Multiple Cancellation notifications for Calendar events

[radarsymphony]

A while ago, I posted Calendar meeting invitations are duplicated. After more investigation and testing, I’ve been able to reliably reproduce one manifestation of this issue.

Issue

The following series of steps has reliably reproduced the behavior where attendees receive multiple notifications for cancelled events. The multiple cancellation notifications are a side-effect of altering events in a series, so this issue may be related to the issue described in Unable to update a single event in a recurring series.

Setup

1. In one account (Organizer), Open the Calendar tab.
2. Drag-select a time range in calendar.
3. Right-click selected range and choose New Meeting Request.
4. Click Recurrence.
5. Click Daily.
6. Click End after [10] occurrences.
7. Click Ok.
8. Add subject.
9. Add attendee address.
10. Click Send.
11. Login to the Attendee account.
12. Open the meeting series invite and click Accept.
13. Leave option at Send the response now and click Ok.

Generating multiple Cancellation notifications

1. Complete “Setup” outlined above.
2. In the Organizer account, double-click on an event in series.
3. Select Open this occurrence.
4. Click Ok.
5. Make a trivial change to the time frame by incrementing start time.
6. Click Send.
7. The attendee can now optionally accept these change notifications, but doing so or not doing so does not seem to affect how many notifications the attendee will receive when the organizer cancels the series. The organizer has already “sliced up” the series and a cancellation notification will be made for each of the disjointed sections and sent to the attendee. (Besides, accepting changes to a series won’t be reflected in the attendee’s calendar anyway as is reported under Instance 1 of Unable to update a single event in a recurring series)
8. In Organizer Calendar, double-click on any event in the series (altered or unaltered).
9. Choose Open series.
10. Click Cancel invitation.
11. Click Ok.
12. In Attendee inbox, see two or more cancellation notifications.

Notes/Observations

There are two different types of cancellation notifications sent. One is prefixed with “Canceled:” and the other has a red “high-importance” exclamation icon next to it, but no “Canceled:” prefix. The first notification type references the whole series time frame, while the second references the single date of the altered event.

A calendar series seems to get “sliced” into several mini-series at each altered event. So each altered event bookends a new mini-series until the next altered event. The whole series can still be cancelled as one unit, but the user receives a cancellation for each of the mini-series that were created and each of the unique “altered” events that were initially part of that series. Or that seems to be the general pattern.

Our System:

• Kopano Core 11.0.2
• PHP 7.3.33
• Zend Engine v3.3.33
• Nginx version 1.21.4
• Kopano Webapp v5.2.0
• Debian 10 Buster
• Z-push 2.6.4

[radarsymphony]

This issue was still present when testing in KC 10. It was lessened when testing in Kopano Core 8.7.25. In 8.7, the attendees only receive a cancellation message for the series as a whole and one for each “altered” event. In 10 and 11, the attendee would receive several duplicate messages for both the series as a whole and for each altered event.