move memory implementations to core micro repo

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

sync/memory.go

@@ -0,0 +1,199 @@
+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),
+	}
+}