snapshot of https://github.com/nats-io/nats-server.git (main, 2026-09-15; blobs > 131072B omitted)

server/pse/pse_linux.go

@@ -0,0 +1,128 @@
+// Copyright 2015-2025 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"
+	"os"
+	"sync/atomic"
+	"syscall"
+	"time"
+)
+
+var (
+	procStatFile string
+	ticks        int64
+	lastTotal    int64
+	lastSeconds  int64
+	ipcpu        int64
+	pageSize     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())
+	pageSize = int64(os.Getpagesize())
+	periodic()
+}
+
+// Sampling function to keep pcpu relevant.
+func periodic() {
+	contents, err := os.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)
+}
+
+// ProcUsage returns CPU usage
+func ProcUsage(pcpu *float64, rss, vss *int64) error {
+	contents, err := os.ReadFile(procStatFile)
+	if err != nil {
+		return err
+	}
+	fields := bytes.Fields(contents)
+
+	// Memory
+	*rss = (parseInt64(fields[rssPos])) * pageSize
+	*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
+}