load credential for in-flights requests as singleflight (#19920)

avoid concurrent callers for LoadUser() to even initiate
object read() requests, if an on-going operation is in progress.

this avoids many callers hitting the drives causing I/O
spikes, also allows for loading credentials faster.

cmd/iam-store.go

@@ -33,8 +33,10 @@ import (
 	"github.com/minio/minio/internal/auth"
 	"github.com/minio/minio/internal/config/identity/openid"
 	"github.com/minio/minio/internal/jwt"
+	"github.com/minio/pkg/v3/console"
 	"github.com/minio/pkg/v3/policy"
 	"github.com/puzpuzpuz/xsync/v3"
+	"golang.org/x/sync/singleflight"
 )
 
 const (
@@ -633,6 +635,8 @@ func (store *IAMStoreSys) LoadIAMCache(ctx context.Context, firstTime bool) erro
 // layer.
 type IAMStoreSys struct {
 	IAMStorageAPI
+
+	group *singleflight.Group
 }
 
 // HasWatcher - returns if the storage system has a watcher.
@@ -1800,6 +1804,7 @@ func (store *IAMStoreSys) DeleteUser(ctx context.Context, accessKey string, user
 		err = nil
 	}
 	delete(cache.iamUsersMap, accessKey)
+	store.group.Forget(accessKey)
 
 	cache.updatedAt = time.Now()
 
@@ -1875,6 +1880,7 @@ func (store *IAMStoreSys) DeleteUsers(ctx context.Context, users []string) error
 			err := store.deleteUserIdentity(ctx, user, userType)
 			iamLogIf(GlobalContext, err)
 			delete(cache.iamUsersMap, user)
+			store.group.Forget(user)
 
 			deleted = true
 		}
@@ -2563,10 +2569,14 @@ func (store *IAMStoreSys) UpdateUserIdentity(ctx context.Context, cred auth.Cred
 
 // LoadUser - attempts to load user info from storage and updates cache.
 func (store *IAMStoreSys) LoadUser(ctx context.Context, accessKey string) {
+	// We use singleflight to de-duplicate requests when server
+	// is coming up and loading accessKey and its associated assets
+	val, err, shared := store.group.Do(accessKey, func() (interface{}, error) {
 		cache := store.lock()
-	defer store.unlock()
+		defer func() {
-
 			cache.updatedAt = time.Now()
+			store.unlock()
+		}()
 
 		_, found := cache.iamUsersMap[accessKey]
 
@@ -2625,6 +2635,13 @@ func (store *IAMStoreSys) LoadUser(ctx context.Context, accessKey string) {
 				}
 			}
 		}
+
+		return "done", nil
+	})
+
+	if serverDebugLog {
+		console.Debugln("loadUser: loading shared", val, err, shared)
+	}
 }
 
 func extractJWTClaims(u UserIdentity) (*jwt.MapClaims, error) {

cmd/iam.go

@@ -52,6 +52,7 @@ import (
 	"github.com/minio/pkg/v3/ldap"
 	"github.com/minio/pkg/v3/policy"
 	etcd "go.etcd.io/etcd/client/v3"
+	"golang.org/x/sync/singleflight"
 )
 
 // UsersSysType - defines the type of users and groups system that is
@@ -177,9 +178,9 @@ func (sys *IAMSys) initStore(objAPI ObjectLayer, etcdClient *etcd.Client) {
 	}
 
 	if etcdClient == nil {
-		sys.store = &IAMStoreSys{newIAMObjectStore(objAPI, sys.usersSysType)}
+		sys.store = &IAMStoreSys{newIAMObjectStore(objAPI, sys.usersSysType), &singleflight.Group{}}
 	} else {
-		sys.store = &IAMStoreSys{newIAMEtcdStore(etcdClient, sys.usersSysType)}
+		sys.store = &IAMStoreSys{newIAMEtcdStore(etcdClient, sys.usersSysType), &singleflight.Group{}}
 	}
 }
 

go.mod

@@ -95,6 +95,7 @@ require (
 	golang.org/x/crypto v0.24.0
 	golang.org/x/exp v0.0.0-20240531132922-fd00a4e0eefc
 	golang.org/x/oauth2 v0.21.0
+	golang.org/x/sync v0.7.0
 	golang.org/x/sys v0.21.0
 	golang.org/x/term v0.21.0
 	golang.org/x/time v0.5.0
@@ -250,7 +251,6 @@ require (
 	go.uber.org/multierr v1.11.0 // indirect
 	golang.org/x/mod v0.18.0 // indirect
 	golang.org/x/net v0.26.0 // indirect
-	golang.org/x/sync v0.7.0 // indirect
 	golang.org/x/text v0.16.0 // indirect
 	golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d // indirect
 	google.golang.org/genproto v0.0.0-20240528184218-531527333157 // indirect