Not today... - Listing directory with wsgi

Thu Jul 2 2015

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Listing directory with wsgi

Tagged dev , python

Recently I ran into an issue with my blog and pelican (the blogging engine I use). For some reasons (which I explain here) I had to develop a small wsgi app which act like the python SimpleHTTPServer.

I tried a lot of things but they never worked as I wanted them to. So, I decided to do this by myself.

Specifications

Here are the features I wanted:

Define a directory as the root (/) directory from which all the files will be served.
If this directory contains an index.html file, serves it to the user.
If there is no index.html file list all the subdirectories and files in a simple page and provide links to navigate.

Tools

For this little project I need a simple server which is available directly in the stdlib.
I will use the famous path.py lib for handling all the interactions with the FS.
Then Jinja for all the rendering.

Hello world!

First of all, making it works for the most simple use case

import wsgiref.simple_server

def application(environ, start_response):
	"""Return a simple Hello World when accessing an url (anyone) on the server
	"""
	# send status_code and headers
	start_response('200 OK', [('Content-Type', 'text/html')])
	# send body
	return ['Hello World!']

if __name__ == '__main__':
	# create a server on 'localhost' and port 8080 using the application
	srv = wsgiref.simple_server.make_server('localhost', 8080, application)
	# serve...
	srv.serve_forever()

Routing

Then I have to handle the request, translate the url in a possible path in the FS, and dispatch to the different choices available.

import wsgiref.simple_server
import path

ROOT = path.path('/tmp') # The root directory from which I will serve the files

def application(environ, start_response):
	"""Route to the dedicated functions"""

	# build the possible path of the file to serve or directory to list
	path = ROOT + environ.get('PATH_INFO')

	# build the possible path of the index file if the path is a directory
    path_index = path + 'index.html'


	# checks if the path exists, if not want to send a 404 not found
    if not path.exists():
        return not_found(start_response)

	# checks if the path links to a file, in this case serve the file
    if path.isfile():
        return serve_file(path, start_response)

	# now we are sure that the user asks for a directory, checks if the
	# directory has an index.html file, if so, serve it.
    if path_index.exists():
        return serve_file(path_index, start_response)

	# last case we want to list what is in the directory
    return list_dir(path, start_response)


if __name__ == '__main__':
	srv = wsgiref.simple_server.make_server('localhost', 8080, application)
	srv.serve_forever()

Serve content

Return 404

Most simple use case, return a 404 error and a small message

	def not_found(start_response):
		# status code and header
        start_response('404 NOT FOUND', [('Content-Type', 'text/plain')])
		# simplest message ever
        return ['Not Found']

Serve file

import mimetypes

chunk_size = 64 * 1024

def serve_file(filepath, start_response):
	# retrieve mimetype for serving purpose
	mime = mimetypes.guess_type(f)

	# start response with the given mimetype
	sr('200 OK', [('Content-Type', mime[0])])

	# yield the file content through network (chunks function from path.py)
	return f.chunks(chunk_size, 'rb')

List directory

Last but not least, the listing of the directory. Here I use Jinja for the templating.

import jinja2

# setup my jinja environment with the templates directory containing my
# template files
env = jinja2.Environment(
    loader=jinja2.PackageLoader('my_wsgi_listdir', 'templates')
)


def list_dir(directory, start_response):

	# start a response as an html page
	start_response('200 OK', [('Content-Type', 'text/html')])

	# retrieve informations from FS through path.py API
	context = {
		'directory': directory.relpath(ROOT),
		'links': [ f.relpath(directory) for f in d.listdir() ]
	}

	# render the template with the informations and return the stream
	return env.get_template('list_dir.tplt').stream(**context))

Here is the list_dir.tplt file

<html>
<head>
  <title>Directory listing for {{directory}}</title>
</head>
<body>
  <h2>Directory listing for {{directory}}</h2>
  <hr>
  <ul>
  {% for link in links %}
    <li><a href="{{ link }}">{{ link }}</a></li>
  {% endfor %}
  </ul>
  <hr>
</body>
</html>

And that’s all, simple and efficient this little wsgi application fits my needs.