Run(ctx)
fs.Debugf(b, "march completed. err: %v", err)
if err == nil {
err = firstErr
}
if err != nil {
b.handleErr("march", "error during march", err, true, true)
b.abort = true
return ls1, ls2, err
}
// save files
if b.opt.Compare.DownloadHash && ls1.hash == hash.None {
ls1.hash = hash.MD5
}
if b.opt.Compare.DownloadHash && ls2.hash == hash.None {
ls2.hash = hash.MD5
}
err = ls1.save(ctx, b.newListing1)
b.handleErr(ls1, "error saving ls1 from march", err, true, true)
err = ls2.save(ctx, b.newListing2)
b.handleErr(ls2, "error saving ls2 from march", err, true, true)
return ls1, ls2, err
}
// SrcOnly have an object which is on path1 only
func (b *bisyncRun) SrcOnly(o fs.DirEntry) (recurse bool) {
fs.Debugf(o, "path1 only")
b.parse(o, true)
return isDir(o)
}
// DstOnly have an object which is on path2 only
func (b *bisyncRun) DstOnly(o fs.DirEntry) (recurse bool) {
fs.Debugf(o, "path2 only")
b.parse(o, false)
return isDir(o)
}
// Match is called when object exists on both path1 and path2 (whether equal or not)
func (b *bisyncRun) Match(ctx context.Context, o2, o1 fs.DirEntry) (recurse bool) {
fs.Debugf(o1, "both path1 and path2")
marchAliasLock.Lock()
b.aliases.Add(o1.Remote(), o2.Remote())
marchAliasLock.Unlock()
b.parse(o1, true)
b.parse(o2, false)
return isDir(o1)
}
func isDir(e fs.DirEntry) bool {
switch x := e.(type) {
case fs.Object:
fs.Debugf(x, "is Object")
return false
case fs.Directory:
fs.Debugf(x, "is Dir")
return true
default:
fs.Debugf(e, "is unknown")
}
return false
}
func (b *bisyncRun) parse(e fs.DirEntry, isPath1 bool) {
switch x := e.(type) {
case fs.Object:
b.ForObject(x, isPath1)
case fs.Directory:
if b.opt.CreateEmptySrcDirs {
b.ForDir(x, isPath1)
}
default:
fs.Debugf(e, "is unknown")
}
}
func (b *bisyncRun) setupListing() {
ls1 = newFileList()
ls2 = newFileList()
// note that --ignore-listing-checksum is different from --ignore-checksum
// and we already checked it when we set b.opt.Compare.HashType1 and 2
ls1.hash = b.opt.Compare.HashType1
ls2.hash = b.opt.Compare.HashType2
}
func (b *bisyncRun) ForObject(o fs.Object, isPath1 bool) {
tr := accounting.Stats(marchCtx).NewCheckingTransfer(o, "listing file - "+whichPath(isPath1))
defer func() {
tr.Done(marchCtx, nil)
}()
var (
hashVal string
hashErr error
)
ls := whichLs(isPath1)
hashType := ls.hash
if hashType != hash.None {
hashVal, hashErr = o.Hash(marchCtx, hashType)
marchErrLock.Lock()
if firstErr == nil {
firstErr = hashErr
}
marchErrLock.Unlock()
}
hashVal, hashErr = tryDownloadHash(marchCtx, o, hashVal)
marchErrLock.Lock()
if firstErr == nil {
firstErr = hashErr
}
if firstErr != nil {
b.handleErr(hashType, "error hashing during march", firstErr, false, true)
}
marchErrLock.Unlock()
var modtime time.Time
if b.opt.Compare.Modtime {
modtime = o.ModTime(marchCtx).In(TZ)
}
id := "" // TODO: ID(o)
flags := "-" // "-" for a file and "d" for a directory
marchLsLock.Lock()
ls.put(o.Remote(), o.Size(), modtime, hashVal, id, flags)
marchLsLock.Unlock()
}
func (b *bisyncRun) ForDir(o fs.Directory, isPath1 bool) {
tr := accounting.Stats(marchCtx).NewCheckingTransfer(o, "listing dir - "+whichPath(isPath1))
defer func() {
tr.Done(marchCtx, nil)
}()
ls := whichLs(isPath1)
var modtime time.Time
if b.opt.Compare.Modtime {
modtime = o.ModTime(marchCtx).In(TZ)
}
id := "" // TODO
flags := "d" // "-" for a file and "d" for a directory
marchLsLock.Lock()
ls.put(o.Remote(), -1, modtime, "", id, flags)
marchLsLock.Unlock()
}
func whichLs(isPath1 bool) *fileList {
ls := ls1
if !isPath1 {
ls = ls2
}
return ls
}
func whichPath(isPath1 bool) string {
s := "Path1"
if !isPath1 {
s = "Path2"
}
return s
}
func (b *bisyncRun) findCheckFiles(ctx context.Context) (*fileList, *fileList, error) {
ctxCheckFile, filterCheckFile := filter.AddConfig(ctx)
b.handleErr(b.opt.CheckFilename, "error adding CheckFilename to filter", filterCheckFile.Add(true, b.opt.CheckFilename), true, true)
b.handleErr(b.opt.CheckFilename, "error adding ** exclusion to filter", filterCheckFile.Add(false, "**"), true, true)
ci := fs.GetConfig(ctxCheckFile)
marchCtx = ctxCheckFile
b.setupListing()
fs.Debugf(b, "starting to march!")
// set up a march over fdst (Path2) and fsrc (Path1)
m := &march.March{
Ctx: ctxCheckFile,
Fdst: b.fs2,
Fsrc: b.fs1,
Dir: "",
NoTraverse: false,
Callback: b,
DstIncludeAll: false,
NoCheckDest: false,
NoUnicodeNormalization: ci.NoUnicodeNormalization,
}
err = m.Run(ctxCheckFile)
fs.Debugf(b, "march completed. err: %v", err)
if err == nil {
err = firstErr
}
if err != nil {
b.handleErr("march", "error during findCheckFiles", err, true, true)
b.abort = true
}
return ls1, ls2, err
}
// ID returns the ID of the Object if known, or "" if not
func ID(o fs.Object) string {
do, ok := o.(fs.IDer)
if !ok {
return ""
}
return do.ID()
}