* Refactor stats to use atomics
When we are dealing with a high number of connections, generated
stats cannot be consumed fast enough by the stats collector loop.
This makes the stats subsystem inconsistent and a log of
warning messages are thrown due to unregistered server/clients.
This change refactors the stats subsystem so it uses atomics:
- Now counters are handled using U64 atomics
- Event system is dropped and averages are calculated using a loop
every 15 seconds.
- Now, instead of snapshots being generated ever second we keep track of servers/clients
that have registered. Each pool/server/client has its own instance of the counter and
makes changes directly, instead of adding an event that gets processed later.
* Manually mplement Hash/Eq in `config::Address` ignoring stats
* Add tests for client connection counters
* Allow connecting to dockerized dev pgcat from the host
* stats: Decrease cl_idle when idle socket disconnects
This is an implementation of Query mirroring in PgCat (outlined here #302)
In configs, we match mirror hosts with the servers handling the traffic. A mirror host will receive the same protocol messages as the main server it was matched with.
This is done by creating an async task for each mirror server, it communicates with the main server through two channels, one for the protocol messages and one for the exit signal. The mirror server sends the protocol packets to the underlying PostgreSQL server. We receive from the underlying PostgreSQL server as soon as the data is available and we immediately discard it. We use bb8 to manage the life cycle of the connection, not for pooling since each mirror server handler is more or less single-threaded.
We don't have any connection pooling in the mirrors. Matching each mirror connection to an actual server connection guarantees that we will not have more connections to any of the mirrors than the parent pool would allow.
