The document discusses transitioning from a monolithic application architecture to a microservices architecture. It describes some of the challenges with monolithic architectures like tight coupling between components and difficulties scaling individual parts of the system. The document then outlines some of the key principles of microservices like loose coupling, encapsulation, and separation of concerns. It provides examples of how microservices can be broken out by domain and deployed independently to improve scalability, resilience, and development workflows.

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From Monolith to Microservices
by Andrew Rea

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From Monolith to Microservices by Andrew Rea
Know your Monolith
API CONUSMERS
APPLICATION
DATABASE
API
BUSINESS LOGIC
DATA ACCESS
PRESENTATION
APIAPI
DATABASE
Service 1 Service 2 Service “n”
DB DB DB
Service 1 Service 2 Service “n”
Access
Postgres
MSSQL
WORD
DOCUMENT
EXCEL
DOCUMENT
VBA
APPLICATION
UI Business Logic
Data
Access
Database
Logging Reports
Open Monolith Database Monolith Distributed Monolith
Paper Monolith Office Monolith
Closed Monolith

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That’s another fine mess you’ve gotten me into
APPLICATION
DATABASE
CODE
CODECODE
CODE
TABLE
TABLETABLE
TABLE
STRONG CODE COUPLING
STRONG DB COUPLING
DATABASE COUPLING
NO DOMAIN BOUNDARIES
IMPLICIT RELATIONSHIPS

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That’s another fine mess you’ve gotten me into
APPLICATION
DATABASE
CODE
CODECODE
CODE
TABLE
TABLETABLE
TABLE
£ £ £
INCREASES COST
INCREASES IMPLEMENTATION TIME
DECREASES VELOCITY
INCREASES RISK
INCREASES DEPLOYMENT SIZE
INCREASES COMPLEXITY
INCREASES CODE FEAR
INCREASES BUILD TIME
INCREASES TEST TIME

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Microservices?
APPLICATION
DATABASE
SERVICE
SERVICESERVICE
SERVICE
TABLE TABLE
TABLE
TABLE
NOT YET
BUT…
THIS IS MANAGEABLE

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APPLICATION
DATABASE
SERVICE
SERVICESERVICE
SERVICE
TABLE TABLE
TABLE
TABLE
Microservices?
NOT YET BUT… THIS IS MANAGEABLE
LOOSE COUPLING
HIGH COHESION
ENCAPSULATION
DATABASE DECOUPLING
DOMAIN BOUNDARIES
EXPLICIT RELATIONSHIPS
SERVICE INTEGRATION
SERVICE COMPOSITION

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What are Microservices?
SMALL
HOW SMALL?
INTEROPERABLE
HOW?
INDEPENDENT
HOW?
A REASON TO RE-STRUCTURE YOUR TEAMS
WHY? RESILIENT
HOW?

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How do you get there?
GOOD DESIGN PRACTICES
& PRINCIPLES

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SEPARATE PROCESS PER SERVICE
APPLICATIONS
DATABASES
TABLE
TABLE
EASIER TO ADOPT DIFFERENT TECH
INDEPENDENTLY HOSTED
INDEPENDENTLY DEPLOYABLE
INDEPENDENTLY SCALABLE
SERVICE SERVICE
SERVICE
SERVICE
GRAPH
KEY /
VALUEDOC

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INDEPENDENT - HOW?
DEVELOP INDEPENDENTLY
DEPLOY INDEPENDENTLY
BUILD INDEPENDENTLY
OPERATE INDEPENDENTLY
MONITOR INDEPENDENTLY
SURVIVE INDEPENDENTLY
VERSION INDEPENDENTLY
PROCESS
CONTINUOUS
INTEGRATION
CODE REPOSITORY
DATA STORES
CONTAINER
IMAGE
SERVICE
DISCOVERY
DNS (A-RECORD)
QUEUES
PROVISIONING
SCRIPTS
CERITIFICATES
LOGICAL
Encapsulation
Boundary
REQUIREMENTS
LOAD BALANCER
POOL
MONITORING
GROUP
SERVICE
PHYSICAL
Encapsulation
Boundary
VERSION

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INTEROPERABLE - HOW?
COMMON TRANSPORT PROTOCOL
RESTFUL API
PUBLISH AND SUBSCRIBE CAPABILITY
EVENT STREAM
STRUCTURED LOGGING IN COMMON FORMAT
SERVICE
RESTFUL API OVER HTTPS
COMMANDS QUERIES EVENTS
STD OUTMETRICS STD ERROR
LOG AGENT
LOG
AGGREGATOR

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SEPARATE SERVICES BY BUSINESS CAPABILITY
SERVICE
DOMAIN 1
DOMAIN 2
DOMAIN 3
SERVICE 1
DOMAIN 1
SERVICE 2
DOMAIN 2
SERVICE 3
DOMAIN 3
Monolith Microservices

