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Merge pull request #4784 from MichaelEischer/rework-backend-retries

Rework backend retries
This commit is contained in:
Michael Eischer 2024-05-24 20:29:54 +02:00 committed by GitHub
commit 16ef4d515b
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7 changed files with 198 additions and 49 deletions

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@ -9,7 +9,9 @@ downloading are now forcibly interrupted. This ensures that stuck requests are
retried after a short timeout.
Attempts to access a missing file or a truncated file will no longer be retried.
This avoids unnecessary retries in those cases.
This avoids unnecessary retries in those cases. All other backend requests are
retried for up to 15 minutes. This ensures that a temporarily interrupted network
connections can be tolerated.
If a download yields a corrupt file or blob, then the download will be retried once.
@ -26,3 +28,4 @@ https://github.com/restic/restic/issues/4515
https://github.com/restic/restic/issues/1523
https://github.com/restic/restic/pull/4520
https://github.com/restic/restic/pull/4800
https://github.com/restic/restic/pull/4784

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@ -416,12 +416,16 @@ func OpenRepository(ctx context.Context, opts GlobalOptions) (*repository.Reposi
}
report := func(msg string, err error, d time.Duration) {
Warnf("%v returned error, retrying after %v: %v\n", msg, d, err)
if d >= 0 {
Warnf("%v returned error, retrying after %v: %v\n", msg, d, err)
} else {
Warnf("%v failed: %v\n", msg, err)
}
}
success := func(msg string, retries int) {
Warnf("%v operation successful after %d retries\n", msg, retries)
}
be = retry.New(be, 10, report, success)
be = retry.New(be, 15*time.Minute, report, success)
// wrap backend if a test specified a hook
if opts.backendTestHook != nil {

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@ -18,9 +18,9 @@ import (
// backoff.
type Backend struct {
backend.Backend
MaxTries int
Report func(string, error, time.Duration)
Success func(string, int)
MaxElapsedTime time.Duration
Report func(string, error, time.Duration)
Success func(string, int)
failedLoads sync.Map
}
@ -32,32 +32,64 @@ var _ backend.Backend = &Backend{}
// backoff. report is called with a description and the error, if one occurred.
// success is called with the number of retries before a successful operation
// (it is not called if it succeeded on the first try)
func New(be backend.Backend, maxTries int, report func(string, error, time.Duration), success func(string, int)) *Backend {
func New(be backend.Backend, maxElapsedTime time.Duration, report func(string, error, time.Duration), success func(string, int)) *Backend {
return &Backend{
Backend: be,
MaxTries: maxTries,
Report: report,
Success: success,
Backend: be,
MaxElapsedTime: maxElapsedTime,
Report: report,
Success: success,
}
}
// retryNotifyErrorWithSuccess is an extension of backoff.RetryNotify with notification of success after an error.
// success is NOT notified on the first run of operation (only after an error).
func retryNotifyErrorWithSuccess(operation backoff.Operation, b backoff.BackOff, notify backoff.Notify, success func(retries int)) error {
var operationWrapper backoff.Operation
if success == nil {
return backoff.RetryNotify(operation, b, notify)
}
retries := 0
operationWrapper := func() error {
err := operation()
if err != nil {
retries++
} else if retries > 0 {
success(retries)
operationWrapper = operation
} else {
retries := 0
operationWrapper = func() error {
err := operation()
if err != nil {
retries++
} else if retries > 0 {
success(retries)
}
return err
}
return err
}
return backoff.RetryNotify(operationWrapper, b, notify)
err := backoff.RetryNotify(operationWrapper, b, notify)
if err != nil && notify != nil {
// log final error
notify(err, -1)
}
return err
}
func withRetryAtLeastOnce(delegate *backoff.ExponentialBackOff) *retryAtLeastOnce {
return &retryAtLeastOnce{delegate: delegate}
}
type retryAtLeastOnce struct {
delegate *backoff.ExponentialBackOff
numTries uint64
}
func (b *retryAtLeastOnce) NextBackOff() time.Duration {
delay := b.delegate.NextBackOff()
b.numTries++
if b.numTries == 1 && b.delegate.Stop == delay {
return b.delegate.InitialInterval
}
return delay
}
func (b *retryAtLeastOnce) Reset() {
b.numTries = 0
b.delegate.Reset()
}
var fastRetries = false
@ -74,9 +106,25 @@ func (be *Backend) retry(ctx context.Context, msg string, f func() error) error
}
bo := backoff.NewExponentialBackOff()
bo.MaxElapsedTime = be.MaxElapsedTime
if feature.Flag.Enabled(feature.BackendErrorRedesign) {
bo.InitialInterval = 1 * time.Second
bo.Multiplier = 2
}
if fastRetries {
// speed up integration tests
bo.InitialInterval = 1 * time.Millisecond
maxElapsedTime := 200 * time.Millisecond
if bo.MaxElapsedTime > maxElapsedTime {
bo.MaxElapsedTime = maxElapsedTime
}
}
var b backoff.BackOff = withRetryAtLeastOnce(bo)
if !feature.Flag.Enabled(feature.BackendErrorRedesign) {
// deprecated behavior
b = backoff.WithMaxRetries(b, 10)
}
err := retryNotifyErrorWithSuccess(
@ -89,7 +137,7 @@ func (be *Backend) retry(ctx context.Context, msg string, f func() error) error
}
return err
},
backoff.WithContext(backoff.WithMaxRetries(bo, uint64(be.MaxTries)), ctx),
backoff.WithContext(b, ctx),
func(err error, d time.Duration) {
if be.Report != nil {
be.Report(msg, err, d)

