mirror of
https://github.com/octoleo/restic.git
synced 2024-11-18 11:05:18 +00:00
8e1e3844aa
The SemaphoreBackend now uniformly enforces the limit of concurrent backend operations. In addition, it unifies the parameter validation. The List() methods no longer uses a semaphore. Restic already never runs multiple list operations in parallel. By managing the semaphore in a wrapper backend, the sections that hold a semaphore token grow slightly. However, the main bottleneck is IO, so this shouldn't make much of a difference. The key insight that enables the SemaphoreBackend is that all of the complex semaphore handling in `openReader()` still happens within the original call to `Load()`. Thus, getting and releasing the semaphore tokens can be refactored to happen directly in `Load()`. This eliminates the need for wrapping the reader in `openReader()` to release the token.
32 lines
712 B
Go
32 lines
712 B
Go
// Package sema implements semaphores.
|
|
package sema
|
|
|
|
import (
|
|
"github.com/restic/restic/internal/debug"
|
|
"github.com/restic/restic/internal/errors"
|
|
)
|
|
|
|
// A semaphore limits access to a restricted resource.
|
|
type semaphore struct {
|
|
ch chan struct{}
|
|
}
|
|
|
|
// newSemaphore returns a new semaphore with capacity n.
|
|
func newSemaphore(n uint) (semaphore, error) {
|
|
if n == 0 {
|
|
return semaphore{}, errors.New("capacity must be a positive number")
|
|
}
|
|
return semaphore{
|
|
ch: make(chan struct{}, n),
|
|
}, nil
|
|
}
|
|
|
|
// GetToken blocks until a Token is available.
|
|
func (s semaphore) GetToken() {
|
|
s.ch <- struct{}{}
|
|
debug.Log("acquired token")
|
|
}
|
|
|
|
// ReleaseToken returns a token.
|
|
func (s semaphore) ReleaseToken() { <-s.ch }
|