Challenge to Advanced API Architecture in Go

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Challenge to Advanced API Architecture in Go Seiji Takahashi (@__timakin__ ) / Gunosy Inc. September 29th, 2017 golang.tokyo#9

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About me • Seiji Takahashi • Github: timakin / Twitter: @__timakin__ • Gunosy Inc. Business Development Team • Go / Swift • Just a little bit contributed to Go.

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Preface • Finding the sample projects of API server, based on maintainable and feature-rich Go code is so hard. • So I’ve tried to write an operable API server with plain and standard packages like   net/http on myself. • This is just the result of my best-effort challenge, and not the collective opinion of Go community.

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Agenda • General problems when you write API server in Go. • Advanced API architecture in Go,  which is adaptable for your production environment. • The introductions of simple & practical   packages you can use in your team tomorrow.

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How do you write API in ɹɹ ɹɹ ʁ

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How do you write API in Go? • Use Frameworks?

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How do you write API in Go? • Use Frameworks? • echo / gin / goji / goa

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How do you write API in Go? • Use Frameworks? • echo / gin / goji / goa • net/http

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How do you write API in Go? • Use Frameworks? • echo / gin / goji / goa • net/http • Use ORMs?

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How do you write API in Go? • Use Frameworks? • echo / gin / goji / goa • net/http • Use ORMs? • gorm / xorm / gorp / dbr

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How do you write API in Go? • Use Frameworks? • echo / gin / goji / goa • net/http • Use ORMs? • gorm / xorm / gorp / dbr • database/sql

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How do you write API in Go? • Use Frameworks? • echo / gin / goji / goa • net/http • Use ORMs? • gorm / xorm / gorp / dbr • database/sql • Which platform?

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How do you write API in Go? • Use Frameworks? • echo / gin / goji / goa • net/http • Use ORMs? • gorm / xorm / gorp / dbr • database/sql • Which platform? • AWS / GCP

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General problems when you write API server in Go • It’s easy to encounter circular import.

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General problems when you write API server in Go • It’s easy to encounter circular import. • context.Context handling

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General problems when you write API server in Go • It’s easy to encounter circular import. • context.Context handling • error handling

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General problems when you write API server in Go • It’s easy to encounter circular import. • context.Context handling • error handling • Passing middleware objects without context.Context pollution • Mature Go hackers say “your shouldn’t use a framework. Just use net/http.”, however, it sounds there are too much stuff to do.

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Any good sample?

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Inspirations from goddd • marcusolsson/goddd

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Inspirations from goddd • marcusolsson/goddd • Well-capsuled repository with Interface

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Inspirations from goddd • marcusolsson/goddd • Well-capsuled repository with Interface • encoder / decoder for req / res payload.

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Inspirations from goddd • marcusolsson/goddd • Well-capsuled repository with Interface • encoder / decoder for req / res payload. • DDD-based architecture enables you to easily avoid a circular import.

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How to write API inspired by goddd with   plain packages?

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Background • I wrote the sample project: “govod”. • Sorry, it’s a closed project because it includes some secrets.ʕ>ϖ<ʔ • Go video on demand API. • Deploy to Google App Engine • Features (≒ domains) • Authentication • Streaming

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ex) /api/videos with paging interface

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Directory tree Isolate main.go to app directory with   app.yaml (GAE conﬁg) to   avoid the go-app-builder error.

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Directory tree `domain` and `repository` are main directories that have the business logics and data accessors. `middleware` has the http.Handler implementations.  

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Inside of domain - Payload en/decoder - Error types - DI object - Business Logic - Interface of Repository - Routing - Paging token parset - etc…

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Initializes the router with `gorilla/mux`

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Combine middlewares for the simple declaration of http.Handler with `justinas/alice`. You can get stats with kicking the endpoint   “/api/stats” (`fukata/golang-stats-api-handler`)

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Initialize repository, service (business logic), and dependency injector for HTTP Handler.

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Declare the dependency injected to the custom handler. (If it’s not GAE `Dependency` may have `Logger`, or other middlewares…) Handler with DI enables you to handle middleware   without setting them in context.Context.  

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Registration of the routings with CustomHandler and DI object.

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Request handler with payload decoder/encoder. Decoder contains the validator. (`go-playground/validator.v9`) Response payload will be wrapped   with `unrolled/render`. It may results to return the error object given a detail context with `pkg/errors`

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Paging token parser which returns pager cursor required by Datastore.

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Call StreamingService with context and paging opts, and if it succeeded, return the encoded payload.

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GetVideoCollection will return 1. videos 2. JWT which contains a pager cursor. 3. error JWT is generated by using `dgrijalva/jwt-go`

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Access to data storage, with repository   which implements GetVideos.

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Repository is an Interface. It hides which data adapter you depend on. This means you can deﬁne MockRepository and replace to them in test code.

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Access to Datastore on Google Cloud Platform. (with `mjibson/goon`) You can switch the adapter to the clients of MySQL, Postgres, or in-memory database etc…

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Conclusion • DDD-like architecture is good for Go API development. You can cleverly escape from hell of circular imports. • Repository Interface makes the way to access data pluggable. • In combination with some packages,   net/http is surely enough to implement API server. (But there are few samples so it looks hard at ﬁrst.)

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Thanks! • Questions? Come talk to me or   contact to the following accounts! • @__timakin__ • [email protected]