[Posteo] Server didn't provide ETag

[zWhdmB5T]

Problem scope

• I'm sure that this is a DAVx⁵ problem.

App version

• I'm using the latest available DAVx⁵ version.

Android version and device/firmware type

Samsung Galaxy Tab A8 SM-X200 X200XXS6DYG6/X200OXM6DYG6 Android 14

Steps to reproduce

System with Issue

• Samsung Galaxy Tab A8 SM-X200 X200XXS6DYG6/X200OXM6DYG6 Android 14
• DAVx⁵ 4.5.3-ose (F-Droid)
• Posteo: CalDAV and CardDAV (account x)
• error message "HTTP-Serverfehler - Server didn't provide ETag"

System without Issue

• Google Pixel 6a bluejy-16.5-13291547 2025090300 Android 16
• DAVx⁵ 4.5.3-ose (F-Droid)
• Posteo: CalDAV and CardDAV (account y — different to account x)
• no such error message

Further info

• DAVx⁵ is configured equally on both devices

debug-info.txt
logcat.txt

[rfc2822]

Tried with our Posteo test account and couldn't reproduce the problem.

The part of the logs look like a server problem:

09-06 08:42:41.882 14806 15156 E .davdroid.sync.CalendarSyncManager: Caused by: net.fortuna.ical4j.data.ParserException: Error at line 1:Expected [BEGIN], read [��8묥�&�Qk6���#�]
09-06 08:42:41.882 14806 15156 E .davdroid.sync.CalendarSyncManager: at net.fortuna.ical4j.data.CalendarParserImpl.assertToken(SourceFile:16)
09-06 08:42:41.882 14806 15156 E .davdroid.sync.CalendarSyncManager: at net.fortuna.ical4j.data.CalendarParserImpl.parseCalendarList(SourceFile:8)
09-06 08:42:41.882 14806 15156 E .davdroid.sync.CalendarSyncManager: at net.fortuna.ical4j.data.CalendarParserImpl.parse(SourceFile:13)
...
09-06 08:42:41.903 14806 15156 W .davdroid.sync.CalendarSyncManager: Ignoring multi-get response without calendar-data
09-06 08:42:41.904 14806 15156 W .davdroid.sync.CalendarSyncManager: Ignoring multi-get response without calendar-data
09-06 08:42:41.906 14806 15156 W .davdroid.sync.CalendarSyncManager: Ignoring multi-get response without calendar-data

The responses look invalid and empty. There are neither event data nor an ETag.

I doubt it's a DAVx5 problem.

Does it happen for every sync on your affected device or only at certain times?

Does it happen when you only sync another, empty calendar, on the affected device?

Can you provide the debug info of the specific error (tap the DAVx5 error notification and then share)?

[devvv4ever]

Could you try "account x" also on "System without Issue". Is the error happening there?

It could be that the calendar is corrupt on the server(!) - could you create a new calendar and sync with only this calendar?

[zWhdmB5T]

Well…

1. On the device with the issue, I stopped the app DAVx⁵.
2. I deleted the app data.
3. I newly set up all the settings and the credentials.
4. This issue seems to be gone now.
5. But, very curious: just after deleting app data, when open DAVx⁵ is still showed my previous set account — it didn't show the previously configured address book and calendar for that account, but it actually showed the account name. I guess this very weird because I did delete app data. Like a had to set Android settings for the app again. How can that be?
6. I then deleted that rest of account (delete account) and did set up the account completely new and entirely.
7. I haven't gotten the ETag related message.
8. But on initial sync I got a message of a curropted/failed calendar entry. — Maybe my calender is corrupted…? The whole calendar or just one entry? I mean: what it be sufficient to delete just one specific entry or do I have t set up the whole calendar again?

[devvv4ever]

5. But, very curious: just after deleting app data, when open DAVx⁵ is still showed my previous set account — it didn't show the previously configured address book and calendar for that account, but it actually showed the account name. I guess this very weird because I did delete app data. Like a had to set Android settings for the app again. How can that be?

Currently (technically) DAVx5 is split into system parts (DAVx5 system accounts) and DAVx5's own parts. When manually removing an account in DAVx5 the standard procedure kicks in and removes everything tied to this account in a standardized way.

When deleting DAVx5's app data only the DAVx5 database is deleted/cleared - the rest remains - and thus you see this orphaned account(s). We are more and more changing this in the background so that DAVx5 itself gets more control over all things that matter. More or less because the base System of Android seems to become less reliable in the last 5 years and we need to get rid of most system parts. And also because we moved away from the Android Sync Framework to the Work Manager approach. It also blocks a lot of future features we have in mind for DAVx5.

[zWhdmB5T]

When deleting DAVx5's app data only the DAVx5 database is deleted/cleared - the rest remains - and thus you see this orphaned account(s). We are more and more changing this in the background so that DAVx5 itself gets more control over all things that matter. More or less because the base System of Android seems to become less reliable in the last 5 years and we need to get rid of most system parts. And also because we moved away from the Android Sync Framework to the Work Manager approach. It also blocks a lot of future features we have in mind for DAVx5.

I guess this could be the reason one is asked when expecting issues with an app (some app, not specifically yours) first to delete app data and in a second try to delete the whole app and reinstall it. … I have always wondered why I should delete and reinstall the app when I already deleted the app data. So far, I was guessing deleting app data deletes all of the app data, just like it is installed freshly.

[zWhdmB5T]

Thank you, lads and lasses for your contributions!

[VolMi]

I've had this problem for a very long time now, probably almost a year, and finally decided to do something about it...
It happened when syncing my address book with Posteo.
I did the following steps and now the error seems to be gone:

1. disable syncing said address book in DAVx⁵
2. stopped DAVx⁵
3. cleared cache for DAVx⁵ (but kept data)
4. cleared the app password in posteo and created a new one
5. added the new app password to DAVx⁵
6. enabled syncing the address book again in DAVx⁵

Steps 4 and 5 were probably pointless, but I don't know.