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This presentation gives a broad overview of the microservice architectural style. It highlights the difference between microservices and SOA, the challenges and pattern and popular tools to implement an microservice architecture
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Tom De Wolf Technical Lead
Stijn Van den Enden CTO
www.aca-it.be
Thomas Borghs Solution Engineer
MICRO SERVICESYet another architectural style?
Concepts - What are Micro services?
Patterns - How to solve the challenges?
Technology - Using what?
The microservice architectural style is an approach to developing a single application as a suite of small services, each running in its own process and
communicating with lightweight mechanisms, often an HTTP resource API. These services are built around business capabilities and independently deployable by
fully automated deployment machinery. There is a bare minimum of centralized management of these services, which may be written in different programming
languages and use different data storage technologies. !
Martin Fowler
SERVICE ORIENTED ARCHITECTURE?Yes, it’s SOA … but different implementation approach:
Classic SOA integrates different applications as a set of services
Microservices architect a single application as a set of services
Classic SOA integrates different applications as a set of services
Microservices
Enterprise Service Bus
WS* WS* WS* WS* WS*
WS* WS* WS* WS* WS*
Workflow Engine
Intelligence
Orchestration
business platform
integrates different applications as a set of services
Microservices architect a single application as a set of services
accounting service contract
service
ordering service
logistics service
prospects service
capability X service
capability Y service
external integrationsbackends
{ API } { API }{ API }
{ API } { API }
{ API }{ API }
{ API } { API }
{ API } { API }
Classic SOA integrates different applications as a set of services
Microservices architect a single application as a set of services
Typical implementation solution differs!
Heavy-weight
ESBWS*/SOAP
Orchestration
License-drivenTarget problem:
Integrate (Legacy) Software
Intelligent Communication Layer
Light-weight
HTTP/REST/JSON
Choreography
Target problem: Architect new Business Platform
Dumb Communication Layer
Intelligent Services
WHY
SOAWHY - DIFFERENTIATE FROM SOA
App Server
WAR/EAR
Ordering
Inventory
Billing
UI
WHY - THE CURSE OF THE MONOLITH
Database
Simple to scaleSimple to develop Simple to deploy
WHY - THE CURSE OF THE MONOLITHApp Server
WAR/EAR
Ordering
Inventory
Billing
UI
Large Code Intimidates DevelopersHard to understand
and modify
Development slows down
Overloaded IDE
Overloaded web container
WHY - THE CURSE OF THE MONOLITH
Small Change - Big ImpactAny change requires
full rebuild, test and deploy
Impact analysis is huge effort and takes long
Obstacle for frequent changes and deployments
App Server
WAR/EAR
Ordering
Inventory
Billing
UI
WHY - THE CURSE OF THE MONOLITH
Big Risk for Re-Write
App Server
WAR/EAR
Ordering
Inventory
Billing
UI
No hard module boundaries quality and modularity breaks down over time this enforces eventual need for re-write
Re-write = complete re-write no partial re-write
Long term commitment to technology stack change or try-out new technology implies re-write
WHY - THE CURSE OF THE MONOLITHApp Server
WAR/EAR
Ordering
Inventory
Billing
UI Failure in monolith brings it down
Little Resilience to Failure
WHY - THE CURSE OF THE MONOLITHApp Server
WAR/EAR
Ordering
Inventory
Billing
UI
Mostly Horizontal scaling many load balanced instances
Scaling can be difficult
Hard to scale to data growth cope with all data
Different components have different resource needs
Scaling development implies coordination overhead
WHY - TYPES OF SCALING
App Server
WAR/EAR
Ordering
Inventory
Billing
UI
Database All data
App Server
WAR/EAR
Ordering
Inventory
Billing
UI
App Server
WAR/EAR
Ordering
Inventory
Billing
UI
Horizontal Scaling(monolith)
Vertical Scaling
App Server
WAR/EAR
Ordering
Inventory
Billing
UI
App Server
WAR/EAR
Ordering
Inventory
Billing
UI
Database All data
(monolith)Data Scaling
App Server
WAR/EAR
Ordering
Inventory
Billing
UI
Database segment
App Server
WAR/EAR
Ordering
Inventory
Billing
UI
App Server
WAR/EAR
Ordering
Inventory
Billing
UI
Database segment
Database segment
(monolith)
WHY - TYPES OF SCALING
Database Ordering
Container
UI
Functional Scaling
Container
Ordering
Container
Inventory
Container
Billing
Container
Ordering
Container
Ordering
Container
Billing
Database Inventory Database
Billing
(micro-services)Team Scaling
Container
Ordering
Container
Inventory
Container
Billing
(micro-services)
balances application and development complexity
• Small and focussed on 1 capability • easier to understand • IDE and deployment faster for 1 service
• Independent • Release and deployment • Scaling • Development
• Loosely Coupled • through lightweight communication
• Fault Isolation vs bring all down.
