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If you are contributing code to Network Administration Visualized, please read this first.
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, Launchpad, and the wiki and Mercurial repositories hosted at http://metanav.uninett.no/ . At times, UNINETT also arranges workshops and gatherings for its customers: Norwegian universities, university colleges and research institutions.
To contribute:
Go to http://metanav.uninett.no/ and
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 Mercurial repository at http://metanav.uninett.no/hg/default/. Most new development takes place on this branch. * Take a look at the [[:navprojects|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.
If you wish to contribute code to the project, please tell us about it on the nav-dev mailing list. It is always a good idea to check if someone is already working on something similar, and to get some helpful tips on how to integrate your code with the rest of the project. If you already went ahead and wrote a patch, announce it on nav-dev and provide a link to the patch so it can be studied for possible inclusion into NAV.
A rough guide to the source tree:
conf/ | Files related to the autoconf build system. |
doc/ | User and developer documentation, SQL scripts and example NAV configuration files. |
tools/ | Tool scripts for the build and release processes. |
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. |
packages/ | Stuff to help packaging NAV for various platforms, such as RedHat, CentOS, FreeBSD, Debian and soforth. |
src/ | Source code to Java subsystems of NAV (here for historic reasons). |
subsystem/ | Source code to the rest of NAV - most of it Python. NAV is loosely divided into subsystems, and each one of these has its own subdirectory in here. |
subsystem/lib-python/ | Python libraries & APIs. Please check what's already there before you roll your own. |
subsystem/lib-perl/ | Perl libraries & APIs. Only a single piece of Perl code remains in NAV; once this has been replaced, this directory will cease to exist. |
subsystem/webfront/ | Python libraries for the web interface and front-page handler modules for mod_python. |
For historic reasons, different parts of NAV are written in different programming languages (Perl, Java, PHP and Python). This has been unfortunate in may ways, not at least for the sake of consistency and maintenance, but fortunately we have a long-term goal of reducing the number of languages and dependencies. The last few years we've spent a significant amount of time rewriting parts that were written in Perl and PHP to Python, which is the language we are currently gravitating towards.
Currently (as of February 2009), major parts of NAV are written in
Python and Java, while only a single Perl program remains
(makecricketconfig.pl
).
subsystems, use the language that subsystem was written in.
Python and Django. The legacy parts of the web system interface
directly with ''mod_python'', using Cheetah for HTML templating. Anything written in 2008 and later uses Django. There is also [[devel:django_introduction|a guide for interfacing Django applications with the legacy web code]]. - If your subsystem is a new back-end tool/daemon, please use Python. The NAV Python API is more complete than for any of the other languages, and you will receive a lot for free.
If these rules are not followed, your patches will not be accepted into NAV (but if they are really good, we will consider including them in the contrib directory).
If YOU are willing to invest in porting some of the existing Java/Perl code to Python, then you will be celebrated as a NAV hero!
Much of the legacy NAV code was written without using any coding style guidelines. This has resulted in some chaotic combination of styles, which we hope to reduce in the future. For new code, please follow these guidelines:
Java Programming Language”: http://java.sun.com/docs/codeconv/
Code” http://www.python.org/doc/peps/pep-0008/
Add info about header guidelines for Python files.
If you see violations of these guidelines, don't hesitate to fix them. If you fix file-wide indentation problems etc., please submit this as a separate patch to make your other patches look clean and readable.
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:
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. |
NOTE: The following is Python-specific, more info should be added for the other languages used in NAV.
To obtain a connection to the NAV database, use the 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, returns the already existing connection from a connection cache.
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
raise an exception in nav.db.getConnection()
.
NAV 3.5 and on includes Django models for the most widely used database tables. If no SQL magic is needed to perform your database voodoo, it is recommended that you use these models, located in the module nav.models
. You do not need to explicitly establish a db connection to use these models, as Django takes care of all that.
When making changes to NAV's legacy web code, a few special considerations need to be made.
Legacy web code interfaces directly with mod_python, and uses Cheetah for HTML templating.
Global Cheetah templates are found in
subsystem/webfront/nav/web/templates/
, while local templates are
located in the subdirectories of their respective subsystems. All
Python modules compiled from Cheetah templates should be installed in the
nav.web.templates
package.
Use the nav.db.getConnection()
call to open or retrieve an
existing database connection. All NAV web modules share the same
interpreter and namespace per Apache process, which also means that
database connections will be shared between the modules running in
each process. Therefore, the following conventions apply for
connections obtained from nav.db.getConnection()
:
connection between client requests. Make sure to retrieve a new
connection at the start of each request cycle - the API will cache connections between requests, and will automagically re-open broken connections. As the connection is shared between several modules, retained references may be invalid in the next request cycle. * **Do not explicitly close database connections.** Although the API will try to reopen any closed or broken connections, you create extra overhead, and you don't play nice with the other web modules. * **The obtained connections will use an isolation level of //read committed//**, i.e. no autocommits. Be careful to commit the current transaction if you modify any data. A mod_python cleanuphandler will try to automatically commit all open transactions as the request cycle ends, but this may change in the future, so you must not rely on it. * **Do not change the isolation level of a connection** without restoring it to its original value before the end of the request cycle.
If you are writing a new web application / tool for NAV, please use the Django framework. Here's a quick primer.