TUN-4356: Set AUTOMAXPROCS to the CPU limit when running in a Linux container

vendor/go.uber.org/automaxprocs/internal/cgroups/subsys.go

@@ -0,0 +1,102 @@
+// Copyright (c) 2017 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+// +build linux
+
+package cgroups
+
+import (
+	"bufio"
+	"os"
+	"strconv"
+	"strings"
+)
+
+const (
+	_cgroupSep       = ":"
+	_cgroupSubsysSep = ","
+)
+
+const (
+	_csFieldIDID = iota
+	_csFieldIDSubsystems
+	_csFieldIDName
+	_csFieldCount
+)
+
+// CGroupSubsys represents the data structure for entities in
+// `/proc/$PID/cgroup`. See also proc(5) for more information.
+type CGroupSubsys struct {
+	ID         int
+	Subsystems []string
+	Name       string
+}
+
+// NewCGroupSubsysFromLine returns a new *CGroupSubsys by parsing a string in
+// the format of `/proc/$PID/cgroup`
+func NewCGroupSubsysFromLine(line string) (*CGroupSubsys, error) {
+	fields := strings.SplitN(line, _cgroupSep, _csFieldCount)
+
+	if len(fields) != _csFieldCount {
+		return nil, cgroupSubsysFormatInvalidError{line}
+	}
+
+	id, err := strconv.Atoi(fields[_csFieldIDID])
+	if err != nil {
+		return nil, err
+	}
+
+	cgroup := &CGroupSubsys{
+		ID:         id,
+		Subsystems: strings.Split(fields[_csFieldIDSubsystems], _cgroupSubsysSep),
+		Name:       fields[_csFieldIDName],
+	}
+
+	return cgroup, nil
+}
+
+// parseCGroupSubsystems parses procPathCGroup (usually at `/proc/$PID/cgroup`)
+// and returns a new map[string]*CGroupSubsys.
+func parseCGroupSubsystems(procPathCGroup string) (map[string]*CGroupSubsys, error) {
+	cgroupFile, err := os.Open(procPathCGroup)
+	if err != nil {
+		return nil, err
+	}
+	defer cgroupFile.Close()
+
+	scanner := bufio.NewScanner(cgroupFile)
+	subsystems := make(map[string]*CGroupSubsys)
+
+	for scanner.Scan() {
+		cgroup, err := NewCGroupSubsysFromLine(scanner.Text())
+		if err != nil {
+			return nil, err
+		}
+		for _, subsys := range cgroup.Subsystems {
+			subsystems[subsys] = cgroup
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+
+	return subsystems, nil
+}