headless9/main.go

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package main
import (
"bufio"
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"errors"
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"flag"
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"fmt"
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"log"
"os"
"os/exec"
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"strings"
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"time"
)
var (
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serviceFile = "/adm/services"
services = make(map[string]Service)
controlSocket = "/adm/headless9/ctl/headless9.ctl"
logPath = "/adm/headless9/log/"
execWait = false
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headless9Start = time.Now()
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)
func main() {
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flag.Parse()
if flag.NArg() == 0 {
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logFile, err := os.Create(fmt.Sprintf("%+v/%+v.log", logPath, "headless9"))
if err != nil {
panic(err)
}
log.SetOutput(logFile)
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log.Println(DAEMON_START)
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runDaemon()
}
if flag.NArg() != 2 {
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log.Println(CMD_SYNTAX)
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return
}
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verb := flag.Args()[0]
service := flag.Args()[1]
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f := getCtl()
_, err := fmt.Fprintf(f, "%+v %+v", verb, service)
if err != nil {
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log.Fatalf(CTL_UNABLE_WRITE, controlSocket)
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}
f.Close()
err = watchFile(controlSocket)
if err != nil {
log.Println(err)
}
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fmt.Println(sysTail(10, controlSocket))
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}
func getCtl() *os.File {
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f, err := os.OpenFile(controlSocket, os.O_TRUNC, 0660)
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if err != nil {
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log.Fatalf(CTL_NOT_OPEN, controlSocket)
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}
err = f.Truncate(0)
if err != nil {
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log.Fatalf(CTL_NOT_CLEAR, controlSocket)
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}
_, err = f.Seek(0, 0)
if err != nil {
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log.Fatalf(CTL_NOT_REWOUND, controlSocket)
}
f, err = os.OpenFile(controlSocket, os.O_RDWR, 0660)
if err != nil {
log.Fatalf(CTL_NOT_OPEN, controlSocket)
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}
return f
}
func runDaemon() {
go headlessControls()
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for {
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log.Printf(DAEMON_FILE_REFRESH, serviceFile)
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startup, err := readLines(serviceFile)
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if err != nil {
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if errors.Is(err, os.ErrNotExist) {
test, err := os.Create(serviceFile)
if err != nil {
log.Fatalln(err)
}
test.Close()
} else {
log.Fatalln(err)
}
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}
for _, svc := range startup {
running := false
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svcArgs := strings.Split(svc, " ")
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for runningProc := range services {
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if svcArgs[0] == runningProc {
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running = true
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log.Printf(DAEMON_SVC_EXISTS, svcArgs[0], services[svcArgs[0]])
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}
}
if !running {
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log.Printf(DAEMON_SVC_MISSING, svcArgs[0])
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go execCommand(svcArgs[0], svcArgs[1:]...)
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}
}
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err = watchFile(serviceFile)
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if err != nil {
log.Println(err)
}
}
}
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func headlessControls() {
for {
err := watchFile(controlSocket)
if err != nil {
log.Println(err)
}
pendingCommands, err := readLines(controlSocket)
if err != nil {
log.Println(err)
} else {
for _, cmd := range pendingCommands {
log.Printf(DAEMON_CTL_PROCESSING, cmd)
start := time.Now()
err = processCommand(cmd)
if err != nil {
log.Printf(DAEMON_CTL_FAILED, err, time.Since(start))
} else {
log.Printf(DAEMON_CTL_PROCESSED, cmd, time.Since(start))
}
}
}
}
}
func processCommand(cmd string) error {
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defer PanicSafe()
parts := strings.Split(cmd, " ")
verb := parts[0]
svc := parts[1]
start := time.Now()
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messages := 0
if verb == "restart" || verb == "stop" {
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f, err := os.OpenFile(fmt.Sprintf("/proc/%d/ctl", services[svc].ProcessHandle.Pid), os.O_WRONLY, 0660)
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if err != nil {
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log.Printf(DAEMON_CTL_FAILED, err, time.Since(start))
messages++
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}
defer f.Close()
_, err = f.WriteString("kill")
if err != nil {
log.Printf(DAEMON_CTL_FAILED, err, time.Since(start))
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messages++
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} else {
delete(services, svc)
log.Printf(DAEMON_CTL_PROCESSED, svc, time.Since(start))
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messages++
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}
}
if verb == "restart" || verb == "start" {
startup, err := readLines(serviceFile)
if err != nil {
log.Fatalln(err)
}
for _, testSvc := range startup {
svcArgs := strings.Split(testSvc, " ")
if svc != testSvc {
continue
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}
log.Printf(DAEMON_SVC_MISSING, svcArgs[0])
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messages++
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execWait = true
go execCommand(svcArgs[0], svcArgs[1:]...)
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}
}
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for execWait {
time.Sleep(5 * time.Millisecond)
}
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ctlOut := ""
if verb == "status" {
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ctlOut += fmt.Sprintf("%+v up %+v PID %+v\n", svc, time.Since(services[svc].StartTime), services[svc].ProcessHandle.Pid)
ctlOut += strings.Join(sysTail(5, fmt.Sprintf("%+v/%+v.log", logPath, svc)), "\n")
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} else {
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ctlOut += fmt.Sprintf("%+v up %+v\n", "headless9", time.Since(headless9Start))
ctlOut += strings.Join(sysTail(messages, fmt.Sprintf("%+v/%+v.log", logPath, "headless9")), "\n")
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}
f := getCtl()
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_, err := fmt.Fprintf(f, "%s", ctlOut)
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if err != nil {
log.Printf(CTL_UNABLE_WRITE, controlSocket)
}
f.Close()
return nil
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}
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func execCommand(cmd string, arg ...string) {
defer PanicSafe()
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if len(cmd) < 2 {
log.Printf(DAEMON_SVC_INVALID, cmd, arg)
return
}
if strings.HasPrefix(cmd, "#") {
log.Printf(DAEMON_SVC_DISABLED, cmd)
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return
}
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proc := exec.Command(cmd, arg...)
// open the out file for writing
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outfile, err := os.Create(fmt.Sprintf("%+v/%+v.log", logPath, cmd))
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if err != nil {
panic(err)
}
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infile, err := os.Create(fmt.Sprintf("%+v/%+v.ctl", logPath, cmd))
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if err != nil {
panic(err)
}
defer outfile.Close()
defer infile.Close()
proc.Stderr = outfile
proc.Stdout = outfile
proc.Stdin = infile
err = proc.Start()
if err != nil {
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log.Printf(DAEMON_SVC_FAIL, cmd)
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return
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}
services[cmd] = Service{
ProcessHandle: proc.Process,
StartupArgs: arg,
StartTime: time.Now(),
}
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execWait = false
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proc.Wait()
}
// readLines reads a whole file into memory
// and returns a slice of its lines.
func readLines(path string) ([]string, error) {
file, err := os.Open(path)
if err != nil {
return nil, err
}
defer file.Close()
var lines []string
scanner := bufio.NewScanner(file)
for scanner.Scan() {
lines = append(lines, scanner.Text())
}
return lines, scanner.Err()
}
func watchFile(filePath string) error {
initialStat, err := os.Stat(filePath)
if err != nil {
return err
}
for {
stat, err := os.Stat(filePath)
if err != nil {
return err
}
if stat.Size() != initialStat.Size() || stat.ModTime() != initialStat.ModTime() {
break
}
time.Sleep(250 * time.Millisecond)
}
return nil
}
// PanicSafe is a deferrable function to recover from a panic operation.
func PanicSafe(a ...interface{}) {
if r := recover(); r != nil {
log.Printf("Panic detected: %+v", r)
log.Printf("Optional panic data: %+v", a...)
}
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}
// count for number of lines, path of file
func sysTail(count int, path string) []string {
c := exec.Command("tail", fmt.Sprintf("-%d", count+1), path)
output, _ := c.Output()
lines := strings.Split(string(output), "\n")
return lines[:len(lines)-1]
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}