core.async/thread failing silently
Consider the following function that adds two numbers exceptionally inefficiently by creating lots of threads: user=> (require '[clojure.core.async :refer [thread (defn thread-add [x y] #_=> (thread #_=> (if (zero? y) #_=> x #_=> (let [t (thread-add (inc x) (dec y))] #_=> ( ( ( (msgCount++ Silverstone, Brands Hatch, Donington Park... Who says I have a one track mind? http://www.paulbutcher.com/ LinkedIn: http://www.linkedin.com/in/paulbutcher Skype: paulrabutcher -- -- 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.
Re: core.async/thread failing silently
Errors are most likely occurring on a thread different than main. Assuming you're using nrepl, have you looked at the nrepl-error buffer? On Saturday, December 7, 2013 7:27:35 PM UTC-6, Paul Butcher wrote: > > Consider the following function that adds two numbers exceptionally > inefficiently by creating lots of threads: > > user=> (require '[clojure.core.async :refer [thread nil > user=> (defn thread-add [x y] > #_=> (thread > #_=> (if (zero? y) > #_=> x > #_=> (let [t (thread-add (inc x) (dec y))] > #_=> ( #'user/thread-add > > > This works for small numbers: > > user=> ( 20 > user=> ( 1010 > > > Unsurprisingly, it fails after a certain point, because the JVM simply > can't create enough threads. But what I find surprising is that it fails > completely silently - no error message, just a nil return: > > user=> ( nil > > > Is this what I should expect? Is there any way to persuade the REPL to > show me errors in this kind of situation? > > -- > paul.butcher->msgCount++ > > Silverstone, Brands Hatch, Donington Park... > Who says I have a one track mind? > > http://www.paulbutcher.com/ > LinkedIn: http://www.linkedin.com/in/paulbutcher > Skype: paulrabutcher > > > > > -- -- 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.
Re: core.async/thread failing silently
On 8 Dec 2013, at 05:04, Alex Miller wrote: > Errors are most likely occurring on a thread different than main. Assuming > you're using nrepl, have you looked at the nrepl-error buffer? Thanks. I wasn't aware of nrepl-error. Some quick googling has turned up a few articles about how to see nrepl-error when using emacs, but I'm afraid that I'm not - I'm starting nREPL with "lein repl" at the bash prompt. I'd be grateful for any pointers to how to view nrepl-error in this scenario. Thanks, -- paul.butcher->msgCount++ Silverstone, Brands Hatch, Donington Park... Who says I have a one track mind? http://www.paulbutcher.com/ LinkedIn: http://www.linkedin.com/in/paulbutcher Skype: paulrabutcher -- -- 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.
Re: core.async/thread failing silently
If you're starting with lein repl then I would expect errors to be printed at the console - that's the actual process running the code. It's also possible that the thread's untaught exception handler doesn't print. I know that the expectation for async go blocks is that you should catch and handle any error. Have tried catching Throwable in your thread block and printing? -- -- 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.
Re: core.async/thread failing silently
On 8 Dec 2013, at 14:21, Alex Miller wrote: > If you're starting with lein repl then I would expect errors to be printed at > the console - that's the actual process running the code. It's also possible > that the thread's untaught exception handler doesn't print. I know that the > expectation for async go blocks is that you should catch and handle any > error. Have tried catching Throwable in your thread block and printing? Yup - that works fine (see below). The implication, I guess, is that nrepl doesn't set the default uncaught exception handler? I find that surprising? user=> (require '[clojure.core.async :refer [thread (defn thread-add [x y] #_=> (thread #_=> (try #_=> (if (zero? y) #_=> x #_=> (let [t (thread-add (inc x) (dec y))] #_=> ( (catch Throwable e (println e) #'user/thread-add user=> ( (msgCount++ Silverstone, Brands Hatch, Donington Park... Who says I have a one track mind? http://www.paulbutcher.com/ LinkedIn: http://www.linkedin.com/in/paulbutcher Skype: paulrabutcher On 8 Dec 2013, at 14:21, Alex Miller wrote: > If you're starting with lein repl then I would expect errors to be printed at > the console - that's the actual process running the code. It's also possible > that the thread's untaught exception handler doesn't print. I know that the > expectation for async go blocks is that you should catch and handle any > error. Have tried catching Throwable in your thread block and printing? > > -- > -- > 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. -- -- 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.
Re: core.async/thread failing silently
I've run this a bunch of times (in BOTH `lein repl` and `java -cp [...] clojure.main`), and have observed both this code printing the OOM exception, and it being silent as you observed. The difference in trials *seems* to be that if I skip the intermediate steps, going straight for the big one - (https://github.com/clojure/core.async/blob/ae37883a10dc9249ac5f204f6900e7bb0dbe1e04/src/main/clojure/clojure/core/async.clj#L381-L382 Maybe whether the error prints or not depends on whether the exception gets raised on the receiving side (the main thread) or the sending side (presumably on an Executor)? On Sunday, December 8, 2013 9:27:44 AM UTC-6, Paul Butcher wrote: > > On 8 Dec 2013, at 14:21, Alex Miller > > wrote: > > If you're starting with lein repl then I would expect errors to be printed > at the console - that's