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KYIV 2019
Dan Patrascu-Baba
Microservices from the trenches
.NET CONFERENCE #1 IN UKRAINE

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.NET LEVEL UP .NET CONFERENCE #1 IN UKRAINE KYIV 2019
Dan Patrascu-Baba
BIO: Software developer @Amdaris, Founder
@Codewrinkles, Co-organizer @ApexVox
Blog: http://danpatrascu.com
Twitter: @danpdc

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Agenda
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• Microservices architecture overview
• The project
• Lessons learned:
Decomposing services
Messaging
The API gateway
• Conclusions

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Microservices architecture

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Possible app architecture
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Services are…
.NET CONFERENCE #1 IN UKRAINE KYIV 2019
• small in size
• messaging enabled
• bounded by contexts
• autonomously developed
• independently deployable
• decentralized
• built and released with automated processes

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Benefits
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• Scalability
• Agility
• Availability
• Innovation

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Drawbacks?
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Let's discuss them at the end :)

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The project
.NET CONFERENCE #1 IN UKRAINE KYIV 2019
• The customer is a provider of integrated systems
for Contact Centers
• Rich application ecosystem
• Goal: Rebuild the Time and Attendance solution to
meet modern software architecture standards and
business needs
• How? Use Microservices architecture

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Lessons learned:
1. Scoping / decomposing services

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Decomposing models
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• By business capability and define services corresponding to business
capabilities
• By DDD bounded contexts
• By verb or use case and define services that are responsible for
particular actions. e.g. a Shipping Service that’s responsible for
shipping complete orders
• By nouns or resources by defining a service that is responsible for all
operations on entities/resources of a given type. e.g. an Account
Service that is responsible for managing user accounts

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Issues
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• How to identify the bounded contexts?
• How to identify business capabilities?
• Which decomposition model is suitable for a given scenario?
• Is it really possible to decompose everything in a meaningful way
following only one model?

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DEMO:
Decomposing services

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Lessons learned:
2. Messaging

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Issues
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• A microservices architecture is all about communication
• How should services communicate in any given business scenario?
• Should they call each other synchronously?
• Should they communicate via asynchronous messaging?
• What are the pros and cons of the chosen message brokering
technology?

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Communication patterns
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Synchronous Calls if:
• we want to query some data, because a query is not changing any state so we don’t have to
worry about distributed transactions and data consistency across service boundaries
• the call is allowed to fail and we don’t need a sophisticated retry mechanism
Simple Messaging if:
we want to send state-changing commands
• the operation must be performed eventually, even if it fails the first couple times
• we don’t care about potentially complex message structure
Transactional Messaging if:
• we want to send state-changing commands only when the local database transaction has
been successful

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Message broker concepts
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• Producer - User application that sends messages to an exchange.
• Exchange - Pushes messages into queues. Exchange types define what to do
with the message when it’s received, whether. appended to a one queue, to
many queues, or discarded. Example exchange types are direct, topic and
fanout.
• Queue - Each exchange contains a buffer, or queue, that stores messages. A
queue is only bound by the host’s memory & disk limits, it’s essentially a large
message buffer. Many producers can send messages that go to one queue, and
many consumers can try to receive data from one queue.
• Consumer - User application that receives messages.

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DEMO:
Messaging infrastructure

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Lessons learned:
3. The API gateway

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What should an API gateway do?
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• Proxying
• Service discovery
• Response aggregation
• Header translation
• Protocol translation
• Load balancing
• Authorization
• Rate limiting

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Available options
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• All the major cloud providers offer such services
• Kubernetes has such a functionality
Drawbacks
• Technology debt
• Additional complexity when setting up environments
• Not very flexible

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A possible solution in the .NET world…
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• Meets all discussed requirements
• Easy to configure
• Can be extended with own
functionality

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DEMO:
Ocelot

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Conclusions
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• A microservices architecture adds a lot of complexity that we might tend to
oversea in the planning phase
• Are the benefits really outnumbering the complexities?
• A microservices architecture is not only about software architecture, but also
about the organization and how teams are set up

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Before deciding on going for a
microservices architecture try to
ask yourself if it’s worth

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Questions?

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Thank you!