@latech/moleculer-apollo-server

moleculer-apollo-server

Apollo GraphQL server mixin for Moleculer API Gateway

Features

Install

npm i @latech/moleculer-apollo-server moleculer-web 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));
                }
            }
        }
    }
};

File Uploads

moleculer-apollo-server supports file uploads through the GraphQL multipart request specification.

To enable uploads, the Upload scalar must be added to the Gateway:

"use strict";

const ApiGateway 	= require("moleculer-web");
const { ApolloService, GraphQLUpload } = require("moleculer-apollo-server");

module.exports = {
    name: "api",

    mixins: [
        // Gateway
        ApiGateway,

        // GraphQL Apollo Server
        ApolloService({

            // Global GraphQL typeDefs
            typeDefs: ["scalar Upload"],

            // Global resolvers
            resolvers: {
                Upload: GraphQLUpload
            },

            // 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
                }
            }
        })
    ]
};

Then a mutation can be created which accepts an Upload argument. The fileUploadArg property must be set to the mutation's argument name so that moleculer-apollo-server knows where to expect a file upload. When the mutation's action handler is called, ctx.params will be a Readable Stream which can be used to read the contents of the uploaded file (or pipe the contents into a Writable Stream). File metadata will be made available in ctx.meta.$fileInfo.

files.service.js

module.exports = {
    name: "files",
    settings: {
        graphql: {
            type: `
                """
                This type describes a File entity.
                """			
                type File {
                    filename: String!
                    encoding: String!
                    mimetype: String!
                }
            `
        }
    },
    actions: {
        uploadFile: {
            graphql: {
                mutation: "uploadFile(file: Upload!): File!",
                fileUploadArg: "file",
            },
            async handler(ctx) {
                const fileChunks = [];
                for await (const chunk of ctx.params) {
                    fileChunks.push(chunk);
                }
                const fileContents = Buffer.concat(fileChunks);
                // Do something with file contents
                
                // Additional arguments:
                this.logger.info("Additional arguments:", ctx.meta.$args);

                return ctx.meta.$fileInfo;
            }
        }
    }
};

To accept multiple uploaded files in a single request, the mutation can be changed to accept an array of Uploads and return an array of results. The action handler will then be called once for each uploaded file, and the results will be combined into an array automatically with results in the same order as the provided files.

...
graphql: {
    mutation: "upload(file: [Upload!]!): [File!]!",
    fileUploadArg: "file"
}
...

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
• File Upload
  • npm run dev upload
  • See here for information about how to create a file upload request
• Full
  • npm run dev full
• Full With Dataloader
  • set DATALOADER environment variable to "true"
  • npm run dev full

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) 2020 MoleculerJS