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112 lines
3 KiB
Go
112 lines
3 KiB
Go
package backend
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import (
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"context"
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"fmt"
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"io"
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"time"
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"github.com/cenkalti/backoff"
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"github.com/restic/restic/internal/debug"
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"github.com/restic/restic/internal/errors"
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"github.com/restic/restic/internal/restic"
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)
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// RetryBackend retries operations on the backend in case of an error with a
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// backoff.
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type RetryBackend struct {
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restic.Backend
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MaxTries int
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Report func(string, error, time.Duration)
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}
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// statically ensure that RetryBackend implements restic.Backend.
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var _ restic.Backend = &RetryBackend{}
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// NewRetryBackend wraps be with a backend that retries operations after a
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// backoff. report is called with a description and the error, if one occurred.
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func NewRetryBackend(be restic.Backend, maxTries int, report func(string, error, time.Duration)) *RetryBackend {
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return &RetryBackend{
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Backend: be,
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MaxTries: maxTries,
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Report: report,
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}
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}
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func (be *RetryBackend) retry(ctx context.Context, msg string, f func() error) error {
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err := backoff.RetryNotify(f,
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backoff.WithContext(backoff.WithMaxTries(backoff.NewExponentialBackOff(), uint64(be.MaxTries)), ctx),
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func(err error, d time.Duration) {
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if be.Report != nil {
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be.Report(msg, err, d)
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}
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},
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)
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return err
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}
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// Save stores the data in the backend under the given handle.
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func (be *RetryBackend) Save(ctx context.Context, h restic.Handle, rd io.Reader) error {
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seeker, ok := rd.(io.Seeker)
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if !ok {
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return errors.Errorf("reader %T is not a seeker", rd)
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}
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pos, err := seeker.Seek(0, io.SeekCurrent)
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if err != nil {
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return errors.Wrap(err, "Seek")
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}
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if pos != 0 {
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return errors.Errorf("reader is not at the beginning (pos %v)", pos)
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}
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return be.retry(ctx, fmt.Sprintf("Save(%v)", h), func() error {
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_, err := seeker.Seek(0, io.SeekStart)
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if err != nil {
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return err
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}
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err = be.Backend.Save(ctx, h, rd)
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if err == nil {
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return nil
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}
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debug.Log("Save(%v) failed with error, removing file: %v", h, err)
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rerr := be.Remove(ctx, h)
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if rerr != nil {
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debug.Log("Remove(%v) returned error: %v", h, err)
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}
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// return original error
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return err
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})
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}
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// Load returns a reader that yields the contents of the file at h at the
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// given offset. If length is larger than zero, only a portion of the file
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// is returned. rd must be closed after use. If an error is returned, the
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// ReadCloser must be nil.
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func (be *RetryBackend) Load(ctx context.Context, h restic.Handle, length int, offset int64) (rd io.ReadCloser, err error) {
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err = be.retry(ctx, fmt.Sprintf("Load(%v, %v, %v)", h, length, offset),
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func() error {
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var innerError error
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rd, innerError = be.Backend.Load(ctx, h, length, offset)
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return innerError
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})
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return rd, err
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}
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// Stat returns information about the File identified by h.
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func (be *RetryBackend) Stat(ctx context.Context, h restic.Handle) (fi restic.FileInfo, err error) {
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err = be.retry(ctx, fmt.Sprintf("Stat(%v)", h),
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func() error {
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var innerError error
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fi, innerError = be.Backend.Stat(ctx, h)
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return innerError
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})
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return fi, err
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}
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