isle/go/cmd/entrypoint/main.go

package main

import (
	"context"
	"os"
	"os/signal"
	"path/filepath"
	"syscall"

	"github.com/adrg/xdg"
	"github.com/mediocregopher/mediocre-go-lib/v2/mctx"
	"github.com/mediocregopher/mediocre-go-lib/v2/mlog"
)

// The purpose of this binary is to act as the entrypoint of the isle
// process. It processes the command-line arguments which are passed in, and
// then passes execution along to an appropriate binary housed in AppDir/bin
// (usually a bash script, which is more versatile than a go program).

func getAppDirPath() string {
	appDirPath := os.Getenv("APPDIR")
	if appDirPath == "" {
		appDirPath = "."
	}
	return appDirPath
}

func envOr(name, fallback string) string {
	if v := os.Getenv(name); v != "" {
		return v
	}
	return fallback
}

// RUNTIME_DIRECTORY/STATE_DIRECTORY are used by the systemd service in
// conjunction with the RuntimeDirectory/StateDirectory directives.
var (
	envAppDirPath     = getAppDirPath()
	envRuntimeDirPath = envOr(
		"RUNTIME_DIRECTORY",
		filepath.Join(xdg.RuntimeDir, "isle"),
	)
	envStateDirPath = envOr(
		"STATE_DIRECTORY",
		filepath.Join(xdg.StateHome, "isle"),
	)
	envBinDirPath = filepath.Join(envAppDirPath, "bin")
)

func binPath(name string) string {
	return filepath.Join(envBinDirPath, name)
}

func main() {

	logger := mlog.NewLogger(&mlog.LoggerOpts{
		MessageHandler: newLogMsgHandler(),
		MaxLevel:       mlog.LevelInfo.Int(),
	})
	defer logger.Close()

	ctx, cancel := context.WithCancel(context.Background())

	signalCh := make(chan os.Signal, 2)
	signal.Notify(signalCh, syscall.SIGINT, syscall.SIGTERM)

	go func() {
		sig := <-signalCh
		cancel()

		ctx := mctx.Annotate(ctx, "signal", sig.String())
		logger.Info(ctx, "got signal, exiting gracefully")

		sig = <-signalCh

		ctx = mctx.Annotate(ctx, "signal", sig.String())
		logger.FatalString(ctx, "second signal received, force quitting, there may be zombie children left behind, good luck!")
	}()

	err := subCmdCtx{
		args:   os.Args[1:],
		ctx:    ctx,
		logger: logger,
	}.doSubCmd(
		subCmdAdmin,
		subCmdDaemon,
		subCmdGarage,
		subCmdHosts,
		subCmdNebula,
		subCmdVersion,
	)

	if err != nil {
		logger.Fatal(ctx, "error running command", err)
	}
}