Agenda: Magento 1. Big ball of Mud SOLID and Single Responsibility Performance vs Scalability Coupling vs Cohesion Bounded contexts and their Boundaries CAP Theorem ACID vs BASE Modularity as a first step towards micro-services Headless Magento Service Isolation (Code and DB split) Conway's law Microservice architecture

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A long way from
Monolith to Micro-
Service Architecture
Yesterday, Today and Tomorrow

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Igor Miniailo
Magento Architect,
Community Engineering Team

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Agenda
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• Magento 1. Big ball of Mud
• SOLID and Single Responsibility
• Performance vs Scalability
• Coupling vs Cohesion
• Bounded contexts and their Boundaries
• CAP Theorem
• ACID vs BASE
• Modularity as a first step towards micro-services
• Headless Magento
• Service Isolation (Code and DB split)
• Conway's law
• Microservice architecture

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Magento 1
And all the legacy we got starting Magento 2 development

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Classical N-layered architecture
• Compromise in the design of Data Model
• Not possible to scale separately Read out of
Write operations
• Tend to Anemic Data Model
• Tend to Monolithic Architecture
• An application has to be deployed as a
whole
• An application has to be scaled as a
whole

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Big Ball of Mud
Even though a modular code
structure groups related behavior, it
is easy to introduce an undesired
dependency between application
services, because services are not
deployed and tested independently.

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SOLID comes to rescue

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Modularity as a first step towards
micro-services

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• Every sophisticated business
domain consists of a bunch of
Bounded Contexts
• Each Bounded Context
contains models and maybe
other contexts
• The Bounded Context is also a
boundary for the meaning of a
given model
Bounded Context

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Bounded Context

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CAP Theorem
States that it is impossible for a distributed
data store to simultaneously provide more
than two out of the following three
guarantees:
• Consistency: Every read receives the
most recent write or an error
• Availability: Every request receives a
(non-error) response – without the
guarantee that it contains the most
recent write
• Partition tolerance: The system
continues to operate despite an arbitrary
number of messages being dropped (or
delayed) by the network between nodes

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Asynchronous processing
http://www.enterpriseintegrationpatterns.com/docs/IEEE_Software_Design_2PC.pdf

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Conversation pattern
The interaction between two parties
(customer and coffee shop)
consists of:
• a short synchronous interaction (ordering
and paying)
• and a longer, asynchronous interaction
(making and receiving the drink)
This type of conversation pattern is quite
common in purchasing scenarios.

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Error-handling strategies for loosely coupled systems
(a) Write-off
(b) Retry
(c) Compensating action
(d) Transaction coordinator (two phase commit)

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Implement business transaction that spans multiple
services as a saga
A saga is a sequence of local
transactions
Each local transaction updates
the database and publishes a
message or event to trigger the
next local transaction in the
saga

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Event Sourcing

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*The property of certain operations whereby they can be
applied multiple times without changing the result beyond
the initial application.
Idempotence of operation and at-least-once delivery
Network communication is unreliable.
Retries will be required, and some
messages will be delivered more than
once

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• All operations MUST BE idempotent.
• Sagas SHOULD BE used for consistency of
distributed operations
• All new service contracts SHOULD expose
asynchronous APIs
• All new state modifying operations SHOULD expose
bulk APIs
• All service operations MUST BE stateless
• There MUST BE NO data dependencies between
services
Design Principles to follow

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• Every module defines its APIs (service contracts),
which are PHP interfaces that can be called either
from within a PHP process or remotely through
REST, SOAP or AMQP APIs.
• Every module can call other modules only through
their service contracts.
Service Layer

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Service Layer. Current State
Legacy undesired
dependencies direct
inter-module
- model-to-model
- presentation-to-model
still exist.

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Modules split

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Modules Split. Inventory
• API – service contracts and
extension points
• Implementation (private) -
should not be called directly
from other modules
• Admin UI
• Frontend UI

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Headless Multi-Source Inventory
UI modules are removable if merchant
wants to use external ERP system as a
source of truth where he will manage
inventory

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Desirable State

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Database Split
A service must not talk to other service
database directly, only through service
contracts
TODO:
- Minimize data relations
- Replace the required inter-service db-
level data relations, joins, and transactions
with application-level relations, joins, and
transactions

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Desirable state
Isolated ServicesMonolith

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Monoliths vs Microservices. Scalability

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Conway’s Law
Any organization that designs a system
(defined broadly) will produce a design
whose structure is a copy of the
organization's communication structure.
-- Melvyn Conway, 1967

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2.3 Stage #1 Stage #2 Stage #3 Stage #4 Stage #5
Inventory (MSI) App Framework Order Management CMS Shipping Marketing
Pricing Tax Reports Promotions Risk
Checkout Customer Payments Wishlist
Rewards
Company
Service decomposition

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• Magento Service Isolation Design Document by
Anton Kril
• Magento administrative tool
• Magento MSI
Useful Links

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Q&AFollow me in Twitter
@iminyaylo

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Thank You
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