clock

A demo of peer discovery and bidirectional streaming, and Flatend by itself without its built-in HTTP server.

Run go run main.go on one terminal. Run go run main.go clock on several other terminals.

Watch nodes randomly query and respond to each others requests regarding their current systems time.

[terminal 1] $ go run main.go
2020/06/18 00:06:56 Listening for Flatend nodes on '127.0.0.1:9000'.
2020/06/18 00:06:57 [::]:44369 has connected. Services: [clock]
Got someone's time ('Jun 18 00:06:57')! Sent back ours ('Jun 18 00:06:57').
2020/06/18 00:06:57 [::]:45309 has connected. Services: [clock]
Got someone's time ('Jun 18 00:06:57')! Sent back ours ('Jun 18 00:06:57').
[1] Asked someone for their current time. Ours is 'Jun 18 00:06:57'.
[1] Got a response! Their current time is: 'Jun 18 00:06:57'.
[2] Asked someone for their current time. Ours is 'Jun 18 00:06:57'.
[2] Got a response! Their current time is: 'Jun 18 00:06:57'.
[3] Asked someone for their current time. Ours is 'Jun 18 00:06:58'.

[terminal 2] $ go run main.go clock
2020/06/18 00:06:57 Listening for Flatend nodes on '[::]:44369'.go clock
2020/06/18 00:06:57 You are now connected to 127.0.0.1:9000. Services: [clock]
2020/06/18 00:06:57 Re-probed 127.0.0.1:9000. Services: [clock]
2020/06/18 00:06:57 Discovered 0 peer(s).
[0] Asked someone for their current time. Ours is 'Jun 18 00:06:57'.
[0] Got a response! Their current time is: 'Jun 18 00:06:57'.
2020/06/18 00:06:57 [::]:45309 has connected. Services: [clock]
Got someone's time ('Jun 18 00:06:57')! Sent back ours ('Jun 18 00:06:57').
[1] Asked someone for their current time. Ours is 'Jun 18 00:06:58'.
[1] Got a response! Their current time is: 'Jun 18 00:06:58'.
[2] Asked someone for their current time. Ours is 'Jun 18 00:06:58'.
[2] Got a response! Their current time is: 'Jun 18 00:06:58'.
Got someone's time ('Jun 18 00:06:58')! Sent back ours ('Jun 18 00:06:58').
Got someone's time ('Jun 18 00:06:58')! Sent back ours ('Jun 18 00:06:58').
[3] Asked someone for their current time. Ours is 'Jun 18 00:06:58'.
[3] Got a response! Their current time is: 'Jun 18 00:06:58'.

[terminal 3] $ go run main.go clock
2020/06/18 00:06:57 Listening for Flatend nodes on '[::]:45309'.go clock
2020/06/18 00:06:57 You are now connected to 127.0.0.1:9000. Services: [clock]
2020/06/18 00:06:57 Re-probed 127.0.0.1:9000. Services: [clock]
2020/06/18 00:06:57 You are now connected to [::]:44369. Services: [clock]
2020/06/18 00:06:57 Discovered 1 peer(s).
[0] Asked someone for their current time. Ours is 'Jun 18 00:06:57'.
[0] Got a response! Their current time is: 'Jun 18 00:06:57'.
Got someone's time ('Jun 18 00:06:57')! Sent back ours ('Jun 18 00:06:57').
Got someone's time ('Jun 18 00:06:58')! Sent back ours ('Jun 18 00:06:58').
Got someone's time ('Jun 18 00:06:58')! Sent back ours ('Jun 18 00:06:58').
[1] Asked someone for their current time. Ours is 'Jun 18 00:06:58'.
[1] Got a response! Their current time is: 'Jun 18 00:06:58'.
[2] Asked someone for their current time. Ours is 'Jun 18 00:06:58'.
[2] Got a response! Their current time is: 'Jun 18 00:06:58'.
Got someone's time ('Jun 18 00:06:58')! Sent back ours ('Jun 18 00:06:58').

package main

import (
	"errors"
	"flag"
	"fmt"
	"github.com/lithdew/flatend"
	"io"
	"io/ioutil"
	"math/rand"
	"os"
	"os/signal"
	"strings"
	"time"
)

func check(err error) {
	if err != nil {
		panic(err)
	}
}

func clock(ctx *flatend.Context) {
	latest := time.Now()
	ours := latest.Format(time.Stamp)

	timestamp, err := ioutil.ReadAll(ctx.Body)
	if err != nil {
		return
	}

	fmt.Printf("Got someone's time ('%s')! Sent back ours ('%s').\n", string(timestamp), ours)

	ctx.Write([]byte(ours))
}

func main() {
	flag.Parse()

	node := &flatend.Node{
		SecretKey: flatend.GenerateSecretKey(),
		Services: map[string]flatend.Handler{
			"clock": clock,
		},
	}
	defer node.Shutdown()

	if flag.Arg(0) == "" {
		node.PublicAddr = "127.0.0.1:9000"
		check(node.Start())
	} else {
		check(node.Start("127.0.0.1:9000"))
	}

	exit := make(chan struct{})
	defer close(exit)

	go func() {
		for i := 0; ; i++{
			select {
			case <-exit:
				return
			case <-time.After(time.Duration(rand.Intn(1000)) * time.Millisecond):
				timestamp := time.Now().Format(time.Stamp)
				body := ioutil.NopCloser(strings.NewReader(timestamp))

				stream, err := node.Push([]string{"clock"}, nil, body)
				if err != nil {
					if strings.Contains(err.Error(), "no nodes were able to process") {
						continue
					}
					if errors.Is(err, io.EOF) {
						continue
					}
					check(err)
				}

				fmt.Printf("[%d] Asked someone for their current time. Ours is '%s'.\n", i, timestamp)

				res, err := ioutil.ReadAll(stream.Reader)
				check(err)

				fmt.Printf("[%d] Got a response! Their current time is: '%s'\n", i, string(res))
			}
		}
	}()

	ch := make(chan os.Signal, 1)
	signal.Notify(ch, os.Interrupt)
	<-ch
}

# README

clock