Hacker’s guide to NAV¶

If you are contributing code to Network Administration Visualized, please read this first.

Contributing to NAV¶

Originally, NAV was a closed source project, initiated by the Norwegian University of Science and Technology (NTNU), and eventually sponsored by Uninett on behalf of the Norwegian higher education community. In 2004, however, NTNU and Uninett started distributing NAV under the GNU General Public License, making it a truly free software system.

While Uninett and NTNU are still the main contributors to NAV, developing NAV to support the needs of the Norwegian higher education community, contributions from third parties is highly appreciated.

We communicate mainly through mailing lists, GitHub, and the #nav IRC channel on Libera.Chat. At times, Uninett also arranges workshops and gatherings for its customers: Norwegian universities, university colleges and research institutions.

To contribute:

Go to https://nav.uninett.no/ and

Join the mailing lists. The nav-dev mailing list in particular is for discussing NAV development. So far, this is a low traffic list. We can only hope this will change ;-)
Get a copy of the latest development sources by cloning the Git-repository at GitHub.
Take a look at the project reports from previous development projects at NTNU (NAVMe, NAVMore, tigaNAV and others) - design specifications and other useful bits of historic NAV information is mostly to be found in these. Unfortunately, some of the oldest project documentation is in Norwegian only. Do not hesitate to ask for help on the mailing lists.

Submitting pull requests / patches¶

Unless you are submitting one-off fixes for bugs and small issues, please take the time to discuss your change proposals on the nav-dev mailing list. This will increase the chances of having your patches accepted.

Base your patches on the relevant Git branches. If you are submitting a patch for an issue that affects the latest stable series, base your patch on that series branch (<major>.<minor>.x). If you are submitting patches containing new features, base them on the master branch.

Please submit your changes in the form of a pull request against the official NAV Github repository. From there, we can review and comment on your changes. The entire CI test suite will be automatically run against your pull request, and the automatic CLA signing process is initiated by the CLA Assistant.

Contributor License Agreement¶

To contribute code to NAV, you need to sign our contributor license agreement, straightforwardly based on The Free Software Foundation’s Fiduciary License Agreement 2.0.

To streamline the process, we ask that you sign it digitally, as part of the GitHub pull request process. We have implemented this process through the help of CLA assistant. The assistant will allow you to digitally sign the agreement using your Github account. If you create a pull request against the NAV repository and have not previously signed our agreement, the assistant will automatically post a comment on your pull request with instructions on how to do so.

The full agreement text can be read directly from the GitHub gist used by the CLA assistant.

Rationale¶

NAV is a software project primarily made by Uninett AS. Uninett is a non-profit, government-owned limited company, who builds and operates Norway’s national research and education network.

Due to our experiences with FOSS license compatibility issues, and with switching the 20-year old NAV project explicitly from the GPLv2 to the GPLv3 license, we have decided to implement a contributor license agreement for NAV. This will help us ease the transition if we in the future find we need to switch to yet another FOSS license to keep the project going.

For the sake of transparency, we’ve chosen FLA-2.0, which is a fairly standardized agreement. If you already know the terms of the FLA-2.0, you won’t need to read an entirely new license agreement just to contribute to NAV.

Directory layout¶

A rough guide to the source tree:

Directory	Description
`bin/`	NAV ‘binaries’; executable scripts and programs.
`contrib/`	User contributed NAV tools. NAV doesn’t depend on these, and any maintenance of them is left up to the original developers. We do not offer support for these tools.
`doc/`	User and developer documentation.
`tests/`	Automated tests.
`tools/`	Scripts for aiding in various development, build and release processes.
`python/`	Python source code.
`python/nav/etc/`	Example/initial configuration files.
`python/nav/web/static/`	Static media such as CSS stylesheets, images and JavaScript to be served by a webserver.
`python/nav/web/templates/`	Main/global Django HTML templates. More be located in individual sub-packages/Django apps.
`python/nav/models/sql`	SQL schema definitions.

Development languages and frameworks¶

All NAV back-end code is written in Python. The web-based user interface is implemented using the Python-based Django framework. In addition, there is an increasing amount of Javascript in the web-based user interface.

