At least this appears to be the case, because the function I have created to determine whether Bitcoin Core is "working" does the most minimal/simple API call I could find, which was "uptime", to see if my system can still communicate with Bitcoin Core (on the same computer) or if something has broken.
Since the blockchain has grown to an insane size, I was forced to move my Bitcoin "datadir" from a SSD disk to a mechanical one (due to running out of space on the former). Around the same time, I also configured Bitcoin Core to always use Tor for all connections. The combination of these two things caused the unexpected issue that my "is everything OK still?" script fails for Bitcoin Core when I start the computer after a night's sleep, because Bitcoin Core takes longer than before to get ready. Sometimes it can take like half an hour.
(This same thing also affects my polls for checking the current balance, which at least is understandable because Bitcoin Core probably doesn't want to report an outdated figure if the new data about to be fetched changes the balance.)
All it says in the manual is this: https://bitcoincore.org/en/doc/0.18.0/rpc/control/uptime/
(For some reason, there's no API docs for 0.18.1... the latest version is 0.18.)
- Is this a known issue/bug? Will it be fixed soon?
- Should I be using some other API call to check if Bitcoin Core is running and "can talk to me"?
- Is there a separate API call I could use to determine whether Bitcoin Core is "all ready for action" (fully synced)?