List buckets only once per sub-system initialization (#8333)

Current master repeatedly calls ListBuckets() during
initialization of multiple sub-systems

Use single ListBuckets() call for each sub-system as
follows

- LifeCycle
- Policy
- Notification

cmd/lifecycle.go

@@ -24,9 +24,7 @@ import (
 	"path"
 	"strings"
 	"sync"
-	"time"
 
-	"github.com/minio/minio-go/pkg/set"
 	"github.com/minio/minio/cmd/logger"
 	"github.com/minio/minio/pkg/lifecycle"
 )
@@ -45,6 +43,11 @@ type LifecycleSys struct {
 
 // Set - sets lifecycle config to given bucket name.
 func (sys *LifecycleSys) Set(bucketName string, lifecycle lifecycle.Lifecycle) {
+	if globalIsGateway {
+		// no-op
+		return
+	}
+
 	sys.Lock()
 	defer sys.Unlock()
 
@@ -53,6 +56,16 @@ func (sys *LifecycleSys) Set(bucketName string, lifecycle lifecycle.Lifecycle) {
 
 // Get - gets lifecycle config associated to a given bucket name.
 func (sys *LifecycleSys) Get(bucketName string) (lifecycle lifecycle.Lifecycle, ok bool) {
+	if globalIsGateway {
+		// When gateway is enabled, no cached value
+		// is used to validate life cycle policies.
+		objAPI := newObjectLayerFn()
+		if objAPI == nil {
+			return
+		}
+		l, err := objAPI.GetBucketLifecycle(context.Background(), bucketName)
+		return *l, err == nil
+	}
 	sys.Lock()
 	defer sys.Unlock()
 
@@ -107,26 +120,16 @@ func NewLifecycleSys() *LifecycleSys {
 }
 
 // Init - initializes lifecycle system from lifecycle.xml of all buckets.
-func (sys *LifecycleSys) Init(objAPI ObjectLayer) error {
+func (sys *LifecycleSys) Init(buckets []BucketInfo, objAPI ObjectLayer) error {
 	if objAPI == nil {
 		return errServerNotInitialized
 	}
 
-	defer func() {
-		// Refresh LifecycleSys in background.
-		go func() {
-			ticker := time.NewTicker(globalRefreshBucketLifecycleInterval)
-			defer ticker.Stop()
-			for {
-				select {
-				case <-GlobalServiceDoneCh:
-					return
-				case <-ticker.C:
-					sys.refresh(objAPI)
-				}
-			}
-		}()
-	}()
+	// In gateway mode, we always fetch the bucket lifecycle configuration from the gateway backend.
+	// So, this is a no-op for gateway servers.
+	if globalIsGateway {
+		return nil
+	}
 
 	doneCh := make(chan struct{})
 	defer close(doneCh)
@@ -140,7 +143,7 @@ func (sys *LifecycleSys) Init(objAPI ObjectLayer) error {
 		select {
 		case <-retryTimerCh:
 			// Load LifecycleSys once during boot.
-			if err := sys.refresh(objAPI); err != nil {
+			if err := sys.load(buckets, objAPI); err != nil {
 				if err == errDiskNotFound ||
 					strings.Contains(err.Error(), InsufficientReadQuorum{}.Error()) ||
 					strings.Contains(err.Error(), InsufficientWriteQuorum{}.Error()) {
@@ -156,14 +159,8 @@ func (sys *LifecycleSys) Init(objAPI ObjectLayer) error {
 	}
 }
 
-// Refresh LifecycleSys.
-func (sys *LifecycleSys) refresh(objAPI ObjectLayer) error {
-	buckets, err := objAPI.ListBuckets(context.Background())
-	if err != nil {
-		logger.LogIf(context.Background(), err)
-		return err
-	}
-	sys.removeDeletedBuckets(buckets)
+// Loads lifecycle policies for all buckets into LifecycleSys.
+func (sys *LifecycleSys) load(buckets []BucketInfo, objAPI ObjectLayer) error {
 	for _, bucket := range buckets {
 		config, err := objAPI.GetBucketLifecycle(context.Background(), bucket.Name)
 		if err != nil {
@@ -179,24 +176,6 @@ func (sys *LifecycleSys) refresh(objAPI ObjectLayer) error {
 	return nil
 }
 
-// removeDeletedBuckets - to handle a corner case where we have cached the lifecycle for a deleted
-// bucket. i.e if we miss a delete-bucket notification we should delete the corresponding
-// bucket policy during sys.refresh()
-func (sys *LifecycleSys) removeDeletedBuckets(bucketInfos []BucketInfo) {
-	buckets := set.NewStringSet()
-	for _, info := range bucketInfos {
-		buckets.Add(info.Name)
-	}
-	sys.Lock()
-	defer sys.Unlock()
-
-	for bucket := range sys.bucketLifecycleMap {
-		if !buckets.Contains(bucket) {
-			delete(sys.bucketLifecycleMap, bucket)
-		}
-	}
-}
-
 // Remove - removes policy for given bucket name.
 func (sys *LifecycleSys) Remove(bucketName string) {
 	sys.Lock()