The log tail buffer is an extension to the logging framework. We're going to extend MemoryHandler to slightly alter its behavior. The built-in behavior for MemoryHandler includes three use cases for writing—it will write to another handler when the capacity is reached; it will write any buffered messages when logging shuts down; most importantly, it will write the entire buffer when a message of a given level is logged.
We'll change the first use case slightly. Instead of writing to the output file when the buffer is full, we'll remove the oldest messages, leaving the others in the buffer. The other two use cases for writing on exit and writing when a high-severity record is handled will be left alone. This ...
