Enable filer discovery: pass master addresses to FilerClient

Fix two critical issues:

1. **Filer Discovery Not Working**: Master client was not being passed to
   FilerClient, so peer discovery couldn't work

2. **Credential Store Design**: Already uses FilerClient via GetCurrentFiler
   function - this is the correct design for HA

Changes:

**Command (s3.go):**
- Read master addresses from GetFilerConfiguration response
- Pass masterAddresses to S3ApiServerOption
- Log master addresses for visibility

**S3ApiServerOption:**
- Add Masters []pb.ServerAddress field for discovery

**S3ApiServer:**
- Create MasterClient from Masters when available
- Pass MasterClient + FilerGroup to FilerClient via options
- Enable discovery with 5-minute refresh interval
- Log whether discovery is enabled or disabled

**Credential Store:**
- Already correctly uses filerClient.GetCurrentFiler via function
- This provides HA without tight coupling to FilerClient struct
- Function-based design is clean and thread-safe

Discovery Flow:
1. S3 command reads filer config → gets masters + filer group
2. S3ApiServer creates MasterClient from masters
3. FilerClient uses MasterClient to query for peer filers
4. Background goroutine refreshes peer list every 5 minutes
5. Credential store uses GetCurrentFiler to get active filer

Now filer discovery actually works! ��

weed/command/s3.go

@@ -207,6 +207,7 @@ func (s3opt *S3Options) startS3Server() bool {
 
 	filerBucketsPath := "/buckets"
 	filerGroup := ""
+	var masterAddresses []pb.ServerAddress
 
 	grpcDialOption := security.LoadClientTLS(util.GetViper(), "grpc.client")
 
@@ -222,8 +223,13 @@ func (s3opt *S3Options) startS3Server() bool {
 			}
 			filerBucketsPath = resp.DirBuckets
 			filerGroup = resp.FilerGroup
+			// Get master addresses for filer discovery
+			masterAddresses = pb.ServerAddresses(strings.Join(resp.Masters, ",")).ToAddresses()
 			metricsAddress, metricsIntervalSec = resp.MetricsAddress, int(resp.MetricsIntervalSec)
 			glog.V(0).Infof("S3 read filer buckets dir: %s", filerBucketsPath)
+			if len(masterAddresses) > 0 {
+				glog.V(0).Infof("S3 read master addresses for discovery: %v", masterAddresses)
+			}
 			return nil
 		})
 		if err != nil {
@@ -256,6 +262,7 @@ func (s3opt *S3Options) startS3Server() bool {
 
 	s3ApiServer, s3ApiServer_err = s3api.NewS3ApiServer(router, &s3api.S3ApiServerOption{
 		Filers:                    filerAddresses,
+		Masters:                   masterAddresses,
 		Port:                      *s3opt.port,
 		Config:                    *s3opt.config,
 		DomainName:                *s3opt.domainName,

weed/s3api/s3api_server.go

@@ -34,6 +34,7 @@ import (
 
 type S3ApiServerOption struct {
 	Filers                    []pb.ServerAddress
+	Masters                   []pb.ServerAddress // For filer discovery
 	Port                      int
 	Config                    string
 	DomainName                string
@@ -100,8 +101,26 @@ func NewS3ApiServerWithStore(router *mux.Router, option *S3ApiServerOption, expl
 	// Initialize FilerClient for volume location caching
 	// Uses the battle-tested vidMap with filer-based lookups
 	// Supports multiple filer addresses with automatic failover for high availability
-	filerClient := wdclient.NewFilerClient(option.Filers, option.GrpcDialOption, option.DataCenter)
-	glog.V(0).Infof("S3 API initialized FilerClient with %d filer(s) for volume location caching", len(option.Filers))
+	var filerClient *wdclient.FilerClient
+	if len(option.Masters) > 0 && option.FilerGroup != "" {
+		// Enable filer discovery via master
+		masterMap := make(map[string]pb.ServerAddress)
+		for i, addr := range option.Masters {
+			masterMap[fmt.Sprintf("master%d", i)] = addr
+		}
+		masterClient := wdclient.NewMasterClient(option.GrpcDialOption, option.FilerGroup, "s3", "", "", "", *pb.NewServiceDiscoveryFromMap(masterMap))
+		
+		filerClient = wdclient.NewFilerClient(option.Filers, option.GrpcDialOption, option.DataCenter, &wdclient.FilerClientOption{
+			MasterClient:      masterClient,
+			FilerGroup:        option.FilerGroup,
+			DiscoveryInterval: 5 * time.Minute,
+		})
+		glog.V(0).Infof("S3 API initialized FilerClient with %d filer(s) and discovery enabled (group: %s, masters: %v)", 
+			len(option.Filers), option.FilerGroup, option.Masters)
+	} else {
+		filerClient = wdclient.NewFilerClient(option.Filers, option.GrpcDialOption, option.DataCenter)
+		glog.V(0).Infof("S3 API initialized FilerClient with %d filer(s) (no discovery)", len(option.Filers))
+	}
 
 	// Update credential store to use FilerClient's current filer for HA
 	if store := iam.credentialManager.GetStore(); store != nil {