restart.go

package main

import (
	"errors"
	"fmt"
	"os"
	"time"

	pipe "gopkg.in/pipe.v2"
)

const timespecSep = ':'

const usage = `
restart runs a process and restart it when it ends or after a specified interval.
Call as
  restart TIMESPEC COMMAND ARGUMENTS...
with TIMESPEC <start>:<each>, e.g. 4h:24h for a forced restart each 24 hours, starting in 4 hours.
TIMESPEC may only contain one value when <start> and <each> are the same.
Valid units: "ns", "us", "ms", "s", "m", "h" (nano, micro, milli, ...)
`

func main() {
	var (
		err         error
		timespec    string
		cmd         string
		args        []string
		startingTxt string
		intervalTxt string
		start       time.Duration
		interval    time.Duration
	)
	if len(os.Args) >= 3 {
		timespec, cmd, args = os.Args[1], os.Args[2], os.Args[3:]
		intervalTxt = timespec
		for i := range timespec {
			if timespec[i] == timespecSep {
				startingTxt, intervalTxt = timespec[:i], timespec[i+1:]
			}
		}
		if len(startingTxt) > 0 {
			start, err = time.ParseDuration(startingTxt)
			if err != nil {
				err = errors.New("start time format: " + err.Error())
			}
		}
		interval, err = time.ParseDuration(intervalTxt)
		if err != nil {
			err = errors.New("interval time format: " + err.Error())
		}
	} else {
		err = errors.New("too few arguments")
	}
	if err != nil {
		fmt.Fprintln(os.Stderr, err, usage)
		os.Exit(-1)
	}
	fmt.Printf("[[STARTING]] %s\n", time.Now().Format(time.RFC3339))
	for {
		state := pipe.NewState(os.Stdout, os.Stderr)
		state.Timeout = start
		start = interval
		p := pipe.Exec(cmd, args...)
		err := p(state)
		if err == nil {
			err = state.RunTasks()
		}
		if err == nil {
			fmt.Printf("[[RESTARTING - process ended]] %s\n", time.Now().Format(time.RFC3339))
			continue
		}
		if err.Error() == pipe.ErrTimeout.Error() {
			fmt.Printf("[[RESTARTING - after %s]] %s\n",
				state.Timeout,
				time.Now().Format(time.RFC3339),
			)
			continue
		}
		panic(err)
	}
}