dashboard: CPU, memory, diskIO and traffic on the footer (#15950)

* dashboard: footer, deep state update

* dashboard: resolve asset path

* dashboard: prevent state update on every reconnection

* dashboard: fix linter issue

* dashboard, cmd: minor UI fix, include commit hash

* dashboard: gitCommit renamed to commit

* dashboard: move the geth version to the right, make commit optional

* dashboard: memory, traffic and CPU on footer

* dashboard: fix merge

* dashboard: CPU, diskIO on footer

* dashboard: rename variables, use group declaration

* dashboard: docs

vendor/github.com/elastic/gosigar/sigar_linux.go

@@ -0,0 +1,84 @@
+// Copyright (c) 2012 VMware, Inc.
+
+package gosigar
+
+import (
+	"io/ioutil"
+	"strconv"
+	"strings"
+	"syscall"
+)
+
+func init() {
+	system.ticks = 100 // C.sysconf(C._SC_CLK_TCK)
+
+	Procd = "/proc"
+
+	getLinuxBootTime()
+}
+
+func getMountTableFileName() string {
+	return "/etc/mtab"
+}
+
+func (self *Uptime) Get() error {
+	sysinfo := syscall.Sysinfo_t{}
+
+	if err := syscall.Sysinfo(&sysinfo); err != nil {
+		return err
+	}
+
+	self.Length = float64(sysinfo.Uptime)
+
+	return nil
+}
+
+func (self *FDUsage) Get() error {
+	return readFile(Procd+"/sys/fs/file-nr", func(line string) bool {
+		fields := strings.Fields(line)
+		if len(fields) == 3 {
+			self.Open, _ = strconv.ParseUint(fields[0], 10, 64)
+			self.Unused, _ = strconv.ParseUint(fields[1], 10, 64)
+			self.Max, _ = strconv.ParseUint(fields[2], 10, 64)
+		}
+		return false
+	})
+}
+
+func (self *ProcFDUsage) Get(pid int) error {
+	err := readFile(procFileName(pid, "limits"), func(line string) bool {
+		if strings.HasPrefix(line, "Max open files") {
+			fields := strings.Fields(line)
+			if len(fields) == 6 {
+				self.SoftLimit, _ = strconv.ParseUint(fields[3], 10, 64)
+				self.HardLimit, _ = strconv.ParseUint(fields[4], 10, 64)
+			}
+			return false
+		}
+		return true
+	})
+	if err != nil {
+		return err
+	}
+	fds, err := ioutil.ReadDir(procFileName(pid, "fd"))
+	if err != nil {
+		return err
+	}
+	self.Open = uint64(len(fds))
+	return nil
+}
+
+func parseCpuStat(self *Cpu, line string) error {
+	fields := strings.Fields(line)
+
+	self.User, _ = strtoull(fields[1])
+	self.Nice, _ = strtoull(fields[2])
+	self.Sys, _ = strtoull(fields[3])
+	self.Idle, _ = strtoull(fields[4])
+	self.Wait, _ = strtoull(fields[5])
+	self.Irq, _ = strtoull(fields[6])
+	self.SoftIrq, _ = strtoull(fields[7])
+	self.Stolen, _ = strtoull(fields[8])
+
+	return nil
+}