nm-sudo and nm-dispatcher are very similar from a high level. Both are D-Bus activated
services that exit on idle and all they do, is to provide a simple D-Bus API with no
objects or properties.
Hence it's not surprising that they follow the same structure.
Rename the code to make them look more similar.
After we released the well-known name (or if we failed to ever request
it), we must exit as fast as possible, so that a new instance can
be started to serve new requests.
At that point, reject new requests because they are targeted against the
unique name, which they should not do (when talking to a D-Bus activated
service that exits on idle, it's important to talk to the well-known
name).
Also, if we receive SIGTERM, start releasing the name. We are told to
shut down, and must do so in a timely manner. Again, new requests shall
not be served by this instance.
The advantage of environment variables is that the user can use
`systemctl edit NetworkManager-dispatcher.service` for setting them,
without need to change the ExecStart= line.
Also, enabling debugging from the start is useful, despite that debug
logging can be enabled per-request.
Also, there is a difference whether we want verbose logging or whether
we want to log to stdout. There should be a flag, that only increases the
logging verbosity, but does not change the logging backend.
- exit-on-idle needs to be done correctly. Fix the race, by first
notifying systemd (STOPPING=1), releasing the name, and all the
while continue processing requests.
- don't use g_bus_own_name_on_connection(). That one also listens
to NameLost and NameAcquired signals, but we don't care about those.
systemd will take care to only spawn one process at a time. And
anyway, the well-known name is only important to be reachable, we
don't require it to be functional. We can get the first request
before RequestName completed and we can continue getting requests
after releasing the name.
- use nm_g_timeout_add_source() for millisecond precision of idle timeout.
- schedule the first idle timeout before registering the D-Bus object.
- let the signal handler do nothing, if we are already quitting. In
practice, this only silences the extra logging.
The difference is that nm_g_bus_get_blocking() iterates the GMainContext
of the caller, and thus it can process and handle SIGTERM signals.
Calling g_bus_get_sync() does not iterate the context, and we cannot
handle or detect early cancellation.
Explicitly iterating the context is more flexible, as we can control the
parameters how long we iterate. GMainLoop is essentially a (thread-safe)
iteration around one boolean flag (controlled by g_main_loop_run() and
g_main_loop_quit()). We can maintain that boolean flag ourselves.
Originally, we would define G_LOG_DOMAIN via CFLAGS arguments.
Since commit 341b6e0704 ('all: change G_LOG_DOMAIN to "nm"') we would
instead set it in source and uniformly define it as "nm".
The reasons are that most parts of our source should not use g_log() directly,
and there is an aim to avoid special CFLAGS to simplify the build setup.
However, dispatcher indeed uses g_log() for logging, so the value there
is important.
Fix that, but this time by setting the define in source not via
CFLAGS.
Fixes: 341b6e0704 ('all: change G_LOG_DOMAIN to "nm"')
