ES4X application should create a es4x-launcher during the install phase of npm. If the launcher isn't present, running:

yarn # OR npm install

The launcher should be created in node_modules/.bin/es4x-lancher.*.

Running the application is now as simple as::

yarn start # OR npm start

This command replaces the default npm operation by running the application on the JVM runtime and using the Hello World project the following output should be visible:

Server listening at: http://localhost:8080/
Succeeded in deploying verticle

You can now interact with the application with a browser or a http client:

> curl localhost:8080

Hello from Vert.x Web!

Running without npm/yarn

When deploying applications to production it might feel natural not to bundle a package manager with your application. For this case running the application shall not use npm/yarn. Running the application becomes:


It is possible to customize the startup of the application, do check:

./node_modules/.bin/es4x-launcher -help

Scaling the number of verticles

Scaling the number of verticles (which is some cases increases the performance) can be done as:

# number of verticles to use:
N=2 \
  ./node_modules/.bin/es4x-launcher -instances $N

Usually increasing the number of verticles up to twice the number of cores gives the best performance.


Same as with the number of verticles, an ES4X application can be clustered as simple as:

./node_modules/.bin/es4x-launcher -cluster

To know more about clustering please read the official vert.x documentation.