Posts in 'Web'

uWSGI and Database Lockups with SQLAlchemy

If you’re running a Python-based web application and using SQLAlchemy as your database integration layer (as an ORM or otherwise), you may also be using uWSGI to act as the application container.

If you try and fire up multiple processes to handle greater load coming in with the uWSGI option --processes (or -p, --workers; or uWSGI’s various configuration mechanisms), then you’ll probably find that after a short time, your web application will lock up and refuse to serve requests. For me, this was between 1 and 10 requests with using the cx_Oracle database adapter against an Oracle …

All Fanstatic resources being served with ‘text/html’ mimetype by WebOb/WSGI

If you’re finding that you’re using Fanstatic to serve static resources within your Python-based server process, you may be left scracthing your head if you suddenly find that resources aren’t being served correctly. For me, this was manifesting as an incorrect Content-Type header, always being set to text/html for any type of static file being served. As a side effect, because I’m using Diazo to theme my backend Pyramid application, this was automatically seeing this mimetype being returned to the browser and trying to “theme” the raw files. The global picture looked like a whole …

Attributes not released to new Shibboleth Service Provider (SP)

Just created a new Shibboleth Service Provider (SP) instance and found an Identity Providers (IdPs) is not releasing attributes to you? Don’t worry, you’re not alone. In fact, the issue is far more common than you think, despite a lack of documentation on the web.

Confirming the problem

Firstly, make sure that your Shibboleth SP configuration is, as best you can tell, correct. Also, make sure that your shibd daemon has been restarted after any configuration changes you’ve made (and your FastCGI shibauthorizer and shibresponder applications too, if you’re using those).

If you’re sure about …

uWSGI and libxml2 conflicts (aka Installing uWSGI with a custom libxml2)

If you’re using uWSGI with XML support (this is its default), then it will be requiring you to have libxml2 installed — or something similar that provides xml-config. What you’ll find is some erratic behaviour (or complete failure) when attempting to serve an application that is also relying on libxml2, but a different version.

In my case, my original uWSGI was built with CentOS 5’s stock libxml2 library, but my Python application was using lxml, built with a custom version of libxml2 (via Buildout with the z3c.recipe.staticlxml recipe, in case you were curious). Because of these …

Integrating Nginx and a Shibboleth SP with FastCGI

New location!

The canonical place for this documentation is now the nginx-http-shibboleth custom Nginx module GitHub repository. All updates will be reflected there, and as a result, this page has become severely outdated. Please contribute to that repository!

Original post


With changes in Nginx after version 1.5.4, the auth request module is now built in. This means the following instruction have changed, yet again.

tl;dr: You can have Nginx with Shibboleth. Rebuild Shibboleth with FastCGI support, and recompile Nginx with a custom module. You can now run the Shibboleth FastCGI authorizer and responder applications and successfully …

Setting up a Shibboleth SP with FastCGI support

Good news! The Shibboleth SP software features FastCGI authorizer and responder applications for use with your favourite non-Apache and non-IIS web server. Unfortunately, the default distributions don’t come with it built by default. I’m looking into why this is the case, but for now here’s how to rebuild the RPMs yourself.

Note: if you’re just looking to download something that works and don’t want to rebuild things yourself, we have RHEL 6, x86_64 packages available in a Yum repo at You’ll also need to trust my …

Switching to Nginx from Cherokee: Techincal Guide

This is a follow up to a previous post on Switching to Nginx from Cherokee. Read that in case you’re here and haven’t already.

All information here on a server level is related to RHEL 6. You will need to change some instructions for Debian based systems. CentOS should be fine and needs only a minor URL change in the repo configuration.

  1. Edit /etc/yum.repos.d/nginx.repo and add this:

    name=nginx repo
  2. Run yum install nginx to install Nginx.

  3. Start rebuilding your …

Switching to Nginx from Cherokee: Why

After a switching away from Apache some time ago, our primary web server had been running Cherokee for quite a while - since September 2011, in fact, looking back at the configuration history. More recently, however, I’ve switched us again. This time to Nginx - with impressive improvements in performance and configurability (10x for some static files) — and reliability.


See my technical guide for technical info about switching.


Originally, the selection of Cherokee as web server software looked promising - the Cherokee project had been around for a while, was gathering support, had a reasonable level of uptake, and consistent …

Serving uWSGI Apps on a Sub-directory with Nginx

Serving up uWSGI application using Nginx is super-simple and is configured effectively like a standard reverse proxy_pass. However, the documentation isn’t entirely clear exactly how one can correctly serve an application against a sub-directory — and have the application know its correct path such that it can create correct URLs.

Coming from a background of using the Cherokee webserver, uWSGI operated slightly differently within its configuration. This behaviour, as best I know, must have modified the given uWSGI parameters to correctly handle the sub-directory path. I haven’t looked into it, but it probably just does the same thing that …

Disabling caching for sensitive web pages (aka how to prevent logged out users going ‘back’)

We all see web pages like Internet banking, HR systems, email, and more that allow you to log in, do something and load pages, log out, and then prevent you from using your browser’s history to see that sensitive information.  I’m amazed that in my searches I couldn’t quickly find a definitive source of information on how to achieve this.  Pages across the web in a search for ‘stop caching’ range from blog posts, to forum posts, to other pages, and people asking the question (try it: here, or maybe here).

Maybe I got unlucky, but finding …