Takahiro Suzuki | d7bf820 | 2020-12-17 20:21:59 +0900 | [diff] [blame] | 1 | package mapmutex |
| 2 | |
| 3 | import ( |
| 4 | "math/rand" |
| 5 | "sync" |
| 6 | "time" |
| 7 | ) |
| 8 | |
| 9 | // Mutex is the mutex with synchronized map |
| 10 | // it's for reducing unnecessary locks among different keys |
| 11 | type Mutex struct { |
| 12 | locks map[interface{}]interface{} |
| 13 | m *sync.Mutex |
| 14 | maxRetry int |
| 15 | maxDelay float64 // in nanosend |
| 16 | baseDelay float64 // in nanosecond |
| 17 | factor float64 |
| 18 | jitter float64 |
| 19 | } |
| 20 | |
| 21 | // TryLock tries to aquire the lock. |
| 22 | func (m *Mutex) TryLock(key interface{}) (gotLock bool) { |
| 23 | for i := 0; i < m.maxRetry; i++ { |
| 24 | m.m.Lock() |
| 25 | if _, ok := m.locks[key]; ok { // if locked |
| 26 | m.m.Unlock() |
| 27 | time.Sleep(m.backoff(i)) |
| 28 | } else { // if unlock, lockit |
| 29 | m.locks[key] = struct{}{} |
| 30 | m.m.Unlock() |
| 31 | return true |
| 32 | } |
| 33 | } |
| 34 | |
| 35 | return false |
| 36 | } |
| 37 | |
| 38 | // Unlock unlocks for the key |
| 39 | // please call Unlock only after having aquired the lock |
| 40 | func (m *Mutex) Unlock(key interface{}) { |
| 41 | m.m.Lock() |
| 42 | delete(m.locks, key) |
| 43 | m.m.Unlock() |
| 44 | } |
| 45 | |
| 46 | // borrowed from grpc |
| 47 | func (m *Mutex) backoff(retries int) time.Duration { |
| 48 | if retries == 0 { |
| 49 | return time.Duration(m.baseDelay) * time.Nanosecond |
| 50 | } |
| 51 | backoff, max := m.baseDelay, m.maxDelay |
| 52 | for backoff < max && retries > 0 { |
| 53 | backoff *= m.factor |
| 54 | retries-- |
| 55 | } |
| 56 | if backoff > max { |
| 57 | backoff = max |
| 58 | } |
| 59 | backoff *= 1 + m.jitter*(rand.Float64()*2-1) |
| 60 | if backoff < 0 { |
| 61 | return 0 |
| 62 | } |
| 63 | return time.Duration(backoff) * time.Nanosecond |
| 64 | } |
| 65 | |
| 66 | // NewMapMutex returns a mapmutex with default configs |
| 67 | func NewMapMutex() *Mutex { |
| 68 | return &Mutex{ |
| 69 | locks: make(map[interface{}]interface{}), |
| 70 | m: &sync.Mutex{}, |
| 71 | maxRetry: 200, |
| 72 | maxDelay: 100000000, // 0.1 second |
| 73 | baseDelay: 10, // 10 nanosecond |
| 74 | factor: 1.1, |
| 75 | jitter: 0.2, |
| 76 | } |
| 77 | } |
| 78 | |
| 79 | // NewCustomizedMapMutex returns a customized mapmutex |
| 80 | func NewCustomizedMapMutex(mRetry int, mDelay, bDelay, factor, jitter float64) *Mutex { |
| 81 | return &Mutex{ |
| 82 | locks: make(map[interface{}]interface{}), |
| 83 | m: &sync.Mutex{}, |
| 84 | maxRetry: mRetry, |
| 85 | maxDelay: mDelay, |
| 86 | baseDelay: bDelay, |
| 87 | factor: factor, |
| 88 | jitter: jitter, |
| 89 | } |
| 90 | } |