MongoError:拓扑已关闭，请连接 [英] MongoError: Topology is closed, please connect
问题描述
我是一名前端开发人员，试图在新的Next项目上拓展视野，第一次学习Node，Mongo和GraphQL的服务器端. Apollo吸引了我，因为我已经在以前的项目中使用过客户端Apollo.
我一直在关注官方文档，在这里我了解了 apollo-datasource-mongodb (似乎是插入我的Apollo的最佳方法服务器直接进入本地的Mongo数据库.不幸的是，似乎没有这个软件包的示例存储库可供我欺骗，因此我不得不去摸索.
我有通过mongod在本地运行的mongo，并且可以通过mongo shell成功执行find()查询，因此我知道数据库本身状态良好，并且包含近 600,000条记录(我正在使用相当大的数据集).
我还可以访问localhost:4000处的Apollo游乐场，因此我知道服务器正在正常启动并连接到数据库(具有自此以来一直设法解决的适当的架构提示/错误).
这是我在操场上使用的查询:
{
item(id: 22298006) {
title
}
}
这就是我要回覆的内容:
{
"errors": [
{
"message": "Topology is closed, please connect",
"locations": [
{
"line": 2,
"column": 3
}
],
"path": [
"item"
],
"extensions": {
"code": "INTERNAL_SERVER_ERROR",
"exception": {
"name": "MongoError",
"stacktrace": [
"MongoError: Topology is closed, please connect",
...
]
}
}
}
],
"data": {
"item": null
}
}
我在下面附加了我的服务器文件.我怀疑这可能是某种超时错误，例如花很长时间梳理所有600k记录才能找到具有我提供的ID的记录?当我从MongoClient定义中删除useUnifiedTopology: true时，我得到了另一个错误:
UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
但是我没有使用异步或答应自己.我在想什么-我应该是什么?在等待findOneById()返回时，是否可以以某种方式阻止该过程(如果确实是问题所在)?
顺便说一句，我已经看过至少一个示例代码库，其中MongoClient本身包含了一个Server声明(也来自'mongodb' npm包).这样的实现是否可以使我免于每次我要处理项目时都必须使用mongod阻塞终端窗口的方法?
非常感谢您抽出宝贵的时间！如果我可以完成这项工作，那么我一定会在Medium上进行完整的撰写，或者为其他希望将MongoClient与ApolloServer配对以获得快速简便的API的人铺平道路.
index.js
const { MongoClient } = require('mongodb');
const assert = require('assert');
const { ApolloServer, gql } = require('apollo-server');
const { MongoDataSource } = require('apollo-datasource-mongodb');
const client = new MongoClient('mongodb://localhost:27017/projectdb', { useNewUrlParser: true, useUnifiedTopology: true }, (err) => {
err && console.log(err);
});
client.connect((err) => {
assert.equal(null, err);
client.close();
});
const db = client.db();
class Items extends MongoDataSource {
getItem(id) {
return this.findOneById(id);
}
}
const typeDefs = gql`
type Item {
id: Int!
title: String!
}
type Query {
item(id: Int!): Item
}
`;
const resolvers = {
Query: {
item: (_, { id }, { dataSources }) => dataSources.items.getItem(id),
}
}
const server = new ApolloServer({
typeDefs,
resolvers,
dataSources: () => ({
items: new Items(db.collection('items')),
}),
});
server.listen().then(({ url }) => {
console.log(`Server ready at ${ url }`);
});
感谢GitHub在official docs, where I learned of apollo-datasource-mongodb (seemingly the best way to plug my Apollo Server straight into a local Mongo database. Unfortunately there don't seem to be any example repos of this package in action for me to cheat off of so I've been left to muddle through.
I have mongo running locally via mongod and I can perform successful find() queries through the mongo shell, so I know the database itself is in good shape and contains nearly 600,000 records (I'm working with a rather large dataset).
I also have access to the Apollo Playground at localhost:4000 so I know the server is starting properly and connecting to the database (with appropriate Schema tips/errors I've since managed to resolve).
