Getting Started with OpenShift

Chapter 6. Library Dependencies

All applications beyond the very simple will have a requirement to use outside libraries or dependencies. Examples of dependencies might be libraries for database connectivity, turning images to text (object character recognition or OCR), calculating statistics, or web templating. In this chapter we will show you how to use libraries in your OpenShift applications. We will add the database drivers to our Insult App and then use it to access the insults stored in the database.

Where to Declare Dependencies

All modern programming languages have a “build” process; OpenShift takes advantage of this to build your application dependencies. At the time of this writing we are using the processes listed in Table 6-1 to pull in dependencies for external libraries.

Table 6-1. Dependency mechanisms used by OpenShift, by language

Language	Dependency mechanism
Java	Maven
Python	Pip
Ruby	Gem
Node.js (JavaScript)	NPM
PHP	Pear
Perl	CPAN

We have tried to make the process as close to development on your local machine as possible. So, for example, with Python if you wanted to download the “default” PostgreSQL drivers (psycopg2) to your local machine you would use Pip:

$ pip install psycopg2

This would install the Psycopg2 drivers to a location where Python can see them on your local machine. The way to reproduce this functionality on OpenShift is to include the dependency in the appropriate “application metadata” file. When you include your dependencies in this file, OpenShift will notice ...