Until now, if two copies of one OVS daemon started up at the same time,
then due to races in pidfile creation it was possible for both of them to
start successfully, instead of just one. This was made worse when a
previous copy of the daemon had died abruptly, leaving a stale pidfile.
This commit implements a new pidfile creation and removal protocol that I
believe closes these races. Now, a pidfile is asserted with "link" instead
of "rename", which prevents the race on creation, and a stale pidfile may
only be deleted by a process after it has taken a lock on it.
This may solve mysterious problems seen occasionally on vswitch restart.
I'm still puzzled by these problems, however, because I don't see anything
in our tests cases that would actually cause two copies of a daemon to
start at the same time, which as far as I can see is a necessary
precondition for the problem.
Until now, it has been the responsibility of an individual daemon to call
die_if_already_running() at an appropriate time. A long time ago, this
had to happen *before* daemonizing, because once the process daemonized
itself there was no way to report failure to the process that originally
started the daemon. With the introduction of daemonize_start(), this is
now possible, but we haven't been taking advantage of it.
Therefore, this commit integrates the die_if_already_running() call into
daemonize_start() and deletes the calls to it from individual daemons.
The init script starts monitor-external-ids with --monitor when
configured to do so. Also made changes to guarantee that --monitor
actually restarts ovs-external-ids.
Signed-off-by: Ethan Jackson <ethan@nicira.com>
Opening a file descriptor and then closing it always discards any locks
held on the underlying file, even if the file is still open as another file
descriptor. This meant that calling read_pidfile() on the process's own
pidfile would discard the lock and make other OVS processes think that the
process had died. This commit fixes the problem.
These initial bindings pass a few hundred of the corresponding tests
for C implementations of various bits of the Open vSwitch library API.
The poorest part of them is actually the Python IDL interface in
ovs.db.idl, which has not received enough attention yet. It appears
to work, but it doesn't yet support writes (transactions) and it is
difficult to use. I hope to improve it as it becomes clear what
semantics Python applications actually want from an IDL.
