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restic/internal/backend/backend_error.go
2017-10-17 22:11:38 +02:00

85 lines
2.2 KiB
Go

package backend
import (
"context"
"io"
"io/ioutil"
"math/rand"
"sync"
"github.com/restic/restic/internal/errors"
"github.com/restic/restic/internal/restic"
)
// ErrorBackend is used to induce errors into various function calls and test
// the retry functions.
type ErrorBackend struct {
FailSave float32
FailSaveRead float32
FailLoad float32
FailStat float32
restic.Backend
r *rand.Rand
m sync.Mutex
}
// statically ensure that ErrorBackend implements restic.Backend.
var _ restic.Backend = &ErrorBackend{}
// NewErrorBackend wraps be with a backend that returns errors according to
// given probabilities.
func NewErrorBackend(be restic.Backend, seed int64) *ErrorBackend {
return &ErrorBackend{
Backend: be,
r: rand.New(rand.NewSource(seed)),
}
}
func (be *ErrorBackend) fail(p float32) bool {
be.m.Lock()
v := be.r.Float32()
be.m.Unlock()
return v < p
}
// Save stores the data in the backend under the given handle.
func (be *ErrorBackend) Save(ctx context.Context, h restic.Handle, rd io.Reader) error {
if be.fail(be.FailSave) {
return errors.Errorf("Save(%v) random error induced", h)
}
if be.fail(be.FailSaveRead) {
_, err := io.CopyN(ioutil.Discard, rd, be.r.Int63n(1000))
if err != nil {
return err
}
return errors.Errorf("Save(%v) random error with partial read induced", h)
}
return be.Backend.Save(ctx, h, rd)
}
// Load returns a reader that yields the contents of the file at h at the
// given offset. If length is larger than zero, only a portion of the file
// is returned. rd must be closed after use. If an error is returned, the
// ReadCloser must be nil.
func (be *ErrorBackend) Load(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
if be.fail(be.FailLoad) {
return nil, errors.Errorf("Load(%v, %v, %v) random error induced", h, length, offset)
}
return be.Backend.Load(ctx, h, length, offset)
}
// Stat returns information about the File identified by h.
func (be *ErrorBackend) Stat(ctx context.Context, h restic.Handle) (restic.FileInfo, error) {
if be.fail(be.FailLoad) {
return restic.FileInfo{}, errors.Errorf("Stat(%v) random error induced", h)
}
return be.Stat(ctx, h)
}