Moleculer Runner

Added in: v0.8.0

There is a project runner helper script in the Moleculer project. You can use it if you want to create small repos for services. In this case you don’t need to create a ServiceBroker with options. Just create a moleculer.config.js or moleculer.config.json file in the root of repo fill it with your options and call the moleculer-runner within the NPM scripts.
As an other solution you can put it to the environment variables instead of putting options to file.


In production we recommend to put options to the environment variables! Use the moleculer.config.js only in development.


$ moleculer-runner [options] [service files or directories]

Please note! It’s working in this format in NPM scripts. If you want to call it directly from your console, use the ./node_modules/.bin/moleculer-runner --repl format.


Option Type Default Description
-r, --repl Boolean false If true, it will switch to REPL mode after broker started.
-s, --silent Boolean false Disable the logger of broker. It won’t print anything to the console.
-H, --hot Boolean false Hot reload services if they changed.
-c, --config <file> String null Use it if you store your configuration file in different path or with different filename.

Example NPM scripts

"scripts": {
"dev": "moleculer-runner --repl --hot --config services",
"start": "moleculer-runner services"

As you can see above we defined two scripts. The dev script load the development configurations from the file, start all your services from the services folder, enable hot-reloading and switch to REPL mode. You can call it with npm run dev command.
The start script is try to load the default moleculer.config.js file if it exists, or load options from environment variables. After that, start all your services from the services folder. You can call it with npm start command.

Configuration loading logic

The runner does the following steps to load & merge configurations:

  1. If you defined config file in CLI options, it tries to load it. If it doesn’t exist, throw an error.
  2. If you not defined, it tries to load the moleculer.config.js file from the current directory. If it doesn’t exist, it tries to load the moleculer.config.json file.
  3. If it founds any config file, it loads and merges options with the default options of the ServiceBroker.
  4. The runner walks through the options and tries to override them from environment variables. So if you set logLevel: "warn" in the config file, but define the LOGLEVEL=debug environment variable, the runner will override it and the result will be logLevel: "debug".

Configuration file

The structure of the configuration file is same as the broker options. Every property has the same name. Use shorthand formats in transporter, cacher and serializer options.

Example config file

module.exports = {
nodeID: "node-test",
logger: true,
logLevel: "debug",
transporter: "nats://localhost:4222",
requestTimeout: 5 * 1000,
circuitBreaker: {
enabled: true
metrics: true,
statistics: true

Environment variables

The runner transforms the property names to uppercase. If it is a nested property, it joins names with _

Example environment variables

# Shorthand transporter
# Nested property

Services loading logic

If you define service files or folders in CLI arguments, the runner will try to load them. If you define folder(s), the runner will load all services *.service.js from this folder(s). You can define services & service folder with SERVICES and SERVICEDIR environment variables.

  1. If it find SERVICEDIR env, but isn’t find SERVICES env, it’ll load all services from the SERVICEDIR directory.
  2. If it find SERVICEDIR & SERVICES env, it’ll load the specified services from the SERVICEDIR directory.
  3. If it’s not find SERVICEDIR env but find SERVICES env, load the specified services from the current directory.



It will load the math.service.js, post.service.js and user.service.js files from the services folder.


It will load all *.service.js files from the my-services folder.