Issue with syncing new calendar events

[alkanex-xyz]

Hey,

my wife uses FlexR to enter her shifts in a calendar.

On Syncing with DavX5 the entries get removed because Nexcloud replies with an 412 because of the Asterix in the If-None-Match-Header.

How to solve this?

Thanks

Debug Info:

--- BEGIN DEBUG INFO ---

SOFTWARE INFORMATION

┌───────────────────────────────────┬─────────────────────────────────────────────────┬────────────┬─────────────────────┬───────┐
│ Package                           │ Version                                         │ Code       │ Installer           │ Notes │
├───────────────────────────────────┼─────────────────────────────────────────────────┼────────────┼─────────────────────┼───────┤
│ at.bitfire.davdroid               │ 4.3.12.1-gplay                                  │ 403120101  │ com.android.vending │       │
│ com.android.providers.contacts    │ 14                                              │ 34         │ —                   │       │
│ com.android.providers.calendar    │ 14                                              │ 34         │ —                   │       │
│ com.google.android.calendar       │ 2023.50.1-592177658-release                     │ 2017303236 │ com.android.vending │       │
│ com.google.android.apps.messaging │ messages.android_20231114_01_RC11.phone_dynamic │ 210069063  │ com.android.vending │       │
└───────────────────────────────────┴─────────────────────────────────────────────────┴────────────┴─────────────────────┴───────┘


SYSTEM INFORMATION

Android version: 14 (UQ1A.231205.015)
Device: Google Pixel 6 Pro (raven)

Locale(s): [de_DE]
Time zone: Europe/Berlin
Internal memory (/data): 32 GB free of 110 GB

Log:

2024-01-06 23:19:26 301 [network.HttpClient] --> PUT https://cloud.[REDACTED].cologne/remote.php/dav/calendars/Marina/dienstplan/FlexR-UID-2.ics h2
2024-01-06 23:19:26 301 [network.HttpClient] If-None-Match: *
2024-01-06 23:19:26 301 [network.HttpClient] User-Agent: DAVx5/4.3.12.1-gplay (2023/12/25; dav4jvm; okhttp/4.12.0) Android/14
2024-01-06 23:19:26 301 [network.HttpClient] Accept-Language: de-DE, de;q=0.7, *;q=0.5
2024-01-06 23:19:26 301 [network.HttpClient] Content-Type: text/calendar;charset=utf-8
2024-01-06 23:19:26 301 [network.HttpClient] Content-Length: 258
2024-01-06 23:19:26 301 [network.HttpClient] Host: cloud.[REDACTED].cologne
2024-01-06 23:19:26 301 [network.HttpClient] Connection: Keep-Alive
2024-01-06 23:19:26 301 [network.HttpClient] Accept-Encoding: gzip
2024-01-06 23:19:26 301 [network.HttpClient] Cookie: __Host-nc_sameSiteCookiestrict=true; occxqurkk0nu=d329eokaooc5h31harcs3tgmlp; oc_sessionPassphrase=Vy4YD1UXG%2BHVBXkCQwE9OjS%2BvNyI3TPSVH24VukNLpmSN1ZKaymgm9r%2FPYyAwcQ9mhkkZT%2FhEQtaU5%2BPsJijfhV%2B%2BzTkxiqYvhXinTRJaPAZ7t7kMLdlgePWe8rxXcHc; __Host-nc_sameSiteCookielax=true
2024-01-06 23:19:26 301 [network.HttpClient] 
2024-01-06 23:19:26 301 [network.HttpClient] BEGIN:VCALENDAR
VERSION:2.0
PRODID:DAVx5/4.3.12.1-gplay ical4j/3.2.14 (klwinkel.flexr.pro)
BEGIN:VEVENT
DTSTAMP:20240106T221926Z
UID:FlexR-UID-2
SUMMARY:Urlaub [FlexR]
DTSTART;VALUE=DATE:20231201
DTEND;VALUE=DATE:20231202
END:VEVENT
END:VCALENDAR

