Merge pull request lightninglabs#182 from halseth/flake-state-updates

[flake fix] auctioneer test: synchronize updates to auction state

auctioneer_test.go

@@ -54,13 +54,22 @@ func randomPubKey(t *testing.T) *btcec.PublicKey {
 	return pub
 }
 
+type fetchStateReq struct {
+	resp chan AuctionState
+}
+
 type mockAuctioneerState struct {
 	sync.RWMutex
 
-	state AuctionState
-
+	state            AuctionState
 	stateTransitions chan AuctionState
 
+	// We use a channel to synchronize acccess to the state, such that we
+	// can fetch the current state even though we are waiting for a state
+	// transition to happen.
+	stateSem       chan struct{}
+	fetchStateChan chan *fetchStateReq
+
 	acct *account.Auctioneer
 
 	orders map[orderT.Nonce]order.ServerOrder
@@ -84,10 +93,16 @@ func newMockAuctioneerState(batchKey *btcec.PublicKey,
 		stateTransitionsBuffer = 100
 	}
 
+	// Initialize semaphore with one element.
+	stateSem := make(chan struct{}, 1)
+	stateSem <- struct{}{}
+
 	return &mockAuctioneerState{
 		state:            DefaultState{},
 		batchKey:         batchKey,
 		stateTransitions: make(chan AuctionState, stateTransitionsBuffer),
+		fetchStateChan:   make(chan *fetchStateReq),
+		stateSem:         stateSem,
 		orders:           make(map[orderT.Nonce]order.ServerOrder),
 		batchStates:      make(map[orderT.BatchID]bool),
 		snapshots:        make(map[orderT.BatchID]*subastadb.BatchSnapshot),
@@ -127,20 +142,51 @@ func (m *mockAuctioneerState) BatchKey(context.Context) (*btcec.PublicKey, error
 }
 
 func (m *mockAuctioneerState) UpdateAuctionState(state AuctionState) error {
-	m.stateTransitions <- state
+	// To update the auction state, we must obtain the exclusive state
+	// access semaphore.
+	<-m.stateSem
+	defer func() {
+		m.stateSem <- struct{}{}
+	}()
+
+	for {
+		select {
+		// When the state transition is read, we can update
+		// our state variable and return.
+		case m.stateTransitions <- state:
+			m.state = state
+			return nil
 
-	m.Lock()
-	m.state = state
-	m.Unlock()
+		// If a request to read the current state comes in, we return
+		// the old state, as the state transition hasn't been triggered
+		// yet.
+		case req := <-m.fetchStateChan:
+			req.resp <- m.state
+		}
+	}
 
-	return nil
 }
 
 func (m *mockAuctioneerState) AuctionState() (AuctionState, error) {
-	m.RLock()
-	defer m.RUnlock()
+	req := &fetchStateReq{
+		resp: make(chan AuctionState, 1),
+	}
 
-	return m.state, nil
+	select {
+	// If we get the semaphore we have exclusive access to the state and
+	// can return it directly.
+	case <-m.stateSem:
+		defer func() {
+			m.stateSem <- struct{}{}
+		}()
+
+		return m.state, nil
+
+	// Otherwise some other goroutine has the semaphore, so we ask it to
+	// return the state to us.
+	case m.fetchStateChan <- req:
+		return <-req.resp, nil
+	}
 }
 
 func (m *mockAuctioneerState) ConfirmBatch(ctx context.Context,