Paketo Buildpack for Yarn Start

gcr.io/paketo-buildpacks/yarn-start

The Yarn Start CNB sets the start command for the given application. The start command is generated from the contents of package.json. For example, given a package.json with the following content:

{
  "scripts": {
    "prestart": "<prestart-command>",
    "poststart": "<poststart-command>",
    "start": "<start-command>"
  }
}

The start command will be <prestart-command> && <start-command> && <poststart-command>.

Enabling reloadable process types

You can configure this buildpack to wrap the entrypoint process of your app such that it kills and restarts the process whenever files change in the app's working directory in the container. With this feature enabled, copying new verisons of source code into the running container will trigger your app's process to restart. Set the environment variable BP_LIVE_RELOAD_ENABLED=true at build time to enable this feature.

Integration

This CNB sets a start command, so there's currently no scenario we can imagine that you would need to require it as dependency.

Usage

To package this buildpack for consumption:

$ ./scripts/package.sh --version <version-number>

This will create a buildpackage.cnb file under the build directory which you can use to build your app as follows:

pack build <app-name> -p <path-to-app> -b <path/to/node-engine.cnb> -b \
<path/to/yarn.cnb> -b <path/to/yarn-install.cnb> -b build/buildpackage.cnb

Graceful shutdown and signal handling

You can add signal handlers in your app to support graceful shutdown and program interrupts. If running a node server is the start command, the buildpack runs the node server as the init process, and thus it ignores any signal with the default action. As a result, the process will not terminate on SIGINT or SIGTERM unless it is coded to do so. You can also use docker's --init flag to wrap your node process with an init system that will properly handle signals.

Specifying a project path

To specify a project subdirectory to be used as the root of the app, please use the BP_NODE_PROJECT_PATH environment variable at build time either directly (ex. pack build my-app --env BP_NODE_PROJECT_PATH=./src/my-app) or through a project.toml file. This could be useful if your app is a part of a monorepo.