Nakama metrics wishlist

[redbaron]

Following metrics are missing and would be really handy to have.

HTTP

• Number of client connections by status (idle, serving request, websocket)

RPC

• All rpcs are within the same metric, so instead of: nakama_RPCNAME_latency have nakama_latency{rpc="RPCNAME"}
• introduce "error class" and break down errors by it. example: preconditions
• have RPC metrics tracked per protocol with separate "proto=ws" or "proto=http" labels

SQL

• number of connctions to the database by status (active, free, estblishing)
• stats related to acquiring connection from the pool: queue length, wait latencies (histogram), how long connection was in use (histogram)
• queries stats: counts, times. Track these per RPC context . Probably doesn't worth it to be per query, just as an aggregate.

Matchmaking related stats

TBD