Node plugin tutorial

Let's create a plugin based on the node plugin template. We will called it foo_nodejs.

First, bootstrap the plugin with the command:

bootstrap_plugin.py create --template=node foo_nodejs

Once you have entered this command, you will be asked to fill in some fields to configure and customize your plugin: for now, press [ENTER] to set the default values, you will be able to modify your plugin configuration anytime later.

The plugin is created in the current directory, inside the directory named foo_nodejs.

Check this directory, it contains few files, including:

foo_nodejs directory: the node.js scripts for your project. Its name is the package name you’ll need to use to import anything inside it. This directory contains:
- server.js: An entry-point for Node.js web servers to serve your project.
package.json file: A kind of a manifest for your project. It can do a lot of things, completely unrelated. It’s a central repository of configuration for tools.

Let's now build the plugin by entering the command from the foo_nodejs plugin directory:

make develop

This command will download and install needed Javascript node modules.

A package-lock.json file is automatically generated for any operations where npm modifies either the node_modules tree, or package.json. It describes the exact tree that was generated, such that subsequent installs are able to generate identical trees, regardless of intermediate dependency updates.and some other dependencies.

You may also check the node_modules directory.

What is the difference between package.json and package-lock.json ?

package-lock.json: records the exact version of each installed package which allows you to re-install them. Future installs will be able to build an identical dependency tree. ...
package.json: records the minimum version you app needs.

package-lock.json is intended to be checked into source control, as Git. You should commit this file.

Important

If you are behind a proxy, you have to set http_proxy and https_proxy environment variables in order to be able to download any Python package you may need.

You may also need to disable your Linux firewall:

      systemctl status firewalld
      systemctl stop firewalld.service
      systemctl disable firewalld

Check the foo_nodejs/server.js script. It is a basic Express application (app) which starts a server and listens for connection. This application responds with Hello World from foo_nodejs! for requests to the homepage. For every other path, it will respond with an HTTP 404 Not Found.

Express application uses a callback function whose parameters are request and response objects:

app.get('/foo_nodejs', function (req, res) {
      res.send('Hello World from foo_nodejs!')
})

Now, you can check your application works by invoking the following URL: http://localhost:18868/foo_nodejs (you may replace localhost by your remote host if needed). A HTML page must display Hello World from foo_nodejs!.

We will extend our "Hello World!" application to handle more types of HTTP requests. Edit the the foo_nodejs/server.js script and add the following lines:

// This responds a POST request for the /foo_nodejs home url
app.post('/foo_nodejs', function (req, res) {
   res.send('Hello World foo_nodejs from a POST request');
})

// This responds a GET request for wxy, waxy, w1234bxy, and so on...
app.get('/foo_nodejs/w*xy', function(req, res) {
   res.send('Page Pattern Match foo_nodejs');
})

// This responds a DELETE request for the /foo_nodejs/del_user url.
app.delete('/foo_nodejs/del_user', function (req, res) {
   res.send('Hello World foo_nodejs from a DELETE request');

})

// This responds a GET request for the /foo_nodejs/list_user url.
app.get('/foo_nodejs/list_user', function (req, res) {
   res.send('Page listing foo_nodejs');
})

Build the plugin with make develop command.

Check your application works by invoking the relevant URLs you added.