Api Builder - Scala Up North 2017

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Sean Sullivan July 21, 2017 Scala Up North

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• software engineer • 21 years on the JVM • back ofﬁce systems @ HBC About me

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https://en.wikipedia.org/wiki/Hudson%27s_Bay_Company

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saksﬁfthavenue.com saksoff5th.com lordandtaylor.com gilt.com thebay.com

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API driven development

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API descriptors

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API descriptors are not a new concept

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• 2000: WSDL 1.0 (SOAP) • 2006: WADL (REST) • 2011: Swagger (REST) • 2014: ApiDoc (REST) • 2017: ApiDoc rebranded to ApiBuilder

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www.apibuilder.io

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describe REST API in a JSON ﬁle

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1. start by describing your models 2. map your models to resources

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"models": { "credit_card": { "fields": [ { "name": "guid", "type": "uuid" }, { "name": "user_guid", "type": "uuid" }, { "name": "type", "type": "credit_card_type" }, { "name": "issuer", "type": “string", “required": false }, { "name": "last_four", "type": "string" }, { "name": "expire_date", "type": "string" }, { "name": "billing_address", "type": "address" } ] } }

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"resources": { "credit_card": { "operations": [ { "method": "GET", "path": "/:guid", "description": "Get a credit card.", "responses": { "200": { "type": "credit_card" }, "404": { "type": “unit”, "description": "Card not found." } } } }

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gilt.com

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www.gilt.com

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• Rails app • one Git repo • monolith! Gilt: 2007 => 2008

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• Rails app • JSP web framework • ~10 services (Java) • handcrafted Java clients • weak typing (java.util.HashMap) Gilt: 2009 => 2010

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• JSP’s • 100+ services (Java, Scala) • strongly typed client libraries • Gilt “Commons” library Gilt: 2011 => 2013

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• Gilt Commons library • 250+ services • binary coupling • dependency hell • ApiBuilder project started on Github Gilt: 2014

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Dependency hell Java runtime hell

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• java.lang.NoClassDefFoundError • java.lang.NoSuchFieldError • java.lang.NoSuchMethodError Java runtime hell

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Dependency hell kills productivity

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Mitigating dependency hell • API design must be ﬁrst class • backwards and forward compatibility • accurate documentation • generated client libraries

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• 350+ services • new services built with ApiBuilder + generated clients • Gilt Commons library is deprecated Gilt: 2015 => 2017

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Web Checkout Android Checkout iPhone Checkout Checkout service api.json

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Generating client libraries with ApiBuilder

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Code generators

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Scala client generators • Http4s + Circe JSON • Ning AsyncHttpClient {1.8, 1.9} • Play WS {2.2, 2.3, 2.4, 2.5, 2.6}

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