~bzr-pqm/bzr/bzr.dev

Serving Bazaar with FastCGI

===========================

This document describes one way to set up a Bazaar HTTP smart server,

using Apache 2.0 and FastCGI or mod_python.

For more information on the smart server, and other ways to configure it

see the main `smart server documentation`_.

.. _smart server documentation: #running-a-smart-server

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.

NOTE: If you don't have bzrlib in your PATH, you will be need to change the

following line::

            PythonPath "sys.path+['/srv/example.com/scripts']"

To::

            PythonPath "['/path/to/bzr']+sys.path+['/srv/example.com/scripts']"

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/www/code',

        prefix='/code/',

        path_var='REQUEST_URI',

        readonly=True,

        load_plugins=True, 

        enable_logging=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/www/code',

        prefix='/code/',

        path_var='REQUEST_URI',

        readonly=True,

        load_plugins=True, 

        enable_logging=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://dev.pocoo.org/projects/pocoo/browser/pocoo/wrappers/modpy.py. It is

part of pocoo_. You sould make sure you place modpywsgi.py in the same

directory as bzr-smart.py (ie. /srv/example.com/scripts/).

.. _pocoo: http://dev.pocoo.org/projects/pocoo/

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