@truxie/logger

Structured logging for truxie: an injectable Logger over a transport you can replace.

npm install @truxie/logger

@Module({imports: [LoggerModule.forRoot({level: 'info'})]})
export class AppModule {}

@Injectable()
class UserService {
  constructor(private readonly logger: Logger) {}

  create(email: string) {
    this.logger.child('UserService').info('Created user', {email})
  }
}

The transport is a port

Logger is injected with LOG_TRANSPORT and knows nothing else — not that a console transport exists, and not how to build one. Shipping logs somewhere else is a provider change:

LoggerModule.forRoot({transport: new JsonStdoutTransport()})

// A transport with its own dependencies
LoggerModule.forRootAsync({
  inject: [ConfigService],
  useFactory: (config: ConfigService) => ({
    level: config.get('LOG_LEVEL'),
    transport: new HttpTransport(config.get('LOG_ENDPOINT')),
  }),
})

LogTransport is one method:

interface LogTransport {
  log(entry: LogEntry): void
}

LogEntry carries level, message, timestamp, and optional context and data — enough to render a line or emit JSON, and nothing that assumes either.

Levels and context

debug < info < warn < error. Anything below the configured level is dropped before it reaches the transport, so a filtered-out call costs almost nothing.

logger.child('UserService') returns a logger that tags every entry with that context and inherits the parent's transport and level. Use it per class rather than threading a context argument through every call.

Options

| Option | Default | | |---|---|---| | transport | ConsoleTransport | Any LogTransport. | | level | 'info' | Minimum level that reaches the transport. | | timestamps | true | Include timestamps. |