2024-01-06 23:19:26 301 [network.HttpClient] --> END PUT (258-byte body)
2024-01-06 23:19:26 301 [at.bitfire.dav4jvm.BasicDigestAuthHandler] Adding Basic authorization header for https://cloud.[REDACTED].cologne/remote.php/dav/calendars/Marina/dienstplan/FlexR-UID-2.ics
2024-01-06 23:19:26 301 [network.HttpClient] <-- 412 https://cloud.[REDACTED].cologne/remote.php/dav/calendars/Marina/dienstplan/FlexR-UID-2.ics (110ms)
2024-01-06 23:19:26 301 [network.HttpClient] server: nginx
2024-01-06 23:19:26 301 [network.HttpClient] date: Sat, 06 Jan 2024 22:19:26 GMT
2024-01-06 23:19:26 301 [network.HttpClient] content-type: application/xml; charset=utf-8
2024-01-06 23:19:26 301 [network.HttpClient] expires: Thu, 19 Nov 1981 08:52:00 GMT
2024-01-06 23:19:26 301 [network.HttpClient] cache-control: no-store, no-cache, must-revalidate
2024-01-06 23:19:26 301 [network.HttpClient] pragma: no-cache
2024-01-06 23:19:26 301 [network.HttpClient] content-security-policy: default-src 'none';
2024-01-06 23:19:26 301 [network.HttpClient] strict-transport-security: max-age=15768000; includeSubDomains; preload
2024-01-06 23:19:26 301 [network.HttpClient] referrer-policy: no-referrer
2024-01-06 23:19:26 301 [network.HttpClient] x-content-type-options: nosniff
2024-01-06 23:19:26 301 [network.HttpClient] x-download-options: noopen
2024-01-06 23:19:26 301 [network.HttpClient] x-frame-options: SAMEORIGIN
2024-01-06 23:19:26 301 [network.HttpClient] x-permitted-cross-domain-policies: none
2024-01-06 23:19:26 301 [network.HttpClient] x-robots-tag: noindex, nofollow
2024-01-06 23:19:26 301 [network.HttpClient] x-xss-protection: 1; mode=block
2024-01-06 23:19:26 301 [network.HttpClient] 
2024-01-06 23:19:26 301 [network.HttpClient] <?xml version="1.0" encoding="utf-8"?>
<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
  <s:exception>Sabre\DAV\Exception\PreconditionFailed</s:exception>
  <s:message>An If-None-Match header was specified, but the ETag matched (or * was specified).</s:message>
  <s:header>If-None-Match</s:header>
</d:error>

2024-01-06 23:19:26 301 [network.HttpClient] <-- END HTTP (320-byte body)
2024-01-06 23:19:26 301 [syncadapter.SyncManager] Resource has been modified on the server before upload, ignoring
2024-01-06 23:19:26 301 [syncadapter.SyncManager] Didn't receive new ETag after uploading, setting to null

[rfc2822]

Seems that FlexR sets the UID to FlexR-UID-2 so the file name for the new event is 'FlexR-UID-2.ics`, although this file already exists on the server. DAVx5 has a "server always wins" strategy, so the local file is overwritten by the server version.

I didn't have a look at FlexR and how it works, but a solution could be that FlexR generates a proper UID for events (or sets the uid to null so that DAVx5 generates an UUID).

[alkanex-xyz]

After deleting them from the Database. It syncs again.

I'll report this to the developer. Maybe he can participate here or fix the UID generation.

[klwinkel]

Hi there,

I am the developer of the FlexR app.

Yes I am writing the UID_2445 field:

            Calendar cal = Calendar.getInstance();
            cal.clear();
            long lUID = cal.getTimeInMillis();

            if (lUID <= gcal_UID) {
                gcal_UID++;
            } else {
                gcal_UID = lUID;
            }

            if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
                if (CALENDAR_UID2445_COLUMN.length() > 0) {
                    values.put(Events.UID_2445, "FlexR-UID-" + gcal_UID);
                }
            }

The only reason I am doing this is because it enables me to (easily) find all events in the google calendar that are created by FlexR, in case a users wants to clear all FlexR data from its gcal.

I can't remember the reason for the call to cal.clear(), but it will probably cause the UID value not to be unique.

I am happily willing to change it, is it enough to make the UID value unique? If so, I will put in a normal milliseconds timestamp after the "FlexR-UID-" string:

"FlexR-UID-"

Or I can put in the internal record id of FlexR after the "FlexR-UID-" string:

"FlexR-UID-"

With the record id, the UID will always be the same for the same planned shift in FlexR, with the timestamp, it will have a different UID each time it is synced or updated.

I am (mis)using the UID_2445 column because it seemed unused to me and have had no issues with it so far, another option would be to use another column for FlexR identification.

[rfc2822]

Hi,

Nice to hear from your directly. Yes, making the UIDs unique should be enough as a quick solution.

However maybe there's a better way to detect specific events than using the UID, which is recommended to be an UUID since RFC 7986.

[klwinkel]

I will make it a really UniqueID for now, using the timestamp of sync + a counter, until I find a better solution to identify FlexR calendar events

[alkanex-xyz]

thank you both 👍