schema • Client-side and server-side implement according it • Integration test • Without Schema first development, 
 we can’t start client-side implement until server side implement finished Reference: RubyKaigi 2017 API Development in 2017 https://www.youtube.com/watch?v=a28jJ62ZfZM Rails Developers Meetup 2019: 
 https://speakerdeck.com/aeroastro/rails-meets-protocol-buffers-for-schema-first-development

rule • Actual processing is just REST API • OpenAPI 3 takes full advantage of existing RESTful frameworks and insights • Since REST is a web best practice at the time, various mechanisms such as HTTP cache, monitoring system can also be used

3.0.0 info: title: Sample API version: 0.1.0 paths: "/apps": get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string

application/json openapi: 3.0.0 info: title: Sample API version: 0.1.0 paths: "/apps": get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string

application/json • `page` parameter required and it’s integer openapi: 3.0.0 info: title: Sample API version: 0.1.0 paths: "/apps": get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string

application/json • `page` parameter required and it’s integer • Succeed response includes string array openapi: 3.0.0 info: title: Sample API version: 0.1.0 paths: "/apps": get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string

application/json • `page` parameter required and it’s integer • Succeed response includes string array openapi: 3.0.0 info: title: Sample API version: 0.1.0 paths: "/apps": get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string

get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string Paths Object • API definitions are written in this section • There is path string key and 
 Path Item Object • We can write definition in Path Item Object Path string Path Item Object

method • We can define request parameter openapi: 3.0.0 info: title: Sample API version: 0.1.0 paths: "/apps": get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string

method • We can define request parameter and 
 response parameter schema openapi: 3.0.0 info: title: Sample API version: 0.1.0 paths: "/apps": get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string

all API or specific API • We can use HTTP authentication, API key (like header, query), 
 OAuth2, OpenID Connect type: http scheme: basic type: apiKey name: api_key in: header type: http scheme: bearer bearerFormat: JWT JWT API key basic type: oauth2 flows: implicit: authorizationUrl: https://example.co... scopes: write:pets: modify pets read:pets: read your pets OAuth2

parameters page not exist in #/paths/~1apps/get”} % curl -X GET "http://localhost:4567/apps?page=1" ["1","10"] When `page` parameter exists, get correct response require "sinatra" require "committee" use Committee::Middleware::RequestValidation, schema_path: 'schema.yaml' use Committee::Middleware::ResponseValidation, schema_path: 'schema.yaml' get "/apps" do content_type :json # page should be Integer page = params["page"].to_i [page, (page*10)].map(&:to_s).to_json end

committee converts class using definition type (optional feature) require "sinatra" require "committee" use Committee::Middleware::RequestValidation, schema_path: 'schema.yaml' use Committee::Middleware::ResponseValidation, schema_path: 'schema.yaml' get "/apps" do content_type :json # page should be Integer page = params["page"] [page, (page*10)].map(&:to_s).to_json end

-H "Content-Type: application/json" -d '{"measured_at":"2016-04-01T16:00:00+09:00"}' “http://localhost:4567/apps" {"class":"DateTime"} post: requestBody: content: application/json: schema: type: object properties: measured_at: type: string format: date-time responses: '201': description: no content content: 'application/json': schema: type: object properties: class: type: string • committee coerce parameter in request body • When string in date-time format, 
 committee converts it to DateTime class

do get '/apps?page=1' assert_schema_conform end end % bundle exec ruby committee_test.rb Run options: --seed 62877 # Running: E Finished in 0.023367s, 42.7954 runs/s, 0.0000 assertions/s. 1) Error: Committee::Middleware::Stub::GET /apps#test_0001_conforms to schema: Committee::InvalidResponse: don't exist status code definition in #/paths/~1apps/get/responses • committee provides response format checker for test • When there’re difference, test will fail

many object openapi: 3.0.0 info: title: Sample API version: 0.1.0 paths: "/apps": get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string

many object • Definition is YAML/JSON file so 
 ruby loads it as Hash objects • openapi: 3.0.0 info: title: Sample API version: 0.1.0 paths: "/apps": get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string

to Ruby object using DSL • I implemented few methods to these classes module OpenAPIParser::Schemas class Parameter < Base openapi_attr_values :name, :in, :description, :req openapi_attr_value :allow_empty_value, schema_key: openapi_attr_value :allow_reserved, schema_key: :a def validate_params(params, options)

get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string • Schema is defined separately for each HTTP method in Path Item Object Find schema from URL Path Item Object Path string

get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string • Schema is defined separately for each HTTP method in Path Item Object Find schema from URL Path Item Object

get: parameters: - name: page in: query required: true schema: type: integer responses: '200': description: example content: 'application/json': schema: type: array items: type: string • Schema is defined separately for each HTTP method in Path Item Object • So we should find Path Item Object from requested URL Find schema from URL Path Item Object Path string

