converge listBuckets() as a peer call (#16346)

cmd/peer-s3-client.go

@@ -80,6 +80,51 @@ func NewS3PeerSys(endpoints EndpointServerPools) *S3PeerSys {
 	}
 }
 
+// ListBuckets lists buckets across all servers and returns a possible consistent view
+func (sys *S3PeerSys) ListBuckets(ctx context.Context, opts BucketOptions) (buckets []BucketInfo, err error) {
+	g := errgroup.WithNErrs(len(sys.peerClients))
+
+	localBuckets, err := listBucketsLocal(ctx, opts)
+	if err != nil {
+		return nil, err
+	}
+
+	nodeBuckets := make([][]BucketInfo, len(sys.peerClients)+1)
+	errs := []error{nil}
+	nodeBuckets[0] = localBuckets
+
+	for idx, client := range sys.peerClients {
+		idx := idx
+		client := client
+		g.Go(func() error {
+			if client == nil {
+				return errPeerOffline
+			}
+			localBuckets, err := client.ListBuckets(ctx, opts)
+			if err != nil {
+				return err
+			}
+			nodeBuckets[idx+1] = localBuckets
+			return nil
+		}, idx)
+	}
+
+	errs = append(errs, g.Wait()...)
+
+	quorum := (len(sys.allPeerClients) / 2)
+	if err = reduceReadQuorumErrs(ctx, errs, bucketOpIgnoredErrs, quorum); err != nil {
+		return nil, err
+	}
+
+	for idx, buckets := range nodeBuckets {
+		if errs[idx] == nil {
+			return buckets, nil
+		}
+	}
+
+	return []BucketInfo{}, nil
+}
+
 // GetBucketInfo returns bucket stat info about bucket on disk across all peers
 func (sys *S3PeerSys) GetBucketInfo(ctx context.Context, bucket string, opts BucketOptions) (binfo BucketInfo, err error) {
 	g := errgroup.WithNErrs(len(sys.peerClients))
@@ -127,6 +172,21 @@ func (sys *S3PeerSys) GetBucketInfo(ctx context.Context, bucket string, opts Buc
 	return bucketInfo, nil
 }
 
+func (client *peerS3Client) ListBuckets(ctx context.Context, opts BucketOptions) ([]BucketInfo, error) {
+	v := url.Values{}
+	v.Set(peerS3BucketDeleted, strconv.FormatBool(opts.Deleted))
+
+	respBody, err := client.call(peerS3MethodListBuckets, v, nil, -1)
+	if err != nil {
+		return nil, err
+	}
+	defer xhttp.DrainBody(respBody)
+
+	var buckets []BucketInfo
+	err = gob.NewDecoder(respBody).Decode(&buckets)
+	return buckets, err
+}
+
 // GetBucketInfo returns bucket stat info from a peer
 func (client *peerS3Client) GetBucketInfo(ctx context.Context, bucket string, opts BucketOptions) (BucketInfo, error) {
 	v := url.Values{}