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What is Node.js?
Node.js is a software platform for scalable server-side and networking applications. Node.js applications are written in JavaScript and can be run within the Node.js runtime on Mac OS X, Windows, and Linux without changes.
Node.js applications are designed to maximize throughput and efficiency, using non-blocking I/O and asynchronous events. Node.js applications run single-threaded, although Node.js uses multiple threads for file and network events. Node.js is commonly used for real-time applications due to its asynchronous nature.
Node.js internally uses the Google V8 JavaScript engine to execute code; a large percentage of the basic modules are written in JavaScript. Node.js contains a built-in, asynchronous I/O library for file, socket, and HTTP communication. The HTTP and socket support allows Node.js to act as a web server without additional software such as Apache.
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How to use this image
Create a Dockerfile in your Node.js app project
FROM node:4-onbuild
# replace this with your application's default port
EXPOSE 8888
You can then build and run the Docker image:
$ docker build -t my-nodejs-app .
$ docker run -it --rm --name my-running-app my-nodejs-app
Notes
The image assumes that your application has a file named package.json listing its dependencies and defining its start script.
It also assumes that you have a file named .dockerignore otherwise it will copy your local npm modules:
node_modules
We have assembled a Best Practices Guide for those using these images on a daily basis.
All of the images contain pre-installed versions of node, npm, and yarn. For each supported architecture, the supported variants are different. In the file architectures, it lists all supported variants for all of the architectures that we support now.
Run a single Node.js script
For many simple, single file projects, you may find it inconvenient to write a complete Dockerfile. In such cases, you can run a Node.js script by using the Node.js Docker image directly:
$ docker run -it --rm --name my-running-script -v "$PWD":/usr/src/app -w /usr/src/app node:4 node your-daemon-or-script.js
Verbosity
By default the Node.js Docker Image has npm log verbosity set to info instead of the default warn. This is because of the way Docker is isolated from the host operating system and you are not guaranteed to be able to retrieve the npm-debug.log file when npm fails.
When npm fails, it writes it's verbose log to a log file inside the container. If npm fails during an install when building a Docker Image with the docker build command, this log file will become inaccessible when Docker exits.
The Docker Working Group have chosen to be overly verbose during a build to provide an easy audit trail when install fails. If you prefer npm to be less verbose you can easily reset the verbosity of npm using the following techniques:
Dockerfile
If you create your own Dockerfile which inherits from the node image you can simply use ENV to override NPM_CONFIG_LOGLEVEL.
FROM node
ENV NPM_CONFIG_LOGLEVEL warn
...
Docker Run
If you run the node image using docker run you can use the -e flag to override NPM_CONFIG_LOGLEVEL.
$ docker run -e NPM_CONFIG_LOGLEVEL=warn node ...
NPM run
If you are running npm commands you can use --loglevel to control the verbosity of the output.
$ docker run node npm --loglevel=warn ...