To make your app runnable, a default start command must be set. You’ll need to add the following to the end of your build script:
# ...
# Set default start command
cat > "${CNB_LAYERS_DIR}/launch.toml" << EOL
[[processes]]
type = "web"
command = ["node", "app.js"]
default = true
EOL
# ...
Your full node-js-buildpack/bin/build script should now look like the following:
#!/usr/bin/env bash
set -eo pipefail
echo "---> NodeJS Buildpack"
# 1. CREATE THE LAYER DIRECTORY
node_js_layer="${CNB_LAYERS_DIR}"/node-js
mkdir -p "${node_js_layer}"
# 2. DOWNLOAD node-js
echo "---> Downloading and extracting NodeJS"
node_js_url=https://nodejs.org/dist/v18.18.1/node-v18.18.1-linux-x64.tar.xz
wget -q -O - "$node_js_url" | tar -xJf - --strip-components 1 -C "${node_js_layer}"
# 3. MAKE node-js AVAILABLE DURING LAUNCH
echo -e '[types]\nlaunch = true' > "${CNB_LAYERS_DIR}/node-js.toml"
# ========== ADDED ===========
# 4. SET DEFAULT START COMMAND
cat > "${CNB_LAYERS_DIR}/launch.toml" << EOL
[[processes]]
type = "web"
command = ["node", "app.js"]
default = true
EOL
Then rebuild your app using the updated buildpack:
pack build test-node-js-app --path ./node-js-sample-app --buildpack ./node-js-buildpack
You should then be able to run your new NodeJS app:
docker run --rm -p 8080:8080 test-node-js-app
and see the server log output:
Server running at http://0.0.0.0:8080/
Test it out by navigating to localhost:8080 in your favorite browser!
We can add multiple process types to a single app. We’ll do that in the next section.