soong_ui ninja.go: comment and refactor.

	"android/soong/ui/status"

)

// Constructs and runs the Ninja command line with a restricted set of

// environment variables. It's important to restrict the environment Ninja runs

// for hermeticity reasons, and to avoid spurious rebuilds.

func runNinja(ctx Context, config Config) {

	ctx.BeginTrace(metrics.PrimaryNinja, "ninja")

	defer ctx.EndTrace()

	// Sets up the FIFO status updater that reads the Ninja protobuf output, and

	// translates it to the soong_ui status output, displaying real-time

	// progress of the build.

	fifo := filepath.Join(config.OutDir(), ".ninja_fifo")

	nr := status.NewNinjaReader(ctx, ctx.Status.StartTool(), fifo)

	defer nr.Close()

		"-w", "missingdepfile=err")

	cmd := Command(ctx, config, "ninja", executable, args...)

	// Set up the nsjail sandbox Ninja runs in.

	cmd.Sandbox = ninjaSandbox

	if config.HasKatiSuffix() {

		// Reads and executes a shell script from Kati that sets/unsets the

		// environment Ninja runs in.

		cmd.Environment.AppendFromKati(config.KatiEnvFile())

	}

		cmd.Args = append(cmd.Args, strings.Fields(extra)...)

	}

	logPath := filepath.Join(config.OutDir(), ".ninja_log")

	ninjaHeartbeatDuration := time.Minute * 5

	// Get the ninja heartbeat interval from the environment before it's filtered away later.

	if overrideText, ok := cmd.Environment.Get("NINJA_HEARTBEAT_INTERVAL"); ok {

		// For example, "1m"

		overrideDuration, err := time.ParseDuration(overrideText)

		}

	}

	// Filter the environment, as ninja does not rebuild files when environment variables change.

	// Filter the environment, as ninja does not rebuild files when environment

	// variables change.

	//

	// Anything listed here must not change the output of rules/actions when the value changes,

	// otherwise incremental builds may be unsafe. Vars explicitly set to stable values

	// elsewhere in soong_ui are fine.

	// Anything listed here must not change the output of rules/actions when the

	// value changes, otherwise incremental builds may be unsafe. Vars

	// explicitly set to stable values elsewhere in soong_ui are fine.

	//

	// For the majority of cases, either Soong or the makefiles should be replicating any

	// necessary environment variables in the command line of each action that needs it.

	// For the majority of cases, either Soong or the makefiles should be

	// replicating any necessary environment variables in the command line of

	// each action that needs it.

	if cmd.Environment.IsEnvTrue("ALLOW_NINJA_ENV") {

		ctx.Println("Allowing all environment variables during ninja; incremental builds may be unsafe.")

	} else {

		cmd.Environment.Allow(append([]string{

			// Set the path to a symbolizer (e.g. llvm-symbolizer) so ASAN-based

			// tools can symbolize crashes.

			"ASAN_SYMBOLIZER_PATH",

			"HOME",

			"JAVA_HOME",

			"OUT_DIR",

			"PATH",

			"PWD",

			// https://docs.python.org/3/using/cmdline.html#envvar-PYTHONDONTWRITEBYTECODE

			"PYTHONDONTWRITEBYTECODE",

			"TMPDIR",

			"USER",

			// TODO: remove these carefully

			// Options for the address sanitizer.

			"ASAN_OPTIONS",

			// The list of Android app modules to be built in an unbundled manner.

			"TARGET_BUILD_APPS",

			// The variant of the product being built. e.g. eng, userdebug, debug.

			"TARGET_BUILD_VARIANT",

			// The product name of the product being built, e.g. aosp_arm, aosp_flame.

			"TARGET_PRODUCT",

			// b/147197813 - used by art-check-debug-apex-gen

			"EMMA_INSTRUMENT_FRAMEWORK",

	cmd.Environment.Set("DIST_DIR", config.DistDir())

	cmd.Environment.Set("SHELL", "/bin/bash")

	// Print the environment variables that Ninja is operating in.

	ctx.Verboseln("Ninja environment: ")

	envVars := cmd.Environment.Environ()

	sort.Strings(envVars)

		ctx.Verbosef("  %s", envVar)

	}

	// Poll the ninja log for updates; if it isn't updated enough, then we want to show some diagnostics

	// Poll the Ninja log for updates regularly based on the heartbeat

	// frequency. If it isn't updated enough, then we want to surface the

	// possibility that Ninja is stuck, to the user.

	done := make(chan struct{})

	defer close(done)

	ticker := time.NewTicker(ninjaHeartbeatDuration)

	defer ticker.Stop()

	checker := &statusChecker{}

	ninjaChecker := &ninjaStucknessChecker{

		logPath: filepath.Join(config.OutDir(), ".ninja_log"),

	}

	go func() {

		for {

			select {

			case <-ticker.C:

				checker.check(ctx, config, logPath)

				ninjaChecker.check(ctx, config)

			case <-done:

				return

			}

	cmd.RunAndStreamOrFatal()

}

type statusChecker struct {

	prevTime time.Time

// A simple struct for checking if Ninja gets stuck, using timestamps.

type ninjaStucknessChecker struct {

	logPath     string

	prevModTime time.Time

}

func (c *statusChecker) check(ctx Context, config Config, pathToCheck string) {

	info, err := os.Stat(pathToCheck)

	var newTime time.Time

// Check that a file has been modified since the last time it was checked. If

// the mod time hasn't changed, then assume that Ninja got stuck, and print

// diagnostics for debugging.

func (c *ninjaStucknessChecker) check(ctx Context, config Config) {

	info, err := os.Stat(c.logPath)

	var newModTime time.Time

	if err == nil {

		newTime = info.ModTime()

	}

	if newTime == c.prevTime {

		// ninja may be stuck

		dumpStucknessDiagnostics(ctx, config, pathToCheck, newTime)

	}

	c.prevTime = newTime

		newModTime = info.ModTime()

	}

	if newModTime == c.prevModTime {

		// The Ninja file hasn't been modified since the last time it was

		// checked, so Ninja could be stuck. Output some diagnostics.

		ctx.Verbosef("ninja may be stuck; last update to %v was %v. dumping process tree...", c.logPath, newModTime)

// dumpStucknessDiagnostics gets called when it is suspected that Ninja is stuck and we want to output some diagnostics

func dumpStucknessDiagnostics(ctx Context, config Config, statusPath string, lastUpdated time.Time) {

	ctx.Verbosef("ninja may be stuck; last update to %v was %v. dumping process tree...", statusPath, lastUpdated)

	// The "pstree" command doesn't exist on Mac, but "pstree" on Linux gives more convenient output than "ps"

	// So, we try pstree first, and ps second

	pstreeCommandText := fmt.Sprintf("pstree -pal %v", os.Getpid())

	psCommandText := "ps -ef"

	commandText := pstreeCommandText + " || " + psCommandText

		// The "pstree" command doesn't exist on Mac, but "pstree" on Linux

		// gives more convenient output than "ps" So, we try pstree first, and

		// ps second

		commandText := fmt.Sprintf("pstree -pal %v || ps -ef", os.Getpid())

		cmd := Command(ctx, config, "dump process tree", "bash", "-c", commandText)

		output := cmd.CombinedOutputOrFatal()

		ctx.Verbosef("done\n")

	}

	c.prevModTime = newModTime

}