Problem of notifcations not sent during included timeperiods

Hi,

We’ve witnessed an unexpected behavior for some notifications that should be sent during a timeperiod constructed with “includes”.
Basically, the included timeperiods and the “prefer_includes” attribute don’t seem to have any effect. The included timeperiods don’t override (or complement) what’s in the main timeperiod.

icinga2 --version

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icinga2 - The Icinga 2 network monitoring daemon (version: r2.11.2-1)

Copyright (c) 2012-2020 Icinga GmbH (https://icinga.com/)
License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl2.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

System information:
  Platform: Debian GNU/Linux
  Platform version: 9 (stretch)
  Kernel: Linux
  Kernel version: 4.9.0-11-amd64
  Architecture: x86_64

Build information:
  Compiler: GNU 6.3.0
  Build host: runner-LTrJQZ9N-project-298-concurrent-0

Application information:

General paths:
  Config directory: /etc/icinga2
  Data directory: /var/lib/icinga2
  Log directory: /var/log/icinga2
  Cache directory: /var/cache/icinga2
  Spool directory: /var/spool/icinga2
  Run directory: /run/icinga2

Old paths (deprecated):
  Installation root: /usr
  Sysconf directory: /etc
  Run directory (base): /run
  Local state directory: /var

Internal paths:
  Package data directory: /usr/share/icinga2
  State path: /var/lib/icinga2/icinga2.state
  Modified attributes path: /var/lib/icinga2/modified-attributes.conf
  Objects path: /var/cache/icinga2/icinga2.debug
  Vars path: /var/cache/icinga2/icinga2.vars
  PID path: /run/icinga2/icinga2.pid

Config example

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object HostGroup "critical" { 
}

object Host "crit_vm" {
  import "generic-host"
  groups = [ "critical" ]
  address = "123.123.123.123"
}

object UserGroup "on_call_guys" { 
}

object User "the_warrior" {
  import "generic-user"
  groups = [ "on_call_guys" ]
  types = [ Problem ] // problems only
  enable_notifications = true
}

object TimePeriod "on_call_period" {
  includes = [ vacations" ]
  prefer_includes = true
  ranges = {
    "monday"    = "00:00-8:00,21:00-24:00"
    "tuesday"   = "00:00-8:00,21:00-24:00"
    "wednesday" = "00:00-8:00,21:00-24:00"
    "thursday"  = "00:00-8:00,21:00-24:00"
    "friday"    = "00:00-8:00,21:00-24:00"
    "saturday"  = "00:00-24:00"
    "sunday"    = "00:00-24:00"
  }
}

object TimePeriod "vacations" {
  ranges = {
    "july 30" = "00:00-24:00"
    "july 31" = "00:00-24:00"
    "august 3" = "00:00-24:00"
    "august 4" = "00:00-24:00"
    "august 5" = "00:00-24:00"
    "august 6" = "00:00-24:00"
    "august 7" = "00:00-24:00"
  }
}

apply Notification "on_call_notification" to Host {
  command = "notification-sms"
  user_groups = [ "on_call_guys" ]
  interval = 0 // no re-notification
  period = "on_call_period"
  types = [ Problem ] // problems only
  states = [ Down ] // down only
  assign where "critical" in host.groups
}

What happened

On July 30 (which was a thursday), we made a test. At 17:00 we shut down a critical host.
The main timeperiod stipulates that on thursday, notification should not be sent before 21:00.
On the other hand, the included timeperiod stipulates that on July 30, the notification should always be sent, regardless of the time.
The result of the test is that no notification was sent.
We tried adding the “july 30” directly in the ranges of the main timeperiod, nothing changed.
The notification was sent only when commenting out the “thursday” range and placing “july 30” directly in the ranges.

The question

Was the configuration correct in the first place ?
If yes, then I guess there’s some kind of bug.
If not, then how can we achieve what we’re trying to do ? eg: send notifications only outside of working hours, with the possibility to send notifications regardless of the hour on certain dates.

Cheers

(Incidentally, I’m on vacation starting today, I’ll be back in a week, so don’t feel insulted if I don’t answer in the meantime. Also, note that we did our test in a rush, so we may have missed something. I’ll do more test when I come back.)