Here's the query I'm using in the Playground:
{
item(id: 22298006) {
title
}
}
and here's what I'm getting back in response:
{
"errors": [
{
"message": "Topology is closed, please connect",
"locations": [
{
"line": 2,
"column": 3
}
],
"path": [
"item"
],
"extensions": {
"code": "INTERNAL_SERVER_ERROR",
"exception": {
"name": "MongoError",
"stacktrace": [
"MongoError: Topology is closed, please connect",
...
]
}
}
}
],
"data": {
"item": null
}
}
I've attached my server file below. I have a suspicion that this might be some kind of timeout error, like it takes to long to comb through all 600k records to find the one with the ID I provided? When I remove useUnifiedTopology: true from the MongoClient definition I get a different error:
UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
but I'm not using async or promises myself. Which has me thinking — should I be? Could I somehow hold up the process while I wait for the return from findOneById() (if that is, indeed, the problem)?
As an aside, I've seen at least one example codebase where MongoClient included within itself a Server declaration (also from the 'mongodb' npm package). Would implementing something like that save me from having to block up a terminal window with mongod every time I want to work on my project?
Thank you so much for your time! If I can get this working I'll definitely do a full writeup on Medium or something to pave the way for others looking to pair MongoClient with ApolloServer for a quick and easy API.
index.js
const { MongoClient } = require('mongodb');
const assert = require('assert');
const { ApolloServer, gql } = require('apollo-server');
const { MongoDataSource } = require('apollo-datasource-mongodb');
const client = new MongoClient('mongodb://localhost:27017/projectdb', { useNewUrlParser: true, useUnifiedTopology: true }, (err) => {
err && console.log(err);
});
client.connect((err) => {
assert.equal(null, err);
client.close();
});
const db = client.db();
class Items extends MongoDataSource {
getItem(id) {
return this.findOneById(id);
}
}
const typeDefs = gql`
type Item {
id: Int!
title: String!
}
type Query {
item(id: Int!): Item
}
`;
const resolvers = {
Query: {
item: (_, { id }, { dataSources }) => dataSources.items.getItem(id),
}
}
const server = new ApolloServer({
typeDefs,
resolvers,
dataSources: () => ({
items: new Items(db.collection('items')),
}),
});
server.listen().then(({ url }) => {
console.log(`Server ready at ${ url }`);
});
Thanks to GitHub's "Used By" dropdown on the apollo-datasource-mongodb I was able to cheat off a few other repositories, and here's what I ended up with (with changes marked in comments):
const { MongoClient } = require('mongodb');
const assert = require('assert');
const { ApolloServer, gql } = require('apollo-server');
const { MongoDataSource } = require('apollo-datasource-mongodb');
// Isolated these for prominence and reuse
const dbURL = 'mongodb://localhost:27017';
const dbName = 'projectdb';
// Made each function async/await
// Swapped the datasource's findOneById() for the collection itself & standard Mongo functions
class Items extends MongoDataSource {
async getItem(id) {
return await this.collection.findOne({id: id});
}
}
const typeDefs = gql`
type Item {
id: Int!
title: String!
}
type Query {
item(id: Int!): Item
}
`;
// Made each query async/await
const resolvers = {
Query: {
item: async (_, { id }, { dataSources }) => {
return await dataSources.items.getItem(id);
},
}
}
// Move the ApolloServer constructor to its own function that takes the db
const init = (db) = {
return new ApolloServer({
typeDefs,
resolvers,
dataSources: () => ({
items: new Items(db.collection('items')),
}),
});
}
// Use .connect() instead of new MongoClient
// Pass the new db to the init function defined above once it's been defined
// Call server.listen() from within MongoClient
MongoClient.connect(dbURL, { useNewUrlParser: true, useUnifiedTopology: true }, (err, client) => {
assert.equal(null, err);
const db = client.db(dbName);
console.log(`Mongo database ${ dbName } at ${ dbURL }`);
const server = init(db);
server.listen().then(({ url }) => {
console.log(`Server ready at ${ url }`);
});
});
With these changes, the Apollo Playground at localhost:4000 works great! Now to solve the 400 error I'm getting in my client app when I query...
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