command.go

/*
 Copyright 2024 The lvm2go 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 lvm2go

import (
	"context"
	"fmt"
	"log/slog"
	"os"
	"os/exec"
	"sync"
	"time"
)

const (
	nsenter               = "/usr/bin/nsenter"
	DefaultVolumeGroupEnv = "LVM_VG_NAME"
)

var waitDelayKey = struct{}{}

// DefaultWaitDelay for Commands
// If WaitDelay is zero (the default), I/ O pipes will be read until EOF, which might not occur until orphaned subprocesses of the command have also closed their descriptors for the pipes
// see exec.Cmd.Wait for more information
var DefaultWaitDelay = time.Duration(0)

func SetProcessCancelWaitDelay(ctx context.Context, delay time.Duration) context.Context {
	return context.WithValue(ctx, waitDelayKey, delay)
}

func GetProcessCancelWaitDelay(ctx context.Context) time.Duration {
	if delay, ok := ctx.Value(waitDelayKey).(time.Duration); ok {
		return delay
	}
	return DefaultWaitDelay
}

// CommandContext creates exec.Cmd with custom args. it is equivalent to exec.Command(cmd, args...) when not containerized.
// When containerized, it calls nsenter with the provided command and args.
func CommandContext(ctx context.Context, cmd string, args ...string) *exec.Cmd {
	var c *exec.Cmd

	if IsContainerized(ctx) {
		args = append([]string{"-m", "-u", "-i", "-n", "-p", "-t", "1", cmd}, args...)
		c = exec.CommandContext(ctx, nsenter, args...)
	} else {
		c = exec.CommandContext(ctx, cmd, args...)
	}
	c.WaitDelay = GetProcessCancelWaitDelay(ctx)

	if DefaultVolumeGroup(ctx) != "" {
		c.Env = append(c.Env, fmt.Sprintf("%s=%s", DefaultVolumeGroupEnv, DefaultVolumeGroup(ctx)))
	}

	return CommandWithCustomEnvironment(ctx, c)
}

var defaultVolumeGroupKey = struct{}{}

func WithDefaultVolumeGroup(ctx context.Context, vg string) context.Context {
	return context.WithValue(ctx, defaultVolumeGroupKey, vg)
}

func DefaultVolumeGroup(ctx context.Context) string {
	if vg, ok := ctx.Value(defaultVolumeGroupKey).(string); ok {
		return vg
	}
	return ""
}

var (
	isContainerized     bool
	detectContainerized sync.Once
)

func IsContainerized(ctx context.Context) bool {
	detectContainerized.Do(func() {
		if _, err := os.Stat("/.dockerenv"); err == nil {
			isContainerized = true
		} else if _, err := os.Stat("/.containerenv"); err == nil {
			isContainerized = true
		} else if _, ok := os.LookupEnv("KUBERNETES_SERVICE_HOST"); ok {
			isContainerized = true
		} else if _, err := os.Stat("/var/run/secrets/kubernetes.io/serviceaccount/token"); err == nil {
			isContainerized = true
		}
		if isContainerized {
			slog.InfoContext(ctx, "lvm2go is running in container environment")
		}
	})
	return isContainerized
}

var envContextKey = struct{}{}

func WithCustomEnvironment(ctx context.Context, env map[string]string) context.Context {
	return context.WithValue(ctx, envContextKey, env)
}

func GetCustomEnvironment(ctx context.Context) map[string]string {
	if env, ok := ctx.Value(envContextKey).(map[string]string); ok {
		return env
	}
	return nil
}

func CommandWithCustomEnvironment(ctx context.Context, cmd *exec.Cmd) *exec.Cmd {
	if UseStandardLocale() {
		cmd.Env = append(cmd.Env, "LC_ALL=C")
	}
	if env := GetCustomEnvironment(ctx); env != nil {
		for k, v := range env {
			cmd.Env = append(cmd.Env, k+"="+v)
		}
	}
	return cmd
}

var (
	useStandardLocale   bool
	useStandardLocaleMu sync.Mutex
)

func UseStandardLocale() bool {
	useStandardLocaleMu.Lock()
	defer useStandardLocaleMu.Unlock()
	return useStandardLocale
}

func SetUseStandardLocale(use bool) {
	useStandardLocaleMu.Lock()
	defer useStandardLocaleMu.Unlock()
	useStandardLocale = use
}