internal/pkg/agent/application/paths/common.go

// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
// or more contributor license agreements. Licensed under the Elastic License 2.0;
// you may not use this file except in compliance with the Elastic License 2.0.

package paths

import (
	"errors"
	"flag"
	"fmt"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"sync"

	"github.com/elastic/elastic-agent/internal/pkg/release"
	"github.com/elastic/elastic-agent/pkg/utils"

	// this is not a leftover: this anonymous import is needed for version initialization
	_ "github.com/elastic/elastic-agent/version"
)

const (
	// DefaultConfigName is the default name of the configuration file.
	DefaultConfigName = "elastic-agent.yml"
	// DefaultOtelConfigName is the default name of the otel configuration file.
	DefaultOtelConfigName = "otel.yml"

	// AgentLockFileName is the name of the overall Elastic Agent file lock.
	AgentLockFileName = "agent.lock"

	// ControlSocketName is the control socket name.
	ControlSocketName = "elastic-agent.sock"

	// WindowsControlSocketInstalledPath is the control socket path used when installed on Windows.
	WindowsControlSocketInstalledPath = `npipe:///elastic-agent-system`

	// MarkerFileName is the name of the file that's created by
	// `elastic-agent install` in the Agent's topPath folder to
	// indicate that the Agent executing from the binary under
	// the same topPath folder is an installed Agent.
	MarkerFileName = ".installed"

	tempSubdir      = "tmp"
	tempSubdirPerms = 0o770

	darwin = "darwin"
)

// ExternalInputsPattern is a glob that matches the paths of external configuration files.
var ExternalInputsPattern = filepath.Join("inputs.d", "*.yml")

var (
	topPath           string
	configPath        string
	configFilePath    string
	logsPath          string
	downloadsPath     string
	componentsPath    string
	installPath       string
	controlSocketPath string
	unversionedHome   bool
	tmpCreator        sync.Once
)

func init() {
	// this is the first call where we need version information (it calls isInsideData())
	topPath = initialTop()
	configPath = topPath
	logsPath = topPath
	controlSocketPath = initialControlSocketPath(topPath)
	unversionedHome = false // only versioned by container subcommand

	// these should never change
	versionedHome := VersionedHome(topPath)
	downloadsPath = filepath.Join(versionedHome, "downloads")
	componentsPath = filepath.Join(versionedHome, "components")

	fs := flag.CommandLine
	fs.StringVar(&topPath, "path.home", topPath, "Agent root path")
	fs.BoolVar(&unversionedHome, "path.home.unversioned", unversionedHome, "Agent root path is not versioned based on build")
	fs.StringVar(&configPath, "path.config", configPath, "Config path is the directory Agent looks for its config file")
	fs.StringVar(&configFilePath, "config", DefaultConfigName, "Configuration file, relative to path.config")
	fs.StringVar(&configFilePath, "c", DefaultConfigName, "Configuration file, relative to path.config")
	fs.StringVar(&logsPath, "path.logs", logsPath, "Logs path contains Agent log output")
	fs.StringVar(&controlSocketPath, "path.socket", controlSocketPath, "Control protocol socket path for the Agent")

	// enable user to download update artifacts to alternative place
	// TODO: remove path.downloads support on next major (this can be configured using `agent.download.targetDirectory`)
	// `path.download` serves just as init value for `agent.download.targetDirectory`
	fs.StringVar(&downloadsPath, "path.downloads", downloadsPath, "Downloads path contains binaries Agent downloads")
}

// Top returns the top directory for Elastic Agent, all the versioned
// home directories live under this top-level/data/elastic-agent-${hash}
func Top() string {
	return topPath
}

// SetTop overrides the Top path.
//
// Used by the container subcommand to adjust the overall top path allowing state can be maintained between container
// restarts.
func SetTop(path string) {
	topPath = path
}

// TempDir returns agent temp dir located within data dir.
func TempDir() string {
	tmpDir := filepath.Join(Data(), tempSubdir)
	tmpCreator.Do(func() {
		// create tempdir as it probably don't exists
		_ = os.MkdirAll(tmpDir, tempSubdirPerms)
	})
	return tmpDir
}

