~bzr-pqm/bzr/bzr.dev

===========================
Serving Bazaar with FastCGI
===========================

**This feature is EXPERIMENTAL and is NOT SECURE.  It will allow access to
arbitrary files on your server.**

This document describes one way to setup a Bazaar HTTP smart server, using
Apache 2.0 and FastCGI or mod_python.

Example
=======

You have a webserver already publishing `/srv/example.com/www/code` as
`http://example.com/code/...` with plain HTTP.  It contains bzr branches and
directories like `/srv/example.com/www/code/branch-one` and
`/srv/example.com/www/code/my-repo/branch-two`.  You want to provide read-only
smart server access to these directories in addition to the existing HTTP
access.

Configuring Apache 2.0
----------------------

FastCGI
~~~~~~~

First, configure mod_fastcgi, e.g. by adding lines like these to your
httpd.conf::

    LoadModule fastcgi_module /usr/lib/apache2/modules/mod_fastcgi.so
    FastCgiIpcDir /var/lib/apache2/fastcgi
    
In our example, we're already serving `/srv/example.com/www/code` at
`http://example.com/code`, so our existing Apache configuration would look
like::

    Alias /code /srv/example.com/www/code
    <Directory /srv/example.com/www/code>
        Options Indexes
        # ...
    </Directory>

We need to change it to handle all requests for URLs ending in `.bzr/smart`.  It
will look like::

    Alias /code /srv/example.com/www/code
    <Directory /srv/example.com/www/code>
        Options Indexes, FollowSymLinks
        RewriteEngine On
        RewriteBase /code
        RewriteRule ^(.*/|)\.bzr/smart$ /srv/example.com/scripts/bzr-smart.fcgi
    </Directory>
    
    # bzr-smart.fcgi isn't under the DocumentRoot, so Alias it into the URL
    # namespace so it can be executed.
    Alias /srv/example.com/scripts/bzr-smart.fcgi /srv/example.com/scripts/bzr-smart.fcgi
    <Directory /srv/example.com/scripts>
        Options ExecCGI
        <Files bzr-smart.fcgi>
            SetHandler fastcgi-script
        </Files>
    </Directory>
    
This instructs Apache to hand requests for any URL ending with `/.bzr/smart`
inside `/code` to a Bazaar smart server via FastCGI.

Refer to the mod_rewrite_ and mod_fastcgi_ documentation for further
information.

.. _mod_rewrite: http://httpd.apache.org/docs/2.0/mod/mod_rewrite.html
.. _mod_fastcgi: http://www.fastcgi.com/mod_fastcgi/docs/mod_fastcgi.html

mod_python
~~~~~~~~~~

First, configure mod_python, e.g. by adding lines like these to your
httpd.conf::

    LoadModule python_module /usr/lib/apache2/modules/mod_python.so

Define the rewrite rules with mod_rewrite the same way as for FastCGI, except
change::

    RewriteRule ^(.*/|)\.bzr/smart$ /srv/example.com/scripts/bzr-smart.fcgi

to::

    RewriteRule ^(.*/|)\.bzr/smart$ /srv/example.com/scripts/bzr-smart.py

Like with mod_fastcgi, we also define how our script is to be handled::

    Alias /srv/example.com/scripts/bzr-smart.py /srv/example.com/scripts/bzr-smart.py
    <Directory /srv/example.com/scripts>
        <Files bzr-smart.py>
            PythonPath "sys.path+['/srv/example.com/scripts']"
            AddHandler python-program .py
            PythonHandler bzr-smart::handler
        </Files>
    </Directory>

This instructs Apache to hand requests for any URL ending with `/.bzr/smart`
inside `/code` to a Bazaar smart server via mod_python.

Refer to the mod_python_ documentation for further information.

.. _mod_python: http://www.modpython.org/


Configuring Bazaar
------------------

FastCGI
~~~~~~~

We've configured Apache to run the smart server at
`/srv/example.com/scripts/bzr-smart.fcgi`.  This is just a simple script we need
to write to configure a smart server, and glue it to the FastCGI gateway.
Here's what it looks like::

    import fcgi
    from bzrlib.transport.http import wsgi

    smart_server_app = wsgi.make_app(
        root='/srv/example.com/code',
        prefix='/code/',
        path_var='REQUEST_URI',
        readonly=True)

    fcgi.WSGIServer(smart_server_app).run()
        
The `fcgi` module can be found at http://svn.saddi.com/py-lib/trunk/fcgi.py.  It
is part of flup_.

.. _flup: http://www.saddi.com/software/flup/

mod_python
~~~~~~~~~~

We've configured Apache to run the smart server at
`/srv/example.com/scripts/bzr-smart.py`.  This is just a simple script we need
to write to configure a smart server, and glue it to the mod_python gateway.
Here's what it looks like::

    import modpywsgi
    from bzrlib.transport.http import wsgi

    smart_server_app = wsgi.make_app(
        root='/srv/example.com/code',
        prefix='/code/',
        path_var='REQUEST_URI',
        readonly=True)

    def handler(request):
        """Handle a single request."""
        wsgi_server = modpywsgi.WSGIServer(smart_server_app)
        return wsgi_server.run(request)
        
The `modpywsgi` module can be found at http://trac.pocoo.org/wiki/ModPyWsgi.  It
is part of pocoo_.

.. _pocoo: http://trac.pocoo.org/wiki/

Clients
-------

Now you can use `bzr+http://` URLs, e.g.::

    bzr log bzr+http://example.com/code/my-branch

Plain HTTP access should continue to work::

    bzr log http://example.com/code/my-branch


Advanced configuration
======================

Because the Bazaar HTTP smart server is a WSGI application, it can be used with
any 3rd-party WSGI middleware or server that conforms the WSGI standard.  The
only requirements are:

  * to construct a `SmartWSGIApp`, you need to specify a **root transport** that it
    will serve.
  * each request's `environ` dict must have a **'bzrlib.relpath'** variable set.

The `make_app` helper used in the example constructs a `SmartWSGIApp` with a
transport based on the `root` path given to it, and calculates the
'bzrlib.relpath` for each request based on the `prefix` and `path_var`
arguments.  In the example above, it will take the 'REQUEST_URI' (which is set
by Apache), strip the '/code/' prefix and the '/.bzr/smart' suffix, and set that
as the 'bzrlib.relpath', so that a request for '/code/foo/bar/.bzr/smart' will
result in a 'bzrlib.relpath' of 'foo/bzr'.

It's possible to configure a smart server for a non-local transport, or that
does arbitrary path translations, etc, by constructing a `SmartWSGIApp`
directly.  Refer to the docstrings of `bzrlib.transport.http.wsgi` and the `WSGI
standard`_ for further information.

.. _WSGI standard: http://www.python.org/dev/peps/pep-0333/


Pushing over ``bzr+http://``
----------------------------

It is possible to allow pushing data over the http smart server. The
easiest way to do this, is to just supply ``readonly=False`` to the
``wsgi.make_app()`` call. But be careful, because the smart protocol does
not contain any Authentication. So if you enable write support, you will
want to restrict access to ``.bzr/smart`` URLs to restrict who can
actually write data on your system.  At this time, it is not possible to
allow some people to have read-only access and others to have read-write
access to the same urls. Because at the HTTP layer (which is doing the
Authenticating), everything is just a POST request.  However, it would
certainly be possible to have HTTPS require authentication and use a
writable server, and plain HTTP allow read-only access.


.. 
   vim: ft=rst tw=74 et