Previously, upon receiving a termination signal, the process tries to
flush all changes to the database, retrying every 0.1s until it
succeeds. However, if the database is not set up properly, this always
fails, and spams the terminal/logging with the error message 10 times a
second.
If the user sends another termination signal, the handleTermSignal
function is called once again, and we get twice the number of error
messages.
This commit changes the behaviour in various ways.
(1) It lowers the retry rate to 0.5s, and aborts after 30 seconds.
(2) If the write to the database errored, the error message explains
that this is due to us flushing the final changes.
(3) We replace realtime.maintenance with realtime.state, which is an
Enum with three possible states --- Starting, Running, and Stopping.
If a termination signal is received in the starting state, the
process simply aborts because there is nothing to clean up. This is
the case when the database is misconfigured, since the application
starts up only after connecting to the databse. If it is in the
Stopping state, the handleTermSignal function returns because
another instance of handleTermSignal is already running.
Fixes#408
Signed-off-by: Dexter Chua <dec41@srcf.net>
