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// Copyright 2015-2018 The NATS 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 pse
import (
"bytes"
"fmt"
"io/ioutil"
"os"
"sync/atomic"
"syscall"
"time"
)
var (
procStatFile string
ticks int64
lastTotal int64
lastSeconds int64
ipcpu int64
)
const (
utimePos = 13
stimePos = 14
startPos = 21
vssPos = 22
rssPos = 23
)
func init() {
// Avoiding to generate docker image without CGO
ticks = 100 // int64(C.sysconf(C._SC_CLK_TCK))
procStatFile = fmt.Sprintf("/proc/%d/stat", os.Getpid())
periodic()
}
// Sampling function to keep pcpu relevant.
func periodic() {
contents, err := ioutil.ReadFile(procStatFile)
if err != nil {
return
}
fields := bytes.Fields(contents)
// PCPU
pstart := parseInt64(fields[startPos])
utime := parseInt64(fields[utimePos])
stime := parseInt64(fields[stimePos])
total := utime + stime
var sysinfo syscall.Sysinfo_t
if err := syscall.Sysinfo(&sysinfo); err != nil {
return
}
seconds := int64(sysinfo.Uptime) - (pstart / ticks)
// Save off temps
lt := lastTotal
ls := lastSeconds
// Update last sample
lastTotal = total
lastSeconds = seconds
// Adjust to current time window
total -= lt
seconds -= ls
if seconds > 0 {
atomic.StoreInt64(&ipcpu, (total*1000/ticks)/seconds)
}
time.AfterFunc(1*time.Second, periodic)
}
func ProcUsage(pcpu *float64, rss, vss *int64) error {
contents, err := ioutil.ReadFile(procStatFile)
if err != nil {
return err
}
fields := bytes.Fields(contents)
// Memory
*rss = (parseInt64(fields[rssPos])) << 12
*vss = parseInt64(fields[vssPos])
// PCPU
// We track this with periodic sampling, so just load and go.
*pcpu = float64(atomic.LoadInt64(&ipcpu)) / 10.0
return nil
}
// Ascii numbers 0-9
const (
asciiZero = 48
asciiNine = 57
)
// parseInt64 expects decimal positive numbers. We
// return -1 to signal error
func parseInt64(d []byte) (n int64) {
if len(d) == 0 {
return -1
}
for _, dec := range d {
if dec < asciiZero || dec > asciiNine {
return -1
}
n = n*10 + (int64(dec) - asciiZero)
}
return n
}
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