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// 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 (
"bytes"
"fmt"
"io/ioutil"
"os"
)
// Originally, this USER_HZ value was dynamically retrieved via a sysconf call
// which required cgo. However, that caused a lot of problems regarding
// cross-compilation. Alternatives such as running a binary to determine the
// value, or trying to derive it in some other way were all problematic. After
// much research it was determined that USER_HZ is actually hardcoded to 100 on
// all Go-supported platforms as of the time of this writing. This is why we
// decided to hardcode it here as well. It is not impossible that there could
// be systems with exceptions, but they should be very exotic edge cases, and
// in that case, the worst outcome will be two misreported metrics.
//
// See also the following discussions:
//
// - https://github.com/prometheus/node_exporter/issues/52
// - https://github.com/prometheus/procfs/pull/2
// - http://stackoverflow.com/questions/17410841/how-does-user-hz-solve-the-jiffy-scaling-issue
const userHZ = 100
// ProcStat provides status information about the process,
// read from /proc/[pid]/stat.
type ProcStat struct {
// The process ID.
PID int
// The filename of the executable.
Comm string
// The process state.
State string
// The PID of the parent of this process.
PPID int
// The process group ID of the process.
PGRP int
// The session ID of the process.
Session int
// The controlling terminal of the process.
TTY int
// The ID of the foreground process group of the controlling terminal of
// the process.
TPGID int
// The kernel flags word of the process.
Flags uint
// The number of minor faults the process has made which have not required
// loading a memory page from disk.
MinFlt uint
// The number of minor faults that the process's waited-for children have
// made.
CMinFlt uint
// The number of major faults the process has made which have required
// loading a memory page from disk.
MajFlt uint
// The number of major faults that the process's waited-for children have
// made.
CMajFlt uint
// Amount of time that this process has been scheduled in user mode,
// measured in clock ticks.
UTime uint
// Amount of time that this process has been scheduled in kernel mode,
// measured in clock ticks.
STime uint
// Amount of time that this process's waited-for children have been
// scheduled in user mode, measured in clock ticks.
CUTime uint
// Amount of time that this process's waited-for children have been
// scheduled in kernel mode, measured in clock ticks.
CSTime uint
// For processes running a real-time scheduling policy, this is the negated
// scheduling priority, minus one.
Priority int
// The nice value, a value in the range 19 (low priority) to -20 (high
// priority).
Nice int
// Number of threads in this process.
NumThreads int
// The time the process started after system boot, the value is expressed
// in clock ticks.
Starttime uint64
// Virtual memory size in bytes.
VSize int
// Resident set size in pages.
RSS int
fs FS
}
// NewStat returns the current status information of the process.
func (p Proc) NewStat() (ProcStat, error) {
f, err := os.Open(p.path("stat"))
if err != nil {
return ProcStat{}, err
}
defer f.Close()
data, err := ioutil.ReadAll(f)
if err != nil {
return ProcStat{}, err
}
var (
ignore int
s = ProcStat{PID: p.PID, fs: p.fs}
l = bytes.Index(data, []byte("("))
r = bytes.LastIndex(data, []byte(")"))
)
if l < 0 || r < 0 {
return ProcStat{}, fmt.Errorf(
"unexpected format, couldn't extract comm: %s",
data,
)
}
s.Comm = string(data[l+1 : r])
_, err = fmt.Fscan(
bytes.NewBuffer(data[r+2:]),
&s.State,
&s.PPID,
&s.PGRP,
&s.Session,
&s.TTY,
&s.TPGID,
&s.Flags,
&s.MinFlt,
&s.CMinFlt,
&s.MajFlt,
&s.CMajFlt,
&s.UTime,
&s.STime,
&s.CUTime,
&s.CSTime,
&s.Priority,
&s.Nice,
&s.NumThreads,
&ignore,
&s.Starttime,
&s.VSize,
&s.RSS,
)
if err != nil {
return ProcStat{}, err
}
return s, nil
}
// VirtualMemory returns the virtual memory size in bytes.
func (s ProcStat) VirtualMemory() int {
return s.VSize
}
// ResidentMemory returns the resident memory size in bytes.
func (s ProcStat) ResidentMemory() int {
return s.RSS * os.Getpagesize()
}
// StartTime returns the unix timestamp of the process in seconds.
func (s ProcStat) StartTime() (float64, error) {
stat, err := s.fs.NewStat()
if err != nil {
return 0, err
}
return float64(stat.BootTime) + (float64(s.Starttime) / userHZ), nil
}
// CPUTime returns the total CPU user and system time in seconds.
func (s ProcStat) CPUTime() float64 {
return float64(s.UTime+s.STime) / userHZ
}
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