Debugging PHP extensions with the dynamic linker
By Jason Dixon
February 25, 2011
If you’ve ever had to track down a missing dependency or incompatible libraries, chances are good that you were assisted by the ldd command. This helpful utility reports the list of shared library dependencies required by a binary executable. Or in the typical use case, it will tell you which libraries are missing that your application needs to run.
Fortunately most Linux and BSD distributions do a decent job of enforcing dependencies with their respective package managers. But inevitably, there’s the occasional proprietary, closed-binary third-party application or built-from-source utility that skirts the convenience of mainstream distributions. If you’re lucky, the vendor accurately details which software is required, including specific versions theirs was built against. If you’re not, well, you might have to resort to tools like ldd, or even process tracers like strace (Linux), ktrace (OpenBSD) and truss (Solaris).
I recently had the misfortune of troubleshooting a PHP application that was unable to load imagick.so, a native PHP extension to create and modify images using the ImageMagick API. The problem manifested itself innocently enough:
PHP Warning: PHP Startup: Unable to …linux php tools
Google Earth KML Tour Development Challenges on Liquid Galaxy
By Adam Vollrath
February 24, 2011
Because Liquid Galaxy runs Google Earth, it can easily visualize an organization’s GIS data. End Point also develops tours within Google Earth to better present this data. A Liquid Galaxy’s networked multi-system architecture presents unique technical challenges to these tours.
Many Google Earth tours incorporate animations and dynamic updates using the <gx:AnimatedUpdate> element. KML features in the Earth environment can be modified, changed, or created during a tour, including the size, style, and location of placemarks, the addition of ground overlays, geometry, and more.
However, these updates are only executed on the Liquid Galaxy master system running the tour, not sent to its slaves. Liquid Galaxy nodes communicate primarily via ViewSync UDP datagrams. These datagrams contain only the master’s position in space and time. This means we cannot use <gx:AnimatedUpdate> to animate features across all Liquid Galaxy systems, sharply limiting its utility.
But tours can also use chronological elements to display, animate, and hide features. Using <gx:TimeSpan> or <gx:TimeStamp> within an tour stop enables flying to a specific location in space and time. All …
google-earth visionport kml
Ecommerce Facebook Integration Tips
By Steph Skardal
February 23, 2011
Over the past couple of months, I’ve done quite a bit of Facebook integration work for several clients. All of the clients have ecommerce sites and they share the common goal to improve site traffic and conversion with successful Facebook campaigns. I’ve put together a brief summary of my recent experience.
First, here are several examples of Facebook integration methods I used:
| Name & Notes | Screenshot Examples |
|---|---|
| Link to Facebook Page: This is the easiest integration option. It just requires a link to a Facebook fan page be added to the site. |
 A link to Lots To Live For’s Facebook page was added to the header.
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| Facebook Like Button: Implementation of the like button is more advanced than a simple link. Technical details on implementation are discussed below. This was integrated on multiple product page templates. The "like" event and page shows up on the user’s wall. |
 Like button’s were added throughout Paper Source’s site. The screenshot shown above indicates I’ve liked this product page. "Liking" a product page shows up on my facebook wall.
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| Facebook Like Box: Another example of Facebook integration is adding a “Like Box”. Acting on the Like Box results in liking … |
ecommerce social-networks
GNU Screen + SSH_AUTH_SOCK; my new approach
By David Christensen
February 23, 2011
Over the years, I’ve played around with several different methods of keeping my forwarded SSH-Agent authentication socket up-to-date in long-running screen sessions (referenced via the $SSH_AUTH_SOCK shell variable). The basic issue here is that Screen sees the process environment at the time it was initially launched, not that which exists when reattaching in a subsequent login session. This means that the $SSH_AUTH_SOCK variable as screen sees it will refer to a socket which no longer exists (as it was removed when you logged out after detaching on the initial login when starting screen).
