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 …

in Web · Mon 26 August 2013

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 …

in Web · Mon 29 July 2013

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.

in Web · Tue 28 May 2013

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 …

in Web · Wed 08 May 2013

Integrating Nginx and a Shibboleth SP with FastCGI

in Web · Mon 22 April 2013

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 https://www.hpc.jcu.edu.au/rpm/. You’ll also need to trust my …

in Web · Mon 22 April 2013

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:

   [nginx]
   name=nginx repo
   baseurl=http://nginx.org/packages/rhel/$releasever/$basearch/
   gpgcheck=0
   enabled=1
   

2. Run yum install nginx to install Nginx.

3. Start rebuilding your …

in Web · Fri 12 April 2013

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.

in Web · Thu 11 April 2013

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 …

in Web · Sun 07 April 2013

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 …

in Web · Thu 24 March 2011