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Python

Overview

OpenShift Enterprise provides S2I enabled Python images for building and running Python applications. The Python S2I builder image assembles your application source with any required dependencies to create a new image containing your Python application. This resulting image can be run either by OpenShift Enterprise or by Docker.

Versions

Currently, OpenShift Enterprise provides versions 2.7, 3.3, 3.4, and 3.5 of Python.

Images

This image comes in two flavors, depending on your needs:

  • RHEL 7

  • CentOS 7

RHEL 7 Based Image

The RHEL 7 image is available through Red Hat’s subscription registry using:

$ docker pull registry.access.redhat.com/openshift3/python-33-rhel7

CentOS 7 Based Image

This image is available on DockerHub. To download it:

$ docker pull openshift/python-33-centos7

To use these images, you can either access them directly from these image registries, or push them into your OpenShift Enterprise Docker registry. Additionally, you can create an image stream that points to the image, either in your Docker registry or at the external location. Your OpenShift Enterprise resources can then reference the ImageStream. You can find example image stream definitions for all the provided OpenShift Enterprise images.

Configuration

The Python image supports a number of environment variables which can be set to control the configuration and behavior of the Python runtime.

To set these environment variables, you can place them into a .sti/environment file inside your source code repository, or define them in the environment section of the build configuration’s sourceStrategy definition.

Table 1. Python Environment Variables
Variable name Description

APP_FILE

This variable specifies the file name passed to the python interpreter which is responsible for launching the application. This variable is set to app.py by default.

APP_MODULE

This variable specifies the WSGI callable. It follows the pattern $(MODULE_NAME):$(VARIABLE_NAME), where the module name is a full dotted path and the variable name refers to a function inside the specified module. If you use setup.py for installing the application, then the module name can be read from that file and the variable defaults to application. There is an example setup-test-app available.

APP_CONFIG

This variable indicates the path to a valid Python file with a gunicorn configuration.

DISABLE_COLLECTSTATIC

Set it to a nonempty value to inhibit the execution of manage.py collectstatic during the build. Only affects Django projects.

DISABLE_MIGRATE

Set it to a nonempty value to inhibit the execution of manage.py migrate when the produced image is run. Only affects Django projects.

Hot Deploying

Hot deployment allows you to quickly make and deploy changes to your application without having to generate a new S2I build. If you are using Django, hot deployment works out of the box.

To enable hot deployment while using Gunicorn, ensure you have a Gunicorn configuration file inside your repository with the reload option set to true. Specify your configuration file using the APP_CONFIG environment variable. For example, see the oc new-app command. You can use the oc env command to update environment variables of existing objects.

You should only use this option while developing or debugging; it is not recommended to turn this on in your production environment.

To change your source code in a running pod, use the oc rsh command to enter the container:

$ oc rsh <pod_id>

After you enter into the running container, your current directory is set to /opt/app-root/src, where the source code is located.