If you wish to contribute something really useful that doesn’t use Python, we may consider including it in the contrib/ directory.

Coding style¶

NAV code adheres to the Python style guide documented in PEP 8, with a local convention of a maximum line length of 88 characters. PyLint is used to automatically validate much of these coding styles in our CI system. However, a good tip is to format your code using Black, a great tool for automatically formatting your code, obviating the need for discussing coding style issues in code reviews.

Note

If you are contributing some code to a file that isn’t already formatted using Black, please don’t format the entire file as part of your changes. May we instead suggest using black-macchiato, which can be used by your editor to format selected blocks of code using Black.

Conventions for writing good documentation strings (a.k.a. “docstrings”) are immortalized in PEP 257.

Much of the legacy NAV code was, however, written without using any specific guidelines for coding style. We are working to improve this, and will accept patches that clean existing code.

Python boilerplate headers¶

We will only accept code into NAV if it can be licensed under GPL v3. Each Python source code file should contain the following boilerplate at the top:

#
# Copyright (C) 2018,2019 You or your employer
#
# This file is part of Network Administration Visualized (NAV).
#
# NAV is free software: you can redistribute it and/or modify it under the
# terms of the GNU General Public License version 3 as published by the Free
# Software Foundation.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
# more details.  You should have received a copy of the GNU General Public
# License along with NAV. If not, see <http://www.gnu.org/licenses/>.
#

In this case, “Somebody” is normally you personally, or your employer, depending on who legally owns the copyright of your contribution.

If a file uses non-ASCII characters, it must be encoded as UTF-8, and an encoding statement should be inserted at the top:

# -*- coding: utf-8 -*-

Javascript¶

When writing Javascript code, try to focus on modules, not pages. If the code is HTML-related, it should take selectors or objects as input and concern itself solely about those. This makes for much easier testing and reuse. And of course - write the tests first.

When the module is done you write a controller for the page that plugs the needed plugins to the page elements. This should fail gracefully if the needed elements are not present.

NAV’s Javascript uses RequireJS - use this to create modules and specify dependencies.

Pro tip is to create require_config.dev.js in python/nav/web/static/js/` and add the following configuration to RequireJS:

require.urlArgs = "bust=" +  (new Date()).getTime();

This makes sure your not using cached resources in your browser when developing, something browsers love to do! See config-urlArgs in the RequireJS documentation for details. require_config.dev.js is listed in the repository .gitignore file.

Database¶

NAV uses PostgreSQL as its database backend. Namespaces (schemas) are employed to logically group tables and relations. NAV versions prior to 3.5 employed separate PostgreSQL databases instead of namespaces.

The namespaces currently in use are:

Namespace	Description
manage	The core knowledge database of NAV, containing all sorts of information about the monitored IP Devices, events, alerts, network topology and machine tracking data.
profiles	Contains NAV user accounts and groups, user preferences and alert profiles.
logger	Anything related to NAV’s syslog parser/browser system.
arnold	The port detention system Arnold stores it’s data here.
radius	Radius accounting logs, updated directly by FreeRadius’ PostgreSQL module.

Note

Django vs. the database schema

NAV existed long before Django, which was “shoe-horned” into the legacy NAV application at a later stage. As a consequence of this, NAV is quite tied to PostgreSQL as the database backend, and does not always present itself as as a typical Django application.

The most obvious difference, is that NAV does not employ Django’s ORM for defining the initial schema or the schema migrations. NAV implements its schema definitions as pure SQL scripts, and implements a home-grown system for schema migrations, which also written as pure SQL.

Connecting to the database (Python)¶

Raw SQL / Legacy database connections¶

To obtain a raw SQL connection to the NAV database, use the legacy API accordingly, e.g.:

import nav.db
# Get a connection to the NAV database
connection = nav.db.getConnection('default')

The above code will open a connection to NAV’s database, or, if a previous connection with these parameters is already open in the current process, returns the already existing connection from a connection pool.

