Add basic bandwidth monitoring for replication. (#10501)

This change tracks bandwidth for a bucket and object

- [x] Add Admin API
- [x] Add Peer API
- [x] Add BW throttling
- [x] Admin APIs to set replication limit
- [x] Admin APIs for fetch bandwidth

pkg/madmin/bandwidth.go

@@ -0,0 +1,61 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package madmin
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/minio/minio/pkg/bandwidth"
+)
+
+// GetBucketBandwidth - Get a snapshot of the bandwidth measurements for replication buckets. If no buckets
+// generate replication traffic an empty map is returned.
+func (adm *AdminClient) GetBucketBandwidth(ctx context.Context, buckets ...string) (bandwidth.Report, error) {
+	queryValues := url.Values{}
+	if len(buckets) > 0 {
+		queryValues.Set("buckets", strings.Join(buckets, ","))
+	}
+
+	reqData := requestData{
+		relPath:     adminAPIPrefix + "/bandwidth",
+		queryValues: queryValues,
+	}
+
+	resp, err := adm.executeMethod(ctx, http.MethodGet, reqData)
+	if err != nil {
+		closeResponse(resp)
+		return bandwidth.Report{}, err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return bandwidth.Report{}, httpRespToErrorResponse(resp)
+	}
+	dec := json.NewDecoder(resp.Body)
+	for {
+		var report bandwidth.Report
+		err = dec.Decode(&report)
+		if err != nil && err != io.EOF {
+			return bandwidth.Report{}, err
+		}
+		return report, nil
+	}
+}