1.
Microservice
Architecture with
Reusable Components
Mar 30, 2018

2.
Slides JSFest bot

3.
Nikita
Galkin
Love and Know:
▰ How to make developers and business happy
▰ Technical and process debt elimination
Believe that:
▰ Any problem must be solved at the right level
▰ Software is easy. People are hard
▰ A problem should be highlighted, an idea should
be "sold", a solution should be demonstrated
Links:
Site GitHub Twitter Facebook
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“Wanna do something
good, do it yourself”
Jean-Baptiste
Emanuel Zorg
(Gary Oldman)

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“Almost all the successful
microservice stories have started
with a monolith that got too big and
was broken up”
from MonolithFirst
Martin Fowler

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“I picked Java because I felt the most
people would be able to understand
the code examples if they were
written in Java. That was the case in
1997, but how about in 2017?
…
But I went for the alternative:
JavaScript.”
27 March 2018

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Components

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Best
Practices

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Reusable Components

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Why?

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Don’t
Repeat
Yourself

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What?

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Scoped packages

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Scoped packages
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▶ npm install @zorg/zf
+ @zorg/zf@1.0.5
added 1 package in 1.727s
▶ cat ~/.npmrc
@zorg:registry=http://npm.zorg-weapon.com

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First package
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▰ @your-scope/code-style
▰ Code Style and Violence
by Anton Nemtsev

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What is not
reusable
component?

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“Small, autonomous
services that work
together.
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Evolution

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How?

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Robustness
Engineered for engineers
Useful
Simple
Examples included

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npm i -g how-to-npm
how-to-npm
Or
Free 1,5 hour-long video:
How to Write an Open
Source JavaScript Library

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Git flow
30How to convince the team?

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How to convince the manager?

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“Wanna do
something good,
do it yourself”
Zorg

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“Wanna do
something good,
do it yourself”
Zorg

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“Don't use require(../../utils/logger),
use npm packages” © Galkin
Awesome Pair!
But how reuse code...
Microservices

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How to develop
reusable
components?

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▰ npx scripts
▻ eslint helper
▰ plop
▰ yeoman.io
▰ raml2html
Code, spec, docs generators
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Generators
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Test Driven Development
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FAIL
PASS
TDD
REFACTORING
“Repetition of a very short
development cycle: requirements are
turned into very specific test cases,
then the software is improved to pass
the new tests, only.”
Kent Beck

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Types or Documentation Driven Development
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tsc
Add JSDoc
TDD
▰ choose typescript or JSDoc
▰ autocomplete for engineers
▰ always actual code documentation
▰ puppeteer source-code is
awesome JSDoc example
REFACTORING

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/**
* @typedef {Object} CoverageEntry
* @property {string} url
* @property {string} text
* @property {!Array<!{start: number,
end: number}>} ranges
*/

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Theft Driven Development
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STEAL
ADOPT
TDD
SHARE

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Reusable Components

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I'll show you my
package.json
during speaker
corner

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Where?

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Source code
storage
CI for
build and test
Artifact
storage

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Git flow
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Gitflow

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Git flow
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Gitflow

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Github Flow

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Monorepo with Lerna

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Or one repo for one component?

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Your DevOps Engineer: @#_$!

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Your DevOps Engineer: @#_$!

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12factor.net

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“II. Dependencies
Explicitly declare and
isolate dependencies
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“III. Config
Store config in the
environment
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“V. Build, release, run
Strictly separate build and
run stages
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“VI. Processes
Execute the app as one or
more stateless processes
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“XI. Logs
Treat logs as event
streams
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stdout stderr

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How to develop
microservices?

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MonolithFirst

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How your system works?

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ECB is a variant of Model/View/Controller (MVC). It
was published by Ivar Jacobson (Ericsson Co.) in
the 80's with a focus on separating responsibilities
of elements in Object Oriented Systems.

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Boundary – objects that interface with system
actors (e.g. a user or external service). Side
effected.
Boundary component should be reusable.
EBC Pattern – Boundary
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Boundary place for validation

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▰ Wrapper for Enterprise Bus
▰ File Storage wrapper
(S3/Local FileSystem)
▰ JSON RPC with different
transports
Possible Boundaries Components
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Control – objects that implement business
logic. This code has the main value for
business.
This part of every microservice is unique.
EBC Pattern – Control
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Control – just control.

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Entity – objects representing system data,
often from the domain model. In our
application we use an entity also for
transforming data from one format to another.
For example, from XML to JSON.
Entity can be shared between applications as
interfaces or components.
EBC Pattern – Entity
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Entity for data transform

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microservices base application with:
▰ Base boundary class
▰ App class with start stop
▰ Default logger
▰ Hooks
Basement
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1. Only Boundary provide services for the
"other world".
2. Boundary can call only to Control.
3. Control can call anybody.
4. Entity can't call anybody (!), only be called.
EBC Pattern
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Why does it matter?

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Bootstrapping and Graceful
shutdown

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Interface Microservice {
void start();
void stop();
}
Microservice interface
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Bootstrapping

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1. Attach uncaught exception hooks.
2. Log start of bootstrapping.
3. Verify configuration.
4. Init boundaries and controls.
5. Attach shutdown hooks.
6. Log finish of bootstrapping.
Bootstrapping
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Graceful Shutdown

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For graceful shutdown application should:
1. Log start of graceful shutdown.
2. Close incoming boundaries. For example,
stop accepting new tasks for processing
from queue, stop handling new incoming
http requests, etc.
Graceful shutdown
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3. Set a forced timeout for completion current
tasks or save them for future processing.
Recommended value for this timeout is not
more then 5 second.
4. Notify consumers about shutdown. For
example, send heartbeat-shutdown.
Graceful shutdown
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5. Correctly disconnect from all connections.
For example, database, RabbitMQ, Redis,
etc.
6. Log finish of graceful shutdown and stop
the process.
Graceful shutdown
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83Let’s summarize!

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▰ Reusable Components
▰ Monolith First
▰ The Twelve Factors
▰ EСB (Entity, Boundary, Control) Pattern
▰ Bootstrapping and Graceful shutdown
Microservice Best Practises
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Robustness
Engineered for engineers
Useful
Simple
Examples included

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Thank you for attention!
Be consistent in your
microservices!!!
You can find me on Twitter as @galk_in
Slides are available at speakerdeck.com/galkin
or on my site galk.in

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Slides JSFest bot

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▰ koa
▰ bunyan
▰ dotenv-safe
▰ gatsbyjs
▰ rxjs
My favorite packages
91
▰ pre-commit
▰ eslint
▰ jest
▰ raml-cli
▰ dredd