A quest for simplicity - Speaker Deck

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Arnaud Lauret @apihandyman A quest for simplicity AXA Banque From depths of IS to heights of API

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One does not simply start a quest without a goal The events depicted in this talk are fictitious. Any similarity to any information system living or dead is merely coincidental.

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What is your quest?

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What is your favorite word in API?

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Application?

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Programming?

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Interface?

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Interface!

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The place at which independent and often unrelated systems meet and interact with each other

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Photos of interface with my hands

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What have they in common?

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People (Even APIs)

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API = UI for people building programs

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What’s happening behind an interface? The microwave oven parable

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Abstraction A picture is worth a thousand words

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What do we seek when using an interface (especially an API) ?

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Simplicity

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Easy to use

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Easy to understand Error 1543 Missing email

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Adapted to the targeted audience

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So, what is our quest?

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Simplify

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Core Banking System A long time ago...

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This is an interface

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Access

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IVR

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Interactive Voice Response CBS Database CBS Non CBS Database IVR ZBAL0 ZBALV ZBALA ZBALY

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FWW

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Minitel CBS Database CBS Non CBS Database IVR MIN MQ Message: F1202167754151912540123777463779FRF0300020160917

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Is interfacing with CBS simple? ● Is it easy to use? ● It it easy to understand? ● Is the abstraction adapted to the audience?

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So, it’s not simple

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A few years laters... Web services

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This is a dinosaur

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At that time... CBS Database CBS Non CBS Database IVR MIN WEB

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SOA(P)

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SOA Principles ● Service ● Loose coupling ● Reusability

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SOAP Protocol ● Use HTTP as a transport protocol ● XML based ● Input message contains the action to trigger and the data

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Service or you’re ired!

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SOA(P) CBS Database CBS Non CBS Database MIN IVR WEB SOAP services

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Several years later

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SOA(P) CBS Database CBS Non CBS Database IVR WEB JBOWS IVR WEB

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Is interfacing with SOA simple? ● Is it easy to use? ● It it easy to understand? ● Is the abstraction adapted to the audience?

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Better but not awesome...

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A few years ago ... APIs

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Mobile

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Middleware IVR WEB SOAP services MMW

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ROAST

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ROAST API recipe 1. Take a SOAP/XML web service name add a / before it 2. Choose randomly an HTTP method between GET, PUT, POST, PATCH or DELETE, put it before the / 3. Transform input/output data from XML to JSON 4. If the method is GET or DELETE, put all parameters in query variables 5. And be sure to always return HTTP status 200

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The mobile team discovering GET /cancelTrfr?ztr1={id}

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Several years later

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Seriously

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A REST API

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Design First

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Use resource instead of actions

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A list of wire transfers /transfers

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A wire transfers /transfers/{transferId}

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Use relevant HTTP method

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Create a transfer POST /transfers

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Delete a pending wire transfer DELETE /transfers/{transferId}

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Update a customer email PATCH /customers/me

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Update a customer phone number PATCH /customers/me

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Use relevant HTTP status

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403 Not enough money

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503 No transfer between 1 am and 2 am

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Provide hypermedia controls

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GET /accounts/C1 { “id”: “C1”, “balance”: , “actions”: [ { “name”: “transfer”, “method”: “POST”, “href”: “https://bank.com/transfers”} ] }

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Different ways to fill the set of actions

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#1 Takeshi’s Castle Knock Knock

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403 Forbidden { “code”: 1012, “message”: “Insufficient balance.” }

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503 Service unavailable { “code”: 1214, “message”: “No transfer between 1am and 2am.” }

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#2 This is bowling. There are rules.

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GET /accounts/C1 { “id”: “C1”, “balance”: -200, “actions”: [ ] }

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GET /accounts/C1 { “id”: “C1”, “balance”: 20000, “actions”: [ ] }

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#3 The Dude abides.

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GET /accounts/C1 { “id”: “C1”, “balance”: -200, “actions”: [ { “name”: “transfer”, “status”: 403, “error”: { “code”: 1012, “message”: “Insufficient balance.”} } ] }

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GET /accounts/C1 { “id”: “C1”, “balance”: 20000, “actions”: [ { “name”: “transfer”, “status”: 503, “error”: { “code”: 1214, “message”: “No transfer between 1am and 2am.”} } ] }

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It it really so simple to design an API?

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Is interfacing with a RESTful API simple? ● Is it easy to use? ● It it easy to understand? ● Is the abstraction adapted to the audience?