This presentation is Part 8 of the EWD 3 Training Course. It diagrammatically explains what happens throughout the life-cycle of a QEWD message round-trip.

1. Copyright © 2016 M/Gateway Developments Ltd
EWD 3 Training Course
Part 8
Anatomy of the QEWD
Messaging Cycle
Rob Tweed
Director, M/Gateway Developments Ltd
Twitter: @rtweed

2. Copyright © 2016 M/Gateway Developments Ltd
Let's summarise what happens..
• During the QEWD Message Round-trip

3. Copyright © 2016 M/Gateway Developments Ltd
The QEWD Message Round-trip
• Generate an event in the browser
• Send a message to the QEWD back-end
• At the back-end, a handler function for that
message type processes the message and
usually creates a response message
• Response message is returned to the browser
where a handler function processes it and
usually modifies the User Interface

4. Copyright © 2016 M/Gateway Developments Ltd
QEWD
Node.js Worker Process
Master Node.js Process
Queue
Queue
processor/
dispatcher
qewd
cache.node
ewd-qoper8-cache
Global
Storage
Database
ewd-document-store
Globals
ewd-session
Express
HTTP(S)
Interface
WebSocket
socket.io
Interface
browserewd-client
Custom Worker
Module
ewd-qoper8

5. Copyright © 2016 M/Gateway Developments Ltd
After registration
Browser QEWD
Caché,
GT.M or
Redis
socket.io
socket.io
Token stored within
Closure in browser
ewd-client
token
ewd-session

6. Copyright © 2016 M/Gateway Developments Ltd
Button clicked
Browser QEWD
socket.io
socket.io
ewd-client
token
Event fired
EWD.send() invoked

7. Copyright © 2016 M/Gateway Developments Ltd
Message sent
Browser QEWD
socket.io
socket.io
ewd-client
token
Message augmented
with token and
sent to QEWD
master process
Message object
Type + payload
ewd-qoper8
queue

8. Copyright © 2016 M/Gateway Developments Ltd
Message queued
Browser QEWD
socket.io
socket.io
ewd-client
token
Added to queue
ewd-qoper8
queue

9. Copyright © 2016 M/Gateway Developments Ltd
Message dispatched to worker
Browser QEWD
socket.io
socket.io
ewd-client
token
Message dispatched
to available worker
ewd-qoper8
queue
Caché,
GT.M or
Redis

10. Copyright © 2016 M/Gateway Developments Ltd
Session lookup
Browser QEWD
socket.io
socket.io
ewd-client
token
Token used to lookup
QEWD Session
ewd-session
ewd-qoper8
queue
Caché,
GT.M or
Redis

11. Copyright © 2016 M/Gateway Developments Ltd
Application Name lookup
Browser QEWD
socket.io
socket.io
ewd-client
token
Retrieve application name
ewd-session
ewd-qoper8
queue
Caché,
GT.M or
Redis

12. Copyright © 2016 M/Gateway Developments Ltd
Application Name lookup
Browser QEWD
socket.io
socket.io
ewd-client
token
Retrieve application name
Important security feature:
Can't arbitrarily try to run another
application's message handlers
ewd-session
ewd-qoper8
queue
Caché,
GT.M or
Redis

13. Copyright © 2016 M/Gateway Developments Ltd
Load application module
Browser QEWD
socket.io
socket.io
ewd-client
token
Load application
back-end module
(if not already loaded)
ewd-session
ewd-qoper8
queue
Custom Worker
Module
demo1.js
Caché,
GT.M or
Redis

14. Copyright © 2016 M/Gateway Developments Ltd
Invoke message handler
Browser QEWD
socket.io
socket.io
ewd-client
token
Trigger message handler
function for received
message type
ewd-session
ewd-qoper8
queue
Custom Worker
Module
demo1.js
Caché,
GT.M or
Redis

15. Copyright © 2016 M/Gateway Developments Ltd
Invoke message handler
Browser QEWD
socket.io
socket.io
ewd-client
token
Access Global Storage,
Document Store, etc
and user's QEWD Session
ewd-session
ewd-qoper8
queue
Custom Worker
Module
demo1.js
Caché,
GT.M or
Redis

16. Copyright © 2016 M/Gateway Developments Ltd
Return response message(s)
Browser QEWD
socket.io
socket.io
ewd-client
token
Return message
send() – intermediate message
finished() – final message
ewd-session
ewd-qoper8
queue
Custom Worker
Module
demo1.js
Caché,
GT.M or
Redis

17. Copyright © 2016 M/Gateway Developments Ltd
Handle response message(s)
Browser QEWD
socket.io
socket.io
ewd-client
token
Client-side response
handler fires in
app.js
ewd-session
ewd-qoper8
queue
Custom Worker
Module
demo1.js
Caché,
GT.M or
Redis

18. Copyright © 2016 M/Gateway Developments Ltd
Update UI
Browser QEWD
socket.io
socket.io
ewd-client
token
User interface modified
ewd-session
ewd-qoper8
queue
Custom Worker
Module
demo1.js
User
Interface
Caché,
GT.M or
Redis

19. Copyright © 2016 M/Gateway Developments Ltd
Worker released
Browser QEWD
socket.io
socket.io
ewd-client
token
Meanwhile, finished() function
causes release of worker
back to available pool
ewd-qoper8
queue
User
Interface
Custom Worker
Module
demo1.js
Caché,
GT.M or
Redis

20. Copyright © 2016 M/Gateway Developments Ltd
QEWD applications
• Just repeat this pattern over and over
again!