banger/internal/cli/daemon_lifecycle.go

package cli

import (
	"context"
	"fmt"
	"os"
	"os/exec"
	"syscall"
	"time"

	"banger/internal/api"
	"banger/internal/config"
	"banger/internal/model"
	"banger/internal/paths"
	"banger/internal/rpc"
)

// ensureDaemon pings the socket; on miss it auto-starts bangerd, on
// version mismatch it restarts. Every CLI command that needs to talk
// to the daemon routes through here.
func ensureDaemon(ctx context.Context) (paths.Layout, model.DaemonConfig, error) {
	layout, err := paths.Resolve()
	if err != nil {
		return paths.Layout{}, model.DaemonConfig{}, err
	}
	cfg, err := config.Load(layout)
	if err != nil {
		return paths.Layout{}, model.DaemonConfig{}, err
	}
	if ping, err := daemonPingFunc(ctx, layout.SocketPath); err == nil {
		if daemonOutdated(ping.PID) {
			if err := restartDaemon(ctx, layout, ping.PID); err != nil {
				return paths.Layout{}, model.DaemonConfig{}, err
			}
			return layout, cfg, nil
		}
		return layout, cfg, nil
	}
	if err := startDaemon(ctx, layout); err != nil {
		return paths.Layout{}, model.DaemonConfig{}, err
	}
	return layout, cfg, nil
}

// daemonOutdated reports whether the running daemon binary differs
// from the one on disk — useful after `make install` when the user's
// session still holds a handle to an old daemon. os.SameFile compares
// inode + dev, so a fresh binary at the same path registers as
// different.
func daemonOutdated(pid int) bool {
	if pid <= 0 {
		return false
	}
	daemonBin, err := bangerdPathFunc()
	if err != nil {
		return false
	}
	currentInfo, err := os.Stat(daemonBin)
	if err != nil {
		return false
	}
	runningInfo, err := os.Stat(daemonExePath(pid))
	if err != nil {
		return false
	}
	return !os.SameFile(currentInfo, runningInfo)
}

func restartDaemon(ctx context.Context, layout paths.Layout, pid int) error {
	stopCtx, cancel := context.WithTimeout(ctx, 2*time.Second)
	defer cancel()

	_, _ = rpc.Call[api.ShutdownResult](stopCtx, layout.SocketPath, "shutdown", api.Empty{})
	if waitForPIDExit(pid, 2*time.Second) {
		return startDaemon(ctx, layout)
	}
	if proc, err := os.FindProcess(pid); err == nil {
		_ = proc.Signal(syscall.SIGTERM)
	}
	if !waitForPIDExit(pid, 2*time.Second) {
		return fmt.Errorf("timed out restarting stale daemon pid %d", pid)
	}
	return startDaemon(ctx, layout)
}

func waitForPIDExit(pid int, timeout time.Duration) bool {
	deadline := time.Now().Add(timeout)
	for time.Now().Before(deadline) {
		if !pidRunning(pid) {
			return true
		}
		time.Sleep(50 * time.Millisecond)
	}
	return !pidRunning(pid)
}

func pidRunning(pid int) bool {
	if pid <= 0 {
		return false
	}
	proc, err := os.FindProcess(pid)
	if err != nil {
		return false
	}
	return proc.Signal(syscall.Signal(0)) == nil
}

func startDaemon(ctx context.Context, layout paths.Layout) error {
	if err := paths.Ensure(layout); err != nil {
		return err
	}
	logFile, err := os.OpenFile(layout.DaemonLog, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o644)
	if err != nil {
		return err
	}
	defer logFile.Close()

	daemonBin, err := paths.BangerdPath()
	if err != nil {
		return err
	}
	cmd := buildDaemonCommand(daemonBin)
	cmd.Stdout = logFile
	cmd.Stderr = logFile
	cmd.Stdin = nil
	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
	if err := cmd.Start(); err != nil {
		return err
	}
	if err := rpc.WaitForSocket(layout.SocketPath, 5*time.Second); err != nil {
		return fmt.Errorf("daemon failed to start; inspect %s: %w", layout.DaemonLog, err)
	}
	return nil
}

func buildDaemonCommand(daemonBin string) *exec.Cmd {
	return exec.Command(daemonBin)
}