Good reasoning; that makes a lot of sense -- even if intuitively it doesn't follow through.
I'll do some more thinking about my concurrency needs and come back with a follow up question later. Thanks man! On Wed, Jul 31, 2013 at 12:51 PM, Timothy Baldridge <tbaldri...@gmail.com>wrote: > Deadlocks? Imagine a watch that ended up running a transaction against the > ref it was triggered from. Sounds insane, but it could be fairly easy to do > in a situation like this: > > ref -> calls watchers -> calls fn1 -> calls fn 2 -> calls fn3 -> starts > transaction on ref > > Since watchers are notified outside of a ref transaction deadlocking is > impossible. Inside a transaction you'd have a instant deadlock. > > Timothy Baldridge > > > On Wed, Jul 31, 2013 at 10:47 AM, Mike Drogalis <madrush...@gmail.com>wrote: > >> I'll play around with agents for this when I get some more free time. >> >> I find it odd that, as the sole perceiver of an indentity, events are >> capable of being perceived out of order. >> If I were watching a line queue up in person, events are obviously >> "dispatched" in order through my visual perception. >> I trust there's a good reason it's designed this way, at any rate. >> >> >> On Wed, Jul 31, 2013 at 12:25 PM, Timothy Baldridge <tbaldri...@gmail.com >> > wrote: >> >>> You might want to consider switching to agents (or something else) I >>> don't think it's possible to do what you want with refs. >>> >>> Timothy Baldridge >>> >>> >>> On Wed, Jul 31, 2013 at 10:08 AM, Mike Drogalis <madrush...@gmail.com>wrote: >>> >>>> Thanks for the link. :) I understand that the behavior I'm seeing is >>>> correct. Any idea how to achieve the desired behavior, though? >>>> >>>> >>>> On Wed, Jul 31, 2013 at 12:06 PM, Timothy Baldridge < >>>> tbaldri...@gmail.com> wrote: >>>> >>>>> 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 a topic in the >>>>> Google Groups "Clojure" group. >>>>> To unsubscribe from this topic, visit >>>>> https://groups.google.com/d/topic/clojure/0b5HWJE6Jx4/unsubscribe. >>>>> To unsubscribe from this group and all its topics, send an email to >>>>> clojure+unsubscr...@googlegroups.com. >>>>> >>>>> For more options, visit 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 a topic in the >>> Google Groups "Clojure" group. >>> To unsubscribe from this topic, visit >>> https://groups.google.com/d/topic/clojure/0b5HWJE6Jx4/unsubscribe. >>> To unsubscribe from this group and all its topics, send an email to >>> clojure+unsubscr...@googlegroups.com. >>> For more options, visit 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 - 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