Implement timing metrics
ScottMansfield opened this issue · comments
The server-side timing will be critical to understanding the operation of rend under load. In order to capture this information, a new histogram type must be created in the metrics package.
The histogram will capture a sampled stream of the values sent into a circular buffer. It will also track the number of values sent and the true 0th and 100th percentiles. Once the data is requested, the buffer and other data will be atomically reset to a start state. This can be accomplished by keeping two structures around for quick switching during metric recording.
The default buffer size will be 16,384 entries and the default sample rate will be 25%. For now it will not be configurable. The size here reserves approximately 256k of memory per histogram because of the doubling of buffers for quick changeover.