Updated Prometheus metrics (#11141)

* Add metrics for nodes online and offline
* Add cluster capacity metrics
* Introduce v2 metrics

cmd/notification-summary.go

@@ -0,0 +1,54 @@
+/*
+ * 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 cmd
+
+import (
+	"context"
+)
+
+// GetTotalCapacity gets the total capacity in the cluster.
+func GetTotalCapacity(ctx context.Context) (capacity uint64) {
+	d := globalNotificationSys.DiskHwInfo(ctx)
+	for _, s := range d {
+		capacity += s.GetTotalCapacity()
+	}
+	return
+}
+
+// GetTotalUsableCapacity gets the total usable capacity in the cluster.
+func GetTotalUsableCapacity(ctx context.Context, s StorageInfo) (capacity float64) {
+	raw := GetTotalCapacity(ctx)
+	ratio := float64(s.Backend.StandardSCData) / float64(s.Backend.StandardSCData+s.Backend.StandardSCParity)
+	return float64(raw) * ratio
+}
+
+// GetTotalCapacityFree gets the total capacity free in the cluster.
+func GetTotalCapacityFree(ctx context.Context) (capacity uint64) {
+	d := globalNotificationSys.DiskHwInfo(ctx)
+	for _, s := range d {
+		capacity += s.GetTotalFreeCapacity()
+	}
+	return
+}
+
+// GetTotalUsableCapacityFree gets the total usable capacity free in the cluster.
+func GetTotalUsableCapacityFree(ctx context.Context, s StorageInfo) (capacity float64) {
+	raw := GetTotalCapacityFree(ctx)
+	ratio := float64(s.Backend.StandardSCData) / float64(s.Backend.StandardSCData+s.Backend.StandardSCParity)
+	return float64(raw) * ratio
+}