Kelon performance metrics

[containerpope]

Problem Statement

Common questions asked when operating the system are:

• Are there an increase in failures while executing policies ?
• Are policies performing poorly? -> Increase in latency ?

Suggested Solution

To answer all these questions easily, we can implement prometheus metrics that represent exactly that information.
Suggestion would be to provide (counter & summary) metrics for each processed request with the following labels:

• package
• request path
• request method
• result (granted, denied, error)

This would allow to monitor latency and error rate of kelon.

[containerpope]

@dcseifert what do you think?

[containerpope]

Decided not to include request path and package, result is represented by status code if toggled. Also removed database metrics