The default parameter is there for legacy reasons; it specifies the name of a subsystem. The db.conf file allows configuration of separate database users for each subsystem (known as a script in db.conf) of NAV. The default db.conf file specifies a database user for a subsystem called default, and also specifies the same database user for all known subsystem names. At present, using a subsystem name that is not configured in db.conf will cause nav.db.getConnection() to revert to using the default name.

Django ORM¶

Since version 3.5, NAV has provided Django ORM models for its database. Unless you have very specific requirements, only solvable by using pure SQL, you would be best served by accessing the database via the Django ORM.

Most of these models are defined in submodules in in the nav.models package (since NAV was not originally divided into separate “Django applications”).

Changing the schema / migrations¶

The baseline schema is located in python/nav/models/sql/baseline/ - the navsyncdb program is responsible for running this when creating a new database. To make a schema change, you do not change the baseline, but go to the python/nav/models/sql/changes/ directory and create a new schema change script there.

Schema change scripts as numbered, using the following pattern:

sc.<major>.<minor>.<point>.sql

The <major> and <minor> numbers usually correspond to the major and minor number of the next NAV release. The <point> number is a sequence id - pick the next free number when creating a schema change script.

Remember these points when creating a schema change script:

Create separate change scripts for unrelated schema changes.
Remember to write SQL to migrate existing data, if necessary.
Do not use transactional statements - navsyncdb will take care of that.

To apply your change scripts, just run navsyncdb. It will look inside the schema_change_log table to see which change scripts have already been applied, and it will detect your new change script and apply this to the database.

Note

When changing the schema, don’t forget to update the Django models in the nav.models package. An integration test exists to verify that the Django models can at least be used to run proper SELECT statements against the database.

Version Control¶

NAV uses Git for distributed version control. The official repository is located at GitHub . Fork that and submit pull-requests for review.

Push access¶

Push access to the official repositories is limited to developers employed or commissioned by Uninett.

Testing and Continuous Integration¶

Much of NAV is legacy code, as defined by Michael C. Feathers: “Code that has no tests”. We have been making an effort to introduce automated tests into the codebase the past several years, and hope to improve coverage over time.

All test suites (except those for Javascript) are located in the tests/ subdirectory.

Running tests¶

We use a combination of pytest and tox to run the test suite.

There’s also a script to produce an entire test environment as a Docker image and to run the entire test suite inside a Docker container created from that image. This is actually the same method employed by our Jenkins build servers to run the test suite. Take a look in the tests/docker/ directory.

For an interactive testing session with tox, you can utilize the Docker image like thus:

$ cd tests/docker
$ make
...
$ make shell
...
$ tox -e unit-py35-django111
...

Javascript testing¶

Testing javascript in NAV is straightforward. We use Karma as a testrunner, Mocha as testing framework and Chai as assertion library. Assuming you are inside the Docker CI image:

tox -e javascript

This will take of installing the required JS modules using npm, and running the test suite in three different browsers (Chrome, Firefox and PhantomJS).

All tests are located under python/nav/web/static/js/test/. Create new tests there. For syntax, assertions and related stuff take a look at the tests already there and the relevant documentation linked above.

Jenkins and Continuous Integration¶

We use Jenkins multibranch pipelines for continuous integration testing of NAV. The Jenkins pipeline is defined in Jenkinsfile, and is automatically run every time a change is pushed to a branch in the offical NAV Github repository, or when a pull request is opened against this repository.

Our Jenkins installation is available on https://ci.nav.uninett.no/ .

Tips and tricks¶

Make fixtures for integration testing¶

from django.core import serializers
from nav.models.manage import Netbox

fixtures = serializers.serialize("xml", Netbox.objects.all()[:2])

Fixtures can so be used in your integration tests by extending the test case DjangoTransactionTestCase in nav.tests.cases.

See nav.tests.integration.l2trace_test for an example on applying fixtures for your particular test case.

See https://docs.djangoproject.com/en/1.8/topics/serialization/

Force the custom Django 500 error handler to run¶

If working on the custom Django 500 error handler view, nav.django.views.custom_500(), a 500 error can be produced intentionally by browsing the URI /500/ on your NAV installation. This view will by default only be available when logged in as a NAV administrator.