MongoError: pool is draining, new operations prohibited when using MongoMemoryServer in integration test

问题

I'm using MongoMemoryServer to write an integration test. I have two integration test files. When I run the IT tests I see the following. I don't understand why. I'm using jestjs test framework.

I'm seeing the following error when I have two IT test files

MongoError: pool is draining, new operations prohibited

      37 |   for (const key in collections) {
      38 |     const collection = collections[key];
    > 39 |     await collection.deleteMany();
         |                      ^
      40 |   }
      41 | };

Here is my setup

//db-handler.js
const mongoose = require("mongoose");
const { MongoMemoryServer } = require("mongodb-memory-server");
const mongod = new MongoMemoryServer();

module.exports.connect = async () => {
  const uri = await mongod.getConnectionString();

  const mongooseOpts = {
    useNewUrlParser: true,
    autoReconnect: true,
    reconnectTries: Number.MAX_VALUE,
    reconnectInterval: 1000,
  };

  await mongoose.connect(uri, mongooseOpts);
};

module.exports.closeDatabase = async () => {
  await mongoose.connection.dropDatabase();
  await mongoose.connection.close();
  await mongod.stop();
};

module.exports.clearDatabase = async () => {
  const collections = mongoose.connection.collections;

  for (const key in collections) {
    const collection = collections[key];
    await collection.deleteMany();
  }
};

All my IT tests setup looks like this

//example.it.test.js
const supertest = require("supertest");
const dbHandler = require("./db-handler");
const app = require("../../src/app");
const request = supertest(app);

const SomeModel = require("../Some");
beforeAll(async () => await dbHandler.connect());
afterEach(async () => await dbHandler.clearDatabase());
afterAll(async () => await dbHandler.closeDatabase());

describe("Some Test Block", () => {
  it("Test One", async (done) => {
    await SomeModel.create({a: "a", b "b"});

    const response = await request.get("/endPointToTest");
    expect(response.status).toBe(200);

    done();
  });

When I have just a single IT test files, everything works fine. When I introduce a a new IT test file similar setup up as example.it.test.js, then the new test fails. The example error message above.

What am I missing? Does my setup need to change when I have multiple IT test files?

UPDATE ONE: My package.json file looks like

{
  "scripts": {
    "start": "node index.js",
    "dev": "nodemon index.js",
    "test": "jest --runInBand ./tests"
  },
  "devDependencies": {
    "jest": "^25.2.7",
    "mongodb-memory-server": "^6.5.2",
    "nodemon": "^2.0.2",
    "supertest": "^4.0.2"
  },
  "jest": {
    "testEnvironment": "node",
    "coveragePathIgnorePatterns": [
      "/node_modules/"
    ]
  }
}

回答1:

By default Jest runs tests in parallel with a “a worker pool of child processes that run tests” (Jest CLI docs). As per the Jest documentation.

Each test file is making a new connection to the mogodb server which is causing the error.

You could run the Jest test sequentially to avoid this issue.

The --runInBand or -i option of the Jest CLI allows you to run tests sequentially (in non-parallel mode).

This error (pool is draining, new operations prohibited) might occur if you are using the official mongodb library for node js or mongoose. Please specifying pool size while establishing mongodb connection.

module.exports.connect = async () => {
  const uri = await mongod.getConnectionString();
  const mongooseOpts = {
    useNewUrlParser: true,
    autoReconnect: true,
    reconnectTries: Number.MAX_VALUE,
    reconnectInterval: 1000,
    poolSize: 10,
  };
  await mongoose.connect(uri, mongooseOpts);
};

来源：https://stackoverflow.com/questions/61152884/mongoerror-pool-is-draining-new-operations-prohibited-when-using-mongomemoryse

标签

node.js

mongodb

mongoose

jestjs

integration-testing