Logging

For development purposes it might come handy to enable logging and debug mode:

return MikroORM.init({
  debug: true,
});

By doing this MikroORM will start using console.log() function to dump all queries:

[query] select `e0`.* from `author` as `e0` where `e0`.`name` = ? limit ? [took 2 ms]
[query] begin [took 1 ms]
[query] insert into `author` (`name`, `email`, `created_at`, `updated_at`, `terms_accepted`) values (?, ?, ?, ?, ?) [took 2 ms]
[query] commit [took 2 ms]

It is also useful for debugging problems with entity discovery, as you will see information about every processed entity:

[discovery] ORM entity discovery started
[discovery] - processing entity Author
[discovery] - using cached metadata for entity Author
[discovery] - processing entity Book
[discovery] - processing entity BookTag
[discovery] - entity discovery finished after 13 ms

Custom Logger

We can also provide our own logger function via logger option.

return MikroORM.init({
  debug: true,
  logger: msg => myCustomLogger.log(msg),
});

If we want to have more control over logging, we can use loggerFactory and use our own implementation of the Logger interface:

import { Logger, LoggerOptions, MikroORM, Configuration } from '@mikro-orm/core';

class MyLogger implements Logger {
  // ...
}

const orm = await MikroORM.init({
  debug: true,
  loggerFactory: (options: LoggerOptions) => new MyLogger(config),
});

We can also extend the DefaultLogger instead of implementing everything from scratch. It is also exported from the @mikro-orm/core package.

The Logger interface is defined as follows:

interface Logger {
  log(namespace: LoggerNamespace, message: string, context?: LogContext): void;
  error(namespace: LoggerNamespace, message: string, context?: LogContext): void;
  warn(namespace: LoggerNamespace, message: string, context?: LogContext): void;
  logQuery(context: LogContext): void;
  setDebugMode(debugMode: boolean | LoggerNamespace[]): void;
  isEnabled(namespace: LoggerNamespace): boolean;
}

type LoggerNamespace = 'query' | 'query-params' | 'discovery' | 'info';

interface LogContext {
  query?: string;
  params?: unknown[];
  took?: number;
  level?: 'info' | 'warning' | 'error';
  connection?: {
    type?: string;
    name?: string;
  };
}

Disabling colored output

To disable colored output, we can use multiple environment variables:

• NO_COLOR
• MIKRO_ORM_NO_COLOR
• FORCE_COLOR

Logger Namespaces

There are multiple Logger Namespaces that you can specifically request, while omitting the rest. Just specify array of them via the debug option:

return MikroORM.init({
  debug: ['query'], // now only queries will be logged
});

Currently, there are 4 namespaces – query, query-params, discovery and info.

If you provide query-params then you must also provide query in order for it to take effect.

Highlighters

Previously Highlight.js was used to highlight various things in the CLI, like SQL and mongo queries, or migrations or entities generated via CLI. While the library worked fine, it was causing performance issues mainly for those bundling via webpack and using lambdas, as the library was huge.

Since v4, highlighting is disabled by default, and there are 2 highlighters you can optionally use (you need to install them first).

import { SqlHighlighter } from '@mikro-orm/sql-highlighter';

MikroORM.init({
  highlighter: new SqlHighlighter(),
  // ...
});

For MongoDB you can use MongoHighlighter from @mikro-orm/mongo-highlighter package.