Quick Start: REST interface on Apache 2.4 for Windows

This document describes how to get up-and-running with the AIR Equation Scoring Engine‘s RESTful web interface on a Windows machine running Apache httpd version 2.4.

The configuration described herein is meant for testing and development only. You will probably want to set up something more robust for a production system.

Get the Dependencies

Apache httpd

You will need to install the Apache httpd server. These instructions were written for version 2.4.4, but they should apply to any version of Apache 2.2 or 2.4. I used the Windows 64 binary build from Apache Lounge Choose an appropriate download for your architecture (32-bit or 64-bit)

After you have installed the Apache binary, you will want to set it up so that it runs as a Windows service. Open a command window in the Apache bin directory, and execute:

httpd.exe -k install

More information on running Apache on Windows can be found at http://httpd.apache.org/docs/current/platform/windows.html.

Python 2.7

You will need to have the Python programming language installed. The software was developed and tested on Python 2.7.4 for 64-bit Windows. The software should run fine on any version of 2.7. It has not been tested on Python 2.6 or earlier. It will not run on any version of Python 3

A Windows installer for the latest version of Python may be downloaded from here: http://www.python.org/download/

I recommend installing Python’s setuptools (https://pypi.python.org/pypi/setuptools) and pip (https://pypi.python.org/pypi/pip). packages. Once the setuptools are installed, you can install pip using:

c:\Python27\Scripts\easy-install pip

Then use pip to install the remaining Python dependencies:

c:\Python27\Scripts\pip install sympy
c:\Python27\Scripts\pip install django
c:\Python27\Scripts\pip install djangorestframework

mod_wsgi

An Apache plugin called mod_wsgi provides the bridge between Apache and Python. It is easiest to acquire a pre-compiled binary for this package. One is available from http://www.lfd.uci.edu/~gohlke/pythonlibs/#mod_wsgi Be sure to download the version that is appropriate for your Apache version, Python version and Windows architecture. After downloading the zip archive, extract the single file that it contains (should be called mod_wsgi.so) and drop it into the Apache modules directory (this is C:\Program Files\Apache24\modules on my machine)

Fiddler

Finally, in order to test the setup, you will need some way of sending a POST request to the Apache server. These instructions assume that you are using the Fiddler utility (http://fiddler2.com/get-fiddler). If you prefer a different utility, then modify them accordingly.

Download the Software

Download the latest version of the AIR Equation Scoring Engine from https://bitbucket.org/sbacoss/equationscorer/downloads

Unzip the downloaded archive into a directory of your choosing. For security reasons, this should not be a location under your server’s document root. In the rest of this document, we will refer to this directory as {Equation-Scorer-Root}

Configure Apache

All of the remaining configuration is done in the main Apache configuration file, httpd.conf On my machine, this file is located at C:\Program Files\Apache24\conf\httpd.conf. Open this file in your favorite text editor.

First, we need to enable the mod_wsgi. Locate the section that has a whole bunch of lines that begin LoadModule, and add the following:

# MODULE mod_wsgi ADDED XX/XX/20XX
LoadModule wsgi_module modules/mod_wsgi.so

This line enables the link between Apache and Python, but Apache still doesn’t know what Python code to invoke when it sees a particular HTTP request. To enable that, add the following lines at the end of httpd.conf

# Configuration for equation scorer app
WSGIPythonHome C:/Python27
WSGIPythonPath {Equation-Scorer-Root}/eqscorer_rest;{Equation-Scorer-Root}/lib
WSGIScriptAlias /eq-scorer-rest {Equation-Scorer-Root}/eqscorer_rest/eqscorer_rest/wsgi.py

Where you replace {Equation-Scorer-Root}, everywhere it appears, with the actual directory to which you unzipped the AIR Equation Scoring Engine. If your Python is not installed in the standard location, you will have to change WSGIPythonHome as well.

Although Apache now knows how to run the engine, it will refuse to do so unless you tell it that it is allowed to. To do that, add the following lines to the end of httpd.conf

<Directory "{Equation-Scorer-Root}/eqscorer_rest/eqscorer_rest">
    <Files "wsgi.py">
      Order allow,deny
      Allow from all
      Require all granted
    </Files>
</Directory>

Again, replacing {Equation-Scorer-Root} with the correct value.

Now, from the Windows Services control panel, restart the Apache service. If Apache fails to start, then chances are you mistyped something in the httpd.conf

To test the service, fire up Fiddler, and find the Composer window. Select POST for the request method. For the address, use http://127.0.0.1/eq-scorer-rest/isequivalent, for the request headers, you should specify:

Content-Type: application/json; charset=utf-8
Accept: application/json

And for the request body, you should use:

{
  "answer":"<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mn>1</mn><mi>x</mi><mo>≤</mo><mn>3</mn></math>",
  "rubric":"<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mn>1</mn><mi>x</mi><mo>≤</mo><mn>3</mn></math>",
  "parameters":{}
}

Push the Execute button to submit the request. After a short delay (while Python starts and loads all of its libraries), you should get a response of 200 OK. If you switch to Fiddler’s Inspectors tab, you should see something like this:

HTTP/1.1 200 OK
Date: Fri, 14 Jun 2013 16:38:55 GMT
Server: Apache/2.4.4 (Win64) mod_wsgi/3.5-BRANCH Python/2.7.4
Vary: Accept,Cookie
Allow: POST, OPTIONS
Transfer-Encoding: chunked
Content-Type: application/json; charset=utf-8

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{"correct": true, "reason": ""}
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Now read the API Documentation, and have fun!