Add Profiler Admin API (#6463)

Two handlers are added to admin API to enable profiling and disable
profiling of a server in a standalone mode, or all nodes in the
distributed mode.

/minio/admin/profiling/start/{cpu,block,mem}:
  - Start profiling and return starting JSON results, e.g. one
    node is offline.

/minio/admin/profiling/download:
  - Stop the on-going profiling task
  - Stream a zip file which contains all profiling files that can
    be later inspected by go tool pprof

pkg/madmin/profiling-commands.go

@@ -0,0 +1,104 @@
+/*
+ * Minio Cloud Storage, (C) 2017, 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 madmin
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+)
+
+// ProfilerType represents the profiler type
+// passed to the profiler subsystem, currently
+// it can be only "cpu", "mem" or "block"
+type ProfilerType string
+
+const (
+	// ProfilerCPU represents CPU profiler type
+	ProfilerCPU = ProfilerType("cpu")
+	// ProfilerMEM represents MEM profiler type
+	ProfilerMEM = ProfilerType("mem")
+	// ProfilerBlock represents Block profiler type
+	ProfilerBlock = ProfilerType("block")
+)
+
+// StartProfilingResult holds the result of starting
+// profiler result in a given node.
+type StartProfilingResult struct {
+	NodeName string `json:"nodeName"`
+	Success  bool   `json:"success"`
+	Error    string `json:"error"`
+}
+
+// StartProfiling makes an admin call to remotely start profiling on a standalone
+// server or the whole cluster in  case of a distributed setup.
+func (adm *AdminClient) StartProfiling(profiler ProfilerType) ([]StartProfilingResult, error) {
+	path := fmt.Sprintf("/v1/profiling/start/%s", profiler)
+	resp, err := adm.executeMethod("POST", requestData{
+		relPath: path,
+	})
+	defer closeResponse(resp)
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, httpRespToErrorResponse(resp)
+	}
+
+	jsonResult, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	var startResults []StartProfilingResult
+	err = json.Unmarshal(jsonResult, &startResults)
+	if err != nil {
+		return nil, err
+	}
+
+	return startResults, nil
+}
+
+// DownloadProfilingData makes an admin call to download profiling data of a standalone
+// server or of the whole cluster in  case of a distributed setup.
+func (adm *AdminClient) DownloadProfilingData() (io.ReadCloser, error) {
+	path := fmt.Sprintf("/v1/profiling/download")
+	resp, err := adm.executeMethod("GET", requestData{
+		relPath: path,
+	})
+
+	if err != nil {
+		closeResponse(resp)
+		return nil, err
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		closeResponse(resp)
+		return nil, httpRespToErrorResponse(resp)
+	}
+
+	if resp.Body == nil {
+		return nil, errors.New("body is nil")
+	}
+
+	return resp.Body, nil
+}