http://particular.net

Powering front end apps with NServiceBus

Sean Farmar – Mauro Servienti

Solution Architects @ Particular Software

Agenda

• Targeted responses overview

• Scale out issues

• Technical solutions

• Architectural implications

Targeted responses overview

• Also identified as Request/Reply

• Technical requirements may drive in the Request/Reply direction:• As seen with Elton Stoneman: SignalR clients

• IoT devices that cannot participate in a pub/sub based architecture

• Integrations with third party services or legacy systems

Queue

Request / Reply scenario

SignalRclient

HTTP basedFront-end

Back-endsystem

Message MessageSocket

Reply MessageReply Message

Queue

Request / Reply “Scale out” issue

SignalRclient

Front-endInstance-1

Back-endsystem

Message MessageSocket

Reply MessageReply Message

Front-endInstance-2

Front-endInstance-n

Socket

Instances Cluster

Request / Reply “Callbacks” scenario

Queue

SignalRclient

Front-endInstance-1

Back-endsystem

Message MessageSocket

Return Message

Front-endInstance-2

Front-endInstance-n

Instances Cluster

Retu

rnM

essage

“Callbacks” Scale Out issue

Queue

SignalRclient

Front-endInstance-1

Back-endsystem

Message MessageSocket

Return Message

Front-endInstance-2

Front-endInstance-n

Instances Cluster

Retu

rnM

essage

Backplane: transport agnostic

Queue

SignalRclient

Front-endInstance-1

Back-endsystem

Message MessageSocket

Reply / Event

Front-endInstance-2

Front-endInstance-n

Instances Cluster

backp

lane

Reply Message CopyNote: A backplane is a Single Point of Failure

Unique Queue Per Endpoint Instance

SignalRclient

Front-endInstance-1

Back-endsystem

Message MessageSocket

Reply / EventFront-endInstance-2

Front-endInstance-n

Instances Cluster

Exchange

Reply / Event Copy

Instance-2 binding

Note: Transport dependent

Demo

Single Responsibility Principle

• Backplanes and Unique Qs force endpoints to have one responsibility:• Talk to the SignalR client (in our sample)

• Be the bridge connecting 2 different infrastructures using different transports

• Such endpoints can’t have any business responsibility:• All the instances would receive a copy of the message

• All the instances would try to execute the same business logic

NSBCon – Dallas, TXDecember 1 – 4 – http://particular.net/nsbcon2015

Q&AThank you!