Python Docker image =================== This repository contains the source for building various versions of the Python application as a reproducible Docker image using [source-to-image](https://github.com/openshift/source-to-image). Users can choose between RHEL and CentOS based builder images. The resulting image can be run using [Docker](http://docker.io). Usage --------------------- To build a simple [python-sample-app](https://github.com/openshift/s2i-python/tree/master/3.6/test/setup-test-app) application using standalone [S2I](https://github.com/openshift/source-to-image) and then run the resulting image with [Docker](http://docker.io) execute: * **For RHEL based image** ``` $ s2i build https://github.com/sclorg/s2i-python-container.git --context-dir=3.6/test/setup-test-app/ rhscl/python-36-rhel7 python-sample-app $ docker run -p 8080:8080 python-sample-app ``` * **For CentOS based image** ``` $ s2i build https://github.com/sclorg/s2i-python-container.git --context-dir=3.6/test/setup-test-app/ centos/python-36-centos7 python-sample-app $ docker run -p 8080:8080 python-sample-app ``` **Accessing the application:** ``` $ curl 127.0.0.1:8080 ``` Repository organization ------------------------ * **``** * **Dockerfile** CentOS based Dockerfile. * **Dockerfile.rhel7** RHEL based Dockerfile. In order to perform build or test actions on this Dockerfile you need to run the action on a properly subscribed RHEL machine. * **`s2i/bin/`** This folder contains scripts that are run by [S2I](https://github.com/openshift/source-to-image): * **assemble** Used to install the sources into the location where the application will be run and prepare the application for deployment (eg. installing dependencies, etc.) * **run** This script is responsible for running the application by using the application web server. * **usage*** This script prints the usage of this image. * **`contrib/`** This folder contains a file with commonly used modules. * **`test/`** This folder contains a [S2I](https://github.com/openshift/source-to-image) test framework with a simple server. * **`setup-test-app/`** Simple Gunicorn application used for testing purposes by the [S2I](https://github.com/openshift/source-to-image) test framework. * **`standalone-test-app/`** Simple standalone application used for testing purposes by the [S2I](https://github.com/openshift/source-to-image) test framework. * **run** Script that runs the [S2I](https://github.com/openshift/source-to-image) test framework. Environment variables --------------------- To set these environment variables, you can place them as a key value pair into a `.s2i/environment` file inside your source code repository. * **APP_SCRIPT** Used to run the application from a script file. This should be a path to a script file (defaults to `app.sh` unless set to null) that will be run to start the application. * **APP_FILE** Used to run the application from a Python script. This should be a path to a Python file (defaults to `app.py` unless set to null) that will be passed to the Python interpreter to start the application. * **APP_MODULE** Used to run the application with Gunicorn, as documented [here](http://docs.gunicorn.org/en/latest/run.html#gunicorn). This variable specifies a WSGI callable with the pattern `MODULE_NAME:VARIABLE_NAME`, where `MODULE_NAME` is the full dotted path of a module, and `VARIABLE_NAME` refers to a WSGI callable inside the specified module. Gunicorn will look for a WSGI callable named `application` if not specified. If `APP_MODULE` is not provided, the `run` script will look for a `wsgi.py` file in your project and use it if it exists. If using `setup.py` for installing the application, the `MODULE_NAME` part can be read from there. For an example, see [setup-test-app](https://github.com/openshift/s2i-python/tree/master/3.6/test/setup-test-app). * **APP_HOME** This variable can be used to specify a sub-directory in which the application to be run is contained. The directory pointed to by this variable needs to contain `wsgi.py` (for Gunicorn) or `manage.py` (for Django). If `APP_HOME` is not provided, the `assemble` and `run` scripts will use the application's root directory. * **APP_CONFIG** Path to a valid Python file with a [Gunicorn configuration](http://docs.gunicorn.org/en/latest/configure.html#configuration-file) file. * **DISABLE_COLLECTSTATIC** Set this variable to a non-empty value to inhibit the execution of 'manage.py collectstatic' during the build. This only affects Django projects. * **DISABLE_MIGRATE** Set this variable to a non-empty value to inhibit the execution of 'manage.py migrate' when the produced image is run. This only affects Django projects. * **PIP_INDEX_URL** Set this variable to use a custom index URL or mirror to download required packages during build process. This only affects packages listed in requirements.txt. * **UPGRADE_PIP_TO_LATEST** Set this variable to a non-empty value to have the 'pip' program be upgraded to the most recent version before any Python packages are installed. If not set it will use whatever the default version is included by the platform for the Python version being used. * **WEB_CONCURRENCY** Set this to change the default setting for the number of [workers](http://docs.gunicorn.org/en/stable/settings.html#workers). By default, this is set to the number of available cores times 2. Source repository layout ------------------------ You do not need to change anything in your existing Python project's repository. However, if these files exist they will affect the behavior of the build process: * **requirements.txt** List of dependencies to be installed with `pip`. The format is documented [here](https://pip.pypa.io/en/latest/user_guide.html#requirements-files). * **setup.py** Configures various aspects of the project, including installation of dependencies, as documented [here](https://packaging.python.org/en/latest/distributing.html#setup-py). For most projects, it is sufficient to simply use `requirements.txt`. Run strategies -------------- The Docker image produced by s2i-python executes your project in one of the following ways, in precedence order: * **Gunicorn** The Gunicorn WSGI HTTP server is used to serve your application in the case that it is installed. It can be installed by listing it either in the `requirements.txt` file or in the `install_requires` section of the `setup.py` file. If a file named `wsgi.py` is present in your repository, it will be used as the entry point to your application. This can be overridden with the environment variable `APP_MODULE`. This file is present in Django projects by default. If you have both Django and Gunicorn in your requirements, your Django project will automatically be served using Gunicorn. * **Django development server** If you have Django in your requirements but don't have Gunicorn, then your application will be served using Django's development web server. However, this is not recommended for production environments. * **Python script** This would be used where you provide a Python code file for running you application. It will be used in the case where you specify a path to a Python script via the `APP_FILE` environment variable, defaulting to a file named `app.py` if it exists. The script is passed to a regular Python interpreter to launch your application. * **Application script file** This is the most general way of executing your application. It will be used in the case where you specify a path to an executable script file via the `APP_SCRIPT` environment variable, defaulting to a file named `app.sh` if it exists. The script is executed directly to launch your application. Hot deploy --------------------- If you are using Django, hot deploy will work out of the box. To enable hot deploy while using Gunicorn, make sure you have a Gunicorn configuration file inside your repository with the [`reload`](https://gunicorn-docs.readthedocs.org/en/latest/settings.html#reload) option set to `true`. Make sure to specify your config via the `APP_CONFIG` environment variable. To change your source code in running container, use Docker's [exec](https://docs.docker.com/reference/commandline/exec/) command: ``` docker exec -it /bin/bash ``` After you enter into the running container, your current directory is set to `/opt/app-root/src`, where the source code is located.