// Home returns a directory where binary lives
func Home() string {
	return HomeFrom(topPath)
}

func HomeFrom(topDirPath string) string {
	if unversionedHome {
		return topDirPath
	}

	return VersionedHome(topDirPath)
}

// IsVersionHome returns true if the Home path is versioned based on build.
func IsVersionHome() bool {
	return !unversionedHome
}

// SetVersionHome sets if the Home path is versioned based on build.
//
// Used by the container subcommand to adjust the home path allowing state can be maintained between container
// restarts.
func SetVersionHome(version bool) {
	unversionedHome = !version
}

// Config returns a directory where configuration file lives
func Config() string {
	return configPath
}

// SetConfig overrides the Config path.
//
// Used by the container subcommand to adjust the overall config path allowing state can be maintained between container
// restarts.
func SetConfig(path string) {
	configPath = path
}

// ConfigFile returns the path to the configuration file.
func ConfigFile() string {
	return configFileWithDefaultOverride(DefaultConfigName)
}

// OtelConfigFile returns the path to the otel configuration file.
func OtelConfigFile() string {
	return configFileWithDefaultOverride(DefaultOtelConfigName)
}

// configFileWithDefaultOverride returns the path to the configuration file overriding default value.
func configFileWithDefaultOverride(defaultConfig string) string {
	if configFilePath == "" || configFilePath == DefaultConfigName {
		return filepath.Join(Config(), defaultConfig)
	}
	if filepath.IsAbs(configFilePath) {
		return configFilePath
	}
	return filepath.Join(Config(), configFilePath)
}

// ExternalInputs returns the path to load external inputs from.
func ExternalInputs() string {
	return filepath.Join(Config(), ExternalInputsPattern)
}

// Data returns the data directory for Agent
func Data() string {
	return DataFrom(Top())
}

// DataFrom returns the data directory for Agent using the passed directory as top path
func DataFrom(topDirPath string) string {
	if unversionedHome {
		// unversioned means the topPath is the data path
		return topDirPath
	}
	return filepath.Join(topDirPath, "data")
}

// Run returns the run directory for Agent
func Run() string {
	return filepath.Join(Home(), "run")
}

// Components returns the component directory for Agent
func Components() string {
	return componentsPath
}

// Logs returns the log directory for Agent
func Logs() string {
	return logsPath
}

// SetLogs updates the path for the logs.
func SetLogs(path string) {
	logsPath = path
}

// VersionedHome returns a versioned path based on a TopPath and used commit.
func VersionedHome(base string) string {
	versionedHomePath := filepath.Join(base, "data", fmt.Sprintf("elastic-agent-%s-%s", release.VersionWithSnapshot(), release.ShortCommit()))
	_, err := os.Stat(versionedHomePath)
	if errors.Is(err, os.ErrNotExist) {
		// fallback to the legacy elastic-agent-<commit> path
		versionedHomePath = filepath.Join(base, "data", fmt.Sprintf("elastic-agent-%s", release.ShortCommit()))
	}
	return versionedHomePath
}

// Downloads returns the downloads directory for Agent
func Downloads() string {
	return downloadsPath
}

// SetDownloads updates the path for the downloads.
func SetDownloads(path string) {
	downloadsPath = path
}

// Install returns the install directory for Agent
func Install() string {
	if installPath == "" {
		return filepath.Join(Home(), "install")
	}
	return installPath
}

// SetInstall updates the path for the install.
func SetInstall(path string) {
	installPath = path
}

// ControlSocket returns the control socket directory for Agent
func ControlSocket() string {
	return controlSocketPath
}

// SetControlSocket overrides the ControlSocket path.
//
// Used by the container subcommand to adjust the control socket path.
func SetControlSocket(path string) {
	controlSocketPath = path
}

