/etc/logrotate.d/icinga2 is in icinga2-common 2.1.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 | /var/log/icinga2/icinga2.log /var/log/icinga2/debug.log {
       	daily
	rotate 7
	su nagios nagios
	compress
	delaycompress
       	missingok
       	notifempty
       	create 644 nagios nagios
	copytruncate
	postrotate
		if ! killall -q -USR1 icinga2; then
			exit 1
		fi
       	endscript
}
/var/log/icinga2/error.log {
	daily
	su nagios nagios
	rotate 90
	compress
	delaycompress
	missingok
	notifempty
	create 644 nagios nagios
	copytruncate
	# TODO: figure out how to get Icinga to re-open this log file
}
 |