As of 1.3 you can spawn custom applications via the :doc:`Emperor<Emperor>`.
Non-uWSGI Vassals should never daemonize, to maintain a link with the Emperor. If you want/need better integration with the Emperor, implement the Emperor protocol.
An environment variable UWSGI_EMPEROR_FD is passed to every vassal,
containing a file descriptor number.
import os
has_emperor = os.environ.get('UWSGI_EMPEROR_FD')
if has_emperor:
print "I'm a vassal snake!"Or in Perl,
my $has_emperor = $ENV{'UWSGI_EMPEROR_FD'}
if ($has_emperor) {
print "I am a vassal.\n"
}Or in C,
int emperor_fd = -1;
char *has_emperor = getenv("UWSGI_EMPEROR_FD");
if (has_emperor) {
emperor_fd = atoi(has_emperor);
fprintf(stderr, "I am a vassal.\n");
}From now you can receive (and send) messages from (and to) the Emperor over this file descriptor.
Messages are byte sized (0-255), and each number (byte) has a meaning.
| 0 | Sent by the Emperor to stop a vassal |
| 1 | Sent by the Emperor to reload a vassal / sent by a vassal when it has been spawned |
| 2 | Sent by a vassal to ask the Emperor for configuration chunk |
| 5 | Sent by a vassal when it is ready to accept requests |
| 17 | Sent by a vassal after the first request to announce loyalty |
| 22 | Sent by a vassal to notify the Emperor of voluntary shutdown |
| 26 | Heartbeat sent by the vassal. After the first received heartbeat, the Emperor will expect more of them from the vassal. |
| 30 | Sent by the vassal to ask for :doc:`Broodlord` mode. |