Standardize on exit() / _exit() (this depends whether we are considered
to be the "main" fork, which should run anything registered with atexit()).
Exclude `return false` and throwing exceptions.
This fixes the error path for fork(). Daemonize() would return false, but
the `return false` error convention was not tested in the caller.
It also fixes the error message for fork() to show the error code.
Everyone loves `strace`, but sysadmins should not have to rerun their
daemons under it just to see an error code.
Also in case an exception is thrown, show its diagnostic information
instead of dropping it on the floor. In the log message, I mention why we
are uninitializing and then initializing the app at this point.
For the reader, it pushes all the weirdness into the error convention of
Daemonize(). This comes back to the exit() / _exit() distinction. Once
we have forked, we technically don't want to allow the parent process to
exit(), so we don't want to return to the caller.
It's called "Console", which would be line-buffered anyway. But, it's
implemented as std::cout. This might be piped to a logger, as in
daemontools or systemd. In this case it will not be a TTY, and log lines
should be flushed without too much delay. Let's just flush each message.
Let's not introduce a static instance of StreamLogger (flushed by interval
timer). That's too stressful to read, because static instances are really
annoying to order. Example citation: "Yay, our static destructors are
pretty much beyond repair at this point." -- application.cpp.
I don't know if there will be any need to optimize logging syscalls. The
init script uses `--daemonize`. I think the systemd service should also
avoid using the "Console" log after startup (see next commit). The
documentation does not warn that the syslog feature is less efficient
in system calls than mainlog; deferred flusing does not seem to be a highly
prominent feature. There's no cool comment in the code about how much the
syscalls were slowing down some use case (or qualifying that this
optimization can only eliminate syscalls on platforms with both mutexes and
clocks that can work without syscalls).
Precedence as follows:
- DEnvironment=...
- const Environment = ...
- object IcingaApplication "app" { environment = "..." }
The wrapped script constant handling is required
since we cannot directly link from libremote (SNI handling)
to libicinga where the object resides. Instead we'll
use the Application class helpers for hiding the ScriptGlobal
calls.
