moleculer-apollo-server 
Apollo GraphQL server mixin for Moleculer API Gateway
Features
Install
npm i moleculer-apollo-server moleculer-web@next graphql
Usage
This example demonstrates how to setup a Moleculer API Gateway with GraphQL mixin in order to handle incoming GraphQL requests via the default /graphql endpoint.
"use strict";
const ApiGateway = require("moleculer-web");
const { ApolloService } = require("moleculer-apollo-server");
module.exports = {
name: "api",
mixins: [
// Gateway
ApiGateway,
// GraphQL Apollo Server
ApolloService({
// Global GraphQL typeDefs
typeDefs: ``,
// Global resolvers
resolvers: {},
// API Gateway route options
routeOptions: {
path: "/graphql",
cors: true,
mappingPolicy: "restrict"
},
// https://www.apollographql.com/docs/apollo-server/v2/api/apollo-server.html
serverOptions: {
tracing: true,
engine: {
apiKey: process.env.APOLLO_ENGINE_KEY
}
}
})
]
};Start your Moleculer project, open http://localhost:3000/graphql in your browser to run queries using graphql-playground, or send GraphQL requests directly to the same URL.
Define queries & mutations in service action definitions
module.exports = {
name: "greeter",
actions: {
hello: {
graphql: {
query: "hello: String"
},
handler(ctx) {
return "Hello Moleculer!"
}
},
welcome: {
params: {
name: "string"
},
graphql: {
mutation: "welcome(name: String!): String"
},
handler(ctx) {
return `Hello ${ctx.params.name}`;
}
}
}
};Generated schema
type Mutation {
welcome(name: String!): String
}
type Query {
hello: String
}Resolvers between services
posts.service.js
module.exports = {
name: "posts",
settings: {
graphql: {
type: `
"""
This type describes a post entity.
"""
type Post {
id: Int!
title: String!
author: User!
votes: Int!
voters: [User]
createdAt: Timestamp
}
`,
resolvers: {
Post: {
author: {
// Call the `users.resolve` action with `id` params
action: "users.resolve",
rootParams: {
"author": "id"
}
},
voters: {
// Call the `users.resolve` action with `id` params
action: "users.resolve",
rootParams: {
"voters": "id"
}
}
}
}
}
},
actions: {
find: {
//cache: true,
params: {
limit: { type: "number", optional: true }
},
graphql: {
query: `posts(limit: Int): [Post]`
},
handler(ctx) {
let result = _.cloneDeep(posts);
if (ctx.params.limit)
result = posts.slice(0, ctx.params.limit);
else
result = posts;
return _.cloneDeep(result);
}
},
findByUser: {
params: {
userID: "number"
},
handler(ctx) {
return _.cloneDeep(posts.filter(post => post.author == ctx.params.userID));
}
},
}
};users.service.js
module.exports = {
name: "users",
settings: {
graphql: {
type: `
"""
This type describes a user entity.
"""
type User {
id: Int!
name: String!
birthday: Date
posts(limit: Int): [Post]
postCount: Int
}
`,
resolvers: {
User: {
posts: {
// Call the `posts.findByUser` action with `userID` param.
action: "posts.findByUser",
rootParams: {
"id": "userID"
}
},
postCount: {
// Call the "posts.count" action
action: "posts.count",
// Get `id` value from `root` and put it into `ctx.params.query.author`
rootParams: {
"id": "query.author"
}
}
}
}
}
},
actions: {
find: {
//cache: true,
params: {
limit: { type: "number", optional: true }
},
graphql: {
query: "users(limit: Int): [User]"
},
handler(ctx) {
let result = _.cloneDeep(users);
if (ctx.params.limit)
result = users.slice(0, ctx.params.limit);
else
result = users;
return _.cloneDeep(result);
}
},
resolve: {
params: {
id: [
{ type: "number" },
{ type: "array", items: "number" }
]
},
handler(ctx) {
if (Array.isArray(ctx.params.id)) {
return _.cloneDeep(ctx.params.id.map(id => this.findByID(id)));
} else {
return _.cloneDeep(this.findByID(ctx.params.id));
}
}
}
}
};Dataloader
moleculer-apollo-server supports DataLoader via configuration in the resolver definition. The called action must be compatible with DataLoader semantics -- that is, it must accept params with an array property and return an array of the same size, with the results in the same order as they were provided.
To activate DataLoader for a resolver, simply add dataLoader: true to the resolver's property object in the resolvers property of the service's graphql property:
settings: {
graphql: {
resolvers: {
Post: {
author: {
action: "users.resolve",
dataLoader: true,
rootParams: {
author: "id",
},
},
voters: {
action: "users.resolve",
dataLoader: true,
rootParams: {
voters: "id",
},
},
...Since DataLoader only expects a single value to be loaded at a time, only one rootParams key/value pairing will be utilized, but params and GraphQL child arguments work properly.
You can also specify options for construction of the DataLoader in the called action definition's graphql property. This is useful for setting things like `maxBatchSize'.
resolve: {
params: {
id: [{ type: "number" }, { type: "array", items: "number" }],
graphql: { dataLoaderOptions: { maxBatchSize: 100 } },
},
handler(ctx) {
this.logger.debug("resolve action called.", { params: ctx.params });
if (Array.isArray(ctx.params.id)) {
return _.cloneDeep(ctx.params.id.map(id => this.findByID(id)));
} else {
return _.cloneDeep(this.findByID(ctx.params.id));
}
},
},It is unlikely that setting any of the options which accept a function will work properly unless you are running moleculer in a single-node environment. This is because the functions will not serialize and be run by the moleculer-web Api Gateway.
Examples
-
Simple
npm run dev
-
Full
npm run dev full
-
Full With Dataloader
- set
DATALOADERenvironment variable to"true" npm run dev full
- set
Test
$ npm test
In development with watching
$ npm run ci
Contribution
Please send pull requests improving the usage and fixing bugs, improving documentation and providing better examples, or providing some testing, because these things are important.
License
The project is available under the MIT license.
Contact
Copyright (c) 2019 MoleculerJS
