Add thread safety to FilerEtcStore and clarify credential store comments

Address review suggestions for better thread safety and code clarity:

1. **Thread Safety**: Add RWMutex to FilerEtcStore
   - Protects filerAddressFunc and grpcDialOption from concurrent access
   - Initialize() uses write lock when setting function
   - SetFilerAddressFunc() uses write lock
   - withFilerClient() uses read lock to get function and dial option
   - GetPolicies() uses read lock to check if configured

2. **Improved Error Messages**:
   - Prefix errors with "filer_etc:" for easier debugging
   - "filer address not configured" → "filer_etc: filer address function not configured"
   - "filer address is empty" → "filer_etc: filer address is empty"

3. **Clarified Comments**:
   - auth_credentials.go: Clarify that initial setup is temporary
   - Document that it's updated in s3api_server.go after FilerClient creation
   - Remove ambiguity about when FilerClient.GetCurrentFiler is used

Benefits:
- Safe for concurrent credential operations
- Clear error messages for debugging
- Explicit documentation of initialization order

weed/credential/filer_etc/filer_etc_policy.go

@@ -20,8 +20,12 @@ func (store *FilerEtcStore) GetPolicies(ctx context.Context) (map[string]policy_
 		Policies: make(map[string]policy_engine.PolicyDocument),
 	}
 
-	// Check if filer client is configured
-	if store.filerAddressFunc == nil {
+	// Check if filer client is configured (with mutex protection)
+	store.mu.RLock()
+	configured := store.filerAddressFunc != nil
+	store.mu.RUnlock()
+	
+	if !configured {
 		glog.V(1).Infof("Filer client not configured for policy retrieval, returning empty policies")
 		// Return empty policies if filer client is not configured
 		return policiesCollection.Policies, nil

weed/credential/filer_etc/filer_etc_store.go

@@ -2,6 +2,7 @@ package filer_etc
 
 import (
 	"fmt"
+	"sync"
 
 	"github.com/seaweedfs/seaweedfs/weed/credential"
 	"github.com/seaweedfs/seaweedfs/weed/pb"
@@ -18,6 +19,7 @@ func init() {
 type FilerEtcStore struct {
 	filerAddressFunc func() pb.ServerAddress // Function to get current active filer
 	grpcDialOption   grpc.DialOption
+	mu               sync.RWMutex // Protects filerAddressFunc and grpcDialOption
 }
 
 func (store *FilerEtcStore) GetName() credential.CredentialStoreTypeName {
@@ -30,9 +32,11 @@ func (store *FilerEtcStore) Initialize(configuration util.Configuration, prefix
 		filerAddr := configuration.GetString(prefix + "filer")
 		if filerAddr != "" {
 			// Static configuration - use fixed address
+			store.mu.Lock()
 			store.filerAddressFunc = func() pb.ServerAddress {
 				return pb.ServerAddress(filerAddr)
 			}
+			store.mu.Unlock()
 		}
 		// TODO: Initialize grpcDialOption based on configuration
 	}
@@ -43,23 +47,30 @@ func (store *FilerEtcStore) Initialize(configuration util.Configuration, prefix
 // SetFilerAddressFunc sets a function that returns the current active filer address
 // This enables high availability by using the currently active filer
 func (store *FilerEtcStore) SetFilerAddressFunc(getFiler func() pb.ServerAddress, grpcDialOption grpc.DialOption) {
+	store.mu.Lock()
+	defer store.mu.Unlock()
 	store.filerAddressFunc = getFiler
 	store.grpcDialOption = grpcDialOption
 }
 
 // withFilerClient executes a function with a filer client
 func (store *FilerEtcStore) withFilerClient(fn func(client filer_pb.SeaweedFilerClient) error) error {
+	store.mu.RLock()
 	if store.filerAddressFunc == nil {
-		return fmt.Errorf("filer address not configured")
+		store.mu.RUnlock()
+		return fmt.Errorf("filer_etc: filer address function not configured")
 	}
 
 	filerAddress := store.filerAddressFunc()
+	dialOption := store.grpcDialOption
+	store.mu.RUnlock()
+	
 	if filerAddress == "" {
-		return fmt.Errorf("filer address is empty")
+		return fmt.Errorf("filer_etc: filer address is empty")
 	}
 
 	// Use the pb.WithGrpcFilerClient helper similar to existing code
-	return pb.WithGrpcFilerClient(false, 0, filerAddress, store.grpcDialOption, fn)
+	return pb.WithGrpcFilerClient(false, 0, filerAddress, dialOption, fn)
 }
 
 func (store *FilerEtcStore) Shutdown() {

weed/s3api/auth_credentials.go

@@ -137,18 +137,15 @@ func NewIdentityAccessManagementWithStore(option *S3ApiServerOption, explicitSto
 		glog.Fatalf("failed to initialize credential manager: %v", err)
 	}
 
-	// For stores that need filer client details, set them
-	// Use SetFilerAddressFunc to provide current active filer for HA
+	// For stores that need filer client details, set them temporarily
+	// This will be updated to use FilerClient's GetCurrentFiler after FilerClient is created
 	if store := credentialManager.GetStore(); store != nil {
 		if filerFuncSetter, ok := store.(interface {
 			SetFilerAddressFunc(func() pb.ServerAddress, grpc.DialOption)
 		}); ok {
-			// Use FilerClient's GetCurrentFiler for HA
-			// Note: FilerClient is created later, so we need to capture it
-			// For now, use first filer - this will be updated when FilerClient is available
+			// Temporary setup: use first filer until FilerClient is available
+			// See s3api_server.go where this is updated to FilerClient.GetCurrentFiler
 			if len(option.Filers) > 0 {
-				// Create a closure that will use the first filer initially
-				// This will be updated later to use FilerClient's current filer
 				getFiler := func() pb.ServerAddress {
 					if len(option.Filers) > 0 {
 						return option.Filers[0]
@@ -156,7 +153,7 @@ func NewIdentityAccessManagementWithStore(option *S3ApiServerOption, explicitSto
 					return ""
 				}
 				filerFuncSetter.SetFilerAddressFunc(getFiler, option.GrpcDialOption)
-				glog.V(1).Infof("Credential store configured with filer function (will be updated to use FilerClient)")
+				glog.V(1).Infof("Credential store configured with temporary filer function (will be updated after FilerClient creation)")
 			}
 		}
 	}