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Thoughts from two software engineers. You can filter posts by tags or by category.

Introduction to SQL databases Part 1

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Whether you are running a web app, a financial system or a game, you need some method of storing your data. SQL allows you to query most traditional databases, like MySQL or PostgreSQL. Let’s take a look.

What is the CAP theorem?

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The CAP theorem is one of the most fundamental principles of distributed system design. Yet, it is often misunderstood or outright disregarded.

Filtering spam with Exim and Spamassassin (properly)

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SpamAssassin is a frequently used companion for Exim. However, most people set it up in a synchronous manner – spam is checked directly when the SMTP session is opened. While this is certainly a valid technique, it has it’s drawbacks. It leaves the server vulnerable to DOS attacks because the spam filtering is a big resource hog. Having SpamAssassin headers in the mail from the remote servers is also an issue, because the $h_X-Spam-* variables will start misbehaving suddenly.

Fixing RDNS_NONE with Spamassassin

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When dealing with SpamAssassin and Exim, one may often encounter a mysterious RDNS_NONE

Proper time handling with PHP and MySQL

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Few developers actually know that not only character encodings but also time handling can cause you headaches when it comes to PHP and MySQL. Contrary to popular belief, PHP’s time handling actually works quite reasonably if you know how time actually works. If you don’t, you may be in for a big surprise when you add 3 days to a date and end up with a date 4 days from now. The answer lies within the *NIX time handling.

Setting up Apache with PHP-FPM

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Nowadays nginx seems to experience a serious growth in terms of numbers when looking at HTTP server software. Almost all articles regarding PHP-FPM detail the setup with nginx, very few talk about the good old Apache HTTPd. Admittedly, it’s a little harder to set up due to the myriad hacks layered in it’s internal infrastructure. It has one major advantage however: it handles .htaccess files which allows customers to configure their own little corner of the webserver without poking the admin or endangering the server’s stability.

Don't use FTP — Here's why

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FTP has been around since the early days of the internet. Even though it’s old and cranky a lot of sysadmins, especially those just getting into managing a server, still don’t know anything else. FTP is outdated, has a lot of problems and sometimes it can be outright dangerous, however it’s wide spread acceptance as an easy way for transferring files makes it hard to switch to alternative protocols. If you have a choice, don’t use it. I’ll show you why.

Filtering spam with Exim only

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Defense against spam has always been a hassle. Statistical filters only get you so far and they consume a LOT of resources. For exactly that reason I like to employ basic checking policies before accepting e-mail at all. These policies have gotten me pretty far and my false positive rate is pretty low.

Logging PHP errors to syslog-ng

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Ever so often I get to set up hosts for running PHP. When running a load balanced solution, you have more hosts and reading logs gets complicated, development gets tedious. So what helps, is a central logging server. This is pretty easy to set up with syslog-ng, however PHP has a annoying habit of logging everything with the NOTICE error level.