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HOW DO THEY SCALE?
SERVICE
DOMAIN 1
DOMAIN 2
DOMAIN 3
SERVICE
DOMAIN 1
SERVICE
DOMAIN 2
SERVICE
DOMAIN 3
SERVICE
DOMAIN 1
DOMAIN 2
DOMAIN 3
SERVICE
DOMAIN 1
DOMAIN 2
DOMAIN 3
SERVICE
DOMAIN 3
SERVICE
DOMAIN 1
SERVICE
DOMAIN 3
SERVICE
DOMAIN 3
SERVICE
DOMAIN 3
SERVICE
DOMAIN 2
SERVICE
DOMAIN 2
SERVICE
DOMAIN 1
Monolith Microservices
SAVES MONEY

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DOES THIS HELP SECURITY?
WE CAN DEPLOY SEPARATE INSTANCES OF THE SAME SERVICE IN DIFFERENT SECURITY ZONES TO MATCH
THE SENSITIVITY OF THE DATA WHICH THE SERVICE INSTANCE WILL BE HANDLING.
TRUST 1 TRUST 2
SERVICE
SEARCH
SERVICE
SEARCH
SERVICE
SEARCH
SERVICE
SEARCH
SERVICE
SEARCH
SERVICE
BOOKING
SERVICE
BOOKING
SERVICE
BOOKING
SERVICE
AVAILABILITY
SERVICE
AVAILABILITY
SERVICE
AVAILABILITY
SERVICE
AVAILABILITY
DMZ
SERVICE
SEARCH
SERVICE
BOOKING
SERVICE
AVAILABILITY

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SEPARATE BUILD PIPELINES
SERVICE
1
SERVICE
2
SERVICE
3
COMMIT FUNCTIONAL NON-FUNCTIONAL SMOKE TESTSRELEASE
SERVICE
1
SERVICE
1
SERVICE
1
SERVICE
1
INDEPENDENT BUILD PIPELINES
INDEPENDENT BUILD SCRIPTS
INDEPENDENT PROVISION SCRIPT
ISOLATED TEST ENVIRONMENTS

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SEPARATE SOURCE CONTROL
SERVICE
SERVICE
SERVICE
SERVICE
SERVICE
SERVICE SERVICE SERVICE
SERVICE SERVICE
GIVE EACH SERVICE ITS OWN SOURCE REPOSITORY

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SEPARATE SOURCE CONTROL
GIVE EACH SERVICE ITS OWN SOURCE REPOSITORY
TEAMTEAM
TEAM
SERVICE
SERVICE
SERVICE
SERVICE
SERVICE
SERVICE SERVICE SERVICE
SERVICE SERVICE
Who
Owns
This?

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A REASON TO RESTRUCTURE YOUR TEAMS
SERVICE
AVAILABILITY
SERVICE
BOOKING
SERVICE
SEARCH
SERVICE
PROVIDERS
SERVICE
SEARCH
SERVICE
PROVIDERS
SERVICE
AVAILABILITY
SERVICE
BOOKING
SERVICE (NOT COMPONENT) TEAMS
FEATURE TEAMS
OR BOTH?BOTH CAN PLAY A VALUABLE PART IN A MICROSERVICES ARCHITECTURE
BOTH HAVE THE SAME TEAM STRUCTURE
PULL REQUESTS ANYONE?

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HOW SMALL (OR LARGE)?
2000 LINES OF CODE?
TWO PIZZA TEAM SIZE?
CAN BE RE-WRITTEN IN TWO WEEKS?
MODELS A SINGLE CONTEXT?
HOW ABOUT ALL OF THE ABOVE?
What thought processes do the above questions trigger about your design?
TOO BIG? MAKE SMALLER, TOO SMALL? MAKE BIGGER

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HOW DO THEY COMMUNICATE
CALL
CALL
CALL
SERVICE
DOMAIN 1
SUBSCRIBE
SUBSCRIBE
SUBSCRIBE
CALL
CALL
CALL
OR BOTH
DIRECT INVOCATION EVENT DRIVEN
SERVICE
DOMAIN 1
SERVICE
DOMAIN 2
SERVICE
DOMAIN 3
SERVICE
DOMAIN 4
SERVICE
DOMAIN 2
SERVICE
DOMAIN 3
SERVICE
DOMAIN 4

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WHAT ABOUT MONITORING?
CALL
CALL
CALL
META ENDPOINTS
MESSAGE CORRELATION
SYNTHETIC MONITORING
HEALTH CHECK
METRICS
INFORMATION
STRUCTURED LOGGINGBUSINESS APPLICATION INFRASTRUCTURENETWORK
LOCAL -> AGENT -> REMOTE

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HOW DO CONSUMING APPS GET STABILITY?
SERVICE
DOMAIN 1
Stable Next Latest
CONSUMER A
DEVELOPERS
VERSIONS WITH DIFFERENT LEVELS OF
STABILITY
Consuming “Stable” in Production
Testing integration with “Next”
Researching “Latest”

