S03L03 Transitioning the API Code.md

Transitioning the API Code

Get a Copy of the Code

The Plant Shop code can be found in GitHub at https://github.com/ACloudGuru/ctaws-plant-shop. Feel free to make your own fork of the project!

Log into the AWS management console, then search for and navigate to the CloudShell service.

If you wish, you can also work with the code on your own machine, or directly via GitHub (if you make your own fork).

Get a copy of the source code:

git clone https://github.com/ACloudGuru/ctaws-plant-shop.git

The main source code file for the API is api/server.js. We will need to edit this source code to bo ready for Lambda.

If you want to see an example of how it should look at the end, a Lambda-ready version of the code can be found in the project at api/lambda/index.js.

Modify the Code

The main change is to remove the built-in express web server and run the code in an event handler instead. Lambda has no need of a built-in web server, as it will handle all web request functionality. Instead, Lambda will pass an "event" to our code, and our code needs to be set up to process the event.

cd ctaws-plant-shop

cp api/server.js api/lambda/index.js

vi api/lambda/index.js

We can set up an event handler with exports.handler. The final version could look something like this:

var mysql = require('mysql');

exports.handler = (event, context, callback) => {

    var connection = mysql.createConnection({
        host: process.env.DB_HOST,
        user: process.env.DB_USER,
        password: process.env.DB_PASS,
        database: "plantshop",
    });

    connection.query('select * from items', function (error, results, fields) {
        if (error) {
            connection.destroy();
            throw error;
        } else {
            // connected!
            console.log("Query result:");
            console.log(results);
            callback(error, {items: results});
            connection.end(function (err) { callback(err, results);});
        }
    });
};