- Microservices are small, autonomous services that work together to form applications. Each service focuses on doing a single job and communicates through well-defined interfaces. - There are several common design approaches for microservices including business capability services, API gateways, load balancers, message queues, caching, and circuit breakers. Choreography is preferred over orchestration. - Implementing microservices provides benefits like independent deployability and scalability but also introduces complexity around distribution, eventual consistency, and operations.

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Building microServices
Yuriy Chapran

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Monolith
What are microservies ?
Design approaches used with microservices
Questions
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02
03
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How will you write service application ?
Section Title
− One or many processes ?
− Database or standalone file ?
− How will they all communicate ?
− How will you upgrade ?
− What if maximum amount of
users will triple in first week ?
− And grow ten times in a month ?

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Monolith01

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Characteristics and Benefits
Monolith
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− One build and deployment unit
− One code base
− One technology stack
−Simple mental model for
developers
−Simple scaling model for
operations - run multiple copies
behind a load balancer

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Problems
Monolith
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− Huge and intimidating code base
for developers
−Development tools get
overburdened
−Scaling is limited
−Deployment frequency is limited

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Characteristics and Benefits
Layered systems
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− A layered system decomposes a
monolith into layers, usually:
presentation, logic, data access
− At most one technology stack per
layer
− Simple mental model, simple
dependencies
− Simple deployment and scaling
model

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Problems
Layered systems
Section Title
− Still huge codebases (one per
layer)
−Scaling works better, but still
limited
−Staff growth is limited: roughly
speaking, one team per layer
works well

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What are microservies ?02

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History
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−2011: First discussions using this term
at a software architecture workshop
near Venice
−May 2012: microservices settled as
the most appropriate term
−March 2012: “Java, the Unix Way” at
33rd degree by James Lewis
−September 2012: “µService
Architecture“ at Baruco by Fred George
−All along, Adrian Cockroft pioneered
this style at Netflix as “fine grained
SOA”

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Section Title
What are Microservices ?
Microservices are small, autonomous services
that work together.

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Small with a single responsibility
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−Each application does only one
thing
−Small enough to fit in your head
−Small enough that you can throw
them away
−Rewrite over Maintain

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Autonomous
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−Embedded container or package (deb or
rpm etc.)
−Packaged as a single executable
−Along with their configuration files
−And unix standard rc.d scripts
−Installed separately
−Communicating with other services over
network, uses and exposes versioned API
−No DB or files shared between two
services

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Located in different SVC roots
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−Each application is completely
separate
−Domains in different bounded
contexts should be distinct – and it's
ok to have duplication – Use
physical separation to enforce this
−There will be common code, but it
should be library and infrastructure
code – treat it as you would any
other open source library

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Microservices provide benefits…
Tradeoffs
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− Strong Module Boundaries: Microservices
reinforce modular structure, which is
particularly important for larger teams.
− Independent Deployment: Simple services
are easier to deploy, and since they are
autonomous, are less likely to cause
system failures when they go wrong.
− Technology Diversity: With microservices
you can mix multiple languages,
development frameworks and data-storage
technologies.
…but come with costs
− Distribution: Distributed systems are
harder to program, since remote calls are
slow and are always at risk of failure.
− Eventual Consistency: Maintaining strong
consistency is extremely difficult for a
distributed system, which means everyone
has to manage eventual consistency.
− Operational Complexity: You need a
mature operations team to manage lots of
services, which are being redeployed
regularly.
https://martinfowler.com/articles/microservice-trade-offs.html

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Service-oriented architecture (SOA)
Section Title

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Design approaches used with microservices03

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Business microservice
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− Design the application with a set
of modules where each is an
independent business function
with its own data, developed by a
separate team and deployed in a
separate process

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API gateway
Section Title
− Exposes system API to outer
world - single entry point
− Has no business logic!
− Requests required information
from specific microservices
− Can perform protocol translation
− Must be highly available

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Load balancers and Message queues
Section Title
−Decoupled and
asynchronous using of
messaging/events to remove
peer-to-peer dependencies
−Using Message Broker
pattern
−RabbitMQ, ZeroMQ

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Results cache
Section Title
−Some services, when called
repeatedly, return the same
data every time and don’t
cause any side effects
−Results Cache can be as
simple as a Key-Value Store
−Set lifetime limit for cache,
from few seconds to few
hours

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Circuit breaker
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Service registry + self registration + 3rd party
registration + configuration as a service
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−Knows about all running
services - physical IP
address and service type
−Gathers services health
information, like status,
uptime
−Can gather and aggregate
some microservices metrics

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Favour choreography over orchestration
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Adapter microservice
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− Converts existing service’s non
microservice API to an API that
client microservice will expect.
− One of the first steps on
migrating from Monolith to
microServices

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Log aggregator
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Correlation ID
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− How do you debug a complex call
graph when you do not know
where in the set of microservices
along that call graph the problem
may have been introduced?
−Simple identifier (usually just a
number)
−Passed into every service
request
−Is printed in the every log entry
related to the request

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Health Check API
Section Title
− How to detect that a running
service instance is unable to
handle requests?
−An alert should be generated
when a service instance fails
−Requests should be routed to
working service instances
− A service has an health check
API endpoint that returns the
health of the service

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Section Title
− You need to know when and where to
scale up or down
− Bould with Load balancer and Service
registry
− Aggregating monitors with alers
− Good, thought through metrics
− processing rate - amount of processed
req/sec
− amount of succeeded and failed requests
− length of requests queue - min, max, latest
− connections status
Application metrics

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Infrastructure automation - CI/CD
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Still there are much more ...
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Summary04

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Section Title

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This is cool
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−We haven’t even talked about
−Versioning
−Integration
−Testing
−Deployment
−Security
−Anti-patterns
−Nanoservices
−Data driven migration
−...

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Literature
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Questions06

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Contact Info
Thank You

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Literature
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− http://2012.33degree.org/pdf/JamesLewisMicroServices.pdf
− http://www.braveterry.com/2014/04/10/presentation-service-architecture/
− http://www.pst.ifi.lmu.de/Lehre/wise-14-15/mse/microservice-architectures.pdf
− https://martinfowler.com/microservices/
− http://nealford.com/downloads/Building_Microservice_Architectures_Neal_Ford.pdf
− https://www.nginx.com/wp-content/uploads/2015/01/Building_Microservices_Nginx.pdf
− http://transform.ca.com/API-microservice-architecture-oreilly-book.html
− https://www.amazon.com/Microservices-Discover-Manage-Architecture/dp/151939733X
− https://www.openshift.com/promotions/microservices.html
− http://microservices.io
− http://www.vinaysahni.com/best-practices-for-building-a-microservice-architecture