NestJS & TypeORM Error: Cannot Connect to MySQL Database

Encountering a database connection error can be a frustrating issue when developing with modern frameworks such as NestJS, combined with an ORM like TypeORM. The Cannot connect to MySQL database error in this stack usually triggers due to misconfigurations or network issues between the nest application and the MySQL server. In this article, we’ll cover the common reasons behind these errors and walk you through the steps to resolve the issue in your NestJS project with TypeORM.

Understand the Error

Before proceeding with solutions, understanding why the error might occur is crucial. Most of the time, this error happens because of reasons like incorrect database credentials, incorrect configuration in the TypeORM connection settings, the database server not running, or network restrictions that prevent the application from talking to the database server.

Check MySQL Server Status

First, ensure that the MySQL database server is up and running. Issues with the server’s operation, such as the service being down or starting errors, can lead to this problem. You would need to consult your database server’s documentation or logs to verify that it is running correctly and is accessible.

Review Database Credentials

Next, confirm that the credentials and other connection details provided to TypeORM are accurate. These include the host, port, username, password, and database name. Any discrepancy between these credentials and what your MySQL server expects will prevent a successful connection. Be extra cautious about typographical errors, which might not be immediately obvious.

Examine TypeORM Configuration

Ensure that your TypeORM’s configuration aligns with your database setup. The configuration is often done through a file like ormconfig.json or directly within your NestJS service code. Look into properties such as type, which should be ‘mysql’, and other TypeORM-specific settings like entities, and synchronize. The configuration should be tailor-fit to your application’s database schema and operational parameters.

Configure Network Access

If your NestJS application and the MySQL server are on different machines or in different network segments, you may need to configure network access. For local development, ‘localhost’ is usually used, but for production, you might need to provide an IP address or domain name accessible from the application’s environment. Additionally, you may need to adjust firewall settings or access control lists within your MySQL server to allow connections from the application’s host.

Debugging and Logs

To find the root of the problem, include more logs inside your application. NestJS has a robust logging system that can be configured to show more verbose error details, which can lead you to the exact point of failure in your database connection process. You should also enable MySQL server logging if it isn’t already to check for incoming connections and errors from the server side.

Working Code Example

Below is a complete code example that you can run, which illustrates how to set up a working connection from NestJS to a MySQL database using TypeORM:

import { Module } from '@nestjs/common';
import { TypeOrmModule } from '@nestjs/typeorm';

@Module({
    imports: [
        TypeOrmModule.forRoot({
            type: 'mysql',
            host: 'localhost',
            port: 3306,
            username: 'your_username',
            password: 'your_password',
            database: 'your_db_name',
            entities: [/* your entities go here */],
            synchronize: true, // Note: use 'synchronize: true' only in development
        })
    ],
    controllers: [],
    providers: [],
})
export class AppModule {}

In this code:

• The TypeOrmModule is imported and configured within the imports array of the @Module decorator.
• The configuration object for TypeORM includes the database connection details. Replace 'your_username', 'your_password', and 'your_db_name' with your actual MySQL credentials and database name.
• The entities array should contain your entity classes.
• The synchronize: true option automatically synchronizes the database schema with your models. It’s convenient for development but should be used with caution in production environments.

Adapt the above configuration, filling in your MySQL server details appropriately. Remember to replace your_username, your_password, and your_db_name with your actual database access credentials.

Like always, local development environments can have their unique issues not covered here, but following the steps described should help you to understand and resolve most instances of the Cannot connect to MySQL database error with NestJS and TypeORM.