a case study of forex information website using socket.io

1. Socket.IO
on
SmartFX
Takeshi Morita @takeshy
Minkabu Inc.

2. CONTENTS
 What is SmartFX?
 Coding Hints for the usage of Socket.IO
 Considerations on using Socket.IO
 The Middleware, Socket.IO-ReqEv
 Operation of Socket.IO server
 Redundancy and load balancing
 Shutdown in case of deploy

3. What is SmartFX?

4. What is SmartFX?
 A free site for smartphone developed by Minkabu to
provide FX information including news, charts and
predictions
 A real-time Single Page Application based on
Socket.IO and Backbone.js
Go to -
http://smartfx.jp
or real URL http://smartfx.minkabu.jp

5. Coding Hints
for the usage of Socket.IO

6. Considerations
on using Sockeet.IO
 Socket.IO has powerful Socket managing tools of
“NameSpace”, “Rooms” and “Events”
 Their interchangeable feature, there's more than one
way to manage a broadcast client.
 We, therefore, introduced our own coding rules in
SmartFX

7. Coding Rules in SmartFX
 One Object for One NameSpace
 One Event for One Room with One EventName
 Each event shall be emitted using Room feature
 Define 3 Types of Event of “message”, ”reply”
and ”error”
 “message” shall be used for the data transfer from a client to
the server
 “reply” and ”error” shall be used for from the server to a client

8. The Middleware, Stock.IO-ReqEv
 With coding rules, succeeded to create a Middleware
with specialized feature of Stock.IO procedures
 We named the Middleware “Socket.IO-ReqEv”
 You can install below
npm install socket.io-reqev

9. How to use Socket.IO-ReqEv
-the server side-
Only 2 steps
1. Create a IOReqEv object with an initial value of a
Socket.IO object.
2. Call “register” method giving NameSpace & object met
with the rule of IO-ReqEv
*Example above shows the simplest case of one set of registration. This
“register” method can be called repeatedly.

10. Rules to pass objects to Socke.IO-
ReqEv
1. Set event name to the property of
array “events”
2. Emit event with data, inheriting
EventEmitter
3. Implement a method “request”,
which Socket.IO-ReqEv calls when a
message from client includes a
parameter of “requests” . This works
similar to HTTP GET
*Codes on the left runs to broadcast events
every second/minute and emit the current time

11. How to use Socket.IO-ReqEv
-the client side-
Only 2 steps on browser
1. Create IOReqEvClient, giving the url which includes the
address of Socket.IO and namespace, and callback
2. Call a method “watch” to subscribe an event and to get a
request
*unsubscribe automatically unnecessary events previously called, once the method
“watch” is called again with another events

12. Implementation of Socket.IO-ReqEv
 The library of Socket.IO-ReqEv is written with just less
than 60 coding lines
 Moreover, the library is written with public properties
only on Socket.IO 1.0, while there were some non-
public properties on 0.9.x
 The source code of Socket.IO-ReqEv is available at url
below
https://github.com/takeshy/socket.io-reqev

13. Operation of Socket.IO server

14. System Configulation

15. Redundancy and Load Balancing
 Redundancy and load balancing are accomplished-
 Socket.IO server updates its record on the DB periodically
 WebServer gets a list of address of Socket.IO server recently
updated from the DB
 WebServer Returns one of them randomly to a client

16. Redundancy and Load Balancing
Sequences

17. Shutdown in case of Deploy
 Delete command in demon management tool of pm2
does not work under the situation of Socket.IO being
always connected to client
 To solve this problem, developed a self-shutdown
mechanism of Socket.IO server

18. The Workflow of Deploy
 Update app source code in the Socket.IO server, and run the script
which executes pm2 command of “delete” and “start”. (by capistrano)
 Set “inactive” to the status field of the Socket.IO record on the DB
 Once the Socket.IO detects its own record set as “inactive”, the server
broadcasts inactive event to clients and set timer to kill itself a minute
later
 A client which received inactive event displays a popup message saying
“disconnected the server” in case the user stays more than 1 minute.
(in case a user goes to different page, the client gets another server
address, then network connection stays)
 Set “activate” to the status field of the Socket.IO record on the DB

19. Socket.IO Shutdown
Sequences

20. Thank you!