Go Synchronized
Andrej Vckovski
What I want to transmit

 Go is useful and neat for heavily
concurrent applications
 Webrockets socks!

Go synchronized
...
A small poll

Point your [smartphone] browser to

nca.me/l
Go synchronized

3
nca.me/l

Go synchronized

4
nca.me/l

Go synchronized

5
About go
 Started by Robert Griesemer, Rob Pike and Ken
Thompson in Fall 2007,
Open-sourced 2009, Go 1 March 2012
 Main ...
Concurrency?
 Separate, potentially simultaneously executed
computations
 Usually somehow interacting
 Candidates to le...
Go and concurrency
Communicating Sequential Processes (CSP) pattern
(C. A. R. Hoare, 1978)
1. Channels
2. Go-routines
3. s...
Example
package main
import ("fmt"; "time"; "math/rand")
func main() {
table := make(chan string)
for _, player := range [...
The application:
Very Instant Massive (Audience) Polling
 Presentations
like this one
 TV shows with
added
interactivity...
Browser
JS
that
displays
questions
and
allows
voting

System context

go

Browser
JS
that
displays
questions
and
allows
vo...
Browser
JS
that
displays
questions
and
allows
voting

WebSockets

go

 Full-duplex conversation
ipoll
over TCP connection...
Multiplexer
and
Demultiplexer

Browser
that
displays
questions
and
allows
voting

Browser
that
displays
questions
and
allo...
Small Demo

Point your smartphone browser to

nca.me/l
Go synchronized

14
Demo: New Question 1

nca.me/l
Go synchronized

15
Demo: New Question 2

nca.me/l
Go synchronized

16
Demo: New Question 3

nca.me/l
Go synchronized

17
WebSocket on server side (go)
func startWebserver() {
// [...]

http.HandleFunc("/svy", surveyHandler)
}

Go

// [...]

fu...
Core data massaged at a single place:
The “model” implements an event-loop
func (s *Survey) surveyHub() {
// [...]
t := ti...
Conclusions

 Go (or “CSP”-design) has massively
simplified the concurrency challenges
 WebSockets are easy to use and w...
http://golang.org
Rob Pike on “concurrency is not parallelism”:
http://vimeo.com/49718712
(mascot by Renée French)
Bonus poll

Go synchronized

nca.me/l

22
Thanks for the attention!
andrej.vckovski@netcetera.com
netcetera.com
ipoll.ch
(coming soon)
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Go Synchronized

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Concurrent programming with go and WebSockets
Instant Polling application.
CSP Pattern

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Go Synchronized

  1. 1. Go Synchronized Andrej Vckovski
  2. 2. What I want to transmit  Go is useful and neat for heavily concurrent applications  Webrockets socks! Go synchronized 2
  3. 3. A small poll Point your [smartphone] browser to nca.me/l Go synchronized 3
  4. 4. nca.me/l Go synchronized 4
  5. 5. nca.me/l Go synchronized 5
  6. 6. About go  Started by Robert Griesemer, Rob Pike and Ken Thompson in Fall 2007, Open-sourced 2009, Go 1 March 2012  Main features – C/Pascal/Modula-like, garbage collected, no pointer arithmetics, type safe, very fast compiler – Simple type system without hierarchies – Concepts for concurrent programming in the “CSP”-style – Embeds dependency management – Today about similar memory/execution-performance as Java or Node. Go synchronized 6
  7. 7. Concurrency?  Separate, potentially simultaneously executed computations  Usually somehow interacting  Candidates to leverage multi-{core|cpu|node} environments  Usually but not necessarily correspond to multiple users  Often on the server side And hard to make it right Go synchronized 7
  8. 8. Go and concurrency Communicating Sequential Processes (CSP) pattern (C. A. R. Hoare, 1978) 1. Channels 2. Go-routines 3. select-statement “Do not communicate by sharing memory; instead, share memory by communicating” Occam, Erlang, Newsqueak, Limbo, Clojure and many more Go synchronized 8
  9. 9. Example package main import ("fmt"; "time"; "math/rand") func main() { table := make(chan string) for _, player := range [...]string{"alice", "bob"} { go func(who string) { num := 0; for { ball := <- table; fmt.Printf("player %s: %sn", who, ball) table <- fmt.Sprintf("tick-%s-%d",who,num) time.Sleep(time.Millisecond * time.Duration(rand.Intn(1000))) num++ } }(player) } table <- "go" time.Sleep(10 * time.Second) } Go synchronized 9
  10. 10. The application: Very Instant Massive (Audience) Polling  Presentations like this one  TV shows with added interactivity  Pause entertainment in a stadium  Flipped Classrooms Go synchronized © Nhenze © Chris Lawrence © Loozrboy © Jeff Chenqinyi 10
  11. 11. Browser JS that displays questions and allows voting System context go Browser JS that displays questions and allows voting ipoll server Presentation Software (e.g., PowerPoint) JS Browser JS that displays questions and allows voting Go synchronized Browser that displays voting results 11
  12. 12. Browser JS that displays questions and allows voting WebSockets go  Full-duplex conversation ipoll over TCP connectionserver  JS RFC 6455  Available in most modern browsers  Simple JavaScript binding JS  Handshake by HTTP then , user-defined messages over the same socket Client (Browser) HTTP GET Request, special attributes HTTP response “switch protocol” Browser that displays questions and allows voting Browser that displays questions and allows voting Go synchronized Server Message Presentation Software (e.g., PowerPoint) JS Message Message Browser that displays voting results Message Message 12
  13. 13. Multiplexer and Demultiplexer Browser that displays questions and allows voting Browser that displays questions and allows voting Browser that displays questions and allows voting Go synchronized ipoll server Presentation Software (e.g., PowerPoint) Browser that displays voting results 13
  14. 14. Small Demo Point your smartphone browser to nca.me/l Go synchronized 14
  15. 15. Demo: New Question 1 nca.me/l Go synchronized 15
  16. 16. Demo: New Question 2 nca.me/l Go synchronized 16
  17. 17. Demo: New Question 3 nca.me/l Go synchronized 17
  18. 18. WebSocket on server side (go) func startWebserver() { // [...] http.HandleFunc("/svy", surveyHandler) } Go // [...] func surveyHandler(c http.ResponseWriter, req *http.Request) { // [...] go websocket.Handler(func (ws *websocket.Conn) { s.VoterHandler(ws)} ).ServeHTTP(c, req) // [...] } func (s *Survey) VoterHandler(ws *websocket.Conn) { defer func() { s.voterChan <- voter{ws, false} log.Printf("connection closed by client") ws.Close() }() s.voterChan <- voter{ws, true} // notify hub of a new voter for { // [...] len, err := ws.Read(buf) // [...] var v vote err = json.Unmarshal(buf, &v) if err == nil { s.voteChan <- v } else { // [...] } } synchronized } 18
  19. 19. Core data massaged at a single place: The “model” implements an event-loop func (s *Survey) surveyHub() { // [...] t := time.NewTicker(100 * time.Millisecond) // [...] for { select { case _ = <-t.C: // tick arrived // [...] case ctrl := <-s.controlChan: // control message // [...] case voter := <-s.voterChan: // voter subscribed // [...] case viewer := <-s.viewerChan: // viewer subscribed // [...] case admin := <-s.adminChan: // admin subscribed // [...] case vote := <-s.voteChan: // a vote arrived // [...] } } } 19
  20. 20. Conclusions  Go (or “CSP”-design) has massively simplified the concurrency challenges  WebSockets are easy to use and will be increasingly popular Go synchronized 20
  21. 21. http://golang.org Rob Pike on “concurrency is not parallelism”: http://vimeo.com/49718712 (mascot by Renée French)
  22. 22. Bonus poll Go synchronized nca.me/l 22
  23. 23. Thanks for the attention! andrej.vckovski@netcetera.com netcetera.com ipoll.ch (coming soon)

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