Simple MultiThread Safe Log Class

Question

What is the best approach to creating a simple multithread safe logging class? Is something like this sufficient? How would I purge the log when it\'s initially created?

Answer 1

Creating a thread-safe logging implementation using a single monitor (lock) is unlikely to yield positive results. While you could do this correctly, and several answers have been posted showing how, it would have a dramatic negative effect on performance since each object doing logging would have to synchronize with every other object doing logging. Get more than one or two threads doing this at the same time and suddenly you may spend more time waiting than processing.

The other problem you run into with the single monitor approach is that you have no guarantee that threads will acquire the lock in the order they initially requested it. So, the log entries may essentially appear out of order. That can be frustrating if you're using this for trace logging.

Multi-threading is hard. Approaching it lightly will always lead to bugs.

One approach to this problem would be to implement the Producer/Consumer pattern, wherein callers to the logger only need to write to a memory buffer and return immediately rather than wait for the logger to write to disk, thus drastically reducing the performance penalty. The logging framework would, on a separate thread, consume the log data and persist it.