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What's the scariest thing about serverless?

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@slobodan_ Long-running tasks?

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@slobodan_ Compliance?

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@slobodan_ Using binaries and large dependencies?

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@slobodan_ Cold start?

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@slobodan_ Cold start with VPN?

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@slobodan_ Node.js?

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@slobodan_ But, what about…

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@slobodan_ BIG

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@slobodan_ BAD

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@slobodan_ VENDOR LOCK-IN

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@slobodan_

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@slobodan_ What is vendor lock-in?

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@slobodan_ "In economics, vendor lock-in, makes a customer dependent on a vendor for products and services, unable to use another vendor without substantial switching costs."

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@slobodan_

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@slobodan_

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@slobodan_

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@slobodan_ A guy with a lot of servers.
 Let's call him Jeff.

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@slobodan_ A guy with a lot of servers.
 Let's call him Jeff.

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@slobodan_ Jeff is smart, and he knows how do you use his servers.

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@slobodan_ Jeff is smart, and he knows how do you use his servers.

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@slobodan_ Jeff is smart, and he knows how do you use his servers.

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@slobodan_ Jeff is smart, and he knows how do you use his servers.

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@slobodan_ Jeff is smart, and he knows how do you use his servers.

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@slobodan_ Jeff is smart, and he knows how do you use his servers.

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@slobodan_ Jeff is smart, and he knows how do you use his servers.

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@slobodan_ But what if Jeff is actually a villain?

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@slobodan_ But what if Jeff is actually a villain?

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@slobodan_ But what if Jeff is actually a villain?

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@slobodan_ Your wallet would not be happy…

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@slobodan_

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@slobodan_ Another guy with a lot of servers.
 Let's call him Bill.

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@slobodan_ Another guy with a lot of servers.
 Let's call him Bill.

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@slobodan_ Another guy with a lot of servers.
 Let's call him Bill.

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@slobodan_ Another guy with a lot of servers.
 Let's call him Bill.

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@slobodan_ Another guy with a lot of servers.
 Let's call him Bill.

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@slobodan_ That's vendor lock-in in the cloud

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@slobodan_ "My train of thought went like this: the term “lock-in” is misleading. We are really talking about switching costs." Mark Schwartz
 Enterprise Strategist at AWS

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@slobodan_ "As soon as you commit yourself to a platform or a vendor you will have switching costs if you later decide to change." Mark Schwartz
 Enterprise Strategist at AWS

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@slobodan_ How to fight vendor lock-in?

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@slobodan_ Or how to keep your switching costs reasonable?

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@slobodan_ • Planning and analysis • Good architecture • Deployment procedures How likely will I need to switch? What would be the cost?

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@slobodan_ That leads us to our topic…

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Designing testable serverless apps using hexagonal architecture

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@slobodan_ But, before we continue…

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Slobodan Stojanovic CTO @ Cloud Horizon & CTO @ Vacation Tracker co-author of Serverless Applications with Node.js book AWS Serverless Hero @slobodan_ serverless.pub

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@slobodan_ Designing testable serverless apps using hexagonal architecture

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@slobodan_ Why is testing important for serverless apps?

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@slobodan_ Most of the time serverless apps are not fully isolated monoliths without integrations

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@slobodan_ Instead, they contain many services interacting with each other and with external dependencies

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@slobodan_

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@slobodan_ Integrations can change every moment!

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@slobodan_ Tests don't prevent changes. They make sure your changes are not accidental.

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@slobodan_ But how do you know what should you test in a serverless app?

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@slobodan_ Testing pyramid

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@slobodan_

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@slobodan_ Testing pyramid vs "Serverless testing pyramid"

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@slobodan_

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@slobodan_ Integration tests are cheaper, but also more important, because the common serverless app is split into many small pieces

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@slobodan_ Designing testable serverless apps using hexagonal architecture

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@slobodan_ Ok, so which architecture is the best for serverless apps?

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@slobodan_ Any architecture that will let you test your serverless app easily and keep switching costs low.

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@slobodan_ Because sooner or later you'll need to switch/migrate pieces of your app.