"/pets/0": … Requested path Definition path /pets/mine -> "/pets/mine" /pets/1 -> "/pets/{petId}" /pets/2 -> "/pets/{petId}" /pets/0 -> "/pets/0" 
 /pets/1/food -> "/pets/{petId}/food" /pets/0/food -> "/pets/0/food/" • If there are both with and without parameters, the one without parameters takes precedence

"/pets/0": … Requested path Definition path /pets/mine -> "/pets/mine" /pets/1 -> "/pets/{petId}" /pets/2 -> "/pets/{petId}" /pets/0 -> "/pets/0" 
 /pets/1/food -> "/pets/{petId}/food" /pets/0/food -> "/pets/0/food/" • If there are both with and without parameters, the one without parameters takes precedence • So we should find Path Item Object according this rule

node from root • If there isn’t matched node, 
 use parameter node (OpenAPI 3 definition) Find defined path from patricia tree {id} users meals me steps lunch /users/meals/42/lunch public root

node from root • If there isn’t matched node, 
 use parameter node (OpenAPI 3 definition) Find defined path from patricia tree {id} users meals me steps lunch /users/meals/42/lunch public root

node from root • If there isn’t matched node, 
 use parameter node (OpenAPI 3 definition) Find defined path from patricia tree {id} users meals me steps lunch /users/meals/42/lunch public root

node from root • If there isn’t matched node, 
 use parameter node (OpenAPI 3 definition) Find defined path from patricia tree {id} users meals me steps lunch /users/meals/42/lunch public root

node from root • If there isn’t matched node, 
 use parameter node (OpenAPI 3 definition) Find defined path from patricia tree {id} users meals me steps lunch /users/meals/{id}/lunch public root

node from root • If there isn’t matched node, 
 use parameter node (OpenAPI 3 definition) • Get Path Item Object from matched Find defined path from patricia tree {id} users meals me steps lunch /users/meals/{id}/lunch public root

`properties` which has property name and schema • This type can be mapped to Hash in ruby 
 and property name is represented as hash key Object validation schema: type: object nullable: false properties: nickname: type: string

`properties` which has property name and schema • This type can be mapped to Hash in ruby 
 and property name is represented as hash key Object validation schema: type: object nullable: false properties: nickname: type: string schema.properties.each do |name, child_schema| child_schema.validate(parameter[name]) end

mapped Array • The `array` type has items schema definition • Check all item in array is according to schema Array validation schema: type: array items: type: object required: ... array_parameter.all? do |item| items_schema.validate(item) end

openapi_parser
 and it’s separated from committee # load OpenAPI 3 definition root = OpenAPIParser.parse(YAML.load_file('open_api_3/schema.yml')) # get schema from HTTP method (POST) and path (/validate) op = root.request_operation(:post, '/validate') # validate request body ret = op.validate_request_body('application/json', params)

openapi_parser
 and it’s separated from committee • So if you want to create OpenAPI 3 tool, this gem help for you # load OpenAPI 3 definition root = OpenAPIParser.parse(YAML.load_file('open_api_3/schema.yml')) # get schema from HTTP method (POST) and path (/validate) op = root.request_operation(:post, '/validate') # validate request body ret = op.validate_request_body('application/json', params)

method • If you want to divide by namespace, use tags in OpenAPI 3
 (OpenAPI 3 allow add tag per HTTP method) api_instance = OpenapiClient::DefaultApi.new page = 56 result = api_instance.apps_get(page) users_api = OpenapiClient::UsersApi.new limit = 10 users_api.blogs_get(limit)

objects • OpenAPI Generator convert request / response parameter as method argument and return value and outputs these as YARD style comments with description # get app names by array # @param page specific page setting # @param [Hash] opts the optional parameters # @return [Array<String>] def apps_get(page, opts = {})

definition (.rbi) • And we can generate server side code like Hanami with .rbi class DefaultApi def apps_get: (page: Integer) -> Array<String> end module Web module Controllers module Home class Index include Web::Action def call(params) end end

schema • OpenAPI 3 has various tools • Request/Respones validation • Client library generation • Interactive document • If you want to create new OpenAPI tool, it’s not so difficult

schema • OpenAPI 3 has various tools • Request/Respones validation • Client library generation • Interactive document • If you want to create new OpenAPI tool, it’s not so difficult

schema • OpenAPI 3 has various tools • Request/Respones validation • Client library generation • Interactive document • If you want to create new OpenAPI tool, it’s not so difficult

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use request validator and coerce all value in production • But we don’t use response validator in production, we use staging only • Because if we implement request/response by correct in staging, we don’t need check in production • committee has parameter coercer so we use request validation in production

Small benchmark have 1 query parameter • Big benchmark have 2600 objects • Check enable/disable committee and request 1000 times • I don’t check response validation benchmark because we don’t use it in production • Benchmark script is here
 https://gist.github.com/ota42y/3ed68a2cb0dc7c98122bdfd1a696ab72