Developer guide

Thanks! There are tons of different DNS services, and unfortunately a large portion of them require paid accounts, which makes it hard for us to develop lexicon providers on our own. We want to keep it as easy as possible to contribute to lexicon, so that you can automate your favorite DNS service. There are a few guidelines that we need contributors to follow so that we can keep on top of things.

Potential providers

Potential providers are as follows. If you would like to contribute one, please follow the current document instructions and open a pull request.

Setup a development environment

Fork, then clone the repo:

$ git clone git@github.com:your-username/lexicon.git

Install Poetry if you not have it already:

$ curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py | python

Configure the virtual environment with full providers support and activate it:

$ cd lexicon
$ poetry install -E full
$ source .venv/bin/activate

Make sure the tests pass:

$ tox -e standard

You can test a specific provider using:

$ pytest lexicon/tests/providers/test_foo.py

Note

Please note that by default, tests are replayed from recordings located in tests/fixtures/cassettes, not against the real DNS provider APIs.

Adding a new DNS provider

Now that you have a working development environment, lets add a new provider. Internally lexicon does a bit of magic to wire everything together, so the only thing you’ll really need to do is is create the following file.

  • lexicon/providers/foo.py

Where foo should be replaced with the name of the DNS service in lowercase and without spaces or special characters (eg. cloudflare)

Your provider file should contain 3 things:

  • a NAMESERVER_DOMAINS which contains the domain(s) used by the DNS provider nameservers FQDNs (eg. Google Cloud DNS uses nameservers that have the FQDN pattern ns-cloud-cX-googledomains.com, so NAMESERVER_DOMAINS will be ['googledomains.com']).

  • a provider_parser which is used to add provider specific commandline arguments. eg. If you define two cli arguments: --auth-username and --auth-token, those values will be available to your provider via self._get_provider_option('auth_username') or self._get_provider_option('auth_token') respectively

  • a Provider class which inherits from BaseProvider, which is in the base.py file. The BaseProvider defines the following functions, which must be overridden in your provider implementation:

    • _authenticate
    • _create_record
    • _list_records
    • _update_record
    • _delete_record
    • _request

    It also provides a few helper functions which you can use to simplify your implementation. See the cloudflare.py file, or any provider in the lexicon/providers/ folder for examples

It’s a good idea to review the provider specification to ensure that your interface follows the proper conventions.

Note

Please keep in mind the following:

  • lexicon is designed to work with multiple versions of python. That means your code will be tested against python 3.6 and 3.8 on Windows, Linux and Mac OS X.
  • any provider specific dependencies should be added to the setup.py file, under the extra_requires heading. The group name should be the name of the provider. eg:
extras_require={
    'route53': ['boto3']
}

Testing your provider

Test against the live API

First let’s validate that your provider shows up in the CLI.

$ lexicon foo --help

If everything worked correctly, you should get a help page that’s specific to your provider, including your custom optional arguments.

Now you can run some manual commands against your provider to verify that everything works as you expect.

$ lexicon foo list example.com TXT
$ lexicon foo create example.com TXT --name demo --content "fake content"

Once you’re satisfied that your provider is working correctly, we’ll run the integration test suite against it, and verify that your provider responds the same as all other lexicon providers. lexicon uses vcrpy to make recordings of actual HTTP requests against your DNS service’s API, and then reuses those recordings during testing.

The only thing you need to do is create the following file:

  • lexicon/tests/providers/test_foo.py

Then you’ll need to populate it with the following template:

# Test for one implementation of the interface
from lexicon.tests.providers.integration_tests import IntegrationTestsV2
from unittest import TestCase

# Hook into testing framework by inheriting unittest.TestCase and reuse
# the tests which *each and every* implementation of the interface must
# pass, by inheritance from integration_tests.IntegrationTests
class FooProviderTests(TestCase, IntegrationTestsV2):
    """Integration tests for Foo provider"""
    provider_name = 'foo'
    domain = 'example.com'
    def _filter_post_data_parameters(self):
        return ['login_token']

    def _filter_headers(self):
        return ['Authorization']

    def _filter_query_parameters(self):
        return ['secret_key']

    def _filter_response(self, response):
        """See `IntegrationTests._filter_response` for more information on how
        to filter the provider response."""
        return response

Make sure to replace any instance of foo or Foo with your provider name. domain should be a real domain registered with your provider (some providers have a sandbox/test environment which doesn’t require you to validate ownership).

The _filter_* methods ensure that your credentials are not included in the vcrpy recordings that are created. You can take a look at recordings for other providers, they are stored in the tests/fixtures/cassettes/ sub-folders.

Then you’ll need to setup your environment variables for testing. Unlike running lexicon via the CLI, the test suite cannot take user input, so we’ll need to provide any CLI arguments containing secrets (like --auth-*) using environmental variables prefixed with LEXICON_FOO_.

For instance, if you had a --auth-token CLI argument, you can populate it using the LEXICON_FOO_AUTH_TOKEN environmental variable.

Notice also that you should pass any required non-secrets arguments programmatically using the _test_parameters_override() method. See test_powerdns.py for an example.

Test recordings

Now you need to run the py.test suite again, but in a different mode: the live tests mode. In default test mode, tests are replayed from existing recordings. In live mode, tests are executed against the real DNS provider API, and recordings will automatically be generated for your provider.

To execute the py.test suite using the live tests mode, execute py.test with the environment variable LEXICON_LIVE_TESTS set to true like below:

LEXICON_LIVE_TESTS=true pytest lexicon/tests/providers/test_foo.py

If any of the integration tests fail on your provider, you’ll need to delete the recordings that were created, make your changes and then try again.

rm -rf tests/fixtures/cassettes/foo/IntegrationTests

Once all your tests pass, you’ll want to double check that there is no sensitive data in the tests/fixtures/cassettes/foo/IntegrationTests folder, and then git add the whole folder.

git add tests/fixtures/cassettes/foo/IntegrationTests

Finally, push your changes to your Github fork, and open a PR.

Skipping Tests/Suites

Neither of the snippets below should be used unless necessary. They are only included in the interest of documentation.

In your lexicon/tests/providers/test_foo.py file, you can use @pytest.mark.skip to skip any individual test that does not apply (and will never pass)

@pytest.mark.skip(reason="can not set ttl when creating/updating records")
def test_provider_when_calling_list_records_after_setting_ttl(self):
    return

You can also skip extended test suites by inheriting your provider test class from IntegrationTestsV1 instead of IntegrationTestsV2:

from lexicon.tests.providers.integration_tests import IntegrationTestsV1
from unittest import TestCase

class FooProviderTests(TestCase, IntegrationTestsV1):
    """Integration tests for Foo provider"""

CODEOWNERS file

Finally you should add yourself to the CODEOWNERS file, in the root of the repo. It’s my way of keeping track of who to ping when I need updated recordings as the test suites expand & change.