Node.js

You can see an example of configuring and using TypeScript and Yarn with Batect in the TypeScript sample project, and an example of using Cypress for UI testing with Batect in the Cypress sample project.

The Node.js bundle provides a container with all of these options pre-configured.

Example configuration

batect.yml

containers:
  build-env:
    image: node:15.0.1
    volumes:
      - local: .
        container: /code
      - type: cache
        name: node_modules
        container: /code/node_modules
      - type: cache
        name: yarn_cache
        container: /root/.cache/yarn # Or .cache/yarn in home_directory if run as current user mode is enabled
    working_directory: /code
    enable_init_process: true

Caching dependencies

tip

tl;dr: Mount a cache into your container for the node_modules and ~/.cache/yarn directories, otherwise you'll experience poor performance on macOS and Windows.

Both NPM and Yarn download and store dependencies in the node_modules directory in your application's directory. Yarn also caches downloaded dependencies in ~/.cache/yarn. However, when running on macOS and Windows, Docker exhibits poor I/O performance for directories mounted from the macOS or Windows host, as discussed in the section on caches.

The solution to this is to mount a cache into your container for node_modules and ~/.cache/yarn.

Note that you can't use ~ in the container path for a volume mount:

• If you're using run as current user mode, use the home directory you specified for home_directory.

• If you're not using run as current user mode, use /root as the home directory, as the vast majority of containers default to the root user and use this as the root user's home directory.

Issues with signals not being handled correctly

tip

tl;dr: If signals such as SIGINT (which is generated when you press Ctrl+C) aren't being handled correctly by your Node.js-based application, enable enable_init_process for that container

Node.js does not behave correctly when it is running as process ID 1 (PID 1), which is what happens when running an application inside a container. The most noticeable issue this causes is that applications do not respond correctly to signals such as SIGINT (which is generated when you press Ctrl+C).

The solution is to run another process (an 'init process') as PID 1, which then runs your application and handles and forwards signals to it.

Docker has a slimmed-down init process built in that is designed for just this scenario. You can enable it for a container in Batect by setting enable_init_process to true.

This article has a more detailed explanation of what is happening and why an init process solves this problem.