repmgr repl_status had the column time_lag which was documented to be
the time a standby is behind master. In fact it only works like this
when viewed on the standby and not on the master: there it only was the
time of the last status update. We dropped that column and replaced it
by a new column „communication_time_lag“ which is the content of the
repl_status column on the master. On the standby we contain the time of
the last update in shared mem though refer always to the correct time
nonetheless where repl_status is queried. We also added a new column,
„replication_time_lag“, which refers to the apply delay.
wait_connection_availability() did take at least 2 seconds per call in
the old incarnation. Now we may finish a call without any sleep at all
when the result is already ready at the time called
We had the problem that the log file appeared empty for a long time due
to file buffers. Thus we call fflush() after every log message so the
log file gets written out to disk quickly
Refactoring part: we now use a function to generate the PID
file. Sophistication: we now check if the PID contained in the file is a
valid PID. We ignore the file if it doesn't.
after the setsid() we are the process leader. And as a process leader we
are able to open a new terminal, even if we currently don't own one. So
we do another fork and do not call setsid() and not become a process
leader to avoid that.
when repmgr_funcs is not pre-loaded `repmgr_update_standby_location()`
will return false and `repmgr_get_last_standby_location()` will return
an empty string. Thus we may end in an endless loop. To avoid that we fail.
When not flushing and fsync()ing it the output may be garbled due to
concurrent writes to the file (system() spawns a child process with
stdin/stdout/stderr inherited from it's parent)
sleep_monitor replaces the old SLEEP_MONITOR define and makes it
configurable; this is the interval in which we monitor
sleep_delay replaces the old sleep(300) when waiting for the master to
recover.
