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Is the 'concurrent editing' checking working?

Take a look at the edit history of SO 3780075. There are 5 or more edits (one of them mine) within a single minute - the question went to Community Wiki in record time. I certainly did not get notified of concurrent editing activity.


For the record: the first two edits were made in the same second, and 56 seconds after the question was asked. The next two were a sluggish 70 and 71 seconds after the question was asked. The next was at 93 seconds; the sixth at 2 minutes 1 second; and the seventh edit (eighth revision) was a whole 3 minutes 8 seconds from when the question was asked.

  • Question (revision 1) asked at 45:19
  • Revisions 2 and 3 both timed at 46:15
  • Revision 4 at 46:29
  • Revision 5 at 46:30
  • Revision 6 at 46:52
  • Revision 7 at 47:20
  • Revision 8 at 48:27

Some questions are still waiting for their first views when this one had gone to Community Wiki.

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One of those edits was mine, and I had no idea that I clashed with anyone else. –  jjnguy Sep 23 '10 at 17:09
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2 Answers

up vote 3 down vote accepted

The detection system does work — it fired for me as recently as this week — but it's not instantaneous. It only fires after someone else saves, and even then I believe there's something like 30 seconds of polling delay.

In this case, it seems that a bunch of you noticed the same poorly formatted code almost as soon as the question was posted, and you all jumped on the easy cleanup edit; note how similar all the edits are. Adding four spaces is probably so natural to you all (rep of 3k, 61k, 22k, 30k, 66k) that you all submitted your edits and clobbered each other before the poor detector had a chance to figure out what was going on and send the notification out.

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Sounds plausible: optimistic 'locking' works, but only if you take long enough for it to have time to notice. I noticed that the changes were very similar. I just wasn't sure if something had failed (or been changed) in the last 24 hours or so, or whether there were particular circumstances that applied to this question. I always defer to other edits if notified: that is, I go back to the original (as now amended) and only re-edit if it still seems warranted. But the sheer speed of action blinded the system. Nyquist's Theorem: you have to sample fast enough,and 30 seconds isn't fast enough. –  Jonathan Leffler Sep 23 '10 at 17:39
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I think it's 45 seconds; that's how often a json request to /edit-activity-heartbeat goes out –  Michael Mrozek Sep 23 '10 at 18:38
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@Michael, good call. Thanks. –  Pops Sep 23 '10 at 18:45
    
Since March 2011, a check is also done right after you save. –  Arjan Apr 10 '11 at 20:21
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We now prevent edit collisions on save.

When you click "Save Edits", if the post changed while you were editing, we now return:

{username} edited {tags / body / title} of this post; try refreshing this post and editing again.

It is specific to the area in question, so one user can edit body and you can edit tags without conflicting. (Or title, etc). It's only when you both edit the same field at the same time this error is returned on save.

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Thanks - that will be an improvement. I've not seen anything as dramatic as the situation in the question since asking it. –  Jonathan Leffler Mar 30 '11 at 1:42
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