pidpath.go

Documentation: github.com/chaos-mesh/chaos-mesh/pkg/chaosdaemon/cgroups

     1  // Copyright 2021 Chaos Mesh Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  // http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  //
    15  
    16  package cgroups
    17  
    18  import (
    19  	"bufio"
    20  	"bytes"
    21  	"fmt"
    22  	"io"
    23  	"os"
    24  	"os/exec"
    25  	"strings"
    26  
    27  	"github.com/containerd/cgroups"
    28  	"github.com/pkg/errors"
    29  )
    30  
    31  func V1() ([]cgroups.Subsystem, error) {
    32  	subsystems, err := defaults("/host-sys/fs/cgroup")
    33  	if err != nil {
    34  		return nil, err
    35  	}
    36  	var enabled []cgroups.Subsystem
    37  	for _, s := range pathers(subsystems) {
    38  		// check and remove the default groups that do not exist
    39  		if _, err := os.Lstat(s.Path("/")); err == nil {
    40  			enabled = append(enabled, s)
    41  		}
    42  	}
    43  	return enabled, nil
    44  }
    45  
    46  func PidPath(pid int) cgroups.Path {
    47  	p := fmt.Sprintf("/proc/%d/cgroup", pid)
    48  	paths, err := cgroups.ParseCgroupFile(p)
    49  	if err != nil {
    50  		return func(_ cgroups.Name) (string, error) {
    51  			return "", errors.Wrapf(err, "parse cgroup file %s", p)
    52  		}
    53  	}
    54  
    55  	return func(name cgroups.Name) (string, error) {
    56  		root, ok := paths[string(name)]
    57  		if !ok {
    58  			if root, ok = paths["name="+string(name)]; !ok {
    59  				return "", errors.New("controller is not supported")
    60  			}
    61  		}
    62  
    63  		return root, nil
    64  	}
    65  }
    66  
    67  func V2PidGroupPath(pid int) (string, error) {
    68  	// escape the CGroup Namespace, resolve https://github.com/chaos-mesh/chaos-mesh/pull/2928#issuecomment-1049465242
    69  	// nsenter -C -t 1 cat /proc/$pid/cgroup
    70  	command := exec.Command("nsenter", "-C", "-t", "1", "cat", fmt.Sprintf("/proc/%d/cgroup", pid))
    71  	var buffer bytes.Buffer
    72  	command.Stdout = &buffer
    73  
    74  	err := command.Run()
    75  	if err != nil {
    76  		return "", errors.Wrapf(err, "get cgroup path of pid %d", pid)
    77  	}
    78  	return parseCgroupFromReader(&buffer)
    79  }
    80  
    81  // parseCgroupFromReader is copied from github.com/containerd/cgroups/v2/utils.go
    82  func parseCgroupFromReader(r io.Reader) (string, error) {
    83  	var (
    84  		s = bufio.NewScanner(r)
    85  	)
    86  	for s.Scan() {
    87  		var (
    88  			text  = s.Text()
    89  			parts = strings.SplitN(text, ":", 3)
    90  		)
    91  		if len(parts) < 3 {
    92  			return "", fmt.Errorf("invalid cgroup entry: %q", text)
    93  		}
    94  		// text is like "0::/user.slice/user-1001.slice/session-1.scope"
    95  		if parts[0] == "0" && parts[1] == "" {
    96  			return parts[2], nil
    97  		}
    98  	}
    99  	if err := s.Err(); err != nil {
   100  		return "", err
   101  	}
   102  	return "", fmt.Errorf("cgroup path not found")
   103  }
   104