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.

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_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.

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.

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/).

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.

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.