shadabahmed/example

canary

About

This application puts up a simple website using NodeJS & Express.

The background color changes based on an environment variable:

BGCOLOR=blue
BGCOLOR=green
BGCOLOR=[unset, or anything else] # Makes the background coral

This variable is read each time the page is loaded, so it can be changed without restarting the server. Please remember not to follow this pattern for a real production application, as it can lead to security issues.

Usage

To run locally:

BGCOLOR=blue bin/www
curl localhost:3000

To run using Docker:

docker build -t canary .
docker run -d -p 3000:3000 -e BGCOLOR=blue canary

Tests

Unit tests can be run using either of the following two commands:

npm test
# or #
./node_modules/mocha/bin/mocha

Health Checks

A health check can be reached at the path /health. It will output a JSON message with a given status code, depending on the environment variable HEALTHY:

For the service to appear healthy, leave the environment variable unset, or set it to any value other than false:

HEALTHY=[unset, or anything else]

< HTTP/1.1 200 OK
< X-Powered-By: Express
< Content-Type: application/json; charset=utf-8
< Content-Length: 35
< ETag: W/"23-uQbt7O5sH6wCP1nXebLaRG6IW0I"
< Date: Fri, 15 Feb 2019 17:45:57 GMT
< Connection: keep-alive
< 
* Connection #0 to host localhost left intact
{"status":"OK","message":"Healthy"}

Set the environment variable to false to make the service appear unhealthy:

HEALTHY=false

< HTTP/1.1 500 Internal Server Error
< X-Powered-By: Express
< Content-Type: application/json; charset=utf-8
< Content-Length: 44
< ETag: W/"2c-ZoDT1lW6rXfncQstrBV/2BgGlr8"
< Date: Fri, 15 Feb 2019 17:45:08 GMT
< Connection: keep-alive
< 
* Connection #0 to host localhost left intact
{"status":"ERROR","message":"Generic Error"}