Configuration profiling

Inspect your application's resolved configuration values in the Config panel, with sensitive key masking.

This tutorial shows how to add the config collector to display resolved configuration values in the profiler's Config panel.

Prerequisites

@eleven-labs/nest-profiler installed and configured
@nestjs/config installed with load factories (required — see note below)

Load factories are required

The config collector reads ConfigService's internal config map. This map is only populated when you use the load option with factory functions (the registerAs pattern). If you only pass envFilePath or ignoreEnvFile, the internal config will be empty and the Config tab will show no entries.

Step 1 — Install the package

pnpm add @eleven-labs/nest-profiler-config

Step 2 — Define config factories with registerAs

Create one factory per configuration domain:

config/database.config.ts

import { registerAs } from '@nestjs/config';

export const databaseConfig = registerAs('database', () => ({
  host: process.env.DB_HOST ?? 'localhost',
  port: parseInt(process.env.DB_PORT ?? '5432', 10),
  name: process.env.DB_NAME ?? 'myapp',
  username: process.env.DB_USER ?? 'postgres',
  password: process.env.DB_PASSWORD ?? '',
}));

config/app.config.ts

import { registerAs } from '@nestjs/config';

export const appConfig = registerAs('app', () => ({
  port: parseInt(process.env.PORT ?? '3000', 10),
  env: process.env.NODE_ENV ?? 'development',
  debug: process.env.DEBUG === 'true',
}));

Step 3 — Register the modules

app.module.ts

import { Module } from '@nestjs/common';
import { ConfigModule } from '@nestjs/config';
import { ProfilerModule } from '@eleven-labs/nest-profiler';
import { ConfigCollectorModule } from '@eleven-labs/nest-profiler-config';
import { appConfig } from './config/app.config';
import { databaseConfig } from './config/database.config';

@Module({
  imports: [
    ConfigModule.forRoot({
      isGlobal: true,
      load: [appConfig, databaseConfig],
    }),
    ProfilerModule.forRoot({ isGlobal: true }),
    ConfigCollectorModule.forRoot({
      maskKeys: ['database.password'],
    }),
  ],
})
export class AppModule {}

The maskKeys option accepts dot-notation paths. Matched values are replaced with *** in the profiler UI.

Step 4 — Test it

Start your application and open any profile:

curl -i http://localhost:3000/health

Open /_profiler/{token} and click the Config tab.

You will see the configuration as a flat table of dot-notation keys:

Key	Value
`app.port`	`3000`
`app.env`	`development`
`app.debug`	`false`
`database.host`	`localhost`
`database.port`	`5432`
`database.name`	`myapp`
`database.username`	`postgres`
`database.password`	`***`

The toolbar badge shows the total number of resolved configuration keys (e.g., 8 keys).

Masking additional keys

Any key matching the maskKeys array is masked. Keys are matched by their full dot-notation path:

ConfigCollectorModule.forRoot({
  maskKeys: ['database.password', 'redis.password', 'jwt.secret'],
});

Values matching /password|secret|key|token|credential/i are also masked automatically regardless of maskKeys.

How it works

The collector injects ConfigService and reads its internalConfig map, which is a Map<string, unknown> keyed by the namespace token registered with registerAs. It flattens nested objects into dot-notation keys (e.g., database.host) and applies masking rules before returning the config snapshot.

Since the config is read once per request (at collection time), it reflects the state of the config at request completion.