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The Power of Conversation
aircall.io
Our ongoing journey
from REST to GraphQL
on Android
Julien Salvi - Android GDE | Android @ Aircall
droidcon London 2023
@JulienSalvi
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Bonjour !
Julien Salvi
Lead Android Engineer @
Android GDE
“Android dev in shorts!”
@JulienSalvi
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Intro & context
GraphQL and Apollo Kotlin
REX: GraphQL migration
Conclusion & Resources
Summary
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Introduction
and context
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“
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What’s
GraphQL?
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Efficient data retrieval
What’s GraphQL?
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Single endpoint
simplicity
Strong typing and
introspection
GraphQL optimizes data
fetching by allowing clients to
specify their exact data
requirements, eliminating
over-fetching and
under-fetching.
GraphQL simplifies
client-server interactions by
using a single endpoint,
reducing round trips and
streamlining communication.
GraphQL strong typing system
ensures clarity in data
exchange. Introspection
capabilities enable powerful
tools and automatic API
documentation.
“GraphQL is an open-source query language and runtime that provides an efficient and flexible approach
to data fetching and manipulation. It was developed by Facebook and later open-sourced”
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“
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Why GraphQL
at Aircall?
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Why REST to GraphQL?
Efficiency and data aggregation
The need for efficient microservice
communication and a data aggregator
point.
Scaling of REST API
Wanted to break the REST API into
microservices. It was not modular enough
and has scaling issues.
Minimum disruption
Due to Internal usage of our REST APIs, we
pushed us to take advantage of Graphql
with minimum disruption to our
customers.
Serverless alternative
Desire to create a serverless alternative
API from the existing monolith REST
interface.
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Key points for GraphQL
Data aggregation
Clients can fetch multiple resources in a
single request, reducing the number of
network round trips.
Efficient data loading
GraphQL allows clients to request only the
data they need, minimizing over-fetching
and under-fetching.
Strong typing
GraphQL's type system ensures clear
communication between clients and
servers, reducing errors and providing
reliable data validation.
Federated GraphQL APIs
Enables independent development,
deployment, and scaling of individual
services, resulting in improved
maintainability and scalability of the system.
Real time communication
GraphQL provide a way to establish a
persistent connection between the client
and the server, enabling efficient and
scalable real-time updates without the
need for constant polling.
Reduced latency
GraphQL supports batching multiple
requests into a single round trip, reducing
network latency and improving overall
performance.
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How we use
GraphQL?
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The tech under the hood
● Our infra relies a lot on AWS so our GraphQL backend teams went for
AppSync.
● AppSync offers many capabilities like filtering, real-time or
scalability and has a nice integration with ElasticSearch, DynamoDB
or Cognito.
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The tech under the hood
● On the Android side, we are using the Apollo Kotlin library to
manipulate the GraphQL API.
● offers many advantages:
○ Great interoperability with Kotlin code base (100% Kotlin)
○ Model generation in Kotlin
○ Multiplatform
○ Queries, Mutations and Subscriptions
○ Caching system
○ AppSync and graphql-ws support
○ Awesome community support 💚
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GraphQL API journey
2020 2021 2022 2023
First GraphQL queries
in production
GraphQL API introduction
Monolith transition + GraphQL migration (backend)
Migration of REST endpoints to GraphQL in client
apps
New features with
GraphQL API
GraphQL API in
clients apps
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Now let’s see how we
brought GraphQL to
Android with Apollo 🚀
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GraphQL and
Apollo Kotlin
+
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How to setup
Apollo Kotlin?
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Apollo Kotlin setup
● Let’s see how straightforward is it to setup Apollo Kotlin in your
Android projects.
● Let’s see how to deal with the GraphQL schema (our source of truth).
● Let’s see how to make Queries, Mutations and Subscriptions.
● Let’s see how the Apollo client can coexist with the Retrofit client.
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GraphQL schema
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💡Pro tip IntelliJ
● Take advantage of the GraphQL plugin by Jim Kynde Meyer to have
the autocompletion/deeplink when writing your queries but…
https://plugins.jetbrains.com/plugin/8097-graphql
Add the following graphql.config.yml at the root:
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💡Pro tip IntelliJ
● … There is another one! GraphQL plugin by Apollo 🚀
https://plugins.jetbrains.com/plugin/8097-graphql
Add the following graphql.config.yml at the root:
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Apollo client setup
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GraphQL requests
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Your GraphQL API is
now ready to go in your
Android app 🚀
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REX: GraphQL
migration
🔬
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“
”
Apollo 💚 Kotlin
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Apollo 💚 Kotlin
● Apollo is 100% Kotlin and multiplatform.
● It has a great support for coroutines and Kotlin flows.
● Generates Kotlin code from the schema (data classes for models and
Query/Mutations)
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For Kotlin code gen
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“
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Beware the
timeout
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Beware the timeout
● If your REST API is using a timeout DON’T use the same one for your
GraphQL API.
