The Twelve-Factor App for Node.js Developers by Nikita Galkin Feb 27, 2019 

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 Complicated ▰ A problem should be highlighted, an idea should be "sold", a solution should be demonstrated Links: Site GitHub Twitter Facebook 2 

Takeaway Driven Development 3 TAKEAWAY ADOPT TDD SHARE 

12factor.net 

What is Quality? 5 Motivation ▰ Reduce the onboarding time ▰ A common language with DevOps Engineers ▰ Scale/Cloud/Production/etc -ready 

What is Quality? 6 Talk Structure ▰ Factor ▰ RTFM ▰ how to implement using Node.js ▰ exclusion cases or hacks 

7 I. Codebase 

What is Quality? 8 One codebase tracked in revision control, many deploys ▰ App vs Distributed System ▰ Code sharing by dependency manager. 

What is Quality? 9 How to match codebase and application at env? ▰ semver ▰ version in package.json ▰ git tag ▰ git describe --tag Example 2.2.0-44-g9f84663 

What is Quality? 10 I. Codebase ▰ BE & FE aka Full-stack repo ▰ App & lambda from one src ▰ Monorepo 

11 II. Dependencies 

What is Quality? 12 Explicitly declare and isolate dependencies ▰ declaration VS isolation ▰ never relies on implicit existence ▰ system tool can be a dependency 

What is Quality? 13 Package.json ▰ avoid npm install -g ... ▰ package-lock.json should published in git ▰ node & npm versions fixed at Tech Stack or you will have package-lock diff war ▰ post-install script is a good place for hacking node_modules 

14 Scoped packages 

What is Quality? 15 Shared code ▰ Use scoped packages ▰ @project/code-style is good first chose Check Code Style and Violence by Anton Nemtsev ▰ On self-hosted repo npm config set @myco:registry http://reg.example.com ▰ With a self-hosted repo, use add .npmrc to git 

What is Quality? 16 

What is Quality? 17 node_modules hacks ▰ Embedded or lambda: webpack ▰ Docker ▻ npm install --production ▻ npm prune --production ▻ node-prune ▻ docker in docker 

FROM node:10.15-alpine ENV APP_WORKDIR=/usr/src/app RUN apk update && apk upgrade && \ apk add --virtual build-deps git openssh-client py-pip make COPY package.json yarn.lock $APP_WORKDIR WORKDIR $APP_WORKDIR RUN yarn install COPY . $APP_WORKDIR RUN yarn build RUN rm -rf tsconfig.json src RUN apk del build-deps RUN yarn install --production RUN yarn cache clean EXPOSE 3000 CMD ["node", "dist/index.js"] 

19 III. Config 

What is Quality? 20 Store config in the environment ▰ Config is not part of the artifact ▰ could be made open source at any moment, without compromising any credentials. 

What is Quality? 21 .env ▰ Use .env file for local development ▰ Use .env.example file for description ▰ Use environment variables for any other environment ▰ Don’t use default config values in your code ▰ Break your start process if any value missed 

# .env.example # Default log level LOG_LEVEL=info # Graceful shutdown timeout in milliseconds SHUTDOWN_TIMEOUT=1000 # HTTP Boundary port HTTP_PORT=8000 # Redis connection string REDIS_URI=redis://127.0.0.1:6379 

require('dotenv-safe').load({ allowEmptyValues: true, path: join(__dirname, '..', '.env'), sample: join(__dirname, '..', '.env.example') }); const logger = require('./logger'); logger.levels('stdout', process.env.LOG_LEVEL); const settings = { shutdownTimeout: process.env.SHUTDOWN_TIMEOUT, http: { port: process.env.HTTP_PORT, }, redis: { uri: process.env.REDIS_URI, }, }; module.exports = settings; 

What is Quality? 24 Dima: process.env knows every env var. This is risky! Nikita: Then your project uses only 11 factors. 

25 IV. Backing services 

What is Quality? 26 Treat backing services as attached resources ▰ local and third party parity ▰ Attach URL or other locator/credentials stored in the config 

What is Quality? 27 Nice to have ▰ Tech stack for project or Readme.md with strict versions ▰ For local development docker-compose file or minikube config file 

28 V. Build, release, run 

What is Quality? 29 Strictly separate build and run stages ▰ Artifact ▰ Build ▰ Release ▰ Run time ▰ Dry run 

What is Quality? 30 Node.js artifact ▰ N/A ▰ Docker ▰ Lambda zip ▰ Application Zip ▻ Big size ▻ node-gyp compiled code can be broken on another computer 

31 VI. Processes (stateless) 

What is Quality? 32 Execute the app as one or more stateless processes ▰ stateless ▰ share-nothing ▰ state stored at backing-service 

Awesome Pair! Docker and Node.js has a common thing – single process 

34 6 Done, 6 Left Let’s move faster 

35 VII. Port binding Export services via port binding 

What is Quality? 36 ▰ Don’t hardcode port at the code, use env vars ▰ Bootstrap should fail, if the port is not available ▰ Dockerfile EXPOSE 

37 VIII. Concurrency Параллелизм 

What is Quality? 38 Scale out via the process model ▰ Unix ▰ process ▰ should never daemonize ▰ Use process manager like systemd 

39 IX. Disposability Maximize robustness with fast startup and graceful shutdown 

const server = app.listen(settings.port, () => { logger.info(`Server started on port ${settings.port}`); }); function stopHandler(){ logger.info(`Stopping server on port ${settings.port}`); const timeout = setTimeout(() => { logger.info(`Server on port ${settings.port} stop forcefully`); process.exit(1); }, settings.stopTimeout); server.close(() => { logger.info(`Server on port ${settings.port} stopped`); clearTimeout(timeout); }); }; process.on('exit', (code) => logger.info(`Exit with code: ${code}`)); ['SIGTERM','SIGINT','SIGHUP'] .forEach(signal => process.on(signal, stopHandler); 

41 X. Dev/prod parity Keep development, staging, and production as similar as possible 

What is Quality? 42 ▰ Same backing services ▰ Same lib versions ▰ Same bla-bla for Reproducibility 

43 XI. Logs Treat logs as event streams 

What is Quality? 44 ▰ A twelve-factor app never concerns itself with routing or storage of its output stream ▰ Writes event stream, unbuffered, to stdout/stderr ▰ JSON format for simplification log parsing ▰ bunyan has this format from the box ▰ for local development npm start | bunyan -o short 

stdout stderr 

46 XII. Admin processes Run admin/management tasks as one-off processes 

What is Quality? 47 ▰ Node.js has REPL ▰ Check node_modules/.bin every script starts with #!/usr/bin/env node ▰ Write your own script or reuse packages ▰ Use npx, for example npx https://gist.github.com/galkin/9b54683ec251d77b26fa4c7feec46df2 

12factor.net 

49 THANKS! Happy coding with 12 factors! You can find me on Twitter as @galk_in Slides are available at speakerdeck.com/galkin or at my site galk.in