5.1.2 Common logs
If you’ve been running log_recent(), you’ll probably discover that although it’s useful for getting an idea of what’s happening right now, it’s not very good at telling you whether any important messages were lost in the noise. By recording information about how often a particular message appears, you could then look through the messages ordered by how often they happened to help you determine what’s important.
A simple and useful way of knowing how often a message appears is by storing the message as a member of a ZSET, with the score being how often the message appears. To make sure that we only see recent common messages, we’ll rotate our record of common messages every hour. So that we don’t lose everything, we’ll keep the previous hour’s worth of common messages. Our code for keeping track of and rotating common log messages is shown next.