Building and uploading netcdf4-python wheels

We automate wheel building using this custom github repository that builds on the travis-ci OSX machines and the travis-ci Linux machines.

The travis-ci interface for the builds is https://travis-ci.org/MacPython/netcdf4-python-wheels

The driving github repository is https://github.com/MacPython/netcdf4-python-wheels

How it works

The wheel-building repository:

• does a fresh build of any required C / C++ libraries;
• builds a netcdf4-python wheel, linking against these fresh builds;
• processes the wheel using delocate (OSX) or auditwheel repair (Manylinux1). delocate and auditwheel copy the required dynamic libraries into the wheel and relinks the extension modules against the copied libraries;
• uploads the built wheels to http://wheels.scipy.org (a Rackspace container kindly donated by Rackspace to scikit-learn).

The resulting wheels are therefore self-contained and do not need any external dynamic libraries apart from those provided as standard by OSX / Linux as defined by the manylinux1 standard.

The .travis.yml file in this repository has a line containing the API key for the Rackspace container encrypted with an RSA key that is unique to the repository - see http://docs.travis-ci.com/user/encryption-keys. This encrypted key gives the travis build permission to upload to the Rackspace directory pointed to by http://wheels.scipy.org.

Triggering a build

You will likely want to edit the .travis.yml file to specify the BUILD_COMMIT before triggering a build - see below.

You will need write permission to the github repository to trigger new builds on the travis-ci interface. Contact us on the mailing list if you need this.

You can trigger a build by:

• making a commit to the netcdf4-python-wheels repository (e.g. with git commit --allow-empty); or
• clicking on the circular arrow icon towards the top right of the travis-ci page, to rerun the previous build.

In general, it is better to trigger a build with a commit, because this makes a new set of build products and logs, keeping the old ones for reference. Keeping the old build logs helps us keep track of previous problems and successful builds.

Which netcdf4-python commit does the repository build?

The netcdf4-python-wheels repository will build the commit specified in the BUILD_COMMIT at the top of the .travis.yml file. This can be any naming of a commit, including branch name, tag name or commit hash.

Uploading the built wheels to pypi

Be careful, http://wheels.scipy.org points to a container on a distributed content delivery network. It can take up to 15 minutes for the new wheel file to get updated into the container at http://wheels.scipy.org.

The same contents appear at https://3f23b170c54c2533c070-1c8a9b3114517dc5fe17b7c3f8c63a43.ssl.cf2.rackcdn.com; you might prefer this address because it is https.

When the wheels are updated, you can download them to your machine manually, and then upload them manually to pypi, or by using twine. You can also use a script for doing this, housed at : https://github.com/MacPython/terryfy/blob/master/wheel-uploader

For the wheel-uploader script, you'll need twine and beautiful soup 4.

You will typically have a directory on your machine where you store wheels, called a wheelhouse. The typical call for wheel-uploader would then be something like:

VERSION=1.2.4
CDN_URL=https://3f23b170c54c2533c070-1c8a9b3114517dc5fe17b7c3f8c63a43.ssl.cf2.rackcdn.com
wheel-uploader -r warehouse -u $CDN_URL -s -v -w ~/wheelhouse -t macosx netCDF4 $VERSION
wheel-uploader -r warehouse -u $CDN_URL -s -v -w ~/wheelhouse -t manylinux1 netCDF4 $VERSION

where:

• -r warehouse uses the upcoming Warehouse PyPI server (it is more reliable than the current PyPI service for uploads);
• -u gives the URL from which to fetch the wheels, here the https address, for some extra security;
• -s causes twine to sign the wheels with your GPG key;
• -v means give verbose messages;
• -w ~/wheelhouse means download the wheels from to the local directory ~/wheelhouse.

netCDF4 is the root name of the wheel(s) to download / upload, and 1.2.4 is the version to download / upload.

In order to use the Warehouse PyPI server, you will need something like this in your ~/.pypirc file:

[distutils]
index-servers =
    pypi
    warehouse

[pypi]
username:your_user_name
password:your_password

[warehouse]
repository: https://upload.pypi.io/legacy/
username: your_user_name
password: your_password

So, in this case, wheel-uploader will download all wheels starting with netCDF4-1.2.4- from http://wheels.scipy.org to ~/wheelhouse, then upload them to PyPI.

Of course, you will need permissions to upload to PyPI, for this to work.