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Lumir Balhar
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README.md
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README.md
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Python 3.8 container image
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===================
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=========================
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This container image includes Python 3.8 as a [S2I](https://github.com/openshift/source-to-image) base image for your Python 3.8 applications.
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Users can choose between RHEL and CentOS based builder images.
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The RHEL images are available in the [Red Hat Container Catalog](https://access.redhat.com/containers/),
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the CentOS images are available on [Docker Hub](https://hub.docker.com/r/centos/),
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the CentOS images are available on [Quay.io](https://quay.io/organization/centos7),
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and the Fedora images are available in [Fedora Registry](https://registry.fedoraproject.org/).
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The resulting image can be run using [podman](https://github.com/containers/libpod) or
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[docker](http://docker.io).
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@ -29,28 +29,104 @@ modules for their web applications. There is no guarantee for any specific npm o
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version, that is included in the image; those versions can be changed anytime and
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the nodejs itself is included just to make the npm work.
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Usage
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---------------------
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Usage in Openshift
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------------------
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For this, we will assume that you are using the supported image, available via `python:3.8` imagestream tag in Openshift.
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Building a simple [python-sample-app](https://github.com/sclorg/s2i-python-container/tree/master/3.8/test/setup-test-app) application
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Building a simple [python-sample-app](https://github.com/sclorg/django-ex.git) application
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in Openshift can be achieved with the following step:
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```
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oc new-app python:3.8~https://github.com/sclorg/s2i-python-container.git --context-dir=3.8/test/setup-test-app/
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oc new-app python:3.8~https://github.com/sclorg/django-ex.git
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```
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The same application can also be built using the standalone [S2I](https://github.com/openshift/source-to-image) application on systems that have it available:
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```
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$ s2i build https://github.com/sclorg/s2i-python-container.git --context-dir=3.8/test/setup-test-app/ <image_name> python-sample-app
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```
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Where `<image_name>` is the s2i-python image you [downloaded from RHEL, Centos or Fedora registry](../README.md#Download) or [built](../README.md#Build) from these sources. For example ubi8/python-36, centos/python-36-centos7 or f31/python3.
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**Accessing the application:**
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```
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$ curl 127.0.0.1:8080
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$ oc get pods
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$ oc exec <pod> -- curl 127.0.0.1:8080
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```
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Source-to-Image framework and scripts
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-------------------------------------
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This image supports the [Source-to-Image](https://docs.openshift.com/container-platform/3.11/creating_images/s2i.html)
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(S2I) strategy in OpenShift. The Source-to-Image is an OpenShift framework
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which makes it easy to write images that take application source code as
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an input, use a builder image like this Python container image, and produce
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a new image that runs the assembled application as an output.
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To support the Source-to-Image framework, important scripts are included in the builder image:
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* The `/usr/libexec/s2i/assemble` script inside the image is run to produce a new image with the application artifacts.
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The script takes sources of a given application and places them into appropriate directories inside the image.
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It utilizes some common patterns in Perl application development (see the **Environment variables** section below).
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* The `/usr/libexec/s2i/run` script is set as the default command in the resulting container image (the new image with the application artifacts).
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It runs your application according to settings in `APP_MODULE`, `APP_FILE` or `APP_SCRIPT` environment variables or it tries to detect the best
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way automatically.
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Building an application using a Dockerfile
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------------------------------------------
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Compared to the Source-to-Image strategy, using a Dockerfile is a more
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flexible way to build a Python container image with an application.
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Use a Dockerfile when Source-to-Image is not sufficiently flexible for you or
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when you build the image outside of the OpenShift environment.
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To use the Python image in a Dockerfile, follow these steps:
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#### 1. Pull a base builder image to build on
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```
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podman pull registry.access.redhat.com/ubi8/python-38
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```
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#### 2. Pull and application code
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An example application available at https://github.com/sclorg/django-ex.git is used here. Feel free to clone the repository for further experiments.
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You can also take a look at code examples in s2i-python-container repository: https://github.com/sclorg/s2i-python-container/tree/master/examples
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```
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git clone https://github.com/sclorg/django-ex.git app-src
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```
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#### 3. Prepare an application inside a container
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This step usually consists of at least these parts:
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* putting the application source into the container
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* installing the dependencies
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* setting the default command in the resulting image
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For all these three parts, users can either setup all manually and use commands `python` and `pip` explicitly in the Dockerfile,
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or users can use the Source-to-Image scripts inside the image.
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The manual way comes with the highest level of flexibility but requires you to know how to work
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with modules or software collections manually, how to setup virtual environment with the right version
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of Python and many more. On the other hand, using Source-to-Image scripts makes your Dockerfile
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prepared for a future flawless switch to a newer or different platform.
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To use the Source-to-Image scripts and build an image using a Dockerfile, create a Dockerfile with this content:
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```
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FROM registry.access.redhat.com/ubi8/python-38
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# Add application sources to a directory that the assemble script expects them
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# and set permissions so that the container runs without root access
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USER 0
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ADD app-src /tmp/src
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RUN chown -R 1001:0 /tmp/src
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USER 1001
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# Install the dependencies
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RUN /usr/libexec/s2i/assemble
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# Set the default command for the resulting image
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CMD /usr/libexec/s2i/run
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```
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#### 4. Build a new image from a Dockerfile prepared in the previous step
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```
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podman build -t python-app .
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```
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#### 5. Run the resulting image with final application
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```
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podman run -d python-app
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```
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Environment variables
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@ -244,7 +320,7 @@ following ways, in precedence order:
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application.
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Hot deploy
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---------------------
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----------
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If you are using Django, hot deploy will work out of the box.
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