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Microservices Design Patterns – Friday 17th March

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Rodrigo CaldasSoftware Engineer

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Why do we ask where do we come from?

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Where do Microservices come from?

• Domain Driven Design• Continuous Delivery• On Demand Virtualization• Small Autonomous Teams• Scalability

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Quick Recap… Domain Driven Design

Strategic Design Patterns

Tactical Design Patterns

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What to build

How to build

Quick Recap… Domain Driven Design

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Tactical Patterns

• Domain Events• Domain Services• Anti Corruption Layer• Repository• Unit of Work• Entities• Aggregates• Value Objects• Commands• Queries• Helpers

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Strategic Patterns

• Ubiquitous Language• Domain Model• Bounded Contexts

Building software is already hard enough.Strategic patterns distil the domain knowledge.

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Bounded Contexts at WorldRemit

PayIn

TransactionMonitor

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Systems are not bounded contexts!

NO!

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Bounded Contexts at WorldRemit

CorrespondentIntegrationsCompliancePayments

CustomerServicePresentation

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Where some systems live…

CorrespondentIntegrations

ComplianceTransaction

Monitor

PaymentsPayIn

Service OfferingApi Calculator

PresentationWebsite

Android AppIOS App

CustomerService

Control MoneySalesforce

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MicroservicesDesignPatterns

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Service Orchestration Pattern

Service Choreography Pattern

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Orchestrator Pattern

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Pitfalls of the Orchestrator Pattern

• There is a service rich in Domain knowledge• There are many dumb services

Advantages of the Orchestrator Pattern

• Synchronous services are easier to create

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Choreography Pattern

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Advantages of the Choreography Pattern

• Loose coupling• Adaptive to change

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Choreography Pattern

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Access by Reference Pattern

Access by Value Pattern

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Access by Reference

“this” happened

Sacrifices availability

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Access by Value“what” happened

Sacrifices consistency

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“Freshness” approach

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(Eric Brewer)

1. Consistency2. Availability3. Partition

The CAP theorem

You only get to pick two.

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But the basic premise of a constellation of Microservices is that its Partitioned.

So…

1. Consistency and Partitioning.

2. Availability and Partitioning.

This leaves us with only two options.

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Why does this all matter?

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One of many reasons… The execution timeVisual Basic

Vs.

C++

Which is faster?What if C++ implementation has one IO call?

IO time is everything

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Bulkheads

and

Circuit Breakers

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Bulkheads

• They are the compartments in ships that prevent the whole ship from flooding if the hull is breached.

• They are the staple of Microservices that can handle failure instead of failing

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An example of failure without Bulkheads

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An example of failure with Bulkheads

“ Life is good “

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What about the Error Queue?

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Circuit Breakers

• You have them at home!

• They are your strategy for how to handle failure.

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API Gateway Pattern

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The Problem

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The API Gateway Pattern

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Questions?