1825272 - add metrics to cache manager

Status: NEW

(Socorro :: Processor, task, P2)

Description

[Will Kahn-Greene [:willkg] ET needinfo? me]

The previous cache manager emitted no metrics, so it was hard to see what it was doing. The new cache manager is set up to emit metrics.

There are a couple of things we want to monitor with the cache manager:

1. new files created, files opened, and files deleted
2. total number of files over time

There are probably some other things we want to look at, but these are good ones to start with.