Apollo Server Execution

작성자: J113 양아림

class ApolloServer

options

Schema options

• typeDefs
  • GraphQL 의 schema 를 나타내는 Document or documents
  • gql 태그를 사용하여 SDL(Schema Definition Language)로 나타냄
• resolvers
  • 각각의 schema field를 채우기 위한 function들의 map
• context
  • 모든 resolver에게 전달되는 object 또는 object를 반환하는 함수
  • apollo-server-express 에서는 req, res 가 자동으로 추가되어있음
• introspection
  • schema 의 내용을 client가 확인할 수 있음
  • default 는 true, NODE_ENV가 production이면 false
• schemaDirectives
  • map of custom schema directives
• schema
  • GrphQL 의 Schema
  • Apollo Server가 typeDefs 와 resolvers로부터 생성하기 때문에 대부분의 상황에서는 데이터 필요 없음
  • 주로 Apollo Federation과 같이 사용됨
• persistedQueries
  • caching 과 관련된 옵션
  • APQ(Automated Persisted Queries)
• subscriptions
  • subscription 관련 옵션
  • path, keepAlive. onConnect, onDisconnect 을 명시해줌
• rootValue
• validationRules

Networking options

• cors
  • apollo-server를 사용할 때 CORS 설정
  • apollo-server-{Node.js middleware}같은 다른 미들웨어와 통합하여 사용할때는 각각의 미들웨어 환경에 맞게 설정 해준다. (applyMiddleware)
• cacheControl
• formatError
• formatResponse
• apollo

Lifecycle options

• plugins
• stopOnTerminationSignals

Debugging options

• playground
• debug
• logger
• mocks
• mockEntireSchema

ApolloServer instance

typeDefs

const typeDefs = gql`
  # A library has a branch and books
  type Library {
    branch: String!
    books: [Book!]
  }

  # A book has a title and author
  type Book {
    title: String!
    author: Author!
  }

  # An author has a name
  type Author {
    name: String!
  }

  # Queries can fetch a list of libraries
  type Query {
    libraries: [Library]
  }
`;

Naming Conventions

• Field names: camelCase
• Type names: PascalCase
• Enum names Pascalcase
• Enum values ALL_CAPS

resolvers

// Resolver map
const resolvers = {
  Query: {
    libraries(parent, args, context, info) {
      // Return array of libraries
      return libraries;
    },
  },
  Library: {
    books(parent, args, context, info) {
      // Filter the array of books to only include
      // books that are located at the correct branch
      return books.filter((book) => book.branch === parent.branch);
    },
  },
  Book: {
    // The parent resolver (Library.books) returns an object with the
    // author's name in the "author" field. Return a JSON object containing
    // the name, because this field expects an object.
    author(parent, args, context, info) {
      return {
        name: parent.author,
      };
    },
  },

  // Because Book.author returns an object with a "name" field,
  // Apollo Server's default resolver for Author.name will work.
  // We don't need to define one.
  // Author: {
  //   name(parent, args, context, info) {
  //     return parent.name;
  //   },
  // },
};

instance

• ApolloServer instance를 생성할때 설정한 값에 따라서 아래와 같은 instance가 생성됨

ApolloServer {
  graphqlPath: '/graphql',
  requestOptions: {
    tracing: true,
    cache: InMemoryLRUCache { store: [LRUCache] },
    persistedQueries: { cache: [PrefixingKeyValueCache] }
  },
  plugins: [
    { requestDidStart: [Function: requestDidStart] },
    { requestDidStart: [Function: requestDidStart] }
  ],
  toDispose: Set(2) { [Function (anonymous)], [Function (anonymous)] },
  config: {
    typeDefs: { kind: 'Document', definitions: [Array], loc: [Object] },
    resolvers: {
      Query: [Object],
      Library: [Object],
      Book: [Object],
      Upload: Upload
    },
    tracing: true
  },
  logger: Logger {},
  apolloConfig: { graphVariant: 'current' },
  parseOptions: {},
  context: undefined,
  uploadsConfig: {},
  subscriptionServerOptions: { path: '/graphql' },
  subscriptionsPath: '/graphql',
  playgroundOptions: { version: '1.7.33', settings: undefined },
  schema: GraphQLSchema {
    __validationErrors: [],
    description: undefined,
    extensions: undefined,
    astNode: undefined,
    extensionASTNodes: [],
    _queryType: Query,
    _mutationType: undefined,
    _subscriptionType: undefined,
    _directives: [ @cacheControl, @include, @skip, @deprecated, @specifiedBy ],
    _typeMap: [Object: null prototype] {
      Library: Library,
      String: String,
      Book: Book,
      Author: Author,
      Query: Query,
      CacheControlScope: CacheControlScope,
      Upload: Upload,
      Int: Int,
      Boolean: Boolean,
      __Schema: __Schema,
      __Type: __Type,
      __TypeKind: __TypeKind,
      __Field: __Field,
      __InputValue: __InputValue,
      __EnumValue: __EnumValue,
      __Directive: __Directive,
      __DirectiveLocation: __DirectiveLocation
    },
    _subTypeMap: [Object: null prototype] {},
    _implementationsMap: [Object: null prototype] {}
  schemaDerivedData: Promise {
    {
      schema: [GraphQLSchema],
      schemaHash: '',
      extensions: [],
      documentStore: [InMemoryLRUCache]
    }
  },
  cors: undefined,
  onHealthCheck: undefined
}

Apollo Server 의 GraphQL request 처리 과정

Parsing the query

• 문자열을 AST(Abstract Syntax Tree)로 parsing 한다
• 이 과정에서 에러가 나면 실행을 중단하고 client에게 에러를 return한다.

Validation

• type, arguments, return field 등이 정의된 schema 와 맞는지 확인한다.

Execution

How does a GraphQL server turn a query into a response?