From 6101585fd2af36c2dd147eedec054057469d1033 Mon Sep 17 00:00:00 2001
From: Ingo Oppermann <ingo@datarhei.com>
Date: Thu, 25 Jul 2024 09:30:11 +0200
Subject: [PATCH] Extract linux specifc code from psutils for reading CPU times

---
 go.mod                  |  2 +-
 psutil/process.go       | 20 ---------
 psutil/process_linux.go | 97 +++++++++++++++++++++++++++++++++++++++++
 psutil/process_other.go | 24 ++++++++++
 4 files changed, 122 insertions(+), 21 deletions(-)
 create mode 100644 psutil/process_linux.go
 create mode 100644 psutil/process_other.go

diff --git a/go.mod b/go.mod
index d41163e9..a19cd943 100644
--- a/go.mod
+++ b/go.mod
@@ -40,6 +40,7 @@ require (
 	github.com/stretchr/testify v1.9.0
 	github.com/swaggo/echo-swagger v1.4.1
 	github.com/swaggo/swag v1.16.3
+	github.com/tklauser/go-sysconf v0.3.14
 	github.com/vektah/gqlparser/v2 v2.5.16
 	github.com/xeipuuv/gojsonschema v1.2.0
 	go.etcd.io/bbolt v1.3.10
@@ -104,7 +105,6 @@ require (
 	github.com/shoenig/go-m1cpu v0.1.6 // indirect
 	github.com/sosodev/duration v1.3.1 // indirect
 	github.com/swaggo/files/v2 v2.0.1 // indirect
-	github.com/tklauser/go-sysconf v0.3.14 // indirect
 	github.com/tklauser/numcpus v0.8.0 // indirect
 	github.com/urfave/cli/v2 v2.27.2 // indirect
 	github.com/valyala/bytebufferpool v1.0.0 // indirect
diff --git a/psutil/process.go b/psutil/process.go
index dc190ef3..0789f553 100644
--- a/psutil/process.go
+++ b/psutil/process.go
@@ -142,26 +142,6 @@ func (p *process) Resume() error {
 	return p.proc.Resume()
 }
 
-func (p *process) cpuTimes() (*cpuTimesStat, error) {
-	times, err := p.proc.Times()
-	if err != nil {
-		return nil, err
-	}
-
-	s := &cpuTimesStat{
-		total:  cpuTotal(times),
-		system: times.System,
-		user:   times.User,
-	}
-
-	s.other = s.total - s.system - s.user
-	if s.other < 0.0001 {
-		s.other = 0
-	}
-
-	return s, nil
-}
-
 func (p *process) CPUPercent() (*CPUInfoStat, error) {
 	var diff float64
 
diff --git a/psutil/process_linux.go b/psutil/process_linux.go
new file mode 100644
index 00000000..e5b8894a
--- /dev/null
+++ b/psutil/process_linux.go
@@ -0,0 +1,97 @@
+//go:build linux
+// +build linux
+
+package psutil
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	"github.com/tklauser/go-sysconf"
+)
+
+// Extracted from "github.com/shirou/gopsutil/v3/process/process_linux.go"
+// We only need the CPU times. p.proc.Times() calls a function that is
+// doing more than we actually need.
+
+var clockTicks = 100 // default value
+
+func init() {
+	clkTck, err := sysconf.Sysconf(sysconf.SC_CLK_TCK)
+	// ignore errors
+	if err == nil {
+		clockTicks = int(clkTck)
+	}
+}
+
+func (p *process) cpuTimes() (*cpuTimesStat, error) {
+	value := os.Getenv("HOST_PROC")
+	if value == "" {
+		value = "/proc"
+	}
+
+	path := filepath.Join(value, strconv.FormatInt(int64(p.pid), 10), "stat")
+
+	contents, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	// Indexing from one, as described in `man proc` about the file /proc/[pid]/stat
+	fields := splitProcStat(contents)
+
+	utime, err := strconv.ParseFloat(fields[14], 64)
+	if err != nil {
+		return nil, err
+	}
+
+	stime, err := strconv.ParseFloat(fields[15], 64)
+	if err != nil {
+		return nil, err
+	}
+
+	// There is no such thing as iotime in stat file.  As an approximation, we
+	// will use delayacct_blkio_ticks (aggregated block I/O delays, as per Linux
+	// docs).  Note: I am assuming at least Linux 2.6.18
+	var iotime float64
+	if len(fields) > 42 {
+		iotime, err = strconv.ParseFloat(fields[42], 64)
+		if err != nil {
+			iotime = 0 // Ancient linux version, most likely
+		}
+	} else {
+		iotime = 0 // e.g. SmartOS containers
+	}
+
+	userTime := utime / float64(clockTicks)
+	systemTime := stime / float64(clockTicks)
+	iowaitTime := iotime / float64(clockTicks)
+
+	s := &cpuTimesStat{
+		total:  userTime + systemTime + iowaitTime,
+		system: systemTime,
+		user:   userTime,
+		other:  iowaitTime,
+	}
+
+	if s.other < 0.0001 {
+		s.other = 0
+	}
+
+	return s, nil
+}
+
+func splitProcStat(content []byte) []string {
+	nameStart := bytes.IndexByte(content, '(')
+	nameEnd := bytes.LastIndexByte(content, ')')
+	restFields := strings.Fields(string(content[nameEnd+2:])) // +2 skip ') '
+	name := content[nameStart+1 : nameEnd]
+	pid := strings.TrimSpace(string(content[:nameStart]))
+	fields := make([]string, 3, len(restFields)+3)
+	fields[1] = string(pid)
+	fields[2] = string(name)
+	fields = append(fields, restFields...)
+	return fields
+}
diff --git a/psutil/process_other.go b/psutil/process_other.go
new file mode 100644
index 00000000..f5464906
--- /dev/null
+++ b/psutil/process_other.go
@@ -0,0 +1,24 @@
+//go:build !linux
+// +build !linux
+
+package psutil
+
+func (p *process) cpuTimes() (*cpuTimesStat, error) {
+	times, err := p.proc.Times()
+	if err != nil {
+		return nil, err
+	}
+
+	s := &cpuTimesStat{
+		total:  cpuTotal(times),
+		system: times.System,
+		user:   times.User,
+	}
+
+	s.other = s.total - s.system - s.user
+	if s.other < 0.0001 {
+		s.other = 0
+	}
+
+	return s, nil
+}