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subservice.go
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subservice.go
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package main
import (
"bytes"
"fmt"
"github.com/kballard/go-shellquote"
"github.com/skynetservices/skynet/daemon"
"github.com/skynetservices/skynet/log"
"io"
"os"
"os/exec"
"os/signal"
"path/filepath"
"sync"
"syscall"
"time"
)
const RerunWait = time.Second * 5
type SubService struct {
// ServicePath is the gopath repr of the service binary
ServicePath string
// Args is the unprocessed command line arguments tacked on
// after the binary name.
Args string
// argv is Args after it is properly split up
argv []string
running bool
binPath string
rerunChan chan bool
startMutex sync.Mutex
runSignal sync.WaitGroup
UUID string
pipe *daemon.Pipe
Registered bool
}
func NewSubService(binaryName, args, uuid string, registered bool) (ss *SubService, err error) {
ss = &SubService{
ServicePath: binaryName,
Args: args,
UUID: uuid,
Registered: registered,
}
ss.argv, err = shellquote.Split(args)
if err != nil {
return
}
ss.argv = append([]string{"-uuid", uuid}, ss.argv...)
if !registered {
ss.argv = append(ss.argv, "-registered=false")
}
bindir := os.Getenv("SKYNET_SERVICE_DIR")
if bindir == "" {
bindir = "/usr/bin"
}
ss.binPath = filepath.Join(bindir, binaryName)
return
}
func (ss *SubService) Register() (ok bool) {
ok = ss.sendAdminCommand("REGISTER")
if ok {
ss.Registered = true
}
return ok
}
func (ss *SubService) IsRunning() bool {
return ss.running
}
func (ss *SubService) Unregister() (ok bool) {
ok = ss.sendAdminCommand("UNREGISTER")
if ok {
ss.Registered = false
}
return ok
}
func (ss *SubService) SetLogLevel(level string) bool {
return ss.sendAdminCommand("LOG " + level)
}
func (ss *SubService) Stop() bool {
ss.startMutex.Lock()
defer ss.startMutex.Unlock()
if !ss.running {
return false
}
ss.runSignal.Add(1)
close(ss.rerunChan)
ss.running = false
ss.Unregister()
// halt the rerunner so we can kill the processes without it relaunching
ss.runSignal.Wait()
return ss.sendAdminCommand("SHUTDOWN")
}
func (ss *SubService) Start() (success bool, err error) {
success = false
ss.startMutex.Lock()
defer ss.startMutex.Unlock()
if ss.running {
return
}
ss.running = true
ss.rerunChan = make(chan bool)
go ss.rerunner()
// Block for first start so we can make sure binary exists etc
_, err = ss.startProcess()
if err == nil {
success = true
}
return
}
func (ss *SubService) Restart() bool {
log.Println(log.INFO, "Restarting service intentially "+ss.UUID)
return ss.sendAdminCommand("SHUTDOWN")
}
func (ss *SubService) startProcess() (proc *os.Process, err error) {
cmd := exec.Command(ss.binPath, ss.argv...)
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
dRead, ssWrite, err := os.Pipe()
ssRead, dWrite, err := os.Pipe()
// Store Fd's for us to read/write to SubService
ss.pipe = daemon.NewPipe(dRead, dWrite)
// Pass SubService their side of the connection
cmd.ExtraFiles = append(cmd.ExtraFiles, ssRead, ssWrite)
err = cmd.Start()
proc = cmd.Process
startupTimer := time.NewTimer(RerunWait)
if proc != nil {
go ss.watchSignals()
go ss.watchProcess(proc, startupTimer)
}
return
}
func (ss *SubService) watchProcess(proc *os.Process, startupTimer *time.Timer) {
proc.Wait()
if !ss.running {
startupTimer.Stop()
return
}
select {
case <-startupTimer.C:
// we let it run long enough that it might not be a recurring error, try again
if ss.running {
ss.rerunChan <- true
}
default:
// error happened too quickly - must be startup issue
fmt.Println("Service died too quickly: " + ss.binPath)
startupTimer.Stop()
}
}
func (ss *SubService) rerunner() {
for rerun := range ss.rerunChan {
if !rerun {
break
}
fmt.Println("Restarting service: " + ss.binPath)
_, err := ss.startProcess()
if err != nil {
fmt.Println(err)
}
}
ss.runSignal.Done()
}
func (ss *SubService) watchSignals() {
c := make(chan os.Signal)
signal.Notify(c, syscall.SIGINT, syscall.SIGKILL, syscall.SIGSEGV, syscall.SIGSTOP, syscall.SIGTERM)
for {
select {
case sig := <-c:
switch sig.(syscall.Signal) {
// Trap signals so we don't get restarted
case syscall.SIGINT, syscall.SIGKILL, syscall.SIGQUIT,
syscall.SIGSEGV, syscall.SIGSTOP, syscall.SIGTERM:
ss.Stop()
}
}
}
}
func (ss *SubService) sendAdminCommand(cmd string) bool {
log.Println(log.TRACE, "Writing to admin pipe: "+cmd)
_, err := ss.pipe.Write([]byte(cmd))
if err != nil {
log.Println(log.ERROR, "Failed to write to admin pipe", err)
return false
}
b := make([]byte, daemon.MAX_PIPE_BYTES)
log.Println(log.TRACE, "Reading from admin pipe")
n, err := ss.pipe.Read(b)
if err != nil && err != io.EOF {
log.Println(log.ERROR, "Failed to read from admin pipe", err)
return false
}
if bytes.Equal(b[:n], []byte("ACK")) {
return true
}
return false
}