limit number of concurrent connections about tls-observatory

[0xdiba]

I don't know if SetMaxOpenConns() can help us much , because the api and the scanner are two different binaries so the only thing you can do is just guess and probably set something like ~60% of the open conns to the scanner and ~40% to the api.

More importantly in the scanner, if we pass those limits we might get errors for acknowledged scans.
Maybe a solution that uses DBStats to get the number of open connections to the database and start/postpone the scan depending on whether we are approaching the limit or not.

[jvehent]

Why do you think we would get errors for acknowledged scans? I think if we pass the limit, the scanner will fail to run SELECT FOR UPDATE and thus not acknowledge the scan, so another scanner will pick it up. No?