The answer is here: https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/LockingTransaction.java#L361
Agents and watches are dispatched outside of the transaction locking. This means that multiple transactions could be executing watches in parallel, and hence execute out of order. Timothy Baldridge On Wed, Jul 31, 2013 at 9:43 AM, Michael Drogalis <madrush...@gmail.com>wrote: > I can precisely exemplify the behavior here: > > https://gist.github.com/MichaelDrogalis/6123177 > > > On Wednesday, July 31, 2013 11:13:17 AM UTC-4, Michael Drogalis wrote: >> >> Aaron: Yep, I'm aware - and am using the value provided by the last >> parameter. >> >> This is going to be tough to show the problem without bringing more >> details of my concurrency set up. >> I'm not sure if this will exhibit the problem, but this is what it boils >> down to: >> >> https://gist.github.com/**MichaelDrogalis/6122834<https://gist.github.com/MichaelDrogalis/6122834> >> >> When enough threads are trying to write to the queue, the watches >> triggered later can finish before watches triggered earlier. >> >> >> On Wednesday, July 31, 2013 11:05:16 AM UTC-4, Aaron Cohen wrote: >>> >>> A watcher fn has 4 parameters: key, reference, old-state, new-state >>> >>> If you use old-state and new-state rather than the reference, you should >>> not see your problem. >>> >>> --Aaron >>> >>> >>> On Wed, Jul 31, 2013 at 11:00 AM, Michael Drogalis >>> <madru...@gmail.com>wrote: >>> >>>> Problem: >>>> >>>> I have a ref representing a queue of people in line. >>>> I add a watch to the ref to print out the contents of the queue >>>> whenever it changes. >>>> Naturally, and expected, the following can happen if queuing happens in >>>> rapid succession: >>>> >>>> Queue: [] >>>> <add "Mike" to queue> >>>> <add "John" to queue> >>>> >>>> console: "Queue is Mike, John" >>>> console: "Queue is Mike" >>>> >>>> I'd like to write a UI for this program, but I clearly can't reliably >>>> render based on the result delivered >>>> by the add-watch hook. What's the solution for this problem? >>>> >>>> -- >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "Clojure" group. >>>> To post to this group, send email to clo...@googlegroups.com >>>> Note that posts from new members are moderated - please be patient with >>>> your first post. >>>> To unsubscribe from this group, send email to >>>> clojure+u...@googlegroups.com >>>> For more options, visit this group at >>>> http://groups.google.com/**group/clojure?hl=en<http://groups.google.com/group/clojure?hl=en> >>>> --- >>>> You received this message because you are subscribed to the Google >>>> Groups "Clojure" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to clojure+u...@googlegroups.com. >>>> For more options, visit >>>> https://groups.google.com/**groups/opt_out<https://groups.google.com/groups/opt_out> >>>> . >>>> >>>> >>>> >>> >>> -- > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- “One of the main causes of the fall of the Roman Empire was that–lacking zero–they had no way to indicate successful termination of their C programs.” (Robert Firth) -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
