I will show you how to enable logging in the MongoDB Java driver and also how to set and change the log level. The official mongoDB Java driver uses java.util.logging as its default logging framework or sl4j if the latter is present. It can be very useful to enable logging in the MongoDB drivers to trace how the driver is interacting with the database.

I originally published this post on my old blog in 2009. I’ve edited it a little for readability but left the contents unchanged, so it may be out of date and not reflect the current state of the pantheios library. I also haven’t been using pantheios for logging since about 2010, and have been using Boost.Log instead.

I recently had to come up with a logging solution for C++ code a JNI DLL/shared library that is providing the data translation layer between Java and underlying native C and C++ libraries. As usual, some logging was required to aid fault-finding in a production environment, if necessary. A quick survey of the state of C++ logging showed that not a lot had changed since I last looked at logging libraries. In fact, a lot of them seem to have survived unchanged for several years. I’m not sure if that is a good thing and a sign of maturity or a sign of “making do” and the low priority most projects assign to a performant logging library. Eventually I settled on pantheios as it offered several features that were crucial for this application. The major one was that pantheios it is extremely modular and will only link in the parts you really need. I consider this a major advantage over the more monolithic libraries that pull in all their functionality all the time, especially when you link them in as a static library (yes, log4cxx, I’m looking at you). Linking in the logging library as a static library was necessary to avoid conflicts with other libraries that are being used in the same process.

I recently ran into a requirements for retrofitting a logging library to an existing project. My first instinct was to throw Pantheios at it as I’ve used it before and It Just Worked. Unfortunately in this case, we needed the ability to log to more than two event sinks and it looked like this was getting a little awkward with Pantheios, which prompted me to look at Boost.Log.

After some digging through the documentation and the samples, I managed to get the logging going to the three event sinks we needed. So far, so good, but every time I started up the program it reported an unhandled exception on Windows 7 when it was trying to initialise the simple_event_log backend and the software wasn’t run as administrator. Curiously enough, the log messages still did appear in the event log, just with lots of unnecessary decoration.