Sync problems btw clients with edited events

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blueguitarbob
Posts: 12
Joined: Mon Feb 21, 2011 2:32 pm

Sync problems btw clients with edited events

Post by blueguitarbob » Sat Jul 30, 2011 1:45 pm

Hi Dan,

I'm having a problem with proper synchronization between VueMinder clients with edited events. I can replicate the error.

Here's my config: I have 4 VueMinder clients and one VueMinder server. All of the machines are always on the same network, except one. My laptop client is directly connected to the network when I am at home, and connects through the firewall when I am away. The system works very well. I can create new events on my laptop when I am at a coffee shop or at school, and they sync to the rest of the clients through the firewall fairly quickly.

However, the system does not always work when editing events. Here's a recent example. This morning, using a machine on my local network, I edited the start times of two events this weekend. I also added content to the description field. The changes were pushed to the other clients quickly, completed before I could walk to the other clients.

Then about 3 minutes after I made the edits, I opened my laptop, which was asleep and charging. The laptop connected to the VueMinder server and instantly rescinded my edits to the events, rolling them back to their previous state. I checked the times on all machines, and they were within 4 seconds of each other.

I then re-did the edits, with the laptop connected to the network, and the edits stayed.

I realize that synchronization is a tricky problem, but I am guessing there is a time stamp problem here. The laptop was at most 4 seconds off from the other machines, but it took authority to roll back event edits made more than 3 minutes earlier. I can see where you would have this problem within the 4 second difference between machines, but this was easily outside that window. Either the timestamp on the event edit was wrong in the database, or the laptop client did not correctly check the timestamp when rescinding the edits. The laptop clearly favored an older event for a newer one, which should not happen when synchronizing events.

I have seen this behavior before, where event edits have been mysteriously rolled back, but I had not isolated the cause before. I am able to replicate this behavior. If I make edits when my laptop is asleep, and then reconnect the laptop, the event edits will roll back.

--Robert

ericrep
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Joined: Sat Feb 19, 2011 6:09 am

Re: Sync problems btw clients with edited events

Post by ericrep » Sat Jul 30, 2011 4:30 pm

Dan -

I'm having a similar problem although I haven't tried to track it down and replicate it. New events seem to be okay but we're definitely losing changes to existing events. It happens more when I connect my laptop to our home network. But even with just the two desktop computers that are normally connected, we occasionally lose changes.

The clock on the laptop is about 10-15 seconds behind the clock on the primary desktop (the one with the server installed).

Let me know if there's more information I can give you to help track down the problem.

Eric

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Dan Chartrand
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Re: Sync problems btw clients with edited events

Post by VueSoft » Sat Jul 30, 2011 9:46 pm

Thank you for the information. I'll work on fixing this for the next version and will post a reply when an update is available.
Dan Chartrand, Founder
VueSoft LLC | St. Louis, Missouri, USA

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Dan Chartrand
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Location: St. Louis, Missouri, USA
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Re: Sync problems btw clients with edited events

Post by VueSoft » Sat Aug 13, 2011 10:12 pm

This problem has been fixed for the next version (8.4.0). When a computer is reconnected, it will no longer overwrite all changes made while it was disconnected. Also, those changes will properly sync down to the reconnected computer.

If you'd like an early look, a stable release-candidate beta is available here:
http://www.vueminder.com/forums/phpBB3/ ... ?f=5&t=606

If you try the beta, please make sure to update ALL computers on your network. Otherwise you might still see problems.
Dan Chartrand, Founder
VueSoft LLC | St. Louis, Missouri, USA

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