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parallelize node operations #302
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,62 @@ | ||
| package gceGCEDriver | ||
|
|
||
| import ( | ||
| "github.com/golang/glog" | ||
| "sync" | ||
| ) | ||
|
|
||
| type lockWithWaiters struct { | ||
| mux sync.Locker | ||
| waiters uint32 | ||
| } | ||
|
|
||
| type LockManager struct { | ||
| mux sync.Mutex | ||
| newLocker func(...interface{}) sync.Locker | ||
| locks map[string]*lockWithWaiters | ||
| } | ||
|
|
||
| func NewLockManager(f func(...interface{}) sync.Locker) *LockManager { | ||
| return &LockManager{ | ||
| newLocker: f, | ||
| locks: make(map[string]*lockWithWaiters), | ||
| } | ||
| } | ||
|
|
||
| func NewSyncMutex(lockerParams ...interface{}) sync.Locker { | ||
| return &sync.Mutex{} | ||
| } | ||
|
|
||
| // Acquires the lock corresponding to a key, and allocates that lock if one does not exist. | ||
| func (lm *LockManager) Acquire(key string, lockerParams ...interface{}) { | ||
| lm.mux.Lock() | ||
| lockForKey, ok := lm.locks[key] | ||
| if !ok { | ||
| lockForKey = &lockWithWaiters{ | ||
| mux: lm.newLocker(lockerParams...), | ||
| waiters: 0, | ||
| } | ||
| lm.locks[key] = lockForKey | ||
| } | ||
| lockForKey.waiters += 1 | ||
| lm.mux.Unlock() | ||
| lockForKey.mux.Lock() | ||
| } | ||
|
|
||
| // Releases the lock corresponding to a key, and deallocates that lock if no other thread | ||
| // is waiting to acquire it. Logs an error and returns if the lock for a key does not exist. | ||
| func (lm *LockManager) Release(key string) { | ||
| lm.mux.Lock() | ||
| lockForKey, ok := lm.locks[key] | ||
| if !ok { | ||
| // This should not happen, but if it does the only thing to do is to log the error | ||
| glog.Errorf("the key being released does not correspond to an existing lock") | ||
| return | ||
| } | ||
| lockForKey.waiters -= 1 | ||
| lockForKey.mux.Unlock() | ||
| if lockForKey.waiters == 0 { | ||
| delete(lm.locks, key) | ||
| } | ||
| lm.mux.Unlock() | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,145 @@ | ||
| package gceGCEDriver | ||
|
|
||
| import ( | ||
| "sync" | ||
| "testing" | ||
| "time" | ||
| ) | ||
|
|
||
| // Checks that the lock manager has the expected number of locks allocated. | ||
| // this function is implementation dependant! It acquires the lock and directly | ||
| // checks the map of the lock manager. | ||
| func checkAllocation(lm *LockManager, expectedNumAllocated int, t *testing.T) { | ||
| lm.mux.Lock() | ||
| defer lm.mux.Unlock() | ||
| if len(lm.locks) != expectedNumAllocated { | ||
| t.Fatalf("expected %d locks allocated, but found %d", expectedNumAllocated, len(lm.locks)) | ||
| } | ||
| } | ||
|
|
||
| // coinOperatedMutex is a mutex that only acquires if a "coin" is provided. Otherwise | ||
| // it sleeps until there is both a coin and the lock is free. This is used | ||
| // so a parent thread can control the execution of children's lock. | ||
| type coinOperatedMutex struct { | ||
| mux *sync.Mutex | ||
| cond *sync.Cond | ||
| held bool | ||
| coin chan coin | ||
| t *testing.T | ||
| } | ||
|
|
||
| type coin struct{} | ||
|
|
||
| func (m *coinOperatedMutex) Lock() { | ||
| m.mux.Lock() | ||
| defer m.mux.Unlock() | ||
|
|
||
| for m.held || len(m.coin) == 0 { | ||
| m.cond.Wait() | ||
| } | ||
| <-m.coin | ||
| m.held = true | ||
| } | ||
|
|
