Log functions for prometheus
Tornado log handler for recording RED metrics.
- We record the following metrics:
Rate - the number of requests, per second, your services are serving. Errors - the number of failed requests per second. Duration - The amount of time each request takes expressed as a time interval.
We use a fully qualified name of the handler as a label, rather than every url path to reduce cardinality.
This function should be either the value of or called from a function that is the ‘log_function’ tornado setting. This makes it get called at the end of every request, allowing us to record the metrics we need.
Prometheus metrics exported by Jupyter Server
Read https://prometheus.io/docs/practices/naming/ for naming conventions for metrics & labels.