Building Resilient API Clients

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Building!Resilient!API!Clients !KyleFuller

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Building!Resilient!API!Clients

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How$does$it$work?

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GET /questions

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DELETE /questions/{id}

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GET /questions/{id}

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POST /questions/{id}/choices/{choice_id}

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POST /questions

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Applica'on*was*built*from*an*out3 of3band*speciﬁca'on

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Tight&Coupling

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We#want#to#change#something.

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/v1

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/v2

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Move%Fast%and%Break&Things

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Move%Fast%and%Break%Things

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"Each&version&will&remain&for&at&least& 2&years&from&release."

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Eventually*have*to*switch

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API$Team$maintains$legacy$API

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Move%Fast%and%Break&Nothing

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REST

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What%is%REST?

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“An$cipa$ng*change*is*one*of*the* central*themes*of*REST”

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REST%is%not... • CRUD • Pre)y+URLs • JSON • HTTP+"Verbs" • Rou9ng

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It’s%not%about%exposing%your% database%via%an%API

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These%are%implementa)on%details

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Representa)onal,State,Transfer

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Transfer(State(from(Server(to(Client?

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Ques%on(Resource

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HATEOAS

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Hypermedia*as*the*Engine*of* Applica6on*State

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Ques%ons • create • list

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Ques%on • delete • choices

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Choice • vote

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Teaching)the)client)the)seman.c) meaning)of)the)domain

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Without'knowledge'about'the' implementa3on'details

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Root questions

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Ques%on delete

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Choice vote

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Ques%on create • ques&on • choices

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Why$are$we$not$doing$this?

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Hyperdrive

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One$Does$Not$Simply$Use$JSON

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HAL$+$Siren

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HAL Hypertext(Applica.on(Language

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HAL { "_links": { "self": { "self": "/questions/1" } } }

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HAL { "_embedded": { "choices": [ { "_links": { "self": { "self": "/questions/1/choices/1" } }, "choice": "Swift", "votes": 2048 } ] } }

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Siren { "actions": [ { "name": "vote", "href": "/questions/1/choices/3", "method": "POST" } ] }

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Siren { "actions": [ { "name": "create", "fields": [ { "name": "question", "type": "text", "title": "Question" }, { "name": "choices", "type": "array[text]", "title": "Choices" } ], "method": "POST", "type": "application/json", "href": "/questions" } ] }

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API$Blueprint$+$Hyperdrive

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apiblueprint.org

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hyperdrive.enter("https://polls.apiblueprint.org/") { result }

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representor

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representor • a#ributes • transi,ons

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representor • a#ributes • transi,ons • representors

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if let questions = representor.transitions["questions"] { }

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hyperdrive.request(questions) { result in }

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if let questions = representor.representors["questions"] { map(questions, viewQuestion) }

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} else { println("Looks like there are no questions yet.") }

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func viewQuestion(question:Representor) { println(question.attributes["question"]) if let choices = question.representors["choices"] { map(choices, viewChoice) } else { println("-> This question does not have any choices.") } if let delete = question.transitions["delete"] { // User may delete this question } }

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func viewChoice(choice:Representor) { let text = choice.attributes["choice"] let votes = choice.attributes["votes"] println('-> \(text) (\(votes))') if let vote = choice.transitions["vote"] { // User may vote on this choice } }

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hyperdrive.request(vote)

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if let create = questions.transitions["create"] { // We may create a new question for attribute in create.attributes { // Creation takes `attribute.name` } } else { // Gracefully handle the lack of being able to create a question }

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Why?

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Change'business'rules

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Remove&transi-ons

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Add#transi*ons

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Coupling

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TaaS Toaster(as(a(Service

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Toaster(Applica.on

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Demo

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How$does$API$Blueprint$work?

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## Questions Collection [/questions] ### List All Questions [GET] + Relation: questions + Response 200 (application/json) + Attributes (array[Question])

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### Create a New Question [POST] + Relation: create + Request (application/json) + Attributes + question (string, required) - The question + choices (array[string]) - A collection of choices. + Response 201 (application/json) + Attributes (Question)

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## Question [/questions/{question_id}] + Attributes + question: `Favourite programming language?` (string, required) + published_at: `2014-11-11T08:40:51.620Z` (string) - An ISO8601 date when the question was published + choices (array[Choice], required) - An array of Choice objects

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{ "id": 1, "question": "Favourite programming language?", "choices": [ { "id": 1, "choice": "Swift", "votes": 128 }, { "id": 2, "choice": "Objective-C", "votes": 2 } ] }

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### Delete a Question [DELETE] + Relation: delete + Response 204

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## Choice [/questions/{question_id}/choices/{choice_id}] + Attributes + choice: Swift (string, required) + votes: 0 (number, required)

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### Vote on a Choice [POST] This action allows you to vote on a question's choice. + Relation: vote + Response 201

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Conclusion • Move&Faster • Write&Less&Code • Don't&Break&Things • Embrace&Change

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Move%Fast,%Break%Nothing

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the$hypermedia$project!/!Hyperdrive the$hypermedia$project!/!representor*swi- !apiaryio!/!polls'app apiaryio!/!polls'api