// Copyright 2020 The Prometheus 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 procfs import ( "bufio" "bytes" "fmt" "strconv" "strings" "github.com/prometheus/procfs/internal/util" ) // Cgroup models one line from /proc/[pid]/cgroup. Each Cgroup struct describes the placement of a PID inside a // specific control hierarchy. The kernel has two cgroup APIs, v1 and v2. v1 has one hierarchy per available resource // controller, while v2 has one unified hierarchy shared by all controllers. Regardless of v1 or v2, all hierarchies // contain all running processes, so the question answerable with a Cgroup struct is 'where is this process in // this hierarchy' (where==what path on the specific cgroupfs). By prefixing this path with the mount point of // *this specific* hierarchy, you can locate the relevant pseudo-files needed to read/set the data for this PID // in this hierarchy // // Also see http://man7.org/linux/man-pages/man7/cgroups.7.html type Cgroup struct { // HierarchyID that can be matched to a named hierarchy using /proc/cgroups. Cgroups V2 only has one // hierarchy, so HierarchyID is always 0. For cgroups v1 this is a unique ID number HierarchyID int // Controllers using this hierarchy of processes. Controllers are also known as subsystems. For // Cgroups V2 this may be empty, as all active controllers use the same hierarchy Controllers []string // Path of this control group, relative to the mount point of the cgroupfs representing this specific // hierarchy Path string } // parseCgroupString parses each line of the /proc/[pid]/cgroup file // Line format is hierarchyID:[controller1,controller2]:path. func parseCgroupString(cgroupStr string) (*Cgroup, error) { var err error fields := strings.SplitN(cgroupStr, ":", 3) if len(fields) < 3 { return nil, fmt.Errorf("%w: 3+ fields required, found %d fields in cgroup string: %s", ErrFileParse, len(fields), cgroupStr) } cgroup := &Cgroup{ Path: fields[2], Controllers: nil, } cgroup.HierarchyID, err = strconv.Atoi(fields[0]) if err != nil { return nil, fmt.Errorf("%w: hierarchy ID: %q", ErrFileParse, cgroup.HierarchyID) } if fields[1] != "" { ssNames := strings.Split(fields[1], ",") cgroup.Controllers = append(cgroup.Controllers, ssNames...) } return cgroup, nil } // parseCgroups reads each line of the /proc/[pid]/cgroup file. func parseCgroups(data []byte) ([]Cgroup, error) { var cgroups []Cgroup scanner := bufio.NewScanner(bytes.NewReader(data)) for scanner.Scan() { mountString := scanner.Text() parsedMounts, err := parseCgroupString(mountString) if err != nil { return nil, err } cgroups = append(cgroups, *parsedMounts) } err := scanner.Err() return cgroups, err } // Cgroups reads from /proc/<pid>/cgroups and returns a []*Cgroup struct locating this PID in each process // control hierarchy running on this system. On every system (v1 and v2), all hierarchies contain all processes, // so the len of the returned struct is equal to the number of active hierarchies on this system. func (p Proc) Cgroups() ([]Cgroup, error) { data, err := util.ReadFileNoStat(p.path("cgroup")) if err != nil { return nil, err } return parseCgroups(data) }