||
| func (m *coinOperatedMutex) Unlock() { | ||
| m.mux.Lock() | ||
| defer m.mux.Unlock() | ||
|
|
||
| m.held = false | ||
| m.cond.Broadcast() | ||
| } | ||
|
|
||
| func (m *coinOperatedMutex) Deposit() { | ||
| m.mux.Lock() | ||
| defer m.mux.Unlock() | ||
|
|
||
| m.coin <- coin{} | ||
| m.cond.Broadcast() | ||
| } | ||
|
|
||
| func passCoinOperatedMutex(lockerParams ...interface{}) sync.Locker { | ||
| return lockerParams[0].(*coinOperatedMutex) | ||
| } | ||
|
|
||
| func TestLockManagerSingle(t *testing.T) { | ||
| lm := NewLockManager(NewSyncMutex) | ||
| lm.Acquire("A") | ||
| checkAllocation(lm, 1, t) | ||
| lm.Acquire("B") | ||
| checkAllocation(lm, 2, t) | ||
| lm.Release("A") | ||
| checkAllocation(lm, 1, t) | ||
| lm.Release("B") | ||
| checkAllocation(lm, 0, t) | ||
| } | ||
|
|
||
| func TestLockManagerMultiple(t *testing.T) { | ||
| lm := NewLockManager(passCoinOperatedMutex) | ||
| m := &sync.Mutex{} | ||
| com := &coinOperatedMutex{ | ||
| mux: m, | ||
| cond: sync.NewCond(m), | ||
| coin: make(chan coin, 1), | ||
| held: false, | ||
| t: t, | ||
| } | ||
|
|
||
| // start thread 1 | ||
| t1OperationFinished := make(chan coin, 1) | ||
| t1OkToRelease := make(chan coin, 1) | ||
| go func() { | ||
| lm.Acquire("A", com) | ||
| t1OperationFinished <- coin{} | ||
| <-t1OkToRelease | ||
| lm.Release("A") | ||
| t1OperationFinished <- coin{} | ||
| }() | ||
|
|
||
| // this allows the acquire by thread 1 to acquire | ||
| com.Deposit() | ||
| <-t1OperationFinished | ||
|
|
||
| // thread 1 should have acquired the lock, putting allocation at 1 | ||
| checkAllocation(lm, 1, t) | ||
|
|
||
| // start thread 2 | ||
| // this should allow thread 2 to start the acquire for A through the | ||
| // lock manager, but block on the acquire Lock() of the lock for A. | ||
| t2OperationFinished := make(chan coin, 1) | ||
| t2OkToRelease := make(chan coin, 1) | ||
| go func() { | ||
| lm.Acquire("A") | ||
| t2OperationFinished <- coin{} | ||
| <-t2OkToRelease | ||
| lm.Release("A") | ||
| t2OperationFinished <- coin{} | ||
| }() | ||
|
|
||
| // because now thread 2 is the only thread that can run, we must wait | ||
| // until it runs until it is blocked on acquire. for simplicity just wait | ||
| // 5 seconds. | ||
| time.Sleep(time.Second * 3) | ||
|
|
||
| // this allows the release by thread 1 to complete | ||
| // only the release can run because the acquire by thread 1 can only run if | ||
| // there is both a coin and the lock is free | ||
| t1OkToRelease <- coin{} | ||
| <-t1OperationFinished | ||
|
|
||
| // check that the lock has not been deallocated, since thread 2 is still waiting to acquire it | ||
| checkAllocation(lm, 1, t) | ||
|
|
||
| // this allows t2 to finish its acquire | ||
| com.Deposit() | ||
| <-t2OperationFinished | ||
|
|
||
| // check that the lock has been deallocated, since thread 2 still holds it | ||
| checkAllocation(lm, 1, t) | ||
|
|
||
| // this allows the release by thread 2 to release | ||
| t2OkToRelease <- coin{} | ||
| <-t2OperationFinished | ||
|
|
||
| // check that the lock has been deallocated | ||
| checkAllocation(lm, 0, t) | ||
| } | ||
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this is super cool. Definitely keep this code around and we can reference it for your reviews, though unfortunately sometimes the right thing to do is not the interesting/challenging thing :(