vendor: update all dependencies

vendor/github.com/prometheus/procfs/proc_cgroup.go

@@ -0,0 +1,98 @@
+// 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 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.Split(cgroupStr, ":")
+	if len(fields) < 3 {
+		return nil, fmt.Errorf("at least 3 fields required, found %d fields in cgroup string: %s", len(fields), cgroupStr)
+	}
+
+	cgroup := &Cgroup{
+		Path:        fields[2],
+		Controllers: nil,
+	}
+	cgroup.HierarchyID, err = strconv.Atoi(fields[0])
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse hierarchy ID")
+	}
+	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(fmt.Sprintf("/proc/%d/cgroup", p.PID))
+	if err != nil {
+		return nil, err
+	}
+	return parseCgroups(data)
+}