Startups powered by Seagull: Podcast.de

January 21, 2008 05:14, contributed by: seagull

Thanks to Fabio Bacigalupo for the following article, part of an upcoming mini-series about successful startups built on the Seagull platform.

Running a successful website is a constant balancing act between achieving good performance and scaling smoothly. Read how we have used the Seagull framework to build our portal podcast.de. As a start-up we provide a web-based service to find, comment, play and recommend audio and video podcasts. At the moment the service is intended for a German speaking audience only but we are prepared for internationalisation thanks to Seagull.

In February of 2006 I published the first version of podcast.de based on an early 0.4 release of Seagull. It took me over fourteen months to build the site on top of Seagull to fit my needs. I wrote several new modules and hacked lots of things like clean urls. Many of these things are now part of the core (and are not written by me). One thing did make it into the release, the export module which generates RSS feeds. RSS feeds are what our system is really about. Not knowing any better I built the portal based upon a MySQL database. An XML db might have been a better choice at least in some areas. The biggest table holds over 500.000 entries. These are all the references to podcast episodes and their metadata. Recently we upgraded from a MySQL db version 4.x to the latest, stable version of the 5th release. Database performance has been an issue since the start however at the beginning it was not noticeable. The layout of the database should have been designed in a less complex manner. With the amount of data and the overall usage growing we ran into hown-grown issues. With indexes, query optimisations, better hardware, newer MySQL releases, a migration to split sequence tables, db caching, MySQL tweaking and most importantly the replacement of most DataObjects code we got fairly good performance on the db side.

Caching is really the one lifesaver every webmaster should look out for. Seagull has built-in template and nowadays library caching support which is nice. We used the SGL_Cache class for general purpose data caching as well. With a rising number of pages and a climbing user base the file-based cache turned into a bottleneck as the harddrive had to seek through several thousand files. A different file-system for smaller files might have helped for a while. We chose to replace the file-based caching with a memory-based alternative. It is just a five line hack in SGL_Cache and a little wrapper! In our case we decided to use memcache. Memcache(d) is commonly used. The PHP part is installable through PEAR and with PHP5.x, which we switched to in our development cycle, and you now have an OO interface. Shared memory would have been an alternative. At first memcache worked very well but having a few thousand objects stored slowed it down. For a while we had to flush the cache every now and then because we could not find anything related on the net which explained this behaviour. Migrating to a new server with a newer linux and a newer memcached installed solved the problem. We could not replace the memcached before because of dependency issues.

Another performance issue is rendering the navigation. This got a bit better over time. The solution again is to cache most parts of it. There are still some other minor issues with the DB-based navigation. I have not tried the file-based one, yet. With DB-based nav you are not able to add an alias with two slashes. That is the biggest drawback for us at the moment. I wrote my own alias strategy for this which works well. Proper I18N might be the next issue once we need it.

I am still not friends with emailing in Seagull. As default Seagull sends HTML mails. I am not a big fan of that. I want to send text and HTML mails combined. Ages ago I sent in a patch which did not get accepted. A couple months back an almost identical patch got sent in. Neither did that one get accepted. Anyhow we are using this modification successfully.

Now that I described some of the issues with Seagull let's have a look at the good parts. The overall structure is complex but fairly clean and intuitive once you start working with it. The overall progress might be slow but the framework is steadily improving thanks to Demian, Lakiboy and all the other active developers. The framework is flexible and versatile. We are using it with several different interfaces (web, mobile, iptv, search). I hooked up Zend libs succesfully into the system without problems. We have several crawlers running using cron jobs and the CLI interface. Migrating from 0.4 to 0.6 was an effort but thanks to the loosely coupled core it was possible.

Since the last relaunch of podcast.de at the end of September 07 we are intensively using AJAX. We moved the database to its own server. We have the static properties on another separate server. We tried to use lighttpd as http server instead of Apache's http-server to reduce the load. We failed. I could not get it stable under load.

These days we welcome over 10.000 unique visitors a day. Almost 25.000 people registered for our service. We serve over two million pages a month with one Seagull server. We have 18 custom Seagull modules, 6 different themes (not all in use, yet) and three years of development spent on the system. The database now has 112 tables with around 1 GB of data. The next step in performance upgrades will be a second database server for a read-only slave. Before that we have to modify SQL query executions to differ between read and write operations. At the moment there is room for more so pay us a visit at podcast.de and let us know how you like it!

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