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@ -193,8 +193,9 @@ func TestBackendListRetryErrorBackend(t *testing.T) {
}
TestFastRetries(t)
const maxRetries = 2
retryBackend := New(be, maxRetries, nil, nil)
const maxElapsedTime = 10 * time.Millisecond
now := time.Now()
retryBackend := New(be, maxElapsedTime, nil, nil)
var listed []string
err := retryBackend.List(context.TODO(), backend.PackFile, func(fi backend.FileInfo) error {
@ -207,8 +208,9 @@ func TestBackendListRetryErrorBackend(t *testing.T) {
t.Fatalf("wrong error returned, want %v, got %v", ErrBackendTest, err)
}
if retries != maxRetries+1 {
t.Fatalf("List was called %d times, wanted %v", retries, maxRetries+1)
duration := time.Since(now)
if duration > 100*time.Millisecond {
t.Fatalf("list retries took %v, expected at most 10ms", duration)
}
test.Equals(t, names[:2], listed)
@ -327,7 +329,7 @@ func TestBackendLoadCircuitBreaker(t *testing.T) {
// trip the circuit breaker for file "other"
err := retryBackend.Load(context.TODO(), backend.Handle{Name: "other"}, 0, 0, nilRd)
test.Equals(t, otherError, err, "unexpected error")
test.Equals(t, 3, attempt)
test.Equals(t, 2, attempt)
attempt = 0
err = retryBackend.Load(context.TODO(), backend.Handle{Name: "other"}, 0, 0, nilRd)
@ -407,7 +409,7 @@ func TestBackendRetryPermanent(t *testing.T) {
return errors.New("something")
})
test.Assert(t, !be.IsPermanentErrorFn(err), "error unexpectedly considered permanent %v", err)
test.Equals(t, 3, attempt)
test.Equals(t, 2, attempt)
}
@ -497,3 +499,64 @@ func TestNotifyWithSuccessIsCalled(t *testing.T) {
t.Fatalf("Success should have been called only once, but was called %d times instead", successCalled)
}
}
func TestNotifyWithSuccessFinalError(t *testing.T) {
operation := func() error {
return errors.New("expected error in test")
}
notifyCalled := 0
notify := func(error, time.Duration) {
notifyCalled++
}
successCalled := 0
success := func(retries int) {
successCalled++
}
err := retryNotifyErrorWithSuccess(operation, backoff.WithMaxRetries(&backoff.ZeroBackOff{}, 5), notify, success)
test.Assert(t, err.Error() == "expected error in test", "wrong error message %v", err)
test.Equals(t, 6, notifyCalled, "notify should have been called 6 times")
test.Equals(t, 0, successCalled, "success should not have been called")
}
type testClock struct {
Time time.Time
}
func (c *testClock) Now() time.Time {
return c.Time
}
func TestRetryAtLeastOnce(t *testing.T) {
expBackOff := backoff.NewExponentialBackOff()
expBackOff.InitialInterval = 500 * time.Millisecond
expBackOff.RandomizationFactor = 0
expBackOff.MaxElapsedTime = 5 * time.Second
expBackOff.Multiplier = 2 // guarantee numerical stability
clock := &testClock{Time: time.Now()}
expBackOff.Clock = clock
expBackOff.Reset()
retry := withRetryAtLeastOnce(expBackOff)
// expire backoff
clock.Time = clock.Time.Add(10 * time.Second)
delay := retry.NextBackOff()
test.Equals(t, expBackOff.InitialInterval, delay, "must retry at least once")
delay = retry.NextBackOff()
test.Equals(t, expBackOff.Stop, delay, "must not retry more than once")
// test reset behavior
retry.Reset()
test.Equals(t, uint64(0), retry.numTries, "numTries should be reset to 0")
// Verify that after reset, NextBackOff returns the initial interval again
delay = retry.NextBackOff()
test.Equals(t, expBackOff.InitialInterval, delay, "retries must work after reset")
delay = retry.NextBackOff()
test.Equals(t, expBackOff.InitialInterval*time.Duration(expBackOff.Multiplier), delay, "retries must work after reset")
}

