Migration microservices to GraphQL
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This document discusses migrating a REST API to a GraphQL API. It covers some of the benefits of GraphQL like getting exactly what is needed from the client side, having a rich type system, and being transport agnostic. It provides examples of defining GraphQL types based on a JSON schema and making requests using those types. It also mentions some tools that can help with building and debugging a GraphQL API as well as some precautions to keep in mind during development.
![Resources
PUT/PATCH /users/1
{name: "Homer2"}
{
"name": "Homer",
"children": [
{
"name": "Bart",
},
{
"name": "Lisa"
}
]
}](https://image.slidesharecdn.com/graphql-161013144333/85/Migration-microservices-to-GraphQL-8-320.jpg)
!["/users/findByName": {
"get": {
"description": "Multiple status values can be provided with
comma separated strings",
"operationId": "findUsersByStatus",
"produces": ["application/xml", "application/json"],
"parameters": [{
"name": "name",
"in": "query",
"description": "User name",
"required": true,
"type": "array",
"items": {"type": "string"},
}],
"responses": {
"200": {
"description": "successful operation",
"schema": {"type": "array", "items": {"$ref":
"#/definitions/User"}}
}, "400": {"description": "Invalid status value"}
},
"security": [{"store_auth": ["read:users"]}]](https://image.slidesharecdn.com/graphql-161013144333/85/Migration-microservices-to-GraphQL-18-320.jpg)
Migration microservices to GraphQL
- 2. API
- 3. function getUser(name: string): User { return db.getUserByName(name); } Typed request argumentes Type of response
- 4. RPC (1960s, CORBA, XML, JSON, Thrift) SOAP (WSDL, XML) REST (HTTP)
- 5. REST + People got sick of SOAP + HTTP 1/1 + Extra simplicity = fast development + Good for CRUD
- 6. Resources POST /users {name: "Homer"} OPTIONS /users Access-Control-Request-Method:POST
- 7. Resources GET /users?name=?? GET /users?name=Homer,Marge GET /users?name=..&limit&offcet GET /users?name&limit&token • 1 nesting level • Characters escaping • 2048 characters
- 8. Resources PUT/PATCH /users/1 {name: "Homer2"} { "name": "Homer", "children": [ { "name": "Bart", }, { "name": "Lisa" } ] }
- 9. Backend app.post((req, res) => { const user = getUser(req.headers.user_id); const user = getUser(req.query.user_id); const user = getUser(req.path.user_id); const user = getUser(req.body.user); });
- 10. function getUser(name: string): User { return db.getUserByName(name); } Typed request argumentes Type of response
- 12. GraphQL • Get what you really need • Client specific • Transport agnostic • Rich type system • A lot of web features
- 13. REST GraphQL Auto documented +/- Swagger, ApiDoc, Blueprint + Easy to use +/- + Easy to develop - + Flexible - + Powerful - +
- 14. But REST is still an industry standart
- 15. const QueryType = new GraphQLObjectType({ name: 'DataQuery', fields: () => ({ post: { type: PostType, args: { id: { name: 'id', type: GraphQLInt }, journal: { name: 'journal', description: 'The journal slug', type: GraphQLString }, post: { name: 'post', description: 'The post slug', type: GraphQLString } }, resolve: (user, {id, journal, post}) => { return Post.authorise(user, {id, journal, post}) .then(post => post && post.toJSON()); } } })
- 17. • JSON Schema • Good specification • Bad ecosystem
- 18. "/users/findByName": { "get": { "description": "Multiple status values can be provided with comma separated strings", "operationId": "findUsersByStatus", "produces": ["application/xml", "application/json"], "parameters": [{ "name": "name", "in": "query", "description": "User name", "required": true, "type": "array", "items": {"type": "string"}, }], "responses": { "200": { "description": "successful operation", "schema": {"type": "array", "items": {"$ref": "#/definitions/User"}} }, "400": {"description": "Invalid status value"} }, "security": [{"store_auth": ["read:users"]}]
- 19. Building types
- 20. new GraphQLSchema({ query: new GraphQLObjectType({ name: 'Query', fields: () => ({ get_user_id: { type: UserType, args: { id: { name: 'id', type: GraphQLInt } }, resolve: (id) => buildRequestWithSwagger() } }) }) }); GET /user/123 Swagger parameters
- 22. Gateway GQL request Adapter ms1 ms2 REST request GQL/REST GQL/REST function getUser(name: string): User { return db.getUserByName(name); }
- 23. Frontend Smart caching: GET /users GET /user/123 Helpful tools and debugging (Client knows about our schema and types Get only data that you need
- 24. Frontend • Cursor connections • Subscriptions • Batching • Defered delivering • Fragments composition
- 25. Precautions No GraphQL types namespaces campaigns_get_campaigns_shop_shop_id_products_id No validation for input types lokka React Apollo Vanila