● Sync with your backend/client teams to identify the best timeout to
pass to your GraphQL client
● If you’re using OkHttp, DON’T reuse the same OkClient for your REST
and GraphQL API.
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Lazy loading
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Lazy loading
● When only a part of your app or a feature (eg. under a feature flag) is
using the GraphQL API, use the lazy loading when injecting your client.
● Dagger/Hilt exposed a Lazy interface to defer the resource loading.
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Monitoring
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https://github.com/ChuckerTeam/chucker
Monitoring
● In your develop or prod env. always monitor your requests.
● Take advantage of the OkHttp Interceptor to monitor queries and
mutation.
● ⚙ Use Chucker tool in dev mode to monitor your requests
● 👀 Check Nicola Corti’s talk about Chucker 4.0 at droidcon Berlin
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Monitoring
demo!
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Nested
queries
Great power comes with great responsibilities 🦸
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Nested queries
● GraphQL offers many capabilities and one of them is the support of
nested queries.
● This is pretty efficient when aggregating multiple data at once.
● ⚠ But the response time might increase a lot. Always monitor!
● 🤝 Sync with your backend teams to find the best solution
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Nested queries
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7-10s query 😱
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Optimized
query 😎
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“
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Subscriptions are cool…
but aren’t easy!
Especially with AppSync 😅
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Subscriptions
● Subscriptions are long-lasting operation which can maintain an open
connection (mainly a WebSocket).
● Data is pushed to the socket and listened on the client side.
● Keeping the connection alive isn’t easy!
● … and things might get a bit more complicated with AppSync 😅
● #SpoilerAlert: We had to build our own AppSyncProtol to better
handle the token refresh.
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How is this exception triggered? 🤔
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Subscriptions
While investigating a socket disconnection issue with Apollo and AppSync subs, we saw an
opened issue on their repository 👀
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Auth has to be
passed in the
webSocket Url
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With this
method only
resetting the
client could do
the trick 😣
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Using a lambda will
help us resetting the
URL without resetting
the client 😃
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Subscriptions
But no ongoing develop for that feature 🥲
So let’s contribute to Apollo Kotlin 🚀
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“
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Error
handling
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Error handling
● Error handling with GraphQL is quite different from a REST API
● Errors can be exposed in the Query/Mutation, be directly accessible
in the ApolloResponse class or an Exception can be thrown 🥲
● ApolloResponse exposed a list of potential errors.
● So multiple source of truth and error parsing…
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Work in
progress 🚧
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With Apollo 4.x
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Schema
automation
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Schema automation
● At some point you will ne need to automate the GraphQL schema
update.
● More development on the backend side, more updates on the client
side.
● When working with multiple flavors this will be highly recommended!
● Let’s see how we managed that with our CI.
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Schema automation
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Schema automation
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Schema automation
● When the CI has passed successfully we can merge it to develop branch.
● If the CI failed, we checkout and fix branch.
● If we can’t fix the update, we cancel the MR and sync with the backend
teams.
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Multiple flavors
● When you have multiple flavors (eg. staging/prod or white labels…),
you may have multiple schemas to maintain.
● This will lead to multiple updates and potentially be more error-prone .
● ⚠ More maintenance when dealing with multiple flavors.
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“
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Apollo issue?
Apollo community
💚💪
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Apollo Community 💚
● The community around Apollo GraphQL is amazing!
● Apollo Kotlin is an open-source project .
● Maintainers are very active and very helpful when you have a
question or an issue.
● Open an issue on GitHub or ask a question in the Kotlin slack 🚀
● Many good features to come with Apollo 4.0.0 🤩
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Conclusion
and Resources
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Key takeaways
Why it was the right move
● Apollo Kotlin 🚀
● Easy integration
● Coroutine/Flow support
● Strong typing and contract
with the API
● Combined queries
● Apollo community 💚
● Apollo maintainers 💚
Areas to watch
● Collaborate/speak with your
backend teams.
● Error handling.
● Subscriptions aren’t always
reliable.
● Apollo AppSync support.
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GraphQL documentation https://graphql.org/
Apollo Kotlin https://www.apollographql.com/docs/kotlin/
Apollo Kotlin repository https://github.com/apollographql/apollo-kotlin
Apollo GraphQL Summit
videos
https://www.apollographql.com/events/virtual-event/graphql-summit/
AWS AppSync https://aws.amazon.com/appsync/
AppSync Android SDK https://docs.amplify.aws/sdk/api/graphql/q/platform/android/
https://github.com/awslabs/aws-mobile-appsync-sdk-android
Resources
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Thank you!
Have fun with GraphQL 😃
Julien Salvi - Android GDE | Android @ Aircall
droidcon London 2023
@JulienSalvi