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d1_python

Python components for DataONE clients and servers.

See the documentation on ReadTheDocs.

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v2 and v1 API

v1 API

Contributing

Pull Requests (PRs) are welcome! Before you start coding, feel free to reach out to us and let us know what you plan to implement. We might be able to point you in the right direction.

We try to follow PEP8.

To help keep the style consistent and commit logs, blame/praise and other code annotations accurate, we autoformat all source with Black, isort and docformatter. A script that wraps up the formatting is available at ./dev_tools/src/d1_dev/src-format.py. Simply call it before commit.

Configuration files for isort (./.isort.cfg) and Flake8 (./.style.yapf) are included, and show the formatting options we have selected.

Unit tests

Testing is based on the pytest unit test framework.

Sample files

Most of our tests work by serializing objects generated by the code being tested and comparing them with reference samples stored in files. This allows us to check all properties of generated objects without having to write asserts that check individual properties, eliminating a time consuming and repetitive part of the test writing process.

When writing comparisons manually, one will often select a few properties to check, and when those are determined to be valid, the remaining values are assumed to be correct as well. By comparing complete serialized versions of the objects, we avoid such assumptions.

By storing the expected serialized objects in files instead of in the unit tests themselves, we avoid embedding hard coded documents inside the unit test modules and make it simple to automatically update the expected contents of objects as the code evolves.

When unit tests are being run as part of CI or as a normal guard against regressions in a local development environment, any mismatches between actual and expected serialized versions of objects simply trigger test failures. However, when a test is initially created or the serialized version of an object is expected to change, tests can automatically write or update the sample files they use. This function is enabled by starting pytest with the --sample-ask switch. When enabled, missing or mismatched sample files will not trigger test failures, instead starting an interactive process where differences are displayed together with yes/no prompts for writing or updating the samples. By default, differences are displayed in a GUI window using kdiff3, which provides a nice color coded view of the differences.

The normal procedure for writing a sample based unit test is to just write the test as if the sample already exists, then running the test with --sample-ask and viewing and approving the resulting sample, which is then automatically written to a file. The sample file name is displayed, making it easy to find the file in order to add it to tracking so that it can be committed along with the test module.

When working on large changes that cause many samples to become outdated, reviewing and approving samples can be deferred until the new code approaches stability. This is done by running the tests with --sample-update, which automatically writes or updates samples to match the current results. Then, view and approve the tests with --sample-review before committing.

Typically, it is not desirable to track generated files in Git. However, although the sample files are generated, they are an integral part of the units tests, and should be tracked just like the unit tests themselves.

Also implemented is a simple process for cleaning out unused sample files. Sample files are often orphaned when their corresponding tests are removed or refactored. The process is activated with the --sample-tidy switch. When active, the test session starts by moving all sample files from their default directory, test_docs, to test_docs_tidy. As the sample files are accessed by tests, they are automatically moved back to test_docs, and any files remaining in test_docs_tidy after a complete test run can be untracked and deleted.

When staging test_docs, stage the directory, so that new files are included, and deleted files get deleted on the server:

git add test_utilities/src/d1_test/test_docs
git commit -m 'Update samples'

DataONE Client to Django test adapter

GMN tests are based on an adapter that enables using d1_client with the Django test framework. The adapter mocks Requests to issue requests through the Django test client.

Django includes a test framework with a test client that provides an interface that's similar to that of an HTTP client, but calls Django internals directly. The client enables testing of most functionality of a Django app without actually starting the app as a network service.

For testing GMN's D1 REST interfaces, we want to issue the test requests via the D1 MN client. Without going through the D1 MN client, we would have to reimplement much of what the client does, related to formatting and parsing D1 REST requests and responses.

This module is typically used in tests running under django.test.TestCase and requires an active Django context, such as the one provided by ./manage.py test.

Command line switches

We have added some custom functionality to pytest which can be enabled by launching pytest with the following switches:

Note: None of these switches can be used when running tests in parallel with xdist (-n, --dist, --tx).

Aliases

I have found the following aliases handy for running the tests. If using the bash shell, these can be added to ~/.bashrc.

pytest searches for and runs all tests below the current directory, so starting pytest directly or via one of the aliases from the d1_python directory will run all tests.

