Google CardDAV changes vCard UID - vcf-vcard

Question

I'm integrating the Google CardDAV with my webApplication. I have a strange problem sometimes when I make a PUT of a new vCard.
If the vCard contains a UID and the UID is a GUID Google changes the vCard UID with a 16-char UID.
for example: This is my original vCard
BEGIN:VCARD
VERSION:3.0
N:Pinch;David;;;
FN:David Pinch
REV:2013-01-09T09:26:34Z
UID:6c34bedcf256408780d8ffe269ec2b3b
END:VCARD
So I PUT this into Google CardDAV, into the current url:
https://www.google.com/m8/carddav/principals/__uids__/myusername#gmail.com/lists/default/6c34bedcf256408780d8ffe269ec2b3b
The result is ok, and the contact is really created on Google Contacts.
BUT:
if "now" I retrieve the current vCard from the same URL i have the following response.
BEGIN:VCARD
VERSION:3.0
N:Pinch;David;;;
FN:David Pinch
REV:2013-01-09T09:44:25Z
UID:716212e795884e43
END:VCARD
You can see that UID has changed and passed from original
UID:6c34bedcf256408780d8ffe269ec2b3b
To
UID:716212e795884e43
Curiously if I retrieve the card with the following Request
https://www.google.com/m8/carddav/principals/__uids__/myusername#gmail.com/lists/default/716212e795884e43
I have Exactly the same Response, like the vCard references two different Path url.
However when i retrieve the list of the contact from CardDAV, this return the second URL.
If I does not create the vCard with a GUID but with a 16-char UID, Seems that Google accept this, but sometimes it changes However, so I cannot be sure of the uniqueness of the Card.
A workaround seem to be of re-download the vCard after every PUT, but this causes a payload important that I wanted to avoid.
I use the same procecures with iCloud CardDAV and this doesn't happen.
Anyone can help me?

Answer 1

When you PUT a vCard to Google CardDAV it will recreate a new vCard V3.0 and dispose the original data posted including data loss and the UID / URI path changes you describe.
Other then UID change Google CardDAV has other issues
Data loss
Rejection of valid vCards
Slowness (10-20s per write
operation)
More details in the following Google CardDAV stress test article:
https://evertpot.com/google-carddav-issues/
My advise after still seeing these failures in 2018: its better to use Google's Contacts API instead of there CardDAV implementation.