[Owncloud] Calendar event sync issues

Evert Pot evertpot at gmail.com
Sat Sep 1 11:00:01 UTC 2012

On Aug 31, 2012, at 11:55 PM, Thomas Tanghus wrote:

> On Friday 31 August 2012 15:37 Stephan Hesmer wrote:
>> I have been digging a little more and added a http traffic sniffer in
>> between. The content that gets discarded is sent as part of a PUT request
>> from the iOS to the  owncloud server and it gets an error: HTTP/1.1 412
>> Precondition failed
> I rarely understand 412 errors and what to do to avoid them. It could be that 
> the previous change hasn't been fully synced yet, but I'm only guessing.
> You will probably have  a better chance at the SabreDAV mailing list [*], but 
> for now I've CC'ed Evert who is the author of SabreDAV.

Who summoned me??

The earlier request contains this header:

If-None-Match: *

This means that the client effectively says: I want to PUT this, but only if a resource at the specified url does not yet exists. This allows a client to make sure that no existing resources get overwritten.

So there's two possibilities:

1. Stephen actually did the exact same twice (for debugging?), the second one triggering this error.
2. There's a bug in the owncloud CalDAV backend, causing non-existant resources to be returned as if they do exist.

So I would just try to do that request again, but change the url.. see what happens. It should be possible to just copy-paste that request in telnet.


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