Question

我有两个节点服务器，两者均通过express-graphql提供graphql服务。我希望第一台服务器将其模式与第二台服务器的模式进行缝合。

我已按照以下说明进行操作：https://www.apollographql.com/docs/graphql-tools/remote-schemas

我正在使用graphql-tools。

我能够从我的第二个节点服务器上检索该模式，但是一旦我尝试打印它（仅用console.log），就会出现此错误：

Uncaught exception TypeError: schema.getDirectives is not a function
    at printFilteredSchema (/Users/cchabert/git-repo/client-configuration-api/node_modules/graphql/utilities/schemaPrinter.js:61:27)
    at Object.printSchema (/Users/cchabert/git-repo/client-configuration-api/node_modules/graphql/utilities/schemaPrinter.js:47:10)
    at makeRemoteExecutableSchema (/Users/cchabert/git-repo/client-configuration-api/node_modules/graphql-tools/dist/stitching/makeRemoteExecutableSchema.js:60:30)
    at schema (/Users/cchabert/git-repo/client-configuration-api/app/api/schema.js:68:24)
    at module.exports (/Users/cchabert/git-repo/client-configuration-api/app/routes.js:102:13)
    at Object.<anonymous> (/Users/cchabert/git-repo/client-configuration-api/app/index.js:15:20)
    at Module._compile (internal/modules/cjs/loader.js:799:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:810:10)
    at Module.load (internal/modules/cjs/loader.js:666:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:606:12)
    at Function.Module._load (internal/modules/cjs/loader.js:598:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:862:12)
    at internal/main/run_main_module.js:21:11

这会导致服务器崩溃，但我也能够以某种方式看到该模式：

received schema:  {"_queryType":"Query","_mutationType":"Mutation",
"_subscriptionType":null,"_directives":["@skip","@include","@deprecated"],
"_typeMap":{"Query":"Query","String":"String","Client":"Client",
"ID":"ID","DateTime":"DateTime",[...]}

我确实在远程模式定义中看到了_directives字段，但是文档对于如何处理这个问题并不清楚。

我也浏览了graphql-tools回购的github问题，但找不到任何东西。

这是一个代码段：

const {
  addMockFunctionsToSchema,
  makeExecutableSchema,
  makeRemoteExecutableSchema,
  introspectSchema,
  mergeSchemas
} = require('graphql-tools')
const _ = require('lodash)
const { createHttpLink } = require('apollo-link-http')
const fetch = require('node-fetch')

[..]
const customFetch = (uri, options = {}) => {
  const httpOptions = _.merge(options, {
    headers: {
      'Content-type': 'application/json'
    }
  })
  return fetch(uri, httpOptions)
}

function schema() {
  const Query = `
    type Query {
      _empty: String
    }
    type Mutation {
      _empty: String
    }
  `
  const resolvers = {}

  const mocks = {}

  const localSchema = makeExecutableSchema({
    typeDefs: [Query, [...]],
    resolvers: [resolvers, [...]]
  }) // by itself this schema works without any issues

  const mergedMocks = _.merge(mocks, [...])

  addMockFunctionsToSchema({
    schema: localSchema,
    mocks: mergedMocks,
    preserveResolvers: true
  })

  const infoApiLink = createHttpLink({ uri, fetch: customFetch })

  const remoteSchema = makeRemoteExecutableSchema({
    schema: introspectSchema(infoApiLink).then(remoteSchema => {
      console.log('received schema: ', JSON.stringify(remoteSchema))
      return remoteSchema
    }),
    link: infoApiLink
  })

  return mergeSchemas({ schemas: [localSchema, remoteSchema] })
}

module.exports = {
  schema
}

我也想仅使用https://github.com/apollographql/graphql-tools/blob/master/docs/source/remote-schemas.md#--introspectschemafetcher-context

中提到的Promises（不使用异步/等待）来完成这项工作

欢迎提出任何建议。

Answer 1

makeRemoteExecutableSchema应该传递一个GraphQLSchema的实例，但是您没有这样做-您正在传递的是一个Promise，它将解决为GraphQLSchema，这是行不通的。调用introspectSchema时，它必须进行自省调用，该调用是异步完成的。它返回一个Promise，该Promise解析为结果的GraphQLSchema对象。我们需要使用await或then来获得该值，然后可以根据需要使用它。

无需异步/等待的不必要的混乱方式：

function schema () {
  // ... rest of your code
  return introspectSchema(infoApiLink).then(schema => {
    const remoteSchema = makeRemoteExecutableSchema({ schema, link: infoApiLink })
    return mergeSchemas({ schemas: [localSchema, remoteSchema] })
  })
}

或使用异步/等待：

async function schema () {
  // ... rest of your code
  const schema = await introspectSchema(infoApiLink)
  const remoteSchema = makeRemoteExecutableSchema({ schema, link: infoApiLink })
  return mergeSchemas({ schemas: [localSchema, remoteSchema] })

}

无论哪种方式，请记住通过调用schema函数，您将返回一个Promise，它将解析为mergeSchemas返回的值。因此，在导入函数，调用函数并直接使用结果之前，您将不得不再次使用then或await来获取Promise首先解析的值：

import { schema } from './some-module'

schema()
  .then(schema => {
    const server = new ApolloServer({ schema })
    server.listen()
  })
  .catch(error => {
    // handle the Promise rejecting
  })

使用graphql-tools打印远程模式时发生getDirectives错误

1 个答案: