Thinking in GraphsGraphQL problems and more

Maciej Rybaniec

Plan

1) GraphQL

2) Problemy związane z GraphQL

3) Nowe narzędzia

4) Relay Modern

GraphQL

GraphQL misconceptions

NOT library or storage system

NOT tied with specific language

NOT tied with specific framework

NOT required specific storage system

How it works ?

GraphQL Schema

What I can fetch ?

Client

Back-end Databases, APIs, Services

MongoDB Redis Facebook API

Sposób komunikacji z API

Podstawowe cele

No Overfetching

Be Declarative

Product Development

Autonomy

Versioning Support

Podstawoweoperacje

Queries

Query Response

Allows to fetch data in a declarative way

QueryA GraphQL query is just an instruction for traversing the graph in a specific way, resulting in a tree.

Mutations

Mutation Response

Allows to mutate data in server and fetch new state after change

Problemy

Best practices

Single endpoint

Authorization

Obsługa dostępu w przypadku

zagnieżdżonych relacji

Error handling

Obsługa błędów w przypadku gdy

zapytania mogą być złożone

REST

HTTP Request

Warstwa danych

Middleware

Route Controller

Użytkownik

GraphQLNo middleware and afterware

Resolvers – responsible for handling portions of a request

Resolvers

Sample field resolver

Deliver data based on contract

Can contain arbitrary code

Problem definition

Handle permissions on edges.

Basic Solution

Multiple edges can lead to a particular node

Permissions on edges

Authorization logic in nodes – one function per node.

1) Called by every resolve function of a field that leads to a node of specific type.

2) Called in every field on the specific type before returning anything.

Permissions on nodes

Delegate authorization logic to the business logic layer

Facebook Solution

Sample authorization

Bad practice

Single source of truthBusiness logic layer should act as the single source

of truth for enforcing business domain rules.

1) Move authorization responsibility toresolvers.

2) Client can understand errors without proper status code.

3) Masked Internal errors.

4) DRY

Apollo Solution

Abstract Resolvers

Base root resolver

Chain of resolvers to satisfy individual parts of the overall problem

Abstract Resolvers

Auth Resolver

HTTP Request

Base Resolver

GraphQL Server

Remove User Mutation Resolver

User Query Resolver

getUserByIdremoveUserById

is allowed

pass through

handleerror

handleerror

Base Resolver

Auth Resolver

SubscriptionsLive Queries vs Event-based vs Polling

Real-time APIs

Pull:- Polling

Push:- Live Queries- Subscriptions

GraphQL SubscriptionsClients send the server a GraphQL query and query variables. The server maps these inputs to an event stream and executes the query when the events trigger.

PollingPeriodically issues a request to check on the state of the data it cares about.

When updates are infrequent/unpredictable, polling is wasteful.

1 2 3 4

1 3 4 4

client value over time

server value

Live Queries

Query Fragment

Subscribe to a query, and push update every time the result of that query changes.

Too much events – causing push

1 2 3 4

client value over time

server value

1 2 3 4

Event-based subscriptionsClient tells the server that it cares about one or more events. Whenever those events trigger, the server notifies the client.

2 3

client value over time

server value

2 3

1

Kontrakt

Minimum

Fixed

GraphQL Subscription

Optymalizacja

Optymalizacja

Sample resolver

Resolving lists or complicated structures

Expensive Queries

Facebook DataLoaderWithout a caching or batching mechanism, it's easy for a naive GraphQL server to issue new database requests each time a field is resolved.

Example

Batch Operations

Defer query part

Stream query field

Nowe narzędzia

Sample lodash directives

Allows to modify response shape by providing lodash methods.

Introspection Query

GraphQL VoyagerRepresent any GraphQL API as an interactive graph

Relay Modern

Relay Modern

New things

New version of Relay designed from the ground up to be easier to use

Garbage CollectionRelay EnviromentFlow Type GenerationSubscriptions & Live QueriesRelay Compiler

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