Fix already reserved panic on concurrent invokes

Closes aws#97.

lambda/rapidcore/server.go

@@ -107,59 +107,35 @@ type Server struct {
 var _ interop.Server = (*Server)(nil)
 
 func (s *Server) setRapidPhase(phase rapidPhase) {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
 	s.rapidPhase = phase
 }
 
 func (s *Server) getRapidPhase() rapidPhase {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
 	return s.rapidPhase
 }
 
 func (s *Server) setRuntimeState(state runtimeState) {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
 	s.runtimeState = state
 }
 
 func (s *Server) getRuntimeState() runtimeState {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
 	return s.runtimeState
 }
 
 func (s *Server) SetInvokeTimeout(timeout time.Duration) {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
 	s.invokeTimeout = timeout
 }
 
 func (s *Server) GetInvokeTimeout() time.Duration {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
 	return s.invokeTimeout
 }
 
 func (s *Server) GetInvokeContext() *InvokeContext {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
 	ctx := *s.invokeCtx
 	return &ctx
 }
 
 func (s *Server) setNewInvokeContext(invokeID string, traceID, lambdaSegmentID string) (*ReserveResponse, error) {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
 	if s.invokeCtx != nil {
 		return nil, ErrAlreadyReserved
 	}
@@ -226,9 +202,6 @@ func (s *Server) awaitInitCompletion() {
 }
 
 func (s *Server) setReplyStream(w http.ResponseWriter, direct bool) (string, error) {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
 	if s.invokeCtx == nil {
 		return "", ErrNotReserved
 	}
@@ -248,9 +221,6 @@ func (s *Server) setReplyStream(w http.ResponseWriter, direct bool) (string, err
 
 // Release closes the invocation, making server ready for reserve again
 func (s *Server) Release() error {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
 	if s.invokeCtx == nil {
 		return ErrNotReserved
 	}
@@ -267,9 +237,6 @@ func (s *Server) Release() error {
 
 // GetCurrentInvokeID
 func (s *Server) GetCurrentInvokeID() string {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
-
 	if s.invokeCtx == nil {
 		return ""
 	}
@@ -350,8 +317,6 @@ func (s *Server) sendResponseUnsafe(invokeID string, additionalHeaders map[strin
 
 func (s *Server) SendResponse(invokeID string, resp *interop.StreamableInvokeResponse) error {
 	s.setRuntimeState(runtimeInvokeResponseSent)
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
 	runtimeCalledResponse := true
 	return s.sendResponseUnsafe(invokeID, resp.Headers, resp.Payload, resp.Trailers, resp.Request, runtimeCalledResponse)
 }
@@ -372,8 +337,6 @@ func (s *Server) SendInitErrorResponse(resp *interop.ErrorInvokeResponse) error
 func (s *Server) SendErrorResponse(invokeID string, resp *interop.ErrorInvokeResponse) error {
 	log.Debugf("Sending Error Response: %s", resp.FunctionError.Type)
 	s.setRuntimeState(runtimeInvokeError)
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
 	additionalHeaders := map[string]string{
 		directinvoke.ContentTypeHeader: resp.Headers.ContentType,
 		directinvoke.ErrorTypeHeader:   string(resp.FunctionError.Type),
@@ -501,14 +464,10 @@ func deadlineNsFromTimeoutMs(timeoutMs int64) int64 {
 }
 
 func (s *Server) setInitFailuresChan() {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
 	s.initFailures = make(chan interop.InitFailure)
 }
 
 func (s *Server) getInitFailuresChan() chan interop.InitFailure {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
 	return s.initFailures
 }
 
@@ -593,14 +552,10 @@ func (s *Server) FastInvoke(w http.ResponseWriter, i *interop.Invoke, direct boo
 }
 
 func (s *Server) setCachedInitErrorResponse(errResp *interop.ErrorInvokeResponse) {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
 	s.cachedInitErrorResponse = errResp
 }
 
 func (s *Server) getCachedInitErrorResponse() *interop.ErrorInvokeResponse {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
 	return s.cachedInitErrorResponse
 }
 
@@ -613,8 +568,6 @@ func (s *Server) trySendDefaultErrorResponse(resp *interop.ErrorInvokeResponse)
 }
 
 func (s *Server) CurrentToken() *interop.Token {
-	s.mutex.Lock()
-	defer s.mutex.Unlock()
 	if s.invokeCtx == nil {
 		return nil
 	}
@@ -625,6 +578,9 @@ func (s *Server) CurrentToken() *interop.Token {
 // Invoke is used by the Runtime Interface Emulator (Rapid Local)
 // https://github.com/aws/aws-lambda-runtime-interface-emulator
 func (s *Server) Invoke(responseWriter http.ResponseWriter, invoke *interop.Invoke) error {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
 	resetCtx, resetCancel := context.WithCancel(context.Background())
 	defer resetCancel()