To run a specific test module, add a path to the test module. E.g.:

p d1_python/lib_common/src/d1_common/tests/test_checksum.py

To run only a single test, add a filter on the test number. E.g.:

p d1_python/lib_common/src/d1_common/tests/test_checksum.py -k 1050

Debugging tests with PyCharm

Django

Django database test fixture

The GMN tests run in the context of a database that has been prepopulated with randomized data. The fixture file for the database is a JSON file stored in

./test_utilities/src/d1_test/test_docs/json/db_fixture.json.bz2

After changing any of the ORM classes in models.py, the database test fixture must be regenerated. This will often cause sample files to have to be updated as well, by running the tests with --sample-update.

Generate the fixture file with:

./gmn/src/d1_gmn/tests/mk_db_fixture.py

Fixtures can be loaded directly into the test database from the JSON files but it's much faster to keep an extra copy of the db as a template and create the test db as needed with Postgres' "create database from template" function. So we only load the fixtures into a template database and reuse the template. This is implemented in ./conftest.py.

Create template database from fixture with:

./gmn/src/d1_gmn/tests/mk_db_template.py

The template is reused between test runs.

Science object bytes are stored on disk, so they are not captured in the db fixture. If a test needs get(), getChecksum() and replica() to work, it must first create the correct file in GMN's object store or mock object store reads. The bytes are predetermined for a given test PID. See d1_test.d1_test_case.generate_reproducible_sciobj_str() and d1_gmn.app.util.sciobj_file_path().

Setting up the development environment

These instructions are tested on Linux Ubuntu 22.04 and should also work on close derivatives.

Install packaged dependencies

sudo bash -c '
  apt update
  apt -fy dist-upgrade
  apt install -y \
    build-essential \
    curl \
    gir1.2-gtk-4.0 \
    git \
    libbz2-dev \
    libcairo2-dev \
    libffi-dev \
    libgirepository1.0-dev \
    liblzma-dev \
    libncursesw5-dev \
    libreadline-dev \
    librsync-dev \
    libsmbclient-dev \
    libsqlite3-dev \
    libssl-dev \
    libxml2-dev \
    libxmlsec1-dev \
    libxslt1-dev \
    llvm \
    make \
    openssl \
    postgresql \
    postgresql-server-dev-all \
    python-setuptools \
    python3-dev \
    tk-dev \
    wget \
    xz-utils \
    zlib1g-dev
'

Install pyenv

In general, the system version of Python should not be touched. E.g., avoid installing packages with sudo pip.

pyenv provides a handy way to download and build local versions of Python mostly without sudo and without modifying the system Python environment. The Python environments created and managed by pyenv are stored under ~/.pyenv by default. pyenv automatically switches between Python environments based on the current directory.

Install:

curl https://pyenv.run | bash

Set up a virtual environment for d1_python

This is the environment all of d1_python's packaged Python dependencies will be installed to. It provides the runtime environment for d1_python tests and utilities.

The CONFIGURE_OPTS=--enable-shared setting in the snippet is required for mod_wsgi to be able to run from the environment.

bash -c '
    pyver=3.11.3
    CONFIGURE_OPTS=--enable-shared pyenv install ${pyver}
    pyenv virtualenv ${pyver} d1_python
    pyenv activate d1_python
    pip install --upgrade pip wheel
'

Select a location for the d1_python git repository. Change this as needed.

export d1path=~/dev/d1_python

Download the source from GitHub and install:

bash -c '
    git clone https://github.com/DataONEorg/d1_python.git ${d1path}
    cd ${d1path}
    pyenv activate d1_python
    ./dev_tools/src/d1_dev/setup-all.py --root . develop
'

Postgres

sudo apt install --yes postgresql

Set the password of the postgres superuser account:

sudo passwd -d postgres
sudo su postgres -c passwd

When prompted for the password, enter a new superuser password (and remember it :-).

sudo -u postgres createdb -E UTF8 gmn2
sudo -u postgres createuser --superuser `whoami`

PyCharm (and other IntelliJ based platforms), are not able to connect to database with local (UNIX) sockets. Postgres' convenient "peer" authentication type only works over local sockets. A convenient workaround for this is to set Postgres up to trust local connections made over TCP/IP.

sudo editor /etc/postgresql/14/main/pg_hba.conf

Add line:

host all all 127.0.0.1/32 trust

A similar line for scram-sha-256 may already be present and, if so, must be commented out:

# host all all 127.0.0.1/32 scram-sha-256

Certificates

Copy the OpenSSL config file from the repository.

