forked from jonasschneider/gow
/
backend.go
309 lines (264 loc) · 6.15 KB
/
backend.go
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package main
import (
"bytes"
"errors"
"io"
"io/ioutil"
"log"
"net"
"os"
"os/exec"
"path/filepath"
"strconv"
"strings"
"syscall"
"time"
"github.com/joho/godotenv"
)
type Backend struct {
appPath string
host string
port int
proxy bool
process *os.Process
startedAt time.Time
exited bool
exitChan chan interface{}
activityChan chan interface{}
}
func (b *Backend) Close() {
if b.proxy {
log.Println("Terminating", b.appPath, "proxy")
b.exitChan <- true
<-b.exitChan
log.Println("Terminated", b.appPath)
return
}
log.Println("Terminating", b.appPath, "pid", b.process.Pid)
err := b.process.Signal(syscall.SIGTERM)
if err != nil {
log.Println("failed to kill process: ", err)
return
}
<-b.exitChan
log.Println("Terminated", b.appPath)
}
func (b *Backend) IsRestartRequested() bool {
if b.exited {
return true
}
if b.proxy {
fi, err := os.Stat(b.appPath)
if err != nil {
return false
}
return fi.ModTime().After(b.startedAt)
}
fi, err := os.Stat(b.appPath + "/tmp/restart.txt")
if err != nil {
return false
}
return fi.ModTime().After(b.startedAt)
}
type BootCrash struct {
Log bytes.Buffer
Env []string
Cmd string
Path string
}
func (b BootCrash) Error() string {
return "app crashed during boot"
}
func SpawnBackend(appName string) (*Backend, error) {
pathToApp, err := appDir(appName)
if err != nil {
return nil, err
}
fileInfo, err := os.Stat(pathToApp)
if err != nil {
return nil, err
}
if fileInfo.IsDir() {
return SpawnBackendProcfile(pathToApp)
}
return SpawnBackendProxy(pathToApp)
}
func SpawnBackendProcfile(pathToApp string) (*Backend, error) {
port, err := getFreeTCPPort()
if err != nil {
return nil, err
}
log.Println("Spawning", pathToApp, "on port", port)
env := os.Environ()
pathbytes, err := ioutil.ReadFile(os.Getenv("HOME") + "/.pow/.path")
path := os.Getenv("PATH")
if err == nil {
path = string(pathbytes)
}
// remove the old PATH
for i, v := range env {
if strings.Index(v, "PATH=") == 0 {
env = append(env[:i], env[i+1:]...)
}
}
env = append(env, "PATH="+path, "PORT="+strconv.Itoa(port))
// add .env
entries, err := godotenv.Read(pathToApp + "/.env")
if err == nil {
for k, v := range entries {
env = append(env, k+"="+v)
}
} else {
// allow absence of .env
if !os.IsNotExist(err) {
return nil, err
}
}
procfile, err := ReadProcfile(pathToApp + "/Procfile")
if err != nil {
return nil, err
}
var CmdName string
for _, v := range procfile.Entries {
if v.Name == "web" {
CmdName = v.Command
}
}
if CmdName == "" {
return nil, errors.New("No 'web' entry found in Procfile")
}
cmd := exec.Command("bash", "-c", "exec "+CmdName)
var bootlog bytes.Buffer
toStderrWithCapture := io.MultiWriter(os.Stderr, &bootlog)
cmd.Stdout = toStderrWithCapture // never write to gowd's stdout
cmd.Stderr = toStderrWithCapture
cmd.Dir = pathToApp
cmd.Env = env
err = cmd.Start()
if err != nil {
return nil, err
}
exitChan := make(chan interface{}, 1)
b := &Backend{appPath: pathToApp, host: "127.0.0.1", port: port, proxy: false, process: cmd.Process, startedAt: time.Now(), activityChan: make(chan interface{}), exitChan: exitChan}
booting := true
crashChan := make(chan error, 1)
go func() {
cmd.Wait()
b.exited = true
b.exitChan <- new(interface{})
if booting {
crashChan <- BootCrash{Log: bootlog, Env: env, Cmd: CmdName, Path: pathToApp}
}
}()
log.Println("waiting for spawn result for", pathToApp)
select {
case <-awaitTCP(b.Address()):
log.Println(pathToApp, "came up successfully")
booting = false
go b.watchForActivity()
return b, nil
case <-time.After(30 * time.Second):
log.Println(pathToApp, "failed to bind")
cmd.Process.Kill()
return nil, errors.New("app failed to bind")
case err := <-crashChan:
log.Println(pathToApp, "crashed while starting")
return nil, err
}
}
func SpawnBackendProxy(pathToApp string) (*Backend, error) {
appbytes, err := ioutil.ReadFile(pathToApp)
app := ""
if err == nil {
app = strings.TrimSpace(string(appbytes))
} else {
log.Println("while reading app file:", err)
}
if strings.HasPrefix(app, "http://") {
app = app[7:len(app)]
} else {
app = "127.0.0.1:" + app
}
host, portstring, err := net.SplitHostPort(app)
if err != nil {
return nil, err
}
port, err := strconv.Atoi(portstring)
if err != nil {
return nil, err
}
log.Println("Proxying", pathToApp, "to host", host, "on port", port)
exitChan := make(chan interface{}, 1)
b := &Backend{appPath: pathToApp, host: host, port: port, proxy: true, process: nil, startedAt: time.Now(), activityChan: make(chan interface{}), exitChan: exitChan}
go func() {
<-b.exitChan
b.exited = true
b.exitChan <- new(interface{})
}()
select {
case <-awaitTCP(b.Address()):
log.Println(pathToApp, "came up successfully")
go b.watchForActivity()
return b, nil
case <-time.After(30 * time.Second):
log.Println(pathToApp, "failed to bind")
return nil, errors.New("app failed to bind")
}
}
func (b *Backend) Touch() {
if b.activityChan != nil {
b.activityChan <- new(interface{})
}
}
func (b *Backend) Address() string {
return net.JoinHostPort(b.host, strconv.Itoa(b.port))
}
// Close the backend after inactivity
func (b *Backend) watchForActivity() {
outer:
for {
select {
case _, ok := <-b.activityChan:
if ok {
continue
} else {
b.Close()
b.activityChan = nil
break outer
}
case <-time.After(30 * time.Minute):
log.Println(b.appPath, "backend idling.")
b.Close()
b.activityChan = nil
break outer
}
}
}
func awaitTCP(address string) chan bool {
c := make(chan bool)
go func() {
for {
_, err := net.Dial("tcp", address)
if err == nil {
c <- true
break
}
time.Sleep(200 * time.Millisecond)
}
}()
return c
}
func getFreeTCPPort() (port int, err error) {
// We still have a small race condition here, but meh.
l, err := net.Listen("tcp", "localhost:0")
if err != nil {
return 0, err
}
port = l.Addr().(*net.TCPAddr).Port
l.Close()
return port, nil
}
func appDir(name string) (path string, err error) {
path, err = filepath.EvalSymlinks(os.Getenv("HOME") + "/.pow/" + name)
return
}