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As mentioned in issue [#1560](https://github.com/restic/restic/pull/1560#issuecomment-364689346) this changes the signature for `backend.Save()`. It now takes a parameter of interface type `RewindReader`, so that the backend implementations or our `RetryBackend` middleware can reset the reader to the beginning and then retry an upload operation. The `RewindReader` interface also provides a `Length()` method, which is used in the backend to get the size of the data to be saved. This removes several ugly hacks we had to do to pull the size back out of the `io.Reader` passed to `Save()` before. In the `s3` and `rest` backend this is actively used.
85 lines
2.2 KiB
Go
85 lines
2.2 KiB
Go
package backend
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import (
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"context"
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"io"
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"io/ioutil"
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"math/rand"
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"sync"
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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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// ErrorBackend is used to induce errors into various function calls and test
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// the retry functions.
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type ErrorBackend struct {
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FailSave float32
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FailSaveRead float32
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FailLoad float32
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FailStat float32
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restic.Backend
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r *rand.Rand
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m sync.Mutex
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}
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// statically ensure that ErrorBackend implements restic.Backend.
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var _ restic.Backend = &ErrorBackend{}
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// NewErrorBackend wraps be with a backend that returns errors according to
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// given probabilities.
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func NewErrorBackend(be restic.Backend, seed int64) *ErrorBackend {
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return &ErrorBackend{
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Backend: be,
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r: rand.New(rand.NewSource(seed)),
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}
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}
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func (be *ErrorBackend) fail(p float32) bool {
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be.m.Lock()
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v := be.r.Float32()
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be.m.Unlock()
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return v < p
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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 *ErrorBackend) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader) error {
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if be.fail(be.FailSave) {
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return errors.Errorf("Save(%v) random error induced", h)
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}
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if be.fail(be.FailSaveRead) {
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_, err := io.CopyN(ioutil.Discard, rd, be.r.Int63n(1000))
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if err != nil {
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return err
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}
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return errors.Errorf("Save(%v) random error with partial read induced", h)
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}
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return be.Backend.Save(ctx, h, rd)
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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 *ErrorBackend) Load(ctx context.Context, h restic.Handle, length int, offset int64, consumer func(rd io.Reader) error) error {
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if be.fail(be.FailLoad) {
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return errors.Errorf("Load(%v, %v, %v) random error induced", h, length, offset)
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}
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return be.Backend.Load(ctx, h, length, offset, consumer)
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}
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// Stat returns information about the File identified by h.
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func (be *ErrorBackend) Stat(ctx context.Context, h restic.Handle) (restic.FileInfo, error) {
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if be.fail(be.FailLoad) {
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return restic.FileInfo{}, errors.Errorf("Stat(%v) random error induced", h)
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}
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return be.Stat(ctx, h)
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}
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