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@ -132,7 +132,7 @@ func (l *locker) refreshLocks(ctx context.Context, backend backend.Backend, lock
// remove the lock from the repo
debug.Log("unlocking repository with lock %v", lock)
if err := lock.Unlock(); err != nil {
if err := lock.Unlock(ctx); err != nil {
debug.Log("error while unlocking: %v", err)
logger("error while unlocking: %v", err)
}

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@ -17,6 +17,10 @@ import (
"github.com/restic/restic/internal/debug"
)
// UnlockCancelDelay bounds the duration how long lock cleanup operations will wait
// if the passed in context was canceled.
const UnlockCancelDelay time.Duration = 1 * time.Minute
// Lock represents a process locking the repository for an operation.
//
// There are two types of locks: exclusive and non-exclusive. There may be many
@ -136,7 +140,7 @@ func newLock(ctx context.Context, repo Unpacked, excl bool) (*Lock, error) {
time.Sleep(waitBeforeLockCheck)
if err = lock.checkForOtherLocks(ctx); err != nil {
_ = lock.Unlock()
_ = lock.Unlock(ctx)
return nil, err
}
@ -220,12 +224,15 @@ func (l *Lock) createLock(ctx context.Context) (ID, error) {
}
// Unlock removes the lock from the repository.
func (l *Lock) Unlock() error {
func (l *Lock) Unlock(ctx context.Context) error {
if l == nil || l.lockID == nil {
return nil
}
return l.repo.RemoveUnpacked(context.TODO(), LockFile, *l.lockID)
ctx, cancel := delayedCancelContext(ctx, UnlockCancelDelay)
defer cancel()
return l.repo.RemoveUnpacked(ctx, LockFile, *l.lockID)
}
var StaleLockTimeout = 30 * time.Minute
@ -266,6 +273,23 @@ func (l *Lock) Stale() bool {
return false
}
func delayedCancelContext(parentCtx context.Context, delay time.Duration) (context.Context, context.CancelFunc) {
ctx, cancel := context.WithCancel(context.Background())
go func() {
select {
case <-parentCtx.Done():
case <-ctx.Done():
return
}
time.Sleep(delay)
cancel()
}()
return ctx, cancel
}
// Refresh refreshes the lock by creating a new file in the backend with a new
// timestamp. Afterwards the old lock is removed.
func (l *Lock) Refresh(ctx context.Context) error {
@ -285,7 +309,10 @@ func (l *Lock) Refresh(ctx context.Context) error {
oldLockID := l.lockID
l.lockID = &id
return l.repo.RemoveUnpacked(context.TODO(), LockFile, *oldLockID)
ctx, cancel := delayedCancelContext(ctx, UnlockCancelDelay)
defer cancel()
return l.repo.RemoveUnpacked(ctx, LockFile, *oldLockID)
}
// RefreshStaleLock is an extended variant of Refresh that can also refresh stale lock files.
@ -312,15 +339,19 @@ func (l *Lock) RefreshStaleLock(ctx context.Context) error {
time.Sleep(waitBeforeLockCheck)
exists, err = l.checkExistence(ctx)
ctx, cancel := delayedCancelContext(ctx, UnlockCancelDelay)
defer cancel()
if err != nil {
// cleanup replacement lock
_ = l.repo.RemoveUnpacked(context.TODO(), LockFile, id)
_ = l.repo.RemoveUnpacked(ctx, LockFile, id)
return err
}
if !exists {
// cleanup replacement lock
_ = l.repo.RemoveUnpacked(context.TODO(), LockFile, id)
_ = l.repo.RemoveUnpacked(ctx, LockFile, id)
return ErrRemovedLock
}
@ -331,7 +362,7 @@ func (l *Lock) RefreshStaleLock(ctx context.Context) error {
oldLockID := l.lockID
l.lockID = &id
return l.repo.RemoveUnpacked(context.TODO(), LockFile, *oldLockID)
return l.repo.RemoveUnpacked(ctx, LockFile, *oldLockID)
}
func (l *Lock) checkExistence(ctx context.Context) (bool, error) {