• Allows try-out of new technologies.
• Re-write can be limited to 1 service • Impact Analysis stops at boundary
• Provide firm module boundaries with explicit interface! • Less risk on re-write • Harder to violate boundary in development
• Decentralised choreography • vs central orchestration • vs central point of failure
• Decentralised data • polyglot persistence
WHY - ARCHITECTURAL BENEFITS
WHY - EVOLUTIONARY ARCHITECTURE
1 - Key (business) drivers guide architectural decisions
2 - Postpone decisions to Last Responsible Moment
3 - Architect and develop for Evolvability
Micro-services are organised around business capabilities
Micro-services allow delay of scaling and technological decisions
Micro-services support evolution in technology, scaling, and features
HOW TO
HOW TO
Approach - Key to success
Challenges - And ways to overcome them
Functional decomposition of the business domain
Functional decomposition of the business domain
Software Design Customer Satisfaction
Separation of ConcernsLow Coupling, High Cohesion
Reduce Impact by Encapsulating Source of Change
Predictable Cost of ChangeChanges are Business Driven
Source of Change = Business
Functional Modularisation
B AB
A
Functional decomposition of the business domain
• Change A impacts all modules = costly • Change B requires split of module = costly
• Change A only impacts other module if api change • Change B limited to module
side note: Domain Driven Design
“In order to create good software, you have to know what that software is all about. You cannot create a banking software system unless you have a good understanding
of what banking is all about, one must understand the domain of banking.”
From: Domain Driven Design by Eric Evans.
Tackling complexity by abstracting the business domain concepts and logic into a domain model and using this as a base for software development
Domain driven design deals with large complex models by dividing them into different functionally bounded subdomains and the explicitly describing the
interrelations between these subdomains.
Bounded contexts
Functional decomposition of the business domain
ONLINE STORE
Ordering Billing
Inventory Accounting
Functional decomposition of the business domain
AccountingInventory
BillingOrdering
customer
Invoice
balance
order
item
item
stock order
order
item
incoming cash
outgoing cash
stock
Benefits of functional decomposition
AccountingInventory
BillingOrdering
customer
Invoice
balance
order
item
item
stock order
order
item
incoming cash
outgoing cash
stock
Benefits of functional decomposition
Applying services to bounded contexts
Accounting ServiceInventory Service
Billing ServiceOrdering Service
customer
Invoice
balance
order
item
item
stock order
order
item
incoming cash
outgoing cash
stock
AccountingInventory
BillingOrdering
customer
Invoice
balance
order
item
item
stock order
order
item
incoming cash
outgoing cash
stock
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
Side note: Conway’s Law
Side note: Conway's Law
Technology-based Team Composition Functional Team Composition
Ordering
InventoryBilling
Accounting
Container
Ordering
Container
Billing
Container
Inventory
Container
Accounting
UI
UI
Leads to higher coupling between services
PITFALL: Incorrect functional decomposition
- harder to functionally scale the application - errors will propagate through multiple services - graceful degradation will be harder to achieve
- team development overhead - T-scaling becomes harder
- large communicational overhead between services - large overhead in releasing/deploying business features - refactoring to correct decomposition is costly
most of the microservices architectural benefits are lost
PITFALL: Incorrect functional decomposition
Safer to start with a functionally well decomposed monolith and evolve it to a microservices architecture when the need arises
- rewriting failure scenario’s - decentralised data - service contract redesign
Refactoring the initial functional decomposition will be easier in a monolith
Approach - Key to success
Challenges - And ways to overcome them
- Keep Releases and deployments manageable - high level of automation is needed
- Service monitoring is required - Configuration management becomes more complex
CHALLENGE #1: Operational Complexity
Complex Runtime: many moving parts
- distributed architectural properties to consider: - decentralised data - communication between services - handling failures of components
- testing effort becomes greater
CHALLENGE #2: Distributed Development
Services are deployed on multiple instances
Decentralised data
Each service has its own database - loose coupling Might even be in another database technology
Data duplication between services might be required to ensure loose coupling
When implementing use cases spanning multiple services: distributed transactions vs eventual consistency
Distributed Transactions vs Eventual Consistency
DISTRIBUTED TRANSACTIONS
- data is always consistent !
- reduces system availability - services are more tightly coupled
- has fallen out of favor in modern stacks (REST, NoSQL)
Distributed Transactions vs Eventual Consistency
EVENT-DRIVEN ASYNCHRONOUS UPDATES
- use a message broker to publish use cases to other services - decouples producers and consumers (services) of events - improves availability
- tradeoff between availability and data consistenty - application needs to be able to handle eventually consistent data
Communication between services
Use cases can span multiple services What type of communication is best used to implement such a use case?
