Node.js Buildpack

The Node.js Paketo Buildpack supports several popular configurations for Node.js apps.

To build a sample app locally with this CNB using the pack CLI, run

git clone https://github.com/paketo-buildpacks/samples
cd samples/nodejs/npm
pack build my-app --buildpack gcr.io/paketo-buildpacks/nodejs
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See samples for how to run the app.

Supported dependencies

The Node.js Paketo Buildpack supports several versions of Node.js. For more details on the specific versions supported in a given buildpack version, see the release notes.

Specifying a Node Engine Version

The Node Engine CNB (Cloud Native Buildpack) allows you to specify a version of Node.js to use during deployment. This version can be specified in a number of ways, including through .nvmrc, buildpack.yml, or package.json files. When specifying a version of the Node.js engine, you must choose a version that is available within the buildpack.

The buildpack prioritizes the versions specified in each possible configuration location with the following precedence, from highest to lowest: buildpack.yml, package.json, .nvmrc.

Using buildpack.yml

To configure the buildpack to use Node.js v12.12.0 when deploying your app, include the values below in your buildpack.yml file:

---
nodejs:
  version: 12.12.0
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Using package.json

If your apps use npm or yarn, you can specify the Node.js version your apps use during deployment by configuring the engines field in the package.json file. To configure the buildpack to use Node.js v12.12.0 when deploying your app, include the values below in your package.json file:

{
  "engines": {
    "node": "12.12.0"
  }
}
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For more information about the engines configuration option in the package.json file, see the engines section of the npm-package.json topic in the NPM documentation.

Using .nvmrc

Node Version Manager is a common option for managing the Node.js version an app uses. To specify the Node.js version your apps use during deployment, include a .nvmrc file with the version number. For more information about the contents of a .nvmrc file, see .nvmrc in the Node Version Manager repository on GitHub.

Buildpack-Set Environment Variables

The Node.js CNB sets a number of environment variables during the build and launch phases of the app lifecycle. The sections below describe each environment variable and its impact on your app.

MEMORY_AVAILABLE

The MEMORY_AVAILABLE environment variable reports the total amount of memory available to the app. The Node.js CNB calculates this value from the limits specified by the operating system in /sys/fs/cgroup/memory/memory.limit_in_bytes.

• Set by: profile.d
• Phases: launch
• Value: non-negative integer

NODE_ENV

The NODE_ENV environment variable specifies the environment in which the app runs.

• Set by: node-engine buildpack
• Phases: build
• Value: production

NODE_HOME

The NODE_HOME environment variable sets the path to the node installation.

• Set by: node-engine buildpack
• Phases: build
• Value: path to the node installation

NODE_VERBOSE

The NODE_VERBOSE environment variable adjusts the amount of logging output from NPM during installs.

• Set by: node-engine buildpack
• Phases: build
• Value: false

NPM_CONFIG_LOGLEVEL

The NPM_CONFIG_LOGLEVEL environment variable adjusts the level of logging NPM uses.

• Set by: npm-install buildpack
• Phases: build
• Value: “error”

NPM_CONFIG_PRODUCTION

The NPM_CONFIG_PRODUCTION environment variable installs only production dependencies if NPM install is used.

• Set by: npm-install buildpack
• Phases: build
• Value: false

PATH

The node_modules/.bin directory is appended onto the PATH environment variable

• Set by: yarn-install or npm-install buildpacks
• Phases: build
• Value: path to the node_modules/.bin directory

Enabling Heap Memory Optimization

Node.js limits the total size of all objects on the heap. Enabling the optimize-memory feature sets this value to three-quarters of the total memory available in the container. For example, if your app is limited to 1 GB when pushed, the heap of your Node.js app is limited to 768 MB.

There are two ways to enable memory optimization: through your buildpack.yml file, and by using the OPTIMIZE_MEMORY environment variable.

