package sema import ( "context" "io" "github.com/cenkalti/backoff/v4" "github.com/restic/restic/internal/errors" "github.com/restic/restic/internal/restic" ) // make sure that SemaphoreBackend implements restic.Backend var _ restic.Backend = &SemaphoreBackend{} // SemaphoreBackend limits the number of concurrent operations. type SemaphoreBackend struct { restic.Backend sem semaphore } // New creates a backend that limits the concurrent operations on the underlying backend func New(be restic.Backend) *SemaphoreBackend { sem, err := newSemaphore(be.Connections()) if err != nil { panic(err) } return &SemaphoreBackend{ Backend: be, sem: sem, } } // Save adds new Data to the backend. func (be *SemaphoreBackend) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader) error { if err := h.Valid(); err != nil { return backoff.Permanent(err) } be.sem.GetToken() defer be.sem.ReleaseToken() return be.Backend.Save(ctx, h, rd) } // Load runs fn with a reader that yields the contents of the file at h at the // given offset. func (be *SemaphoreBackend) Load(ctx context.Context, h restic.Handle, length int, offset int64, fn func(rd io.Reader) error) error { if err := h.Valid(); err != nil { return backoff.Permanent(err) } if offset < 0 { return backoff.Permanent(errors.New("offset is negative")) } if length < 0 { return backoff.Permanent(errors.Errorf("invalid length %d", length)) } be.sem.GetToken() defer be.sem.ReleaseToken() return be.Backend.Load(ctx, h, length, offset, fn) } // Stat returns information about a file in the backend. func (be *SemaphoreBackend) Stat(ctx context.Context, h restic.Handle) (restic.FileInfo, error) { if err := h.Valid(); err != nil { return restic.FileInfo{}, backoff.Permanent(err) } be.sem.GetToken() defer be.sem.ReleaseToken() return be.Backend.Stat(ctx, h) } // Remove deletes a file from the backend. func (be *SemaphoreBackend) Remove(ctx context.Context, h restic.Handle) error { if err := h.Valid(); err != nil { return backoff.Permanent(err) } be.sem.GetToken() defer be.sem.ReleaseToken() return be.Backend.Remove(ctx, h) } func (be *SemaphoreBackend) Unwrap() restic.Backend { return be.Backend }