tree 7b0eac14183733c776a0d1f4bb7b9237546b52db
parent 8a492e33f4d5de9778a94ae741e4a14aa5a71004
author Keegan Carruthers-Smith <keegan.csmith@gmail.com> 1584529685 +0200
committer Keegan Carruthers-Smith <keegan.csmith@gmail.com> 1584685901 +0200

shards: prometheus metrics for sharded search

We add several metrics and add the prometheus http handler to zoekt-webserver
if pprof is enabled.

- Gauges for number of running searches and lists.
- Gauges for number of searches and lists within a shard.
- Histogram for search duration.
- Counter for number of search failures.
- A counter per zoekt.Stats

The gauge should for searches should help with noticing a queue forming. The
gauges in shards should be bounded, but are useful to understand load. The
rest of the metrics are pretty straightforward.

Change-Id: I24c55204a0e742479f9bae01301cc258289a4101