Seit etwa einem halben Jahr nutze ich Duplicati, um Sicherungen per WebDAV in das Mediencenter hochzuladen. Seit geraumer Zeit funktioniert das aber nicht mehr wirklich, weil das Mediencenter immer wieder gerade eben erzeugte Dateien (getestet mit 10 MB, 20 MB bzw. 50 MB-Dateien) als Dateien mit der Größe 0 ausweist.

Vermutlich hängt das Problem mit den auch an anderer Stelle erwähnten Problemen mit der WebDAV-Umsetzung zusammen.

Einer der Duplicati-Entwickler hat mir hierzu folgende Analyse zugesendet, die ich hier in der Hoffnung poste, dass sie so den Weg über den Moderator an die zuständigen Techniker findet (via "Kontakt" wird die Nachricht abgeschnitten) - möglicherweise hilft sie bei der Fehlersuche.

Für eine Rückmeldung wäre ich dankbar!

Gruß
Joachim Deckers

Hire die Antwort von René, einem der Duplicati-Entwickler:


In short:

I could reproduce the issue but I don't know what triggers it.
I found a few postings on the internet that described exactly the same issue. No solution though.
The issue itself is very simple: Duplicati creates a new file that should be 25MB big. After the WebDAV server has received it, it says "File successfully created. File size is 0 bytes.".
It seems impossible to get in touch with t-online if you are not a customer. I managed to get into the forums with my mediencenter account but I am not allowed to post anything within the first 14 days.

What to do:
I suggest you to get in touch with the Mediencenter support. Tell them that we think we found a server bug and want to talk to someone who maintains the WebDAV servers. To prove that we are not some stupid posers, here some excerpts from the log file:

Duplicati wants to store a file and sends a first request:

User-Agent: Duplicati WEBDAV Client v1.3.3.1457
Content-Type: application/octet-stream
Authorization: Basic ******
Host: webdav.mediencenter.t-online.de
Content-Length: 26213520
Expect: 100-continue
Connection: Close


The request seems to be ok for the WebDAV server and it replies as expected:

Version = 1.1,
StatusCode = 100,
StatusDescription = Continue.


Then Duplicati sends 26213520 bytes of data to the WebDAV server. The WebDAV server acknowledges the reception of data.

The Mediencenter WebDAV server sends a success message and says it has created the file successfully:

Version = 1.0,

StatusCode = 201,

StatusDescription = Created.

StatusDescription = Created.

Unfortunately, it also reports the created file to be 0 bytes:

Date: Sat, 06 Oct 2012 13:03:26 GMT
Server: Apache-Coyote/1.1
Accept-Ranges: bytes
Content-Length: 0

Content-Type: application/zip


This only happens once in a while. 500 files were ok, 1 was not.

It's ok to give them my email address: (hier im Forum unterdrückt). They can get in touch with me in English or German.


As we (Duplicati) now know this faulty behavior of the Mediencenter WebDAV server, we are able to create a work around. Unfortunately, Kenneth is very busy with other things at the moment and Kenneth is the main developer. I can do analysis but my programming skills are too limited. That's why we would perfer you to get in touch with the Mediencenter customer support first and not wait for a quick fix.


René