"MaxListenersExceededWarning: Possible EventEmitter memory leak detected" when creating models with `autoCreate: true` before `mongoose.connect()`

Do you want to request a feature or report a bug? Bug report

What is the current behavior? When creating more than 10 models MaxListenersExceededWarning appears

If the current behavior is a bug, please provide the steps to reproduce. Create more than 10 models like this:

mongoose.model<DocumentType, ModelType>(name, schema);

If you are using TypeScript, please include your tsconfig.json

{
  "compilerOptions": {
    "target": "es5"  ,
    "module": "commonjs"  ,
    "declaration": true  ,
    "declarationMap": true  ,
    "sourceMap": true  ,
    "outDir": "./dist"  ,
    "strict": true  ,
    "baseUrl": "./",
    "paths": {
      "@sm-errors": [
        "./common-library/errors"
      ],
      "@sm-microsoft-graph-api": [
        "./common-library/microsoft-graph-api"
      ],
      "@sm-shared-models": [
        "./common-library/shared-models"
      ],
      "@sm-shared-services": [
        "./common-library/shared-services"
      ],
      "@sm-lib": [
        "./common-library/lib"
      ]
    },
    "esModuleInterop": true  ,
    "skipLibCheck": true  ,
    "forceConsistentCasingInFileNames": true
  },
  "exclude": [
    "node_modules",
    "dist"
  ]
}

What is the expected behavior? Should create more models without warnings

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that “latest” is not a version.

mongoose: "^5.9.27",
Node 12
MongoDB 4.2.2

Currently I solved the issue by calling the following function each time before creating models:

mongoose.connection.setMaxListeners(MAX_LISTENERS_COUNT);

but I think there should be another solution for this.

[deser]

It also happens when I use autoCreate: true on Schemas. Without that option it is ok

[IslandRhythms]

@vkarpov15 its very finicky but I can reproduce it but I’m not sure what triggers it.