get rid of sync.Map for better go version compatibility

Author: zhijinli

.travis.yml

@@ -1,6 +1,7 @@
 language: go
 go:
   - 1.9
+  - 1.8
 env:
   global:
     - TEST_TIMEOUT_SCALE=40

participant.go

@@ -74,12 +74,11 @@ type participant struct {
 	keyBuilder *KeyBuilder
 	zkClient   *uzk.Client
 	// Mirrors org.apache.helix.participant.HelixStateMachineEngine
-	// stateModelName->stateModelProcessor
-	stateModelProcessors     sync.Map
+	stateModelProcessorsMu   sync.Mutex
+	stateModelProcessors     map[string]*StateModelProcessor // state model name to processor
 	stateModelProcessorLocks map[string]*sync.Mutex
 	stateModel               StateModel
-	sync.Mutex
-	dataAccessor *DataAccessor
+	dataAccessor             *DataAccessor
 
 	// fatalErrChan would notify user when a fatal error occurs
 	fatalErrChan chan error
@@ -122,6 +121,7 @@ func NewParticipant(
 		port:                     port,
 		keyBuilder:               keyBuilder,
 		zkClient:                 zkClient,
+		stateModelProcessors:     make(map[string]*StateModelProcessor),
 		stateModelProcessorLocks: make(map[string]*sync.Mutex),
 		dataAccessor:             newDataAccessor(zkClient, keyBuilder),
 		stateModel:               NewStateModel(),
@@ -159,7 +159,9 @@ func (p *participant) IsConnected() bool {
 
 // RegisterStateModel associates state trasition functions with the participant
 func (p *participant) RegisterStateModel(stateModelName string, processor *StateModelProcessor) {
-	p.stateModelProcessors.Store(stateModelName, processor)
+	p.stateModelProcessorsMu.Lock()
+	p.stateModelProcessors[stateModelName] = processor
+	p.stateModelProcessorsMu.Unlock()
 	p.stateModelProcessorLocks[stateModelName] = &sync.Mutex{}
 }
 
@@ -435,7 +437,7 @@ func (p *participant) handleMsg(msg *model.Message) error {
 	mu, ok := p.stateModelProcessorLocks[msg.GetStateModelDef()]
 	if !ok {
 		p.logger.Error("failed to find state model in stateModelProcessorLocks",
-			zap.String("StateModelDefinition", msg.GetStateModelDef()),
+			zap.String("stateModelDefinition", msg.GetStateModelDef()),
 			zap.Any("stateModelProcessorLocks", p.stateModelProcessorLocks))
 		return errMsgMissingStateModelDef
 	}
@@ -556,8 +558,9 @@ func (p *participant) handleStateTransition(msg *model.Message) error {
 	// set the msg execution time
 	msg.SetExecuteStartTime(time.Now())
 
-	if val, ok := p.stateModelProcessors.Load(msg.GetStateModelDef()); ok {
-		processor := val.(*StateModelProcessor)
+	p.stateModelProcessorsMu.Lock()
+	defer p.stateModelProcessorsMu.Unlock()
+	if processor, ok := p.stateModelProcessors[msg.GetStateModelDef()]; ok {
 		if toStateHandler, ok := processor.Transitions[fromState]; ok {
 			if handler, ok := toStateHandler[toState]; ok {
 				// TODO: deal with handler error