Having an issue during high traffic will get errors in the log with 502, and get these errors--"no live upstreams while connecting to upstream"

In my configs it is set to 5 max fails, default of 10s fail time.

1. Does it try the same session within those 10s--every 2 seconds? If I made it 20 seconds would it try every 4 seconds?
2. If another session fails, is it cumulative in that 10s or is it for each session?
3. If the server is marked unavailable; what about the current sessions?

4. What would be a better solution? Extending the fail time? Lessening the fail time and less attempts?

Thank you