Prometheus endpoint (#5256)

* Add prometheus collector and route

* dep ensure -add github.com/prometheus/client_golang/prometheus

* dep ensure -update github.com/golang/protobuf

* add metrics to reserved usernames

* add comment head in metrics package

* fix style imports

* add metrics settings

* add bearer token check

* mapping metrics configs

* fix lint

* update config cheat sheet

* update conf sample, typo fix

vendor/github.com/prometheus/procfs/proc_limits.go

@@ -0,0 +1,150 @@
+// Copyright 2018 The Prometheus Authors
+// 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 procfs
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+)
+
+// ProcLimits represents the soft limits for each of the process's resource
+// limits. For more information see getrlimit(2):
+// http://man7.org/linux/man-pages/man2/getrlimit.2.html.
+type ProcLimits struct {
+	// CPU time limit in seconds.
+	CPUTime int64
+	// Maximum size of files that the process may create.
+	FileSize int64
+	// Maximum size of the process's data segment (initialized data,
+	// uninitialized data, and heap).
+	DataSize int64
+	// Maximum size of the process stack in bytes.
+	StackSize int64
+	// Maximum size of a core file.
+	CoreFileSize int64
+	// Limit of the process's resident set in pages.
+	ResidentSet int64
+	// Maximum number of processes that can be created for the real user ID of
+	// the calling process.
+	Processes int64
+	// Value one greater than the maximum file descriptor number that can be
+	// opened by this process.
+	OpenFiles int64
+	// Maximum number of bytes of memory that may be locked into RAM.
+	LockedMemory int64
+	// Maximum size of the process's virtual memory address space in bytes.
+	AddressSpace int64
+	// Limit on the combined number of flock(2) locks and fcntl(2) leases that
+	// this process may establish.
+	FileLocks int64
+	// Limit of signals that may be queued for the real user ID of the calling
+	// process.
+	PendingSignals int64
+	// Limit on the number of bytes that can be allocated for POSIX message
+	// queues for the real user ID of the calling process.
+	MsqqueueSize int64
+	// Limit of the nice priority set using setpriority(2) or nice(2).
+	NicePriority int64
+	// Limit of the real-time priority set using sched_setscheduler(2) or
+	// sched_setparam(2).
+	RealtimePriority int64
+	// Limit (in microseconds) on the amount of CPU time that a process
+	// scheduled under a real-time scheduling policy may consume without making
+	// a blocking system call.
+	RealtimeTimeout int64
+}
+
+const (
+	limitsFields    = 3
+	limitsUnlimited = "unlimited"
+)
+
+var (
+	limitsDelimiter = regexp.MustCompile("  +")
+)
+
+// NewLimits returns the current soft limits of the process.
+func (p Proc) NewLimits() (ProcLimits, error) {
+	f, err := os.Open(p.path("limits"))
+	if err != nil {
+		return ProcLimits{}, err
+	}
+	defer f.Close()
+
+	var (
+		l = ProcLimits{}
+		s = bufio.NewScanner(f)
+	)
+	for s.Scan() {
+		fields := limitsDelimiter.Split(s.Text(), limitsFields)
+		if len(fields) != limitsFields {
+			return ProcLimits{}, fmt.Errorf(
+				"couldn't parse %s line %s", f.Name(), s.Text())
+		}
+
+		switch fields[0] {
+		case "Max cpu time":
+			l.CPUTime, err = parseInt(fields[1])
+		case "Max file size":
+			l.FileSize, err = parseInt(fields[1])
+		case "Max data size":
+			l.DataSize, err = parseInt(fields[1])
+		case "Max stack size":
+			l.StackSize, err = parseInt(fields[1])
+		case "Max core file size":
+			l.CoreFileSize, err = parseInt(fields[1])
+		case "Max resident set":
+			l.ResidentSet, err = parseInt(fields[1])
+		case "Max processes":
+			l.Processes, err = parseInt(fields[1])
+		case "Max open files":
+			l.OpenFiles, err = parseInt(fields[1])
+		case "Max locked memory":
+			l.LockedMemory, err = parseInt(fields[1])
+		case "Max address space":
+			l.AddressSpace, err = parseInt(fields[1])
+		case "Max file locks":
+			l.FileLocks, err = parseInt(fields[1])
+		case "Max pending signals":
+			l.PendingSignals, err = parseInt(fields[1])
+		case "Max msgqueue size":
+			l.MsqqueueSize, err = parseInt(fields[1])
+		case "Max nice priority":
+			l.NicePriority, err = parseInt(fields[1])
+		case "Max realtime priority":
+			l.RealtimePriority, err = parseInt(fields[1])
+		case "Max realtime timeout":
+			l.RealtimeTimeout, err = parseInt(fields[1])
+		}
+		if err != nil {
+			return ProcLimits{}, err
+		}
+	}
+
+	return l, s.Err()
+}
+
+func parseInt(s string) (int64, error) {
+	if s == limitsUnlimited {
+		return -1, nil
+	}
+	i, err := strconv.ParseInt(s, 10, 64)
+	if err != nil {
+		return 0, fmt.Errorf("couldn't parse value %s: %s", s, err)
+	}
+	return i, nil
+}