From Monolith to Observable Microservices using DDD Maria Gomez - - PowerPoint PPT Presentation

From Monolith to Observable Microservices using DDD

Maria Gomez @mariascandella Tech Principal

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HOW?

What is Domain Driven Design?

It is an approach to building software that has complex and ever- changing business requirements

Key Concepts

A sphere of knowledge, influence, or activity. What an organisation does, and the world it does it in.

Domain

A system of abstractions describing selected aspects of a Domain. It is used to solve problems related to that Domain

Subdomains

Key Concepts

A Language structured around the Subdomain and used by all team members.

Ubiquitous Language

An explicit boundary within which a Subdomain exists. Inside, all terms have a specific meaning and are part of the Ubiquitous Language

Bounded Context

https://martinfowler.com/bliki/BoundedContext.html

Sales Catalog Support

Event Storming

Event Storming is a workshop format for quickly exploring complex business domains.

http://ziobrando.blogspot.com/2013/11/introducing-event-storming.html By Henning Schwentner - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=57766348

Key Concepts

Something happened, of interest to a domain expert

Domain Event

An external instruction to do something. It triggers a Domain Event.

Command

The portion of the system that receives commands and decides whether to execute them

• r not, thus producing a domain event.

Aggregate

Ticket sent by email Payment confirmed Ticket bought Order created Ticket added to cart Seat reserved Show selected Choose show Choose seat Add ticket to cart

Move to checkout Insert checkout data Process payment Buyer

Accountant

Customer Service

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Payment confirmed Order held Delivery Method added Promo added to Order Order modified Order created

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Promotion

Accountant

Customer Service

Delivery Address Order

What to do when bounded contexts are identified?

• 1. Isolate them
• 2. Extract them into services

Bounded Context

High Cohesion Loose Coupling Represents Business Capability Individual Tech Stacks & Persistence Deploy independently Isolate Failure Individual Scalability

Microservices

+ =

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Accountant

Customer Service

Delivery Address Order

Where to start?

• Pace of change
• Performance
• Security
• Team structure
• Dependencies (internal or external)
• Technology

Identify Business Value

Warner Bros. [Public domain]

But, wait… We’re not done yet!

Iceberg by Oleksandr Panasovskyi from the Noun Project

What to extract Testing Deployment Operations Security

Observability

“Observability is the ability to interrogate your system and get accurate answers that improve your understanding of it”

Tracing Monitoring Alerts Logging

No Logs by Sweet Farm from the Noun Project Alert by ✦ Shmidt Sergey ✦ from the Noun Project traceability by Timofey Rostilov from the Noun Project

Collector Monitoring Query UI

Transform

Logging

Log Structured Data

{ CreationTime: “2017-02-24T17:49:15”, Id: “9fe0650565-3dac-425a-c83e38499c”, Host: “WEBSRVR06”, ServiceId: “MyShoppingCartService”, ComponentId: “DynamoDBWriter”, Message: “Body size exceeded 400kb limit” …. …. }

Monitoring

• What’s relevant for each microservice and for the entire system?
• It could be not just single data points but a combination of things.
• Start with something simple and evolve as things get more complicated.

Allows you to make informed decisions

Semantic Monitoring

Monitoring Overload!

Alerting

• Alerts should be actionable

Things that need immediate reaction

Alerting

• Alerts should be actionable
• Not all alerts need a human. Leverage automation!

Things that need immediate reaction

Tracing

Useful for debugging POST /pay

TraceId TraceId TraceId TraceId

Tracing

Useful for debugging POST /pay

TraceId TraceId TraceId TraceId

Tracing system

Take Away

• Start by identifying business domains, DDD can help you on this.
• Don’t wait until having the perfect list of domains, they will change over time.
• Prioritize decoupling based on business value.
• Include operational concerns in your backlog (logging, monitoring, alerting & tracing)

○

Be intentional about things you log, monitor, and alert on

○

Proactively iterate and eliminate noise

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Evaluate and use existing tools and libraries (ELK stack, OpenTracing, Honeycomb, Datadog, Opsgenie, etc)

Microservices is really not a free lunch!

Thanks!

Maria Gomez @mariascandella