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main.go
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main.go
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package main
import (
crand "crypto/rand"
"encoding/hex"
"errors"
"flag"
"fmt"
"github.com/fzzy/radix/redis"
"io"
"log"
"os"
"os/exec"
"os/signal"
"strconv"
"strings"
"syscall"
"time"
)
const (
DefaultExpires = 86400
ExitCodeError = 111
UnlockLUAScript = "if redis.call(\"get\",KEYS[1]) == ARGV[1]\nthen\nreturn redis.call(\"del\",KEYS[1])\nelse\nreturn 0\nend\n"
Version = "0.0.1.1"
RetryInterval = time.Duration(500) * time.Millisecond
)
var TrapSignals = []os.Signal{
syscall.SIGHUP,
syscall.SIGINT,
syscall.SIGTERM,
syscall.SIGQUIT}
type Options struct {
Redis string
Expires int
Keep bool
Wait bool
ExitCode int
}
func main() {
code := run()
os.Exit(code)
}
func parseOptions() (opt *Options, key string, program string, args []string) {
var redis string
var expires int
var keep bool
var noDelay bool
var delay bool
var exitZero bool
var exitNonZero bool
var showVersion bool
flag.Usage = usage
flag.StringVar(&redis, "redis", "127.0.0.1:6379", "redis-server host:port or unix:/var/run/redis/redis.sock")
flag.IntVar(&expires, "expires", DefaultExpires, "The lock will be auto-released after the expire time is reached.")
flag.BoolVar(&keep, "keep", false, "Keep the lock after invoked command exited.")
flag.BoolVar(&noDelay, "n", false, "No delay. If KEY is locked by another process, go-redis-setlock gives up.")
flag.BoolVar(&delay, "N", true, "(Default.) Delay. If KEY is locked by another process, go-redis-setlock waits until it can obtain a new lock.")
flag.BoolVar(&exitZero, "x", false, "If KEY is locked, go-redis-setlock exits zero.")
flag.BoolVar(&exitNonZero, "X", true, "(Default.) If KEY is locked, go-redis-setlock prints an error message and exits nonzero.")
flag.BoolVar(&showVersion, "version", false, fmt.Sprintf("version %s", Version))
flag.Parse()
if showVersion {
fmt.Fprintf(os.Stderr, "version: %s\n", Version)
os.Exit(0)
}
opt = &Options{
Redis: redis,
Keep: keep,
Wait: true,
ExitCode: ExitCodeError,
Expires: expires,
}
if noDelay {
opt.Wait = false
}
if exitZero {
opt.ExitCode = 0
}
remainArgs := flag.Args()
if len(remainArgs) >= 2 {
key = remainArgs[0]
program = remainArgs[1]
if len(remainArgs) >= 3 {
args = remainArgs[2:]
}
} else {
usage()
}
return opt, key, program, args
}
func usage() {
fmt.Fprintf(os.Stderr, "usage:\n go-redis-setlock [-nNxX] KEY program [ arg ... ]\n\n")
flag.PrintDefaults()
os.Exit(2)
}
func run() int {
opt, key, program, args := parseOptions()
c, err := connectToRedisServer(opt)
if err != nil {
log.Printf("Redis server seems down: %s\n", err)
return ExitCodeError
}
defer c.Close()
if !validateRedisVersion(c) {
return ExitCodeError
}
token, err := tryGetLock(c, opt, key)
if err == nil {
defer releaseLock(c, opt, key, token)
code := invokeCommand(program, args)
return code
} else {
log.Println(err)
return opt.ExitCode
}
}
func connectToRedisServer(opt *Options) (c *redis.Client, err error) {
timeout := 0
if opt.Wait {
timeout = opt.Expires
}
start := time.Now()
for {
prot := "tcp"
server := opt.Redis
if ("unix:" == server[:5]) {
prot = "unix"
server = server[5:]
}
c, err = redis.DialTimeout(prot, server, time.Duration(timeout)*time.Second)
if err == nil {
break
}
end := time.Now()
elapsed := int(end.Sub(start) / time.Millisecond) // msec
if elapsed >= timeout*1000 {
break
}
time.Sleep(RetryInterval)
}
return c, err
}
func validateRedisVersion(c *redis.Client) bool {
version := ""
r := c.Cmd("info")
info, _ := r.Str()
for _, line := range strings.Split(info, "\n") {
pair := strings.SplitN(line, ":", 2)
if pair[0] == "redis_version" {
version = pair[1]
break
}
}
if version == "" {
log.Printf("could not detect Redis server version from INFO outout. %s", info)
return false
}
vNumbers := strings.SplitN(version, ".", 3)
major, _ := strconv.Atoi(vNumbers[0])
minor, _ := strconv.Atoi(vNumbers[1])
rev, _ := strconv.Atoi(vNumbers[2])
if (major >= 3) || (major == 2 && minor >= 7) || (major == 2 && minor == 6 && rev >= 12) {
return true
}
log.Printf("required Redis server version >= 2.6.12. current server version is %s\n", version)
return false
}
func tryGetLock(c *redis.Client, opt *Options, key string) (token string, err error) {
token = createToken()
gotLock := false
for {
r := c.Cmd("SET", key, token, "EX", opt.Expires, "NX")
locked, _ := r.Str()
if locked != "" {
gotLock = true
break
} else if !opt.Wait {
break
} else {
time.Sleep(RetryInterval)
}
}
if gotLock {
return token, nil
} else {
return "", errors.New("unable to lock")
}
}
func releaseLock(c *redis.Client, opt *Options, key string, token string) (err error) {
if opt.Keep {
return nil
} else {
r := c.Cmd("EVAL", UnlockLUAScript, 1, key, token)
return r.Err
}
}
func invokeCommand(program string, args []string) (code int) {
cmd := exec.Command(program, args...)
stdin, err := cmd.StdinPipe()
if err != nil {
log.Println(err)
}
stdout, err := cmd.StdoutPipe()
if err != nil {
log.Println(err)
}
stderr, err := cmd.StderrPipe()
if err != nil {
log.Println(err)
}
err = cmd.Start()
if err != nil {
log.Println(err)
}
go func() {
_, err := io.Copy(stdin, os.Stdin)
if err == nil {
stdin.Close()
} else {
log.Println(err)
stdin.Close()
}
}()
go io.Copy(os.Stdout, stdout)
go io.Copy(os.Stderr, stderr)
var cmdErr error
cmdCh := make(chan error)
go func() {
cmdCh <- cmd.Wait()
}()
signalCh := make(chan os.Signal, 1)
signal.Notify(signalCh, TrapSignals...)
select {
case s := <-signalCh:
cmd.Process.Signal(s) // forward to child
switch sig := s.(type) {
case syscall.Signal:
code = int(sig)
log.Printf("Got signal: %s(%d)", sig, sig)
default:
code = -1
}
<-cmdCh
case cmdErr = <-cmdCh:
}
// http://qiita.com/hnakamur/items/5e6f22bda8334e190f63
if cmdErr != nil {
if e2, ok := cmdErr.(*exec.ExitError); ok {
if s, ok := e2.Sys().(syscall.WaitStatus); ok {
code = s.ExitStatus()
} else {
log.Println("Unimplemented for system where exec.ExitError.Sys() is not syscall.WaitStatus.")
return ExitCodeError
}
}
}
return code
}
func createToken() string {
b := make([]byte, 16)
crand.Read(b)
return hex.EncodeToString(b)
}