blob: 0094a13c05dc7b3847951c27ddc6284f247bfbcb [file] [log] [blame]
khenaidoo26721882021-08-11 17:42:52 -04001// Copyright 2020 The Prometheus Authors
2// Licensed under the Apache License, Version 2.0 (the "License");
3// you may not use this file except in compliance with the License.
4// You may obtain a copy of the License at
5//
6// http://www.apache.org/licenses/LICENSE-2.0
7//
8// Unless required by applicable law or agreed to in writing, software
9// distributed under the License is distributed on an "AS IS" BASIS,
10// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
11// See the License for the specific language governing permissions and
12// limitations under the License.
13
14package procfs
15
16import (
17 "bufio"
18 "bytes"
19 "fmt"
20 "strconv"
21 "strings"
22
23 "github.com/prometheus/procfs/internal/util"
24)
25
26// Cgroup models one line from /proc/[pid]/cgroup. Each Cgroup struct describes the the placement of a PID inside a
27// specific control hierarchy. The kernel has two cgroup APIs, v1 and v2. v1 has one hierarchy per available resource
28// controller, while v2 has one unified hierarchy shared by all controllers. Regardless of v1 or v2, all hierarchies
29// contain all running processes, so the question answerable with a Cgroup struct is 'where is this process in
30// this hierarchy' (where==what path on the specific cgroupfs). By prefixing this path with the mount point of
31// *this specific* hierarchy, you can locate the relevant pseudo-files needed to read/set the data for this PID
32// in this hierarchy
33//
34// Also see http://man7.org/linux/man-pages/man7/cgroups.7.html
35type Cgroup struct {
36 // HierarchyID that can be matched to a named hierarchy using /proc/cgroups. Cgroups V2 only has one
37 // hierarchy, so HierarchyID is always 0. For cgroups v1 this is a unique ID number
38 HierarchyID int
39 // Controllers using this hierarchy of processes. Controllers are also known as subsystems. For
40 // Cgroups V2 this may be empty, as all active controllers use the same hierarchy
41 Controllers []string
42 // Path of this control group, relative to the mount point of the cgroupfs representing this specific
43 // hierarchy
44 Path string
45}
46
47// parseCgroupString parses each line of the /proc/[pid]/cgroup file
48// Line format is hierarchyID:[controller1,controller2]:path
49func parseCgroupString(cgroupStr string) (*Cgroup, error) {
50 var err error
51
52 fields := strings.SplitN(cgroupStr, ":", 3)
53 if len(fields) < 3 {
54 return nil, fmt.Errorf("at least 3 fields required, found %d fields in cgroup string: %s", len(fields), cgroupStr)
55 }
56
57 cgroup := &Cgroup{
58 Path: fields[2],
59 Controllers: nil,
60 }
61 cgroup.HierarchyID, err = strconv.Atoi(fields[0])
62 if err != nil {
63 return nil, fmt.Errorf("failed to parse hierarchy ID")
64 }
65 if fields[1] != "" {
66 ssNames := strings.Split(fields[1], ",")
67 cgroup.Controllers = append(cgroup.Controllers, ssNames...)
68 }
69 return cgroup, nil
70}
71
72// parseCgroups reads each line of the /proc/[pid]/cgroup file
73func parseCgroups(data []byte) ([]Cgroup, error) {
74 var cgroups []Cgroup
75 scanner := bufio.NewScanner(bytes.NewReader(data))
76 for scanner.Scan() {
77 mountString := scanner.Text()
78 parsedMounts, err := parseCgroupString(mountString)
79 if err != nil {
80 return nil, err
81 }
82 cgroups = append(cgroups, *parsedMounts)
83 }
84
85 err := scanner.Err()
86 return cgroups, err
87}
88
89// Cgroups reads from /proc/<pid>/cgroups and returns a []*Cgroup struct locating this PID in each process
90// control hierarchy running on this system. On every system (v1 and v2), all hierarchies contain all processes,
91// so the len of the returned struct is equal to the number of active hierarchies on this system
92func (p Proc) Cgroups() ([]Cgroup, error) {
93 data, err := util.ReadFileNoStat(fmt.Sprintf("/proc/%d/cgroup", p.PID))
94 if err != nil {
95 return nil, err
96 }
97 return parseCgroups(data)
98}