Reconnect TCP on EOF in Go - tcp

Question

I have the following:
//In an init func
if logStashHost != "" {
lsconn, err = net.Dial("tcp", logStashHost)
}
...
ToLogStash(rec, lsconn)
Then Two functions:
func ReadLogStash(conn net.Conn) {
buffer := make([]byte, 256)
for {
_, err := conn.Read(buffer)
if err != nil {
fmt.Println(err)
} else {
fmt.Println(buffer)
}
}
}
func ToLogStash(r *logrow.Record, conn net.Conn) {
b, err := json.Marshal(r)
if err != nil {
fmt.Println(err)
return
}
_, err = fmt.Fprintln(conn, string(b))
if err != nil {
fmt.Println(err)
}
}
Where ReadLogStash is a running goroutine. If the other side closes, I get EOF. What would be a good implementation in ReadLogStash to have it attempt to reestablish the connection every X seconds when it gets an EOF?

Answer 1

Go has channels for synchronization and communication, use them!
Make your connection in a loop, and have it wait for some sort of message to come back on a channel.
...
errCh := make(chan error)
for {
lsconn, err = net.Dial("tcp", logStashHost)
// check error!
go ReadLogStash(lsconn, errCh)
err = <-errCh
if err != nil {
// bad error
break
}
// sleep to backoff on retries?
}
...
func ReadLogStash(conn net.Conn, errCh chan error) {
_, err := io.Copy(os.Stderr, conn)
if err != nil {
fmt.Println(err)
}
// a nil error from io.Copy means you reached EOF.
errCh <- err
}
Unless you have more functionality in ReadLogStash, you can probably just use io.Copy inline, and forget the entire function, but this pattern may come in useful for you anyway.

Answer 2

Here is what I ended up going with, a channel was the right direction:
if logStashHost != "" {
lsc = make(chan *logrow.Record)
go ToLogStash(lsc, logStashHost)
}
...
if lsc != nil {
lsc <- rec
}
...
func ToLogStash(c chan *logrow.Record, logStashHost string) {
var lsconn net.Conn
var enc *json.Encoder
var err error
connect := func() {
for {
lsconn, err = net.Dial("tcp", logStashHost)
if err == nil {
enc = json.NewEncoder(lsconn)
break
}
log.Println(err)
time.Sleep(time.Second)
}
}
connect()
for r := range c {
err = enc.Encode(r)
if err != nil {
lsconn.Close()
log.Println(err)
connect()
}
}
}