Some of my previous methods have included a hard-coded variable for the socket itself (downsides: if it’s a predictable name you’re potentially opening some security issues, plus if you open multiple sessions to the same account, you kill the latest socket), symlinking the latest $SSH_AUTH_SOCK to a hard-coded value on login (similar issues), dumping $SSH_AUTH_SOCK to a file, and aliasing ssh and scp to first source said file to populate the local window’s enviroment (doesn’t work in scripts, too much manual setup when adapting to a new system/environment, won’t work with any other subsystem not …
environment sysadmin tips tools
A Simple WordPress Theme In Action
By Steph Skardal
February 22, 2011
I’m a big fan of WordPress. And I’m a big fan of building WordPress themes from the ground up. Why am I a big fan of building them from the ground up? Because…
- It’s very easy to setup and build if you plan to move to utilize WordPress’s blog architecture for your site, but just have a set of static pages initially.
- It allows you to incrementally add elements to your theme from starting from the ground up, rather than cutting out elements from a complex theme.
- It allows you to leave out features that you don’t need (search, comments, archives, listing of aticles), but still take advantage of the WordPress plugin community and core functionality.
- The learning curve of WordPress APIs and terminology can be complicated. It’s nice to start simple and build up.
Here are some screenshots from my simple WordPress theme in action, a site that contains several static pages.
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The template is comprised of several files:
| File | Notes |
| header.php | Includes doctype, header html, and global stylesheets included here. wp_head() is called in the header, which will call any executables tied to the header hook using WordPress’s hook API. wp_list_pages() is also called, which is … |
php wordpress
Managing Perl environments with perlbrew
By Jason Dixon
February 21, 2011
As a Perl hobbyist, I’ve gotten used to the methodical evolution of Perl 5 over the years. Perl has always been a reliable language, not without its faults, but with a high level of flexibility in syntactical expression and even deployment options. Even neophytes quickly learn how to install their own Perl distribution and CPAN libraries in $HOME. But the process can become unwieldy, particularly if you want to test across a variety of Perl versions.
To contrast, Ruby core development frequently experiences ABI breakages, even between minor releases. In spite of the wide adoption of Ruby as a Web development language (thanks to Ruby on Rails), Ruby developers are able to plod along unconcerned, where these incompatibilities would almost certainly lead to major bickering within the Perl or PHP communities. How do they do it? The Ruby Version Manager.
Ruby Version Manager (RVM) allows users to install Ruby and RubyGems within their own self-contained environment. This allows each user to install all (or only) the software that their particular application requires. Particularly for Ruby developers, this provides them with the flexibility to quickly test upgrades for regressions, ABI …
environment perl ruby
Pausing Hot Standby Replay in PostgreSQL 9.0
By David Christensen
February 12, 2011
When using a PostgreSQL Hot Standby master/replica pair, it can be useful to temporarily pause WAL replay on the replica. While future versions of Postgres will include the ability to pause recovery using administrative SQL functions, the current released version does not have this support. This article describes two options for pausing recovery for the rest of us that need this feature in the present. These two approaches are both based around the same basic idea: utilizing a “pause file”, whose presence causes recovery to pause until the file has been removed.
Option 1: patched pg_standby
pg_standby is a fairly standard tool that is often used as a restore_command for WAL replay. I wrote a patch for it (available at my github repo) to support the “pause file” notion. The patch adds a -p path/to/pausefile optional argument, which if present will check for the pausefile and wait until it is removed before proceeding with recovery.
The benefit of patching pg_standby is that the we’re building on mature production-level code, adding a functionality at its most relevant place. In particular, we know that signal handling is already sensibly handled; (this was something I was less than …
postgres
A Performance Case Study
By Steph Skardal
February 9, 2011
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I’m a sucker for a good performance case study. So, when I came across a general request for performance improvement suggestions at Inspiredology, I couldn’t help but experiment a bit. The site runs on WordPress and is heavy on the graphics as it’s a site geared towards web designers. I inquired to the site administrators about grabbing a static copy of their home page and using it for a case study on our blog. My tools of choice for optimization were webpagetest.org and YSlow. Here are the results of a 4-step optimization in visual form:
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Inspiredology’s complete homepage. |
The graph on the left shows the page load time in seconds for a first time view. Throughout optimization, page load time goes from 13.412 seconds to 9.212 seconds. Each step had a measurable impact. The graph on the right shows the page load time in seconds for a repeated view, and this goes from 7.329 seconds to 2.563 seconds throughout optimization. The first optimization step (CSS spriting and file combination) yielded a large performance improvement. I’m not sure why there’s a slight performance decrease between step 3 and step 4.
And here’s a summary of the changes involved in each step: …
css performance compression optimization