Network properties need to be taken into account
What type of Communication?
SYNCHRONOUS HTTP-BASED
- easy - firewall-friendly, works across the internet
!
- doesn’t support publisher-subscriber patterns - client and server must both be available simultaneously - client needs to know host and port of server
What type of Communication?
ASYNCHRONOUS NON-BLOCKING
- Client doesn’t block calling thread - allows for parallelism
!
- client and server still must both be available simultaneously - client still needs to know host and port of server
What type of Communication?
ASYNCHRONOUS MESSAGING
- For example through a Broker - decouples message producers from consumers - broker can buffer messages - supports a variety of communication patterns
!
- broker is another moving part - adds complexity
- request-reply communication pattern is not a natural fit
What type of Communication?
Accounting ServiceInventory Service
Billing ServiceOrdering Service
Use case: New Order Received
New order Create invoice
Update Incoming CashflowUpdate Stock
Handling Failures
Services can fail at any moment
Design services to handle these kind of failures
Reactive systems are: Responsive
Resilient Elastic
Message Driven !
-- Reactive Manifesto: september 16 2014
Side note: Reactive Programming
Handling Failures
FALLBACK MESSAGE QUEUE
Ordering Service Billing Servicenew order received failure
Fallback queue
Handling Failures
PER-SERVICE THREAD POOLS
Ordering Service Billing Servicenew order received
Thread pool 10 threads
- communication between services is reduced - when functional decomposition is done right - when service size isn’t too small
- reduce communication between clients and Services with an API gateway - executing service calls in parallel reduces impact of communication overhead - reduce unneeded network usage by using circuit breakers
CHALLENGE #3 Minimising Communicational Overhead
Avoid Chatty Communication
Minimising Communicational Overhead
API GATEWAY
Ordering
Inventory
Billing
Accounting
Monolith Micro Services
Container
Ordering
Container
Inventory
Container
Billing
Container
Accounting
Desktop client
Mobile client
Desktop client
Mobile client
Minimising Communicational Overhead
API GATEWAY
Container
Ordering
Container
Inventory
Container
Billing
Container
Accounting
Desktop client
Mobile client
Api gateway
Handling Failures in Communication
CIRCUIT BREAKER
- Wrap a protected function in a circuit breaker - Monitor protected function for failures - The circuit breaks when a predefined threshold of fails is reached - All future calls to the function go to fallback until the circuit is restored
Handling Failures in Communication
CIRCUIT BREAKER
Ordering Service Billing Servicenew order received
Circuit breaker Threshold = 10
Fallback queue
TECHNOLOGY
Microservice Implementation Stack
DROPWIZARD Make features not WAR
DROPW
IZARD
guava
jackson
metrics
Validator
YAML
JDBI
core
migrations
hibernate
jdbi…
java -jar ./target/profileservice-0.1.0-SNAPSHOT.jar server ./src/main/resources/userprofileservice.yml
SPRING BOOT opinionated view of building production-ready Spring applications
•Convention over configuration approach
•Deployable as a Self-contained jar or war
•Tackles dependency-hell via pre-packaging
•Support for monitoring and metrics (actuator module)
Deployment
Compute, Storage, Network
Host OS
Hypervisor
VM1 VM2
MicroService MicroService
Guest OS
JVM
Guest OS
JVM
VM’s abstract underlying hardware, but limit resource utilisation
Compute, Storage, Network
Host OS
container1
container2
container3
container4
JVM JVM JVM
MicroService MicroService MicroService
JVM
MicroService
Containers have own isolated resources
Static website Web frontend User DB Queue Analytics DB
Development VM
QA server Public Cloud Contributor’s laptop
DOCKER IS A SHIPPING CONTAINER SYSTEM FOR CODE M
ultip
licity
of S
tack
sM
ultip
licity
of
hard
war
e en
viro
nmen
ts
Production Cluster
Customer Data Center
Do services and apps interact
appropriately?
Can I m
igrate sm
oothly and quickly
…that can be manipulated using standard operations and run consistently on virtually any hardware platform
An engine that enables any payload to be encapsulated as a lightweight, portable, self-sufficient container…
Static website Web frontend User DB Queue Analytics DB
Development VM
QA server Public Cloud Contributor’s laptop
DOCKER IS A SHIPPING CONTAINER SYSTEM FOR CODE M
ultip
licity
of S
tack
sM
ultip
licity
of
hard
war
e en
viro
nmen
ts
Production Cluster
Customer Data Center
Do services and apps interact
appropriately?
