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TDD a REST API With Node.js and MongoDB

Learn the basics of MongoDB and Node.js by building a REST API. All Things Open 2015.

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TDD a REST API With Node.js and MongoDB

  1. 1. Developing and Testing a MongoDB and Node.js REST API Valeri Karpov Node.js Engineer, MongoDB www.thecodebarbarian.com github.com/vkarpov15 @code_barbarian
  2. 2. * What is this talk about? •Briefly introduce MongoDB and Node.js •MongoDB is great for storing web/mobile app data •So let’s build a REST API using Node.js! •+ learn a bit about test-driven dev with Node.js •+ learn two MongoDB schema design principles •Server-side only •Upcoming EdX course
  3. 3. * What is MongoDB? •Document database - store objects, not columns •Often better* performance • Better data locality than RDBMS for 1 query vs 5 JOINs
  4. 4. * What is MongoDB? •Easier ops • No need to set up databases, tables, schemas, etc. • Run one executable, you now have a working db • MongoDB Cloud Manager and Ops Manager •Developer sanity • In my experience, easiest database to get working • Minimal data transformation between DB and server • Company has dedicated “Developer Experience” team
  5. 5. * Overview •Part 1: Shopping Cart Application • Search for products • Add them to your cart • Check out with Stripe •Part 2: Using Node.js and the Mongoose ODM •Part 3: Schema Design •Part 4: Building an API with the Express framework •Part 5: Testing with Mocha + Superagent
  6. 6. * Part 1: What Does the App Do?
  7. 7. * What Does the App Do?
  8. 8. * What Does the App Do?
  9. 9. * App Structure •"Bad programmers worry about the code. Good programmers worry about data structures and their relationships." - Linus Torvalds •3 schemas for 3 collections: •Products •Categories •Users
  10. 10. * Schema Relationships •Product belongs to one or more categories •Users can have multiple products in their cart •Representing relationships in MongoDB is tricky • MongoDB doesn’t have a JOIN equivalent •But that’s what mongoose is for • Mongoose provides pseudo-JOINs (separate queries)
  11. 11. * Part 2: Using the Mongoose ODM •“Object document mapper” (like ORM, but for MongoDB) •“MongoDB object modeling designed to work in an asynchronous environment” •Written for Node.js •Provides schema validation, pseudo-JOINs, etc.
  12. 12. * Brief Overview of Node.js •require() ● Async I/O
  13. 13. * What Does Async Mean? Register event handler In node.js, you don’t execute I/O imperatively. You register a callback to execute when the I/O is done Single thread - handler can’t be interrupted Prints before “done reading”
  14. 14. * Why Async? •Most web app/mobile app backends are I/O bound • Multi-threading doesn’t help if CPU is just waiting for I/O • Mostly just waiting for database to respond •Nowadays there’s a REST API for everything • Analytics and tracking: Segment • Transactional email: Vero • Mailing lists: MailChimp •Threads are cumbersome for I/O bound programs
  15. 15. * Your First Mongoose Schema matches X@Y.Z
  16. 16. * Using Your Schema Create User Save user to MongoDB Load user from MongoDB Print user to stdout
  17. 17. * Part 2 Takeaways •Mongoose provides several neat features • Model part of MVC • Default values • Schema validation and declarative schema design
  18. 18. * Part 3: Schema Design •3 schemas: • Product • Category • User •Going to use mongoose to define schemas •Will use a couple key schema design principles
  19. 19. * Product Schema
  20. 20. * Product Schema in Action
  21. 21. * Category Schema
  22. 22. * Category Schema Queries •What categories are descendants of “Electronics”? • • •What categories are children of “Non-Fiction”? • •What categories are ancestors of “Phones”?
  23. 23. * Product + Category Schemas
  24. 24. * Category Schema Takeaways •Queries in MongoDB should be simple •Strive for minimal data transformation by server •“Store what you query for” •“If you need [the aggregation framework in a heavily used API endpoint], you're screwed anyway, and should fix your program.” - Linus Torvalds •Good for performance and developer sanity
  25. 25. * User Schema User’s cart as an array of ObjectIds...
  26. 26. * Principle of Least Cardinality •Product and user = many-to-many relationship •Don’t necessarily need a mapping table •User won’t have 1000s of products in cart •Can represent relationship as array in user since one side is small •If one side of many-to-many is bounded and/or small, it is a good candidate for embedding •Arrays that grow without bound are an antipattern! • 16mb document size limit • network overhead
  27. 27. * Part 4: The Express Framework •Most popular Node.js web framework •Simple, pluggable, and fast •Great tool for building REST APIs
  28. 28. * Your First Express App Route Parameter
  29. 29. * What is REST? •Representational State Transfer •HTTP request -> JSON HTTP response •Business logic on top of MongoDB schemas • Access control, emails, analytics, etc.
  30. 30. * Structuring Your REST API
  31. 31. * GET /category/id/:id Find Category Error handling Output JSON
  32. 32. * GET /category/parent/:id
  33. 33. * GET /product/category/:id
  34. 34. * Adding Products to User’s Cart •Recall cart is an array of products
  35. 35. * Adding Products to User’s Cart Get cart from HTTP request Overwrite user’s cart Let mongoose handle casting and validating data
  36. 36. * PUT /me/cart Takeaways •Mongoose lets you be lazy •Access control using subdocs
  37. 37. * Bonus: Stripe Checkout Create a Stripe charge with the npm ‘stripe’ module
  38. 38. * Bonus: Stripe Checkout Error handling Empty user cart on success
  39. 39. * Part 4 Takeaways •Express REST API on top of mongoose • Access control • Business logic • Define what operations user can take on database •Mongoose casting and validation for APIs
  40. 40. * Part 5: Test-Driven Development •Building an API is tricky •Lots of different error conditions •Express has a lot of magic under the hood
  41. 41. * NodeJS Concurrency and Testing •Node.js runs in an event loop •Single threaded •Can run client and server on same thread! • Client sends HTTP request • Client registers a callback awaiting the result • Server’s “on HTTP request” event handler is triggered • Server sends response, continues waiting for events • Client’s callback gets fired •Test server end-to-end
  42. 42. * Superagent •NodeJS HTTP client •Isomorphic: runs in both browser and NodeJS •Same author as Express
  43. 43. * Mocha •Testing Framework for NodeJS •Same author as Express •BDD-style syntax • describe() -> test suite • it() -> individual test
  44. 44. * Setting Up Category API Tests
  45. 45. * Testing GET /category/id/:id
  46. 46. * Part 5 Takeaways •NodeJS concurrency makes testing easy •Not just unit tests - full E2E for your REST API •Can manipulate database and make arbitrary HTTP requests
  47. 47. * •Upcoming EdX Video Course •Slides on http://www.slideshare.net/vkarpov15 •Looking for beta testers! Sign up for notifications • http://goo.gl/forms/0ckaJ4YvJN •Interested in learning about AngularJS? • Professional AngularJS on Amazon •More NodeJS+MongoDB content at: • www.thecodebarbarian.com • Twitter: @code_barbarian Thanks for Listening!

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