Add ServerDrivesPerfInfo() admin API (#6969)

This is part of implementation for mc admin health command. The
ServerDrivesPerfInfo() admin API returns read and write speed
information for all the drives (local and remote) in a given Minio
server deployment.

Part of minio/mc#2606

cmd/endpoint.go

@@ -29,6 +29,7 @@ import (
 
 	"github.com/minio/minio-go/pkg/set"
 	"github.com/minio/minio/cmd/logger"
+	"github.com/minio/minio/pkg/disk"
 	"github.com/minio/minio/pkg/mountinfo"
 )
 
@@ -197,6 +198,34 @@ func (endpoints EndpointList) GetString(i int) string {
 	return endpoints[i].String()
 }
 
+// localEndpointsPerf - returns ServerDrivesPerfInfo for only the
+// local endpoints from given list of endpoints
+func localEndpointsPerf(endpoints EndpointList) ServerDrivesPerfInfo {
+	var dps []disk.Performance
+	var addr string
+	for _, endpoint := range endpoints {
+		// Only proceed for local endpoints
+		if endpoint.IsLocal {
+			addr = GetLocalPeer(endpoints)
+			if _, err := os.Stat(endpoint.Path); err != nil {
+				// Since this drive is not available, add relevant details and proceed
+				dps = append(dps, disk.Performance{Path: endpoint.Path, Error: err.Error()})
+				continue
+			}
+			tempObj := mustGetUUID()
+			fsPath := pathJoin(endpoint.Path, minioMetaTmpBucket, tempObj)
+			dp := disk.GetPerformance(fsPath)
+			dp.Path = endpoint.Path
+			dps = append(dps, dp)
+		}
+	}
+
+	return ServerDrivesPerfInfo{
+		Addr: addr,
+		Perf: dps,
+	}
+}
+
 // NewEndpointList - returns new endpoint list based on input args.
 func NewEndpointList(args ...string) (endpoints EndpointList, err error) {
 	var endpointType EndpointType