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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
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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]