Beginning Microservices with .NET & RabbitMQ

Microservice Architecture

Beginning Microservices with .NET & RabbitMQ

Paul Mooney@daishisystems | www.insidethecpu.com

Overview

Microservice design based on real-world examples

Focus on, but not restricted to .NET and RabbitMQ

Design Patterns

Decoupled Middleware

Circuit Breaker

Flyball Governor

Implementation Problems

Consistent Message Delivery

Load balancing a RabbitMQ Cluster

Selling to the Business

Decoupled MiddlewareD

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SimpleMathMicroservice

Input Queue

Output Queue

Message Bus

Decoupled Middleware

Microservice Daemon

Message Dispatcher

Event Listener

Microservice Daemon

Event Listener

Message Dispatcher

Service Bus

Queue #1

Queue #2

Message Message

Message Message

Circuit Breaker

Filter

Cir

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Bre

aker

Service

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ture

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re 2Fe

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re 3

Client

Request

Circuit Breaker

Filter

Cir

cuit

Bre

aker

Service

Fea

ture

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re 2Fe

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Client

requestCount < threshHold

Circuit Breaker

Filter

Cir

cuit

Bre

aker

Service

Fea

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1Featu

re 2Fe

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Client

RequestrequestCount >= threshHold

Flyball Governor

Flyball Governor

Load never drops to 0% capacity

Load never rises to 100% capacity

Balance is achieved through polling

Requires detailed tuning to establish optimal setting

End result is Autoscaling through natural equilibrium

Flyball Governor

QueueWatch

Inbound Queue

Outbound Queue

Diagnostics Queue

Inbound Queue

Outbound Queue

Diagnostics Queue

Inbound Queue

Outbound Queue

Diagnostics Queue

1

2 2 2

Direct Exchange

3 3 3

Flyball GovernorD

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Input Queue

Output Queue

Message Bus

Flyball GovernorD

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Input Queue

Output Queue

Message Bus

Receivers

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SimpleMathMicroservices 1...n

Microservices as N-Tier Applications

AMQP

AMQP

AMQP

AMQPBrowser API Queue Microservice Instances

HttpRequestMapper

CommandMessageBuilder

MessageDispatcher

ResponseMessageParser

ResponseMessageConsumer CommandMessageParser

CommandMessageMapper

MessageDispatcher

ResponseMessageBuilder

ServiceCommand

2. Map HTTP Request to CommandMessage

3. Build CommandMessage

4. Dispatch CommandMessage to INPUT Queue

5. Parse and extract CommandMessage

6. Map CommandMessage to ServiceCommand

7. Execute ServiceCommand

8. Build ResponseMessage

9. Dispatch ResponseMessage to OUTPUT Queue

10. Consume ResponseMessage

11. Parse Response

SignalR

SignalR

1. Send REST HTTP Request

12. Return Response

WEB #1

APP #1

APP #2

HTTP

To downstream apps


SimpleMath Microservice

Inbound Message Queue

Outbound Message Queue

Inbound Messages

Outbound Messages

1 2

3

4

5

ASP.NET App




Inbound Messages

ASP.NET App

1 2

3

4

4

4

5




Inbound Messages

ASP.NET App

1

3

Queue Pool

2

45

6

Queue Pool Queue

Load Balancing a RabbitMQ Cluster

Node #1 Node #2 Node #3

Load Balancer



Load Balancer

Client Application

1

2

3



Load Balancer

Client Application

NewQueue1 NewQueue2 NewQueue3



Client ApplicationRandomiser



Client Application

Monitor Service

Queue Metadata StoreRandomiser

Selling to the BusinessReal-world example of how to sell Microservices to techies and non-

techies alike.

Monolithic Flow #1

I want to book a flight

Monolithic Flow #2

Here are the available flights

Monolithic Flow #3

I want to book one of those flights

Monolithic Flow #4

Would you like to hire a car?

Business Drawbacks

One-way communication

Customer is in control

Website is idle when user is idle

Limited window of opportunity to interact

Reduced scope for ancillary revenue

Technical Drawbacks

Results in dependencies

Failure affects everything

Change is slow

Scale is expensive (minor features require unilateral scale)

Steep learning curve

Technology stack is limited to specific skillsets

Introduces legal pitfalls (PCI DSS, Compliance)

Duplicated components due to lack of explicit boundaries

Rigid – likely to break under pressure

Microservice Flow #1

Car Hire

Hotel

Flight

Taxi

User Profile

Fare Finder

Flights

Other


Car Hire

Hotel

Flight

Taxi

User Profile

Fare Finder

Flights

Taxis

Other


Car Hire

Hotel

Flight

Taxi

User Profile

Fare Finder

Flights

Taxis

Cars

Other


Car Hire

Hotel

Flight

Taxi

User Profile

Fare Finder

Flights

Taxis

Cars

Hotels

Other

Enhanced Flow Step #5

Car Hire

Hotel

Flight

Taxi

User Profile

Fare Finder

Flights

Taxis

Cars

Fares

Hotels

Other

Business Benefits

Two-way communication

We’re in control (think Google)

APIs are always working

Unlimited opportunities to interact

Broader scope for ancillary revenue

Technical Benefits

Eliminates dependencies

Failure is isolated

React to change quicker

Scale is less expensive (APIs scale individually)

More intuitive learning curve

Technology stack is not limited to specific skillsets

Shielded from legal pitfalls

Reusable components

Flexible – will bend rather than break under pressure

General Advice

Log everything

Log everything

Log some more

If a framework exists, use it

Try to avoid the technical swamp

Let’s Talk Further…

insidethecpu.com (search for “Microservices”)

https://github.com/daishisystems/Daishi.AMQP

@daishisystems

https://ie.linkedin.com/in/daishisystems

Q&A

https://github.com/daishisystems/Daishi.AMQP

Software

Beginning Microservices with .NET & RabbitMQ