Building Federated GraphQL APIs in Flask

Deck of my Flaskcon 2023 Talk on Building Federated GraphQL APIs in Flask (https://www.youtube.com/watch?v=UXJeBvYI9S0 )

Talk slides and demo code are available at https://github.com/adarshdigievo/talks/tree/main/Flaskcon%2023%20-%20Federated%20GraphQL

Transcript

1. Building Federated GraphQL APIs using Flask Adarsh Divakaran
2. REST vs GraphQL
3. REST API URL: localhost:8000/api/v1 Req: GET /greeting Resp: {“greeting” : “hello”}
4. GraphQL
5. REST
6. GraphQL
7. GraphQL Features
8. Single Endpoint REST GraphQL
9. Operations REST GET: Fetch data POST, PUT, PATCH, DELETE: Add, edit, modify and delete operations GraphQL HTTP Method used is POST always. QUERY: Fetch data MUTATION: Modify, update, delete, etc. SUBSCRIPTION: Realtime persistent operations
10. Strong Typing
11. Scalars & Types in GraphQL • Int A signed 32‐bit integer. • Float A signed double-precision floating-point value. • String A UTF‐8 character sequence. • Boolean true or false. • ID The ID scalar type represents a unique identifier Other types/containers: List, NonNull, Enum, Union, Interface (source: graphql.org)
12. Scalars & Types in GraphQL Enumeration enum Episode { NEWHOPE EMPIRE JEDI } Custom type type Character { name: String! appearsIn: [Episode]! } Union type union SearchResult = Human | Droid | Starship
13. Advantages of GraphQL
14. Overfetching Prevention Initial API Version Return a greeting message New Requirement For desktop web clients, return a greeting image along with the greeting message
15. Overfetching Prevention REST - Initial Version
16. Overfetching Prevention REST - Option 1 Disadvantage: For mobile clients, an extra unused field is returned with the response
17. Overfetching Prevention REST - Option 2 - Adding separate endpoint Disadvantage: Extra network call and complexity for web clients
18. Overfetching Prevention GraphQL Solution Query of Mobile client
19. Overfetching Prevention GraphQL Solution - Desktop client GraphQL allows us to query only the fields we need
20. Introspection & Type system • Strongly typed and schema based • All supported operations by a server are returned by ‘introspection’ • Presence of tooling to auto generate client code • REST would require additional doc tools - ‘flasgger’ or ‘flask-rest-api’. • GraphQL development is centered around its schema
21. Choosing a GraphQL Server
22. Schema First vs Code First Code First Schema First
23. Demo
24. GraphQL Federation
25. Apollo Federation • A standard/spec for combining multiple independent GraphQL schemas • Combines multiple related schemas from microservices (subgraphs) to a single unified schema (supergraph) • Abstracts away the microservice design from clients
26. When to use GraphQL & Federation • Use GraphQL where it shines - Example: internal APIs with diverse use cases • Use GraphQL Federation when it fits your architecture / when a monolith becomes unmanageable [ From “8 Years of GraphQL: Unraveling the Trade-Offs” Talk by Marc-Andre Giroux (GraphQL Conf 2023) ]
27. Federation - Concepts
28. Directives A directive decorates part of a GraphQL schema or operation with additional configuration. Denoted using ‘@’ - similar to decorators in Python
29. Directives
30. Entity • An Entity in Federation is an object type that can resolve its fields across multiple subgraphs. • It can be thought of as a GraphQL type which appears across multiple microservice subgraphs.
31. Entity - UserType
32. @key directive • Designates an object type as an entity. • The @key directive is used to indicate fields that can be used to uniquely identify and fetch an object.
33. Federation Gateway/Router • Combines multiple microservice schemas and exposes a single combined endpoint • Intelligent - It holds the logic to resolve entities and shared types
34. Reference resolver function The reference resolver function enables the Federation gateway's query planner to resolve a particular entity by its @key fields.
35. Demo
36. References • Graphql Specification: https://spec.graphql.org/ • Graphql.org Docs: https://graphql.org/learn/ • Apollo Federation Docs: https://www.apollographql.com/docs/federation/ • Strawberry GraphQL Docs: https://strawberry.rocks/docs • 8 Years of GraphQL: Unraveling the Trade-Offs: Marc-Andre Giroux
37. Thank You adarsh-d adarshd905 Slides and Demo code: go.adarsh.pizza/flaskcon