GraphQL on Rails

Transcript

1. GraphQL on Rails
   2019/01/23 Tokyo Rails#38
   Yuki Akamatsu @cookpad
   

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2. Who am I?
   •Yuki Akamatsu
   •id: ukstudio
   •Rails programmer
   •Working at Cookpad
   ‣New service development
   dept.
   

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3. Our project
   •Named Tabedori
   ‣たべかたドリル
   •Improvement cooking
   skills
   •Everyone can cooking
   without recipes
   

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4. Technology stack of Tabedori
   •Mobile app
   ‣ React Native + TypeScript
   •GraphQL Server
   ‣ Ruby on Rails
   •Admin tool(CMS)
   ‣ React.js + TypeScript
   (SBQI2-4FSWFS
   .PCJMFBQQ "ENJOUPPM
   

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5. Agenda
   •What is GraphQL
   •How to implement GraphQL on Rails
   

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6. What is GraphQL
   

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7. Query language
   •GraphQL is a query language for Web API
   ‣ And also server-side runtime
   • Like Node.js, Rails, AppSync, and other things
   

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8. One endpoint
   •GraphQL server has only one
   endpoint
   •All queries are sent to the
   endpoint
   ‣ POST method only
   ‣ All responses are returned with 200
   status
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9. GraphQL Query
   • You can request any fields you
   need
   • You don’t need to receive
   unnecessary data
   • You can get many resources in a
   single request
   • It’s better for performance
   

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10. Error
    • If there is something
    wrong, GraphQL server
    returns a response
    what contains errors
    key
    

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11. Type definition
    •All resources and fields
    have a type
    •You can fetch fields
    what are defined on
    Type
    

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12. Type is good
    •There is no mixing of multiple types
    •Null checking isn’t required
    ‣ Non-null constraint can be defined by using ! in the schema
    •Becoming documentation
    ‣ Can generate documentation from the schema
    

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13. Documentation
    •You can see documentation using IDE or
    documentation tools
    •Documents are very useful for communication
    between client-side programmers and server-side
    programmers
    

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14. GrahpiQL
    •https://github.com/graphql/
    graphiql
    •Graph”i”QL is browser IDE
    for GraphQL
    ‣ It can send requests to
    graphql server
    •You can see document
    quickly
    

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15. GraphiQL is awesome
    •GraphiQL make easy to request to graphql server
    ‣ You can try any queries easily and interactively
    •If you use desktop app, I recommend prisma/
    graphql-playground
    ‣ I’m using this
    

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16. graphql-docs
    •https://github.com/
    gjtorikian/graphql-docs
    •graphql-docs is gem that
    generate documentation
    as html from the schema
    •It might be a good if you
    want to host static file
    

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17. Public APIs
    •You can try GraphQL query on these sites
    •GitHub
    ‣ https://developer.github.com/v4/explorer/
    •SWAPI
    ‣ https://graphql.org/swapi-graphql/
    •And so on
    ‣ https://github.com/APIs-guru/graphql-apis
    

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18. How to implement
    GraphQL on Rails
    

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19. graphql-ruby
    •http://graphql-
    ruby.org/
    •graphql-ruby is
    probably best way in
    now
    

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20. Define types and fields
    •graphql-ruby provides
    DSL for types and fields
    definition
    •You can define Type as
    Ruby class
    

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21. Define resolver (Query)
    •Resolver represents a single field
    •And can be used to fetch data
    from any data source
    ‣In this case, fetching from RDB
    using ActiveRecord
    •Each user is assigned to
    UserType
    

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22. Define resolver (User)
    •“object” is provided graphql-ruby
    •“object” is passed from parent type
    ‣In this case, “object” is User
    instance
    •If resolver isn’t defined, delegate
    to “object” by default
    ‣It means resolver is optional
    ‣In other words, these resolvers in
    this example are unnecessary
    

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23. It works
    •This is the end of the minimal implementation
    •I didn’t tell you about some processes
    ‣ e.g. You need to execute “rails g graphql:install”
    •What matters is defining types and resolvers
    

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24. Need to solve N+1 problem
    •The example has N+1
    problem
    •If There are 20 users,
    this query calls select
    query from posts 20
    times
    ‣It’ too bad
    

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25. Bad way
    •Use eager_load to
    single query to DB
    •It is becoming
    unnecessary cost if you
    don’t need posts
    

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26. graphql-batch
    •https://github.com/Shopify/graphql-batch
    •graphql-batch provides an executor which allows
    queries to be batched
    •It’s inspired by DataLoader created by Facebook
    

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27. AssociationLoader
    •Implement
    AssociationLoader
    ‣You can copy from
    graphql-batch’s
    repository
    •Just use
    AssociationLoader
    

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28. Why was it solved?
    •In brief, graphql-batch collects user’s id at first.
    •Then execute batched query
    ‣ “where(user_id: collected_user_id)”
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29. Pagination
    •I recommend to using connection_type
    ‣ Pros: easy to implementation
    ‣ Cons: provides only Relay cursor-based pagination
    •You need to implement by yourself If you want to
    use another way
    

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30. Relay cursor-based pagination
    •Relay is framework of
    GraphQL created by
    Facebook
    •Cursor-based is suited
    for infinity scroll
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31. connection_type
    •Any object type has
    connection_type method
    •Just use connection_type instead
    of [] in type specification
    

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32. Conclusion
    •What is GraphQL
    ‣ GraphQL is query language for Web API
    ‣ GraphQL is strongly typed
    •How to implement GraphQL on Rails
    ‣ You would use graphql-ruby and graphql-batch
    ‣ connection_type is a way of pagination
    

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33. Thank you
    •There are some topics I didn’t talk
    ‣ How to create/update/destroy data
    ‣ Uploading images, Error handling, Designing schema, and so on
    •The presentation may be insufficient due to my english ability
    •Please feel free to ask me in FAQ or after this talk
    ‣ Please could you speak slowly and simply
    

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