Elixir + GraphQL = Absinthe 2019.04.10

Elixir + GraphQL = Absinthe
Alex Knowles
ChicagoElixir Meetup
April 10, 2019
+ =

Alex Knowles
Software Engineer
CityBase

Bruce Williams
@wbruce
Absinthe co-creator
Ben Wilson
@bewwilson512
Absinthe co-creator

Tonight’s Agenda
● GraphQL Overview
○ Who? What? Why?
○ Building blocks
● Server Demo and Absinthe code
● Dataloader
● On the horizon
● Q & A

[In 2012], our iOS and Android apps were
thin wrappers around views of our
mobile website. While this brought us
close to a platonic ideal of the “write
once, run anywhere” mobile application,
in practice it pushed our mobile-webview
apps beyond their limits. As Facebook’s
mobile apps became more complex, they
suffered poor performance and
frequently crashed.
- Lee Byron, Facebook

Who is GraphQL?
● Developed internally at Facebook in 2012
● Open-sourced in 2015
● GraphQL Foundation announced in November 2018
(hosted under Linux Foundation)
● Apollo launched a full GraphQL Platform in November
2018

What is GraphQL?
GraphQL is a speciﬁcation.
Three parts:
● GraphQL Query Language
● GraphQL Schema Language and Type System
● An algorithm for implementers: how queries should be executed against an
arbitrary type system
Credit: Marc-André Giroux

We were frustrated with the differences
between the data we wanted to use in
our apps and the server queries they
required. We don’t think of data in terms
of resource URLs, secondary keys, or join
tables; we think about it in terms of a
graph of objects and the models we
ultimately use in our apps like NSObjects
or JSON.
- Lee Byron, Facebook

Why GraphQL?
● Types! Types! Types! 💪
● No more overfetching 🍕🍕🍕🍕🍕🍕🍕
● No more underfecthing 🍕
● Introspection 🔍
● More power to API consumers 🔌
● One API for everything

Strong types are so hot right now
● Dialyzer
● TypeScript
● Flow
● GraphQL!

Overfetching &
Underfetching
GET /characters/1002
Don’t care
N + 1!

Introspection
● Built-in types recognized by every GraphQL schema:
○ __Schema
○ __Type
○ __TypeKind
○ __Field
○ __InputValue
○ __EnumValue
○ __Directive
● API clients can form meta-queries to discover the
structure of any schema
● Tools like GraphiQL and Apollo Playground use
introspection to render schema documentation and
power auto-completion

Querying for queries (so meta)

Many articles written on GraphQL focus
on the fact that GraphQL solves the
under-fetching and over-fetching
problems. This is totally true, but to me
is a side effect of something much more
crucial: enabling any number of clients to
coexist, and survive the evolution, of a
single API server.
- Marc-André Giroux, GitHub

GraphQL, compared with RESTful Architecture
REST
● CRUD + stuff
● Lots of routes/endpoints
● API versions -- v2, v3, etc…
● API team designs and
maintains an API that works
for every client ...hopefully.
GraphQL
● Queries (reads) + Mutations (writes)
● One endpoint for all operations
● One version that evolves; deprecation
● API team designs a domain-informed
schema; API consumers build operation
documents to ﬁt their exact needs.

GraphQL Schema
There are three operation types:
● Queries: read data
● Mutations: change data
● Subscriptions: queries, but
pushed by the server

GraphQL Types
Scalar Types (Built-in)
● Boolean
● Float
● ID (String)
● Integer
● String
Scalar Types (Absinthe.Type.Custom)
● Datetime
● NaiveDatetime
● Date
● Time
● Decimal

GraphQL Types
● Object: bag of ﬁelds (output)
● Input Object: bag of ﬁelds (input)
● Interface: contract for Objects (output only)
● Union: (output only)
● List: 0 to many, homogeneous; ex: [Droid]

GraphQL Types: Nullability
● Integer -- an integer (or null)
● Integer! -- an integer
Output types: err on the side of nullable
Input types: err on the side of non-nullable

GraphQL Types: Nullability & Lists
It can get weird

● Eager
● Fetches data
right away

I want Galactic Record THX1138.
...and record A113.
📕 Here it is!
...also XF178-9.
📗 Here it is!
📘 Here it is!
...and THX1138. 📕 Got it again!!1

● Eager
● Fetches data
right away
Oh dear!
● Naive
● Ineﬃcient

● Lazy
● Works smart, not
hard

I want Galactic Record THX1138.
...and record A113.
...also XF178-9.
...and THX1138.
TODO
THX1138
A113
XF178-9
OK, I’m done.
Beep Boop
Whistle
📕📗📘
⁈
High ﬁve!
...

● Lazy
● Works smart, not
hard
● Eﬃcient
● Dataloader

Dataloader
● Originally implemented by Facebook (JS)
● Absinthe team maintains Elixir version
● Batches requests
● Caches results
● Reduces fetches to data store

Elixir + GraphQL = Absinthe 2019.04.10

Topics I didn’t get to tonight
● Middleware and Authentication
● Serving REST via GraphQL (Absinthe.Phoenix.Controller)
● Mutation design
● Schema stitching

Additional reading / viewing
● Marc-André Giroux on Medium -- all of it!
○ GraphQL Mutation Design: Anemic Mutations
○ Backend For Frontends, Optimized Server Adapters, and GraphQL
○ Where we Come From: An Honest Introduction to GraphQL
● Caleb Meredith on Medium
○ When To Use GraphQL Non-Null Fields
○ Designing GraphQL Mutations
● Principled GraphQL, Apollo
● GraphQL Summit 2018, YouTube
○ GraphQL Schema Design @ Scale (Marc-André Giroux)
○ Shipping 'Belonging' with GraphQL & Apollo at Airbnb (Adam Neary)

Thank you!
Alex Knowles
Twitter: @a_lixer
GitHub: alex-knowlesStar Wars Schema in Absinthe
https://github.com/alex-knowles/starwars_graphql_absinthe

Elixir + GraphQL = Absinthe 2019.04.10

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Elixir + GraphQL = Absinthe 2019.04.10