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@slobodan_ Not to another cloud vendor, but to your new service, new or changed integration…

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@slobodan_ Risks to consider when building a serverless app

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@slobodan_ • configuration risks • technical workflow risks • business logic risks • integration risks

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@slobodan_ One of the app architectures that fits these needs is
 hexagonal architecture

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@slobodan_ Designing testable serverless apps using hexagonal architecture

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@slobodan_ "Allow an application to equally be driven by users, programs, automated test or batch scripts, and to be developed and tested in isolation from its eventual run-time devices and databases." Alistair Cockburn
 Creator of Hexagonal architecture

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@slobodan_

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@slobodan_

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@slobodan_ An example

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@slobodan_

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@slobodan_

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@slobodan_

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@slobodan_ Code, please

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@slobodan_ const {
 httpResponse, parseApiEvent,
 SnsRepository
 } = require('../common')
 const main = require('./main')
 async function handler(event) { const { body, headers } = parseApiEvent(event) // Create instance of SNS notification repository
 const notification = new SnsRepository(
 process.env.topic ) // Invoke main function with all dependencies
 await main(body, headers, notification)
 return httpResponse()
 }

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@slobodan_ await main(body, headers, notification)

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@slobodan_ Unit tests

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@slobodan_ await main(body, headers, mockNotification) Mock notification repository instance Some static values

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@slobodan_ Integration tests

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@slobodan_ await main(body, headers, localNotification) Local notification adapter, using JS events for example Some static values

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@slobodan_ Simple and nice

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@slobodan_ But, do you remember…

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@slobodan_ BIG

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@slobodan_ BAD

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@slobodan_ VENDOR LOCK-IN

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@slobodan_

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@slobodan_ How does hexagonal architecture help you fighting vendor lock-in?

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@slobodan_ Story time

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@slobodan_ Vacation Tracker vacationtracker.io

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@slobodan_ vacationtracker.io

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@slobodan_ • Serverless prototype • Small team (1 fulltime developer) • Initial product was Serverless chatbot + Express.js and MongoDB • Growing fast (200+ teams using it)

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@slobodan_ • Express -> Serverless migration • MongoDB -> DynamoDB migration

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@slobodan_ Let's talk about MongoDB -> DynamoDB switch

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@slobodan_

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@slobodan_

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@slobodan_

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@slobodan_ How does this look like?

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@slobodan_ describe('DynamoDB repository', () => { describe('unit', () => { ... }) describe('integration', () => { beforeAll(() => { // Create test DB }) afterAll(() => { // Destroy test DB }) // Tests }) })

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@slobodan_ beforeAll(async () => { const params = { ... } await dynamoDb.createTable(params).promise() await dynamoDb.waitFor('tableExists', { TableName: tableName }).promise() })

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@slobodan_ afterAll(async () => { await dynamoDb.deleteTable({ TableName: tableName }).promise() await dynamoDb.waitFor('tableNotExists', { TableName: tableName }).promise() })

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@slobodan_ And they lived happily ever after…

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@slobodan_ Beyond testing

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@slobodan_ What should we do with things that can't be tested?

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@slobodan_ What should we do with things that can't be tested? For example, Google or someone else deprecated an API while your app is in production

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@slobodan_ Make sure you are monitoring your app and tracking errors

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@slobodan_ Monitoring/error-tracking tools

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@slobodan_ • Built-in tools (CloudWatch, X-Ray) • Epsagon • IOpipe • Thundra • Lumigo • and many others

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@slobodan_ Serverless apps often heavily relies on front end, in those cases you need to track front end errors as well

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@slobodan_ desole.io

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@slobodan_

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@slobodan_

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@slobodan_ Summary

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@slobodan_ • Good architecture helps you to maintain your switching costs low (or at least reasonable) • Hexagonal architecture is a nice fit for serverless apps • Test your integrations (and app in general) • Testing is not enough, you'll need monitoring and error tracking for your serverless apps

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@slobodan_ Links to the things I mentioned

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@slobodan_ • Mark Schwartz - Switching Costs and Lock-In: amzn.to/2S4iT3G • Hexagonal Architecture: bit.ly/hex-arch • Vacation Tracker: vacationtracker.io • Hexagonal Architecture at Vacation Tracker: bit.ly/vt-hex-arch • Desole (error-tracking tool): desole.io

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@slobodan_ One more thing!

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@slobodan_

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@slobodan_ Serverless Applications with Node.js Use claudia40 promo code for 40% off serverless.pub/book @slobodan_

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@slobodan_ Thank you!

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@slobodan_ Thank you! Danke