120 lines
2.1 KiB
Go
120 lines
2.1 KiB
Go
package physical
|
|
|
|
import (
|
|
"fmt"
|
|
"sync"
|
|
)
|
|
|
|
type InmemHABackend struct {
|
|
InmemBackend
|
|
locks map[string]string
|
|
l sync.Mutex
|
|
cond *sync.Cond
|
|
}
|
|
|
|
// NewInmemHA constructs a new in-memory HA backend. This is only for testing.
|
|
func NewInmemHA() *InmemHABackend {
|
|
in := &InmemHABackend{
|
|
InmemBackend: *NewInmem(),
|
|
locks: make(map[string]string),
|
|
}
|
|
in.cond = sync.NewCond(&in.l)
|
|
return in
|
|
}
|
|
|
|
// LockWith is used for mutual exclusion based on the given key.
|
|
func (i *InmemHABackend) LockWith(key, value string) (Lock, error) {
|
|
l := &InmemLock{
|
|
in: i,
|
|
key: key,
|
|
value: value,
|
|
}
|
|
return l, nil
|
|
}
|
|
|
|
// InmemLock is an in-memory Lock implementation for the HABackend
|
|
type InmemLock struct {
|
|
in *InmemHABackend
|
|
key string
|
|
value string
|
|
|
|
held bool
|
|
leaderCh chan struct{}
|
|
l sync.Mutex
|
|
}
|
|
|
|
func (i *InmemLock) Lock(stopCh <-chan struct{}) (<-chan struct{}, error) {
|
|
i.l.Lock()
|
|
defer i.l.Unlock()
|
|
if i.held {
|
|
return nil, fmt.Errorf("lock already held")
|
|
}
|
|
|
|
// Attempt an async acquisition
|
|
didLock := make(chan struct{})
|
|
releaseCh := make(chan bool, 1)
|
|
go func() {
|
|
// Wait to acquire the lock
|
|
i.in.l.Lock()
|
|
_, ok := i.in.locks[i.key]
|
|
for ok {
|
|
i.in.cond.Wait()
|
|
_, ok = i.in.locks[i.key]
|
|
}
|
|
i.in.locks[i.key] = i.value
|
|
i.in.l.Unlock()
|
|
|
|
// Signal that lock is held
|
|
close(didLock)
|
|
|
|
// Handle an early abort
|
|
release := <-releaseCh
|
|
if release {
|
|
i.in.l.Lock()
|
|
delete(i.in.locks, i.key)
|
|
i.in.l.Unlock()
|
|
i.in.cond.Broadcast()
|
|
}
|
|
}()
|
|
|
|
// Wait for lock acquisition or shutdown
|
|
select {
|
|
case <-didLock:
|
|
releaseCh <- false
|
|
case <-stopCh:
|
|
releaseCh <- true
|
|
return nil, nil
|
|
}
|
|
|
|
// Create the leader channel
|
|
i.held = true
|
|
i.leaderCh = make(chan struct{})
|
|
return i.leaderCh, nil
|
|
}
|
|
|
|
func (i *InmemLock) Unlock() error {
|
|
i.l.Lock()
|
|
defer i.l.Unlock()
|
|
|
|
if !i.held {
|
|
return nil
|
|
}
|
|
|
|
close(i.leaderCh)
|
|
i.leaderCh = nil
|
|
i.held = false
|
|
|
|
i.in.l.Lock()
|
|
delete(i.in.locks, i.key)
|
|
i.in.l.Unlock()
|
|
i.in.cond.Broadcast()
|
|
return nil
|
|
}
|
|
|
|
func (i *InmemLock) Value() (bool, string, error) {
|
|
i.in.l.Lock()
|
|
val, ok := i.in.locks[i.key]
|
|
i.in.l.Unlock()
|
|
return ok, val, nil
|
|
}
|