The regex that broke a server

Introduction I’ve never thought I would see an unresponsive server due to a bad regex matcher but that’s just happened to one of our services, yielding it unresponsive. Let’s assume we parse some external dealer car info. We are trying to find all those cars with “no air conditioning” among various available input patterns (but without matching patterns such as “mono air conditioning”).

A beginner’s guide to MongoDB performance turbocharging

Introduction This is the second part of our MongoDB time series tutorial, and this post will be dedicated to performance tuning. In my previous post, I introduced you into our virtual project requirements. In short, we have 50M time events, spanning from the 1st of January 2012 to the 1st of January 2013, with the following structure: We’d like to aggregate the minimum, the maximum, and the average value as well as the entries count for the following discrete time samples: all seconds in a minute all minutes in an hour all… Read More

How to fetch entities multiple levels deep with Hibernate

Introduction It’s quite common to retrieve a root entity along with its child associations on multiple levels. In our example, we need to load a Forest with its Trees and Branches and Leaves, and we will try to see have Hibernate behaves for three collection types: Sets, Indexed Lists, and Bags.