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//go:build linux
// +build linux
// Copyright (c) 2015-2024 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
// Package cgroup implements parsing for all the cgroup
// categories and functionality in a simple way.
package cgroup
import (
"bufio"
"bytes"
"fmt"
"io"
"os"
"os/exec"
"path/filepath"
"strconv"
"strings"
)
// DO NOT EDIT following constants are chosen defaults for any kernel
// after 3.x, please open a GitHub issue https://github.com/minio/madmin-go/v2/issues
// and discuss first if you wish to change this.
const (
// Default string for looking for kernel memory param.
memoryLimitKernelParam = "memory.limit_in_bytes"
// Points to sys path memory path.
cgroupMemSysPath = "/sys/fs/cgroup/memory"
// Default docker prefix.
dockerPrefixName = "/docker/"
// Proc controller group path.
cgroupFileTemplate = "/proc/%d/cgroup"
)
// CGEntries - represents all the entries in a process cgroup file
// at /proc/<pid>/cgroup as key value pairs.
type CGEntries map[string]string
// GetEntries reads and parses all the cgroup entries for a given process.
func GetEntries(pid int) (CGEntries, error) {
r, err := os.Open(fmt.Sprintf(cgroupFileTemplate, pid))
if err != nil {
return nil, err
}
defer r.Close()
return parseProcCGroup(r)
}
// parseProcCGroup - cgroups are always in the following
// format once enabled you need to know the pid of the
// application you are looking for so that the the
// following parsing logic only parses the file located
// at /proc/<pid>/cgroup.
//
// CGROUP entries id, component and path are always in
// the following format. “ID:COMPONENT:PATH“
//
// Following code block parses this information and
// returns a procCGroup which is a parsed list of all
// the line by line entires from /proc/<pid>/cgroup.
func parseProcCGroup(r io.Reader) (CGEntries, error) {
cgEntries := CGEntries{}
// Start reading cgroup categories line by line
// and process them into procCGroup structure.
scanner := bufio.NewScanner(r)
for scanner.Scan() {
line := scanner.Text()
tokens := strings.SplitN(line, ":", 3)
if len(tokens) < 3 {
continue
}
name, path := tokens[1], tokens[2]
for _, token := range strings.Split(name, ",") {
name = strings.TrimPrefix(token, "name=")
cgEntries[name] = path
}
}
// Return upon any error while reading the cgroup categories.
if err := scanner.Err(); err != nil {
return nil, err
}
return cgEntries, nil
}
// Fetch value of the cgroup kernel param from the cgroup manager,
// if cgroup manager is configured we should just rely on `cgm` cli
// to fetch all the values for us.
func getManagerKernValue(cname, path, kernParam string) (limit uint64, err error) {
cmd := exec.Command("cgm", "getvalue", cname, path, kernParam)
var out bytes.Buffer
cmd.Stdout = &out
if err = cmd.Run(); err != nil {
return 0, err
}
// Parse the cgm output.
limit, err = strconv.ParseUint(strings.TrimSpace(out.String()), 10, 64)
return limit, err
}
// Get cgroup memory limit file path.
func getMemoryLimitFilePath(cgPath string) string {
path := cgroupMemSysPath
// Docker generates weird cgroup paths that don't
// really exist on the file system.
//
// For example on regular Linux OS :
// `/user.slice/user-1000.slice/session-1.scope`
//
// But they exist as a bind mount on Docker and
// are not accessible : `/docker/<hash>`
//
// We we will just ignore if there is `/docker` in the
// path ignore and fall back to :
// `/sys/fs/cgroup/memory/memory.limit_in_bytes`
if !strings.HasPrefix(cgPath, dockerPrefixName) {
path = filepath.Join(path, cgPath)
}
// Final path.
return filepath.Join(path, memoryLimitKernelParam)
}
// GetMemoryLimit - Fetches cgroup memory limit either from
// a file path at '/sys/fs/cgroup/memory', if path fails then
// fallback to querying cgroup manager.
func GetMemoryLimit(pid int) (limit uint64, err error) {
var cg CGEntries
cg, err = GetEntries(pid)
if err != nil {
return 0, err
}
path := cg["memory"]
limit, err = getManagerKernValue("memory", path, memoryLimitKernelParam)
if err != nil {
// Upon any failure returned from `cgm`, on some systems cgm
// might not be installed. We fallback to using the the sysfs
// path instead to lookup memory limits.
var b []byte
b, err = os.ReadFile(getMemoryLimitFilePath(path))
if err != nil {
return 0, err
}
limit, err = strconv.ParseUint(strings.TrimSpace(string(b)), 10, 64)
}
return limit, err
}
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