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HOW TO VERSION THE SERVICES?
<MAJOR>.<MINOR>.<PATCH>-<TAG>
https://medium.com/javascript-scene/software-versions-are-broken-3d2dc0da0783#.wcyli1rt2
http://semver.org
<BREAKING>.<FEATURE>.<FIX>-<TAG>
EXAMPLES
v1.0.1 v2.0.1-alpha v2.0.1-beta v2.1.0-latest

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RESILIENT?
DOWNSTREAM
SYSTEMS
CIRCUIT BREAKER
CONFIRMATION BULK HEADS
HEALTH CHECKS
ALIVE READY
EXTERNAL
PERSISTENCE
ACKNOWLEDGEMENT
STATE EVENTS
STATELESS
AUTO-RECOVERY

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RESILIENT?
DOWNSTREAM
SYSTEM
DOWNSTREAM
SYSTEM
TEST HARNESS
SWITCH OUT REAL
SYSTEM WITH A HARNESS RANDOM
STATUS CODE
TEST HARNESS
SLOW
RESPONSE
TEST HARNESS
HUGE
RESPONSE
TEST HARNESS
EMPTY
RESPONSE
TEST HARNESS
BAD
GATEWAY
RESPONSE
TEST
NO RESPONSE
TEST HARNESS
HOW WILL THE SERVICE RESPOND
TO ABNORMAL SYSTEM DEPENDENCIES?
LETS FIND OUT BEFORE WE GO LIVE!

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RESILIENT?
SERVICE TESTING UNIT TESTING INTEGRATION TESTINGACCEPTANCE TESTING
MUTATION TESTING FUZZING TESTINGSTATIC CODE ANALYSIS
PERFORMANCE TESTING LOAD TESTING STRESS TESTING IMPULSE TESTING LONGEVITY TESTING
FAILURE TESTING
SECURITY TESTING
SMOKE TESTING
RELEASE TESTING ROLLBACK TESTING
FUNCTIONAL
CROSS FUNCTIONAL

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WHEN SHOULD THE TEAM DEPLOY?
WHEN CAN THE TEAM DEPLOY?

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A LOT OF THIS IS NOT NEW
GOOD DESIGN PRACTICES
& PRINCIPLES
BUT THEY DON’T COME FOR FREE!

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CHEAT SHEET
EXTERNAL
INTERNAL
AGGREGATION
CORRELATION
VISUALIZATION
REPORTING
API
LOGGING
DATA
MESSAGING
APPLICATION
INTEGRATION
OPERATION
HTTPS
XML JSON
SOAP REST
THROTTLING AUTHENTICATION AUTHORIZATION
CIRCUITBREAKER
INSPECTION ROUTING
CIRCUITBREAKER
BULKHEADS
CIRCUITBREAKER
BULKHEADS
BULKHEADS
RELIABLEMESSAGING
DURABLEMESSAGING
HEALTH
DEPLOYMENT SERVICE REGISTRATION
CONFIGURATION READINESS CHECKS
STRUCTURED
LOGGING
TIMESERIES
BUSINESS
APPLICATION
INFRASTRUCTURE
NETW
ORK
ERRORCATALOG
EVENTCATALOG
INFORMATION DISCOVERABLE API
BACKUP
SECURITYSECURITY SECURITY
TESTHARNESSES
CONTINUOUS
INTEGRATION
CODE REPOSITORY
DATA STORES
Application
Identity
PROTECTIVE
MONITORING
COMMANDS QUERIES
EVENTS
DOMAIN MODEL
DOMAIN SERVICES
VERSIONING
DOMAIN EVENTS
CORRELATION
ID
SERVICE DEPENDENCIES
SUBSCRIBING SERVICES
HORIZONTAL SCALING
FAILOVER
RECOVERY
PUBLISH
EVENT LOG
SUBSCRIBE
SECURITY
KEY SECURITY
ENCRYPTION IN TRANSIT
ENCRYPTION AT REST
SECURE DEVELOPMENT, DEPLOYMENT &
OPERATIONAL PRACTICES AND PRINCIPLES
CONTAINER
IMAGE
CONSISTENCY
BOUNDARY
API
GATEWAY
SERVICE
FABRIC
SERVICE
REGISTRY
LOAD
BALANCER
W
RITESTORE
READ
STORE(S)
REVERSE PROXY
INSPECTION
APPLICATION FIREWALLS
INSPECTION
ENCAPSULATION
BOUNDARY
CONTAINER
REGISTRY
HEXAGANOL ARHCICTECTURE
Version 1 Microservices Infograhic by Andrew Rea
EXTERNAL
MONITORING
MONITORING
MONITORING
?
SERVICE
DISCOVERY
DATA
STOREISOLATION
AMQP
MQTT
HTTP
other…
GRAPH
DOCUMENT
KEY/VALUE
RELATIONAL
COLUMN
FLATFILE