Go Backends for frontends with GraphQL and gRPC

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Go Backends for Frontends with and @__timakin__

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Seiji Takahashi Software Engineer Gunosy Inc. Tokyo, Japan.

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BFF

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Backends For Frontends

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BFF (Web) BFF (Native) User Micro Service Article Micro Service Payment Micro Service Access Controled Web Browser iOS/Android

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Pros of BFF ● Each microservices can focus on only their own responsibility. ● Customize networking protocol for each clients. ● Flexibly change the response ﬁelds.

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BFF Use-cases 1. API Aggregation 2. Session Management 3. SSR 4. File Upload 5. WebSocket

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BFF Use-cases 1. API Aggregation BFF User Micro Service Article Micro Service Comment Micro Service Client Concat every JSON Object from internal APIs Send requests to several services concurrently Request an article entity

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BFF Use-cases 2. Session Management BFF User Micro Service Article Micro Service Comment Micro Service Client Send requests with token Get data from session store Send session_id Session Store

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Page request BFF Use-cases 3. SSR BFF User Micro Service Article Micro Service Comment Micro Service Client Concat every JSON and pass them to HTML renderer Data fetching

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Chunked file upload BFF Use-cases 4. File Upload BFF External File Storage Internal API Client Send a request with filePath Store file

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Connect with WS BFF Use-cases 5. WebSocket/Polling BFF Message Queue Internal API Client Pub/Sub

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Micro Service Today’s CaseStudy BFF Micro Service Micro Service Web Client

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● When they talk about BFF… ○ JavaScript(Node) is popular in most of the cases. ○ Because it eases the communication between frontend & backend engineers. BFF in Go

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● Why Go? ○ If you are a backend engineer, Go BFF will be a good choice from the aspect of performance. ○ With goroutine, Go would handle the concurrent internal accesses rapidly. ■ If you threw away REST and changed into RPC-call, you must send request multiple servers everytime. ■ This means internal latency is critical for UX. ○ Awesome packages for both of GraphQL and gRPC exist in Go community. BFF in Go

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GraphQL

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● GraphQL is a simple query language for API which has the type system. ● Instead of JSON request in like REST API or JSON-RPC, you will send `query` to GraphQL server. ● Implementation in JavaScript is the most active. GraphQL introduction

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Client

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GraphQL vs gRPC ● Generally, GraphQL is hotter than gRPC. ● In a lot of countries GraphQL wins. ● However, in East Asia(especially in China), gRPC has more fans.

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● Client-side-related words like `apollo`, `react`. ● `github` is ranked in the top 10. Related words of each protocols ● Server-side languages like `java` , `goland`, `python` and the format `protobuf`.

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● In-browser playground to explore GraphQL calls. GraphiQL

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● Packages ○ graphql-go/graphql ○ graphql-go/relay ○ samsarahq/thunder ○ 99designs/gqlgen GraphQL in Go

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● Packages ○ graphql-go/graphql ○ graphql-go/relay ○ samsarahq/thunder ○ 99designs/gqlgen GraphQL in Go

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● github.com/99designs/gqlgen ○ Active development ○ Type-Safe ○ Schema Driven ○ Custom middleware appendable GraphQL in Go

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● github.com/99designs/gqlgen ○ Active development ○ Type-Safe ○ Schema Driven ○ Custom middleware appendable GraphQL in Go

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● github.com/99designs/gqlgen-contrib ○ package of middlewares for performance tracing ■ apollo-tracing ■ opencensus ● datadog ■ opentracing ■ prometheus GraphQL in Go

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GraphQL in Go ● Other packages ○ Cannot share schema with frontend ○ Reﬂection based schema ■ A negative effect to latency

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schema.graphql Prepare schemas Instead of auto-generated code, you can use deﬁned structs. gqlgen.yml

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$ gqlgen Code generate

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The implementation inside functions are not automatically generated. Write your own code. grpc client

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When you test GraphQL ● Integration test with input & golden ﬁles. ○ Record a real request and response ○ Mock or temporarily boot internal API ○ Iterate recorded ﬁles and check the equality with the actual responses

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gRPC

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● HTTP/2 networking ● Protobuf serialization ○ template code generation ● Go is one of the most active languages for gRPC implementation. ● Number of Github stars ○ Go > Java > Node > Swift > PHP > Haskell

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● github.com/golang/protobuf/proto ● github.com/golang/protobuf/protoc-gen-go ● google.golang.org/grpc Required packages ● github.com/ktr0731/evans ● github.com/uber/prototool Optional tools

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blog.proto Schema

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uber/prototool strictly checks and formats *.proto Linter

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Linter Deﬁne the rules on prototool.yaml Run commands

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Code Generation github.com/golang/protobuf/protoc-gen-go

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Client

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Client send a request to internal gRPC API

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Server

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Server

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Server Call the logic implemented by yourself e.g. DB access, external API-call

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After implementation ktr0731/evans helps you to explore your gRPC server locally

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Conclusion ● Go is one of the best candidate language for BFF. ● GraphQL + gRPC will empower you with schema-driven-development and low-latency protocol.

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Thank you for listening