Use the buildpack.yml

To enable memory optimization through your buildpack.yml file, add the values below to your buildpack.yml file:

---
nodejs:
  optimize-memory: true
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Use the OPTIMIZE_MEMORY Environment Variable

To enable memory optimization through the OPTIMIZE_MEMORY environment variable, set it to true.

pack build my-app \
  --buildpack gcr.io/paketo-buildpacks/nodejs \
  --env OPTIMIZE_MEMORY=true
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Package Management with NPM

Many Node.js apps require a number of third-party libraries to perform common tasks and behaviors. NPM is an option for managing these third-party dependencies that the Node.js CNB fully supports. Including a package.json file in your app source code triggers the NPM installation process. The sections below describe the NPM installation process run by the buildpack.

NPM Installation Process

NPM supports several distinct methods for installing your package dependencies. Specifically, the Node.js CNB runs either the npm install, npm rebuild, or npm ci commands to build your app with the right set of dependencies. When deciding which installation process to use, the Node.js CNB consults your app source code, looking for the presence of specific files or directories. The installation process used also determines how the Node.js CNB will reuse layers when rebuilding your app.

The table below shows the process the Node.js CNB uses to determine an installation process for NPM packages. When a combination of the files and directories listed in the table below are present in your app source code, the Node.js CNB uses an installation process that ensures the correct third-party dependencies are installed during the build process.

package-lock.json	node_modules	npm-cache	Command
X	X	X	npm install
X	X	✓	npm install
X	✓	X	npm rebuild
X	✓	✓	npm rebuild
✓	X	X	npm ci
✓	X	✓	npm ci
✓	✓	X	npm rebuild
✓	✓	✓	npm ci

The following sections give more information about the files listed in the table above, including how to generate them, if desired.

package-lock.json

The package-lock.json file is generated by running npm install. For more information, see npm-package-lock.json in the NPM documentation.

node_modules

The node_modules directory contains vendored copies of all the packages installed by the npm install process. For more information, see the Node Modules section of the npm-folders topic in the NPM documentation.

npm-cache

The npm-cache directory contains a content-addressable cache that stores all HTTP-request- and package-related data. Additionally, including a cache ensures that the app can be built entirely offline.

To populate an npm-cache directory:

1. Navigate to your source code directory.
2. Run:

   npm ci --cache npm-cache
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For more information about the NPM cache, see npm-cache in the NPM documentation.

Determining Node Modules Layer Reuse

To improve build times for apps, the Node.js CNB has a method for reusing the build results from previous builds. When the CNB determines that a portion of the build process can be reused from a previous build, the CNB uses the previous result. Each installation process uses a different method for determining whether the CNB can reuse a previous build result.

For npm install, the CNB never reuses a node_modules directory from previous builds.

For npm rebuild, the CNB can reuse a node_modules directory from a previous build if the included node_modules directory in the app source code has not changed since the prior build.

For npm ci, the CNB can reuse a node_modules directory from a previous build if the package-lock.json file included in the app source code has not changed since the prior build.

NPM Start Command

As part of the build process, the Node.js CNB determines a start command for your app. The start command differs depending on which package management tooling the Node.js CNB uses. If the Node.js CNB uses npm or yarn to install packages, the start command is generated from the contents of package.json.

Package Management with Yarn

Many Node.js apps require a number of third-party libraries to perform common tasks and behaviors. Yarn is an alternative option to NPM for managing these third-party dependencies. Including package.json and yarn.lock files in your app source code triggers the Yarn installation process.

Yarn Installation Process

The Node.js CNB runs yarn install and yarn check to ensure that third-party dependencies are properly installed. The yarn.lock file contains a fully resolved set of package dependencies that Yarn manages. For more information, see yarn.lock in the Yarn documentation.

Yarn Start Command

As part of the build process, the Node.js CNB determines a start command for your app. The start command differs depending on which package management tooling the Node.js CNB uses. If the Node.js CNB uses yarn to install packages, the start command is yarn start.

Projects Without Package Management

The Node.js CNB also supports simple apps that do not require third-party packages.

Start Command

If no package manager is detected, the Node.js CNB will set the start command node server.js. The app name is not currently configurable.

Stack support

The Node.js Buildpack runs fine on the Base builder for most apps. If your app requires compilation of native extensions using node-gyp, the buildpack requires that you use the Full builder. This is because node-gyp requires python which is excluded from the the Base builder, and the module may require other shared objects.