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

pkg/madmin/API.md

@@ -39,7 +39,7 @@ func main() {
 | Service operations         | Info operations  | Healing operations                    | Config operations        | IAM operations | Misc                                |
 |:----------------------------|:----------------------------|:--------------------------------------|:--------------------------|:------------------------------------|:------------------------------------|
 | [`ServiceStatus`](#ServiceStatus) | [`ServerInfo`](#ServerInfo) | [`Heal`](#Heal) | [`GetConfig`](#GetConfig) | [`AddUser`](#AddUser) | [`SetAdminCredentials`](#SetAdminCredentials) |
-| [`ServiceSendAction`](#ServiceSendAction) | | | [`SetConfig`](#SetConfig) | [`SetUserPolicy`](#SetUserPolicy) | [`StartProfiling`](#StartProfiling) |
+| [`ServiceSendAction`](#ServiceSendAction) | [`ServerDrivesPerfInfo`](#ServerDrivesPerfInfo) | [`SetConfig`](#SetConfig) | [`SetUserPolicy`](#SetUserPolicy) | [`StartProfiling`](#StartProfiling) |
 | | |            | [`GetConfigKeys`](#GetConfigKeys) | [`ListUsers`](#ListUsers) | [`DownloadProfilingData`](#DownloadProfilingData) |
 | | |            | [`SetConfigKeys`](#SetConfigKeys) | [`AddCannedPolicy`](#AddCannedPolicy) | |
 
@@ -204,6 +204,23 @@ Fetches information for all cluster nodes, such as server properties, storage in
 
  ```
 
+<a name="ServerDrivesPerfInfo"></a>
+### ServerDrivesPerfInfo() ([]ServerDrivesPerfInfo, error)
+
+Fetches drive performance information for all cluster nodes. Returned value is in Bytes/s.
+
+| Param | Type | Description |
+|---|---|---|
+|`di.Addr` | _string_ | Address of the server the following information is retrieved from. |
+|`di.Error` | _string _ | Errors (if any) encountered while reaching this node |
+|`di.DrivesPerf` | _disk.Performance_ | Path of the drive mount on above server and read, write speed. |
+
+| Param | Type | Description |
+|---|---|---|
+|`disk.Performance.Path` | _string_ | Path of drive mount. |
+|`disk.Performance.Error` | _string_ | Error (if any) encountered while accessing this drive. |
+|`disk.Performance.WriteSpeed` | _float64_ | Write speed on above path in Bytes/s. |
+|`disk.Performance.ReadSpeed` | _float64_ | Read speed on above path in Bytes/s. |
 
 ## 6. Heal operations
 

pkg/madmin/examples/drives-perf-info.go

@@ -0,0 +1,44 @@
+// +build ignore
+
+/*
+ * Minio Cloud Storage, (C) 2018 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 main
+
+import (
+	"log"
+
+	"github.com/minio/minio/pkg/madmin"
+)
+
+func main() {
+	// Note: YOUR-ACCESSKEYID, YOUR-SECRETACCESSKEY and my-bucketname are
+	// dummy values, please replace them with original values.
+
+	// API requests are secure (HTTPS) if secure=true and insecure (HTTPS) otherwise.
+	// New returns an Minio Admin client object.
+	madmClnt, err := madmin.New("your-minio.example.com:9000", "YOUR-ACCESSKEYID", "YOUR-SECRETACCESSKEY", true)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	st, err := madmClnt.ServerDrivesPerfInfo()
+	if err != nil {
+		log.Fatalln(err)
+	}
+	log.Println(st)
+}

pkg/madmin/info-commands.go

@@ -21,7 +21,10 @@ import (
 	"encoding/json"
 	"io/ioutil"
 	"net/http"
+	"net/url"
 	"time"
+
+	"github.com/minio/minio/pkg/disk"
 )
 
 // BackendType - represents different backend types.
@@ -147,3 +150,46 @@ func (adm *AdminClient) ServerInfo() ([]ServerInfo, error) {
 
 	return serversInfo, nil
 }
+
+// ServerDrivesPerfInfo holds informantion about address and write speed of
+// all drives in a single server node
+type ServerDrivesPerfInfo struct {
+	Addr  string             `json:"addr"`
+	Error string             `json:"error,omitempty"`
+	Perf  []disk.Performance `json:"perf"`
+}
+
+// ServerDrivesPerfInfo - Returns drive's read and write performance information
+func (adm *AdminClient) ServerDrivesPerfInfo() ([]ServerDrivesPerfInfo, error) {
+	v := url.Values{}
+	v.Set("perfType", string("drive"))
+	resp, err := adm.executeMethod("GET", requestData{
+		relPath:     "/v1/performance",
+		queryValues: v,
+	})
+
+	defer closeResponse(resp)
+	if err != nil {
+		return nil, err
+	}
+
+	// Check response http status code
+	if resp.StatusCode != http.StatusOK {
+		return nil, httpRespToErrorResponse(resp)
+	}
+
+	// Unmarshal the server's json response
+	var info []ServerDrivesPerfInfo
+
+	respBytes, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	err = json.Unmarshal(respBytes, &info)
+	if err != nil {
+		return nil, err
+	}
+
+	return info, nil
+}