OpenShift zero-downtime deployment

OpenShift is a great PaaS for developing your webapp. When it gets to production however, you don”t want any downtime when you are deploying.

Luckily there is a simple fix (presuming you set up a scaling app).

Find the cartridge you want to scale (jbossews-2.0 on mine)

rhc show-app yourapp

should show you the cartridges jbossews-2.0 (Tomcat 7 (JBoss EWS 2.0))
Scaling: x2 (minimum: 2, maximum: 16) on small gears
haproxy-1.4 (Web Load Balancer)
Gears: Located with jbossews-2.0
mongodb-2.2 (MongoDB 2.2)
Gears: 1 small
Database Name: api
Password: ZlRiDvsyRqcZ
Username: admin

then run the following to set the minimum number of web workers to 2

rhc scale-cartridge --a api --min 2 --max 16 -c cartridge-name

Next enable hot deployment for your app by adding the following file to your app