Make sure to update the d1path if necessary.

sudo bash -c '
    export d1path=~/dev/d1_python
    mv /etc/ssl/openssl.cnf /etc/ssl/openssl.cnf.bak
    cp ${d1path}/gmn/src/d1_gmn/deployment/openssl.cnf /etc/ssl/openssl.cnf
'

Tests

Run the tests and verify that they all pass:

pyenv activate d1_python
pip install pytest
pytest

PyPI

Set up credentials for working with the DataONE account on PyPI:

Edit ~/.pypirc:

[server-login]
username: dataone
password: <secret>

Running GMN under Apache

The setup above is sufficient for testing against GMN using HTTP and the Django test client, which is normally all that is required. However, if testing over HTTPS or in an environment that is closer to production is required, Apache can be set up to host GMN directly from its location in d1_python, using the d1_python virtual environment.

In such a setup, the GMN source can be open in an IDE and changes made active with an service apache2 reload.

Note that mod_wsgi can only run from a Python environment compiled with --enable-shared, as done in the venv setup above.

The APT package version of mod_wsgi has been compiled to work with the APT package version of Python. The two must be compatible at the ABI level, and Apache can only load a single instance of mod_wsgi. So this uninstalls any installed mod_wsgi APT package before compiling a new version against the Python environment in which it will be used.

sudo bash -c '
    service apache2 stop
    apt remove libapache2-mod-wsgi*
    apt-get update
    apt-get install python libexpat1 apache2 apache2-utils ssl-cert apache2-dev
    setfacl -m u:${SUDO_USER}:w /etc/apache2/mods-available/wsgi.load
'

bash -c '
    pyenv activate d1_python
    pip install mod_wsgi
    mod_wsgi-express module-config >> /etc/apache2/mods-available/wsgi.load
'

sudo bash -c '
    a2enmod wsgi
    service apache2 restart
'

Creating a new release

Updating dependencies

Update all packages managed by pip:

./dev_tools/src/d1_dev/pip-update-all.py

The DataONE Python stack specifies the versions that were tested in CI builds before release as the lowest required versions, and allows any later versions to be installed as part of regular maintenance.

Check that there are no package version conflicts:

pip check

As updating the versions in the setup.py files manually is time consuming and error prone, a script is included that automates the task. The script updates the version information for the dependencies in the setup.py files to match the versions of the currently installed dependencies. Update the setup.py files with:

./dev_tools/src/d1_dev/src-sync-dependencies.py . <version>

The <version> argument specifies what the version will be for the release. E.g., "2.3.1". We keep the version numbers in sync between all of the packages in the d1_python git repository, so only one version string needs to be specified.

The current version can be found in any of the setup.py files and in the VERSION string in ./lib_common/src/d1_common/const.py

Run the tests, ensure that they pass and update sample files as necessary.

The requirements.txt file contains a list of packages and pinned versions that will be used in CI builds. It designates the exact Python environment in which the unit tests will run in CI builds.

Update the requirements.txt file:

./dev_tools/src/d1_dev/update-requirements-txt.py

Commit and push the changes, and check the build on Travis.

Building the release packages

After successful build, clone a fresh copy, which will be used for building the release packages:

Building the release packages from a fresh clone is a simple way of ensuring that only tracked files are released. It is a workaround for the way setuptools works, which is basically that it vacuums up everything that looks like a Python script in anything that looks like a package, which makes it easy to publish local files by accident.

Create a Python venv to use for build and deploy:

Build and publish the packages:

Building the documentation

When d1_python is pushed to GitHub, a signal is sent by GitHub to ReadTheDocs.org, which automatically retrieves the new version of the project from GitHub, builds the documentation and makes it available at

http://dataone-python.readthedocs.io/en/latest/

So it is not absolutely necessary to have a local build environment set up for the documentation, but building locally provides faster feedback when making changes that need to be checked before publishing.

Troubleshooting

Clear out the installed libraries and reinstall:

sudo rm -rf /usr/local/lib/python2.7/dist-packages/d1_*
sudo nano /usr/local/lib/python2.7/dist-packages/easy-install.pth
Remove all lines that are: dataone.*.egg and that are paths to your d1_python.