// initialTop returns the initial top-level path for the binary
//
// When nested in top-level/data/elastic-agent-${hash}/ the result is top-level/.
// The agent executable for MacOS is wrapped in the app bundle, so the path to the binary is
// top-level/data/elastic-agent-${hash}/elastic-agent.app/Contents/MacOS
func initialTop() string {
	return ExecDir(retrieveExecutableDir())
}

// retrieveExecutablePath returns the executing binary, even if the started binary was a symlink
func retrieveExecutableDir() string {
	execPath, err := os.Executable()
	if err != nil {
		panic(err)
	}
	evalPath, err := filepath.EvalSymlinks(execPath)
	if err != nil {
		panic(err)
	}
	return filepath.Dir(evalPath)
}

// isInsideData returns true when the exePath is inside of the current Agents data path.
func isInsideData(exeDir string) bool {
	expectedDirLegacy := binaryDir(filepath.Join("data", fmt.Sprintf("elastic-agent-%s", release.ShortCommit())))
	expectedDirWithVersion := binaryDir(filepath.Join("data", fmt.Sprintf("elastic-agent-%s-%s", release.VersionWithSnapshot(), release.ShortCommit())))
	return strings.HasSuffix(exeDir, expectedDirLegacy) || strings.HasSuffix(exeDir, expectedDirWithVersion)
}

// ExecDir returns the "executable" directory which is:
// 1. The same if the execDir is not inside of the data path
// 2. Two levels up if the execDir inside of the data path on non-macOS platforms
// 3. Five levels up if the execDir inside of the dataPath on macOS platform
func ExecDir(execDir string) string {
	if isInsideData(execDir) {
		execDir = filepath.Dir(filepath.Dir(execDir))
		if runtime.GOOS == darwin {
			execDir = filepath.Dir(filepath.Dir(filepath.Dir(execDir)))
		}
	}
	return execDir
}

// binaryDir returns the application binary directory
// For macOS it appends the path inside of the app bundle
// For other platforms it returns the same dir
func binaryDir(baseDir string) string {
	if runtime.GOOS == darwin {
		baseDir = filepath.Join(baseDir, "elastic-agent.app", "Contents", "MacOS")
	}
	return baseDir
}

// BinaryPath returns the application binary path that is concatenation of the directory and the agentName
func BinaryPath(baseDir, agentName string) string {
	return filepath.Join(binaryDir(baseDir), agentName)
}

// TopBinaryPath returns the path to the Elastic Agent binary that is inside the Top directory.
//
// This always points to the symlink that points to the latest Elastic Agent version.
func TopBinaryPath() string {
	return filepath.Join(Top(), BinaryName)
}

// RunningInstalled returns true when executing Agent is the installed Agent.
func RunningInstalled() bool {
	// Check if install marker created by `elastic-agent install` exists
	markerFilePath := filepath.Join(Top(), MarkerFileName)
	if _, err := os.Stat(markerFilePath); err != nil {
		return false
	}
	return true
}

// ControlSocketFromPath returns the control socket path for an Elastic Agent running
// on the defined platform, and its executing directory.
func ControlSocketFromPath(platform string, path string) string {
	// socket should be inside this directory
	socketPath := filepath.Join(path, ControlSocketName)
	if platform == "windows" {
		// on windows the control socket always uses the fallback
		return utils.SocketURLWithFallback(socketPath, path)
	}
	unixSocket := fmt.Sprintf("unix://%s", socketPath)
	if len(unixSocket) < 104 {
		// small enough to fit
		return unixSocket
	}
	// place in global /tmp to ensure that its small enough to fit; current path is way to long
	// for it to be used, but needs to be unique per Agent (in the case that multiple are running)
	return utils.SocketURLWithFallback(socketPath, path)
}

func pathSplit(path string) []string {
	dir, file := filepath.Split(path)
	if dir == "" && file == "" {
		return []string{}
	}
	if dir == "" && file != "" {
		return []string{file}
	}
	if dir == path {
		return []string{}
	}
	return append(pathSplit(filepath.Clean(dir)), file)
}