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@ -22,7 +22,7 @@ func TestLock(t *testing.T) {
lock, err := restic.NewLock(context.TODO(), repo)
rtest.OK(t, err)
rtest.OK(t, lock.Unlock())
rtest.OK(t, lock.Unlock(context.TODO()))
}
func TestDoubleUnlock(t *testing.T) {
@ -32,9 +32,9 @@ func TestDoubleUnlock(t *testing.T) {
lock, err := restic.NewLock(context.TODO(), repo)
rtest.OK(t, err)
rtest.OK(t, lock.Unlock())
rtest.OK(t, lock.Unlock(context.TODO()))
err = lock.Unlock()
err = lock.Unlock(context.TODO())
rtest.Assert(t, err != nil,
"double unlock didn't return an error, got %v", err)
}
@ -49,8 +49,8 @@ func TestMultipleLock(t *testing.T) {
lock2, err := restic.NewLock(context.TODO(), repo)
rtest.OK(t, err)
rtest.OK(t, lock1.Unlock())
rtest.OK(t, lock2.Unlock())
rtest.OK(t, lock1.Unlock(context.TODO()))
rtest.OK(t, lock2.Unlock(context.TODO()))
}
type failLockLoadingBackend struct {
@ -75,7 +75,7 @@ func TestMultipleLockFailure(t *testing.T) {
_, err = restic.NewLock(context.TODO(), repo)
rtest.Assert(t, err != nil, "unreadable lock file did not result in an error")
rtest.OK(t, lock1.Unlock())
rtest.OK(t, lock1.Unlock(context.TODO()))
}
func TestLockExclusive(t *testing.T) {
@ -83,7 +83,7 @@ func TestLockExclusive(t *testing.T) {
elock, err := restic.NewExclusiveLock(context.TODO(), repo)
rtest.OK(t, err)
rtest.OK(t, elock.Unlock())
rtest.OK(t, elock.Unlock(context.TODO()))
}
func TestLockOnExclusiveLockedRepo(t *testing.T) {
@ -99,8 +99,8 @@ func TestLockOnExclusiveLockedRepo(t *testing.T) {
rtest.Assert(t, restic.IsAlreadyLocked(err),
"create normal lock with exclusively locked repo didn't return the correct error")
rtest.OK(t, lock.Unlock())
rtest.OK(t, elock.Unlock())
rtest.OK(t, lock.Unlock(context.TODO()))
rtest.OK(t, elock.Unlock(context.TODO()))
}
func TestExclusiveLockOnLockedRepo(t *testing.T) {
@ -116,8 +116,8 @@ func TestExclusiveLockOnLockedRepo(t *testing.T) {
rtest.Assert(t, restic.IsAlreadyLocked(err),
"create normal lock with exclusively locked repo didn't return the correct error")
rtest.OK(t, lock.Unlock())
rtest.OK(t, elock.Unlock())
rtest.OK(t, lock.Unlock(context.TODO()))
rtest.OK(t, elock.Unlock(context.TODO()))
}
func createFakeLock(repo restic.SaverUnpacked, t time.Time, pid int) (restic.ID, error) {
@ -296,7 +296,7 @@ func testLockRefresh(t *testing.T, refresh func(lock *restic.Lock) error) {
rtest.OK(t, err)
rtest.Assert(t, lock2.Time.After(time0),
"expected a later timestamp after lock refresh")
rtest.OK(t, lock.Unlock())
rtest.OK(t, lock.Unlock(context.TODO()))
}
func TestLockRefresh(t *testing.T) {