Can I m
igrate sm
oothly and quickly
Operator: Configure Once, Run Anything
Developer: Build Once, Run Anywhere
Static website
Web frontend
Background workers
User DB
Analytics DB
Queue
Development VM QA Server Single Prod
Server Onsite Cluster Public Cloud Contributor’s laptop
Customer Servers
DOCKER SOLVES THE NXN PROBLEM
• Isolation
• namespace
• pid mnt net uts ipc user
• resource usage
• (CPU, memory, disk I/O, etc.)
• Limited impact on Performance - http://ibm.co/V55Otq
• Daemon and CLICompute, Storage, Network
Host OS
container1
container2
container3
container4
JVM JVM JVM
MicroService MicroService MicroService
JVM
MicroService
Source Control System
DockerFile
Continuous Integration Infrastructure
Container Image Repository
Compute, Storage, Network
Host OS
daemon
container1
JVM
MicroService
pull
Slave Node
Host OS
push
build
provision
container1
JVM
MicroService
https://github.com/spotify/helios
http://mesos.apache.org/
https://github.com/openshift/geard
…
PublicHybridPrivate
Compute, Storage, Network
Host OS
Hypervisor
VM1 VM2
MicroService MicroService
Guest OS
JVM
Guest OS
JVM
Compute, Storage, Network
Host OS
container1
container2
container3
container4
JVM JVM JVM
MicroService MicroService MicroService
JVM
MicroService
VM’s abstract underlying hardware, but limit resource utilisation
Containers have own isolated resources
OSGi Runtime
JVM
MicroService
Compute, Storage, Network
Host OS
MicroService MicroService
Microservice run in their own isolated classloader and standbox in the JVM
Balancing Load
Static
Dynamic
Loadbalancer Loadbalancer
MicroService MicroService MicroService MicroService MicroService
Web Front End
Web Front End
Web Front End
Web Front End
Web Front End
MicroService MicroService MicroService MicroService MicroService
A
B
Midtier Service Registry
MicroService
register
renew
get registry
Static
Dynamic
Loadbalancer Loadbalancer
MicroService MicroService MicroService MicroService MicroService
Web Front End
Web Front End
Web Front End
Web Front End
Web Front End
MicroService MicroService MicroService MicroService MicroService
A
B
Midtier Service Registry
MicroService
register
renew
get registry
eureka
ribbon
https://github.com/Netflix/eureka
https://github.com/Netflix/ribbon
The Story
* based on Functional Programming the Netflix API - Ben Christensen
Netflix API
Dependency A
Dependency D
Dependency G
Dependency J
Dependency M
Dependency P
Dependency B
Dependency E
Dependency H
Dependency K
Dependency N
Dependency Q
Dependency C
Dependency F
Dependency I
Dependency L
Dependency O
Dependency R
onsdag den 6. marts 13
* based on Functional Programming the Netflix API - Ben Christensen
Discovery of Rx began with a re-architecture ...
onsdag den 6. marts 13
* based on Functional Programming the Netflix API - Ben Christensen
... that collapsed network traffic into coarse API calls ...
onsdag den 6. marts 13
* based on Functional Programming the Netflix API - Ben Christensen
Iterablepull
Observablepush
T next()throws Exception
returns;
onNext(T)onError(Exception)onCompleted()
!//"Iterable<String>"!//"that"contains"75"Strings!getDataFromLocalMemory()!!.skip(10)!!.take(5)!!.map({!s!%>!!!!return!s!+!"_transformed"})!!.forEach(.....{!println!"next!=>!"!+!it})
!//"Observable<String>"!//"that"emits"75"Strings!getDataFromNetwork()!!.skip(10)!!.take(5)!!.map({!s!%>!!!!return!s!+!"_transformed"})!!.subscribe(.....{!println!"onNext!=>!"!+!it})
onsdag den 6. marts 13
* based on Functional Programming the Netflix API - Ben Christensen
onsdag den 6. marts 13
* based on Functional Programming the Netflix API - Ben Christensen
onsdag den 6. marts 13
* based on Functional Programming the Netflix API - Ben Christensen
+ =
https://github.com/Netflix/Hystrix
HystrixCommand run()
getFallback()
run()
failure/circuit open
public class GetUserPerferencesCommand extends HystrixCommand<UserPreferences> {!// ..//!! @Override! protected UserPreferences run() {! ! ! // call the UserPreferencesService ! }!! @Override! protected UserPreferences getFallback() {! !! return UserPreference.empty();! }!}
Monitoring
MicroService MicroService MicroService MicroService MicroServiceA
Logstash
Log Aggregation
Graphite
Metrics and Monitoring
- Correct Functional decomposition is crucial - reflect it in a organisational structure (Conway’s law) - pretty hard to get right from the start
- A modular system can evolve to microservices - balance the needs (advantages) with the costs (tradeoffs)
Conclusion
Are they here to stay?who can tell? but the monolith is dead