1-hello-world-begin.md

1. Build and Run a Local Hello World application

To introduce the concepts and foundations within OpenShift we are going to start with some simple source and tests of a NodeJS application.

1.1 Simple Application

Start by cloning the repo and using the files needed in this first step. In a terminal window:

git clone https://github.com/jeremycaine/hello-world
cd hello-world
cp ./src/server-v1.js ./server.js
npm install
npm run start

The output will show the build description infromation and the process id the app is running as.

> hello-world@1.0.0 start /Users/jeremycaine/Documents/code/github.com/jeremycaine/hello-world
> node server.js

Build:
-version: v1
-description: Simple server; No Signal intercept

Process ID: 8891
Server version is running on http://localhost:3000

From another terminal check the application is running

$ curl http://localhost:3000
Hello World ! (version v1)

and observe the log output in the original terminal window

...
Server version is running on http://localhost:3000
hello-world called
...

1.2 Add Signal Handling

Next we want to add signal handling to the NodeJS application so it can respond to graceful and unexpected termination signals.

cp ./src/server-v2.js ./server.js
npm install
npm run start

Output has changed to

> hello-world@1.0.0 start /Users/jeremycaine/Documents/code/github.com/jeremycaine/hello-world
> node server.js

Build:
-version: v2
-description: Simple server; With Signal intercept

Server version is running on http://localhost:3000

And if you call curl http://localhost:3000 you see the message Hello World ! (version v2).

But now, the app will respond to a kill action.

Keystroke Ctrl+C is interrupt triggering SIGINT.

...
Process ID: 8891
Server version is running on http://localhost:3000
hello-world called
^CSIGINT signal received
HTTP server closed
hello-world app shutting down

Or if you find the process id (PID) and issue a Kill (SIGTERM) command e.g. kill 9098

Process ID: 9098
Server version is running on http://localhost:3000
SIGTERM signal received
HTTP server closed
hello-world app shutting down

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