micro/sync/memory.go

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package sync
import (
gosync "sync"
"time"
)
type memorySync struct {
options Options
mtx gosync.RWMutex
locks map[string]*memoryLock
}
type memoryLock struct {
id string
time time.Time
ttl time.Duration
release chan bool
}
type memoryLeader struct {
opts LeaderOptions
id string
resign func(id string) error
status chan bool
}
func (m *memoryLeader) Resign() error {
return m.resign(m.id)
}
func (m *memoryLeader) Status() chan bool {
return m.status
}
func (m *memorySync) Leader(id string, opts ...LeaderOption) (Leader, error) {
var once gosync.Once
var options LeaderOptions
for _, o := range opts {
o(&options)
}
// acquire a lock for the id
if err := m.Lock(id); err != nil {
return nil, err
}
// return the leader
return &memoryLeader{
opts: options,
id: id,
resign: func(id string) error {
once.Do(func() {
m.Unlock(id)
})
return nil
},
// TODO: signal when Unlock is called
status: make(chan bool, 1),
}, nil
}
func (m *memorySync) Init(opts ...Option) error {
for _, o := range opts {
o(&m.options)
}
return nil
}
func (m *memorySync) Options() Options {
return m.options
}
func (m *memorySync) Lock(id string, opts ...LockOption) error {
// lock our access
m.mtx.Lock()
var options LockOptions
for _, o := range opts {
o(&options)
}
lk, ok := m.locks[id]
if !ok {
m.locks[id] = &memoryLock{
id: id,
time: time.Now(),
ttl: options.TTL,
release: make(chan bool),
}
// unlock
m.mtx.Unlock()
return nil
}
m.mtx.Unlock()
// set wait time
var wait <-chan time.Time
var ttl <-chan time.Time
// decide if we should wait
if options.Wait > time.Duration(0) {
wait = time.After(options.Wait)
}
// check the ttl of the lock
if lk.ttl > time.Duration(0) {
// time lived for the lock
live := time.Since(lk.time)
// set a timer for the leftover ttl
if live > lk.ttl {
// release the lock if it expired
_ = m.Unlock(id)
} else {
ttl = time.After(live)
}
}
lockLoop:
for {
// wait for the lock to be released
select {
case <-lk.release:
m.mtx.Lock()
// someone locked before us
lk, ok = m.locks[id]
if ok {
m.mtx.Unlock()
continue
}
// got chance to lock
m.locks[id] = &memoryLock{
id: id,
time: time.Now(),
ttl: options.TTL,
release: make(chan bool),
}
m.mtx.Unlock()
break lockLoop
case <-ttl:
// ttl exceeded
_ = m.Unlock(id)
// TODO: check the ttl again above
ttl = nil
// try acquire
continue
case <-wait:
return ErrLockTimeout
}
}
return nil
}
func (m *memorySync) Unlock(id string) error {
m.mtx.Lock()
defer m.mtx.Unlock()
lk, ok := m.locks[id]
// no lock exists
if !ok {
return nil
}
// delete the lock
delete(m.locks, id)
select {
case <-lk.release:
return nil
default:
close(lk.release)
}
return nil
}
func (m *memorySync) String() string {
return "memory"
}
func NewSync(opts ...Option) Sync {
var options Options
for _, o := range opts {
o(&options)
}
return &memorySync{
options: options,
locks: make(map[string]*memoryLock),
}
}