MongoDB Java driver randomness - it's only logging, but

I saw a number or people on Twitter yesterday posting a link to some "interesting" code in MongoDB's Java driver github.

The strange code located inside some exception handling included the following:

                if (!((_ok) ? true : (Math.random() > 0.1))) {

                    return res;

                }

I know my own code isn't always a shining example to be held up as the one true way of doing things, but seriously doubt that I have ever produced something as inexplicable as that.

I briefly tried to trace back the history to determine how long this has been around and whether there is a meaningful commit comment, but was in the middle of other more important things (lunch) and gave up.

The latest theory I have heard is that the code was introduced as an approach to reduce the amount of noise in logging of the exception.  I don't expect to see this recommended as a pattern any time soon.

MongoDB Lightning Talk

My employer recently hosted a gathering of their IT teams from around the world for a two day conference in Madrid.  It was a good opportunity to meet colleagues that I had previously only dealt with by phone and email in a relaxed social setting.

In a moment of madness I volunteered to give a presentation about a topic that I have been dabbling with in recent months - MongoDB.

My agile style of preparation - "delay commitment until the last responsible moment" - could easily have been mistaken for procrastination.  I'm not sure if I would recommend sitting on a sofa watching old episodes of Miami Vice with the laptop drifting in and out of sleep mode as being optimal for all.

Without further ado, here is a high level view of some of the content that I blended together:

• What is MongoDB?
• Non-Relational JSON Document Store
• Dynamic Schema
• Embedding of Documents and Arrays
• Comparison with relational database (Table -> Collection, Row -> Document etc.)
• How to Organise Data
• Entity -> Document
• Embedding vs Referencing
• 16MB document size limit
• Indexing
• How to Query
• Example of find
• Example of insert
• Example of aggregation framework
• What is MongoDB being used for?
• E-commerce
• Analytics and Reporting
• Content Management
• CoreMedia Elastic Social
• Logging
• Language and Framework Support
• Listing of languages and frameworks
• Drivers have semantics to fit with the style of the language
• Replication
• Configurable tags - usable within write concerns
• Configurable delay
• Sharding
• Distribution of writes
• Shard key selection importance
• Scatter-gather for reads not satisfiable by a single shard
• Gotchas
• Database level locking
• Default settings not suitable for all
• Application needs to check for result of operations