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|
package goctl
import (
"encoding/binary"
"errors"
"fmt"
"io"
"net"
"os"
"strings"
"sync/atomic"
"time"
"gopkg.in/inconshreveable/log15.v2"
)
// How long to wait for a response before returning an error.
const timeout = 100 * time.Millisecond
var builtinHandlers []Handler
// Error returned if handler already exists.
var HandlerExists error
var (
lastid uint64
Logger log15.Logger
)
type Goctl struct {
logger log15.Logger
path string
listener net.Listener
handlers map[string]Handler
}
type Handler interface {
Name() string
Run(*Goctl, []string) string
}
func init() {
Logger = log15.New()
Logger.SetHandler(log15.DiscardHandler())
HandlerExists = errors.New("handler exists")
}
func NewGoctl(path string) Goctl {
handlers := make(map[string]Handler)
for _, h := range builtinHandlers {
handlers[h.Name()] = h
}
return Goctl{
logger: Logger.New("id", atomic.AddUint64(&lastid, 1)),
path: path,
handlers: handlers,
}
}
func (gc *Goctl) Start() error {
gc.logger.Info("Starting command listener.")
if pid := gc.isAlreadyRunning(); pid != "" {
gc.logger.Crit("Command listener already running.", "pid", pid)
return fmt.Errorf("already running on pid %s", pid)
} else {
os.Remove(gc.path)
}
var err error
gc.listener, err = net.Listen("unix", gc.path)
if err != nil {
gc.logger.Crit("Couldn't listen on socket.", "path", gc.path, "error", err)
return err
}
go gc.acceptor()
return nil
}
func (gc *Goctl) Stop() {
gc.logger.Info("Stopping command listener.")
if gc.listener != nil {
gc.listener.Close()
os.Remove(gc.path)
}
}
func (gc *Goctl) AddHandler(h Handler) error {
return gc.AddHandlers([]Handler{h})
}
func (gc *Goctl) AddHandlers(handlers []Handler) error {
for _, h := range handlers {
if gc.handlers[h.Name()] != nil {
return HandlerExists
}
gc.handlers[h.Name()] = h
}
return nil
}
func Read(r io.Reader) ([]byte, error) {
var n uint16
if err := binary.Read(r, binary.BigEndian, &n); err != nil {
return nil, err
}
p := make([]byte, n)
if n == 0 {
// Don't attempt to read no data or EOF will be
// returned. Instead, just return an empty byte slice.
return p, nil
}
if _, err := r.Read(p[:]); err != nil {
return nil, err
}
return p, nil
}
func Write(w io.Writer, p []byte) error {
if err := binary.Write(w, binary.BigEndian, uint16(len(p))); err != nil {
return err
}
if _, err := w.Write(p); err != nil {
return err
}
return nil
}
func (gc *Goctl) acceptor() {
for {
c, err := gc.listener.Accept()
if err != nil {
gc.logger.Error("Error accepting connection.", "error", err)
return
}
go gc.reader(c)
}
}
func (gc *Goctl) reader(c io.ReadWriteCloser) error {
defer gc.logger.Info("Connection closed.")
defer c.Close()
gc.logger.Info("New connection.")
for {
buf, err := Read(c)
if err != nil {
gc.logger.Error("Error reading from connection.", "error", err)
return err
}
cmd := strings.Split(string(buf), "\u0000")
gc.logger.Debug("Got command.", "cmd", cmd)
var resp string
if h := gc.handlers[cmd[0]]; h != nil {
resp = h.Run(gc, cmd[1:])
} else {
resp = fmt.Sprintf("ERROR: unknown command: '%s'.", cmd[0])
}
gc.logger.Debug("Responding.", "resp", resp)
Write(c, []byte(resp))
}
/* NOTREACHED */
}
func (gc *Goctl) isAlreadyRunning() string {
c, err := net.Dial("unix", gc.path)
if err != nil {
return ""
}
defer c.Close()
dataChan := make(chan []byte, 1)
c.Write([]byte("pid"))
go func() {
buf := make([]byte, 1024)
n, err := c.Read(buf[:])
if err == nil {
dataChan <- buf[0:n]
}
}()
select {
case buf := <-dataChan:
return string(buf)
case <-time.After(timeout):
gc.logger.Info("Timed out checking PID of existing service.", "path", gc.path)
return ""
}
}
|
