CASSGO-3 detailed description for NumConns

[OleksiienkoMykyta]

Closes #1741 .
There is some unclearness in the NumConns description because there are no details about what it affects, and does it sets any limits. I added a few more details to avoid confusion about it in the future.

[joao-r-reis]

I'm not sure if this is 100% correct, if InitialHostLookup is enabled (it's the default) then the pools for the discovered hosts will be filled during session initialization

[OleksiienkoMykyta]

You are right!
I double-checked it with the timeout, and it turned out that the pool filled during initialization. When I tested it last time the pool had not been filled before the query execution because pool filling runs in separate gorutine and it took more time to finish than the query execution.
Thank you for noticing the issue!
I can replace it with something like

The size of the connection pool for each host. The pool filling runs in separate gourutine during the session initialization phase. 
Also, it describes a maximum number of connections at the same time.
Notice: There is no guarantee that pool filling will be finished in the initialization phase.
Default: 2 

What do you think?

[joao-r-reis]

Hmm interesting, did you use SingleHostReadyPolicy? If you don't use this policy then it should wait until all hosts have at least 1 connection in the pool before the session initialization is done.

Check this and this.

Considering this, it would probably be good to mention that gocql will always try to get 1 connection on each host pool during session initialization AND it will attempt to fill each pool afterwards asynchronously if NumConns > 1

[OleksiienkoMykyta]

What about something like that?

// The size of the connection pool for each host.
// The pool filling runs in separate gourutine during the session initialization phase.
// gocql will always try to get 1 connection on each host pool
// during session initialization AND it will attempt
// to fill each pool afterward asynchronously if NumConns > 1.
// Notice: There is no guarantee that pool filling will be finished in the initialization phase.
// Also, it describes a maximum number of connections at the same time.

I have added gocql will always try to get 1 connection on each host pool during session initialization AND it will attempt to fill each pool afterward asynchronously if NumConns > 1 as you suggested, so there is no more room for unclearness.

[joao-r-reis]

👍