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Deploying your TG application with an Egg and Easy Install

How to Build a .egg File for Your Project

An egg is Python’s new distribution format, comparable to a .jar in Java. It’s basically a zip file with a particular directory structure containing the code and a bit of metadata. You can get details on eggs directly from the inventor at the PEAK Developers’ Center.

A freshly quickstarted project will have a setup.py file. This file allows you to easily package your file for redistribution both for internal use and for sharing on PyPI. Creating an egg is as simple as switching to your project directory and running:

python setup.py bdist_egg

This will produce an egg file for the current version of your project in the ./dist folder.

How to Install Your .egg

The simplest way to use an egg is to copy it over to your production machine and do:

[sudo] easy_install *myapp*.egg

Note

If you do not have easy_install on the target machine, you need to install the setuptools package first to get it, either through your operating system’s software package system or by downloading the bootstrapping program ez_setup.py. Conveniently, ez_setup.py also takes the same arguments that easy_install takes, so python ez_setup.py *myapp*.egg will do the full install. Be sure to switch over to easy_install after the first run.

Installing Dependencies

As long as the setup.py lists TurboGears as a requirement (see the section on adding requirements), it should be possible for somebody to install your application with just the egg and easy_install or ez_setup.py including the installation of TurboGears itself and all its dependencies.

Warning

This is a nice feature for application deployment, but be aware that installing an egg can also upgrade TurboGears and other packages if the egg requires a later version than the system provides. If long term system stability is important to you, you may want to investigate solutions like virtualenv.

Please be also aware that by default the setup.py file of a quickstarted project will require a TurboGears version that is equal or newer than the version which was used to run paster quickstart. This means if you install your application and TurboGears is not installed or only an older version than required, easy_install will fetch and install the newest TurboGears version it can find. This includes beta versions and release candidates of future TurboGears versions with a higher major version number. If you want to ensure that your application will only install a known good TurboGears version, you should add a more specific version constraint for TurboGears in setup.py (again, see adding requirements on how to do this).

Running Your Application

TurboGears apps take advantage of the paster serve functionality by providing a way to start the server as you would any other paste application

Once you have your application installed in the proper location simply cd to that location and type the following command:

$ paster serve production.ini

where production.ini is your production configuration file, which is covered in the next section.

The Production Configuration

To get everything up and running, you also need a production configuration file (usually called production.ini by convention) and pass the name of this file as the first and only argument to your start script.

The Production Database

Your production configuration should specify location and parameters for the production database that your project will use.

This can be the same database as the one you created with paster setup-app while developing your application. If you use a different database for production (a wise decision) you will need to create the tables in the database, before using it for the first time.

paster setup-app production.ini

will create the necessary tables using the database specified in the deployment configuration file production.ini.

Daemonizing your Application

Once you are satisfied with the running of your server, it makes sense to run it in a background mode so that you may log off, leaving your server running. Paste does this with the –daemon argument. It looks something like this:

paster serve production.ini --daemon

To stop your application from running, simply type:

paster serve production.ini --stop-daemon

How to Make Your Project’s .egg Require Additional Packages

By specifying all your dependencies, not just TurboGears, easy_install can completely automate your package setup. You specify dependencies by modifying the requires argument in setup() in your setup.py file to include the name of the package you need. Here is an example that adds the fictional package FooBar as an installation requirement:

setup(
    name="test",
    version=0.1,
    zip_safe=False,
    install_requires = [
        "TurboGears >= 2.1",
        "FooBar"
    ],
    ...

If you need a specific version of the package you can use comparison operators against the version name. You can see that happening in the above example, as this project depends on “TurboGears version 2.1 or greater”. See the setuptools documentation for more information on declaring dependencies.

How to Make Your Project Available on PyPI

If you decide to share your creation with the world, the easiest way to do so is by using the Python Package Index. Before you can upload your project to PyPI, you will need an account. You can create one on the PyPI registration page.

After you have created an account, you will need to tell setuptools your account information for uploading the file. See the distutils documentation for details on this.

Now that you have your account configured and you’ve updated the metadata in setup.py, you need to register a page for your application. setuptools can do this for you automatically with the following command:

python setup.py register

Once you have everything configured, setuptools can upload your egg automatically. Here is the command you need:

python setup.py bdist_egg upload

Any eggs you created in the process should also be available in the dist/ folder of your project.

You can also register projects and upload your eggs manually. This setuptools tutorial should be enough to get you going.

References

Take a look at Generating your own Private Python Package Index to see how to make your own personal PYPI for distribution within a closed environment.