Tickets :: Comment on [#12506] Contacts sync with ActiveSync get duplicates and not sync

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Comment	>> The issue is that Horde "buffers" the replies and send them all at a >> time later. I have always assumed this is right because you need the >> status for the whole Sync and you can not know this until all >> additions are processed. > > This is partially correct. We also need to ensure that the entire > request is handled before we send any responses and the ADD command > may not be the only or last command processed. We process the > incoming data as we receive it so that we don't need to keep all the > incoming message data in memory before we start processing it. > >> By examplle If I use the uploaded patch (hack) it only process the >> first 50 ADDs in the packet, this sortens the GAP to less than 1 >> minute and workarounds the timeout. With this patch (hack) Android >> seems to work fine and sync all contacts with time. > > This patch would completely break synchronization on any EAS client > that actually follows the specs. It ignores incoming changes and > sends no status response on those skipped messages. According to the > specs the client MUST assume the addition worked and should NOT send > the change(s) again. > >>> What probably should happen is when a duplicate addition is detected >>> we should return the existing item's UID as if the addition was >>> successful. Of course, I have no idea what your client will do with >>> this, since it is demonstrating broken behavior anyway, not to >>> mention if the connection continues to timeout, this won't help your >>> original problem anyway. > >> This sounds really interesting, I would test it, I think it should >> work, there are not additions so the GAP should be low. > > Thinking about this some more, I don't think this is the answer > either. When these sync with the server if we send back the same UID > for each one of these (an action which is undefined in the EAS spec), > there could now be multiple copies in the client's datastore that > connect with the same UID on the backend. What happens when a user > deletes one of these? Yup, the (only) copy of it on the server is > deleted. Less worrisome is that there would still be copies of it on > the client not attached to any server side copy. The state is now > corrupt. Even if the client doesn't exhibit the broken behavior yours > does of sending different clientids, it would still be possible for > the user to add the same contact data accidentally. > > If anything is to be done here to mitigate this, I think we need to > totally rewrite the way incoming changes are handled so that we don't > actually process them until they are all read. We will use more > memory on the incoming request but we will be able to start sending > packets back to the client more quickly. I'm not sure I like this, > as one of the things that differentiates Horde's activesync > implementation is relatively low memory consumption per request and I > have not been able to find any protocol related documentation as to > any incoming change time limits. I think the use case of importing > hundreds and hundreds of new contacts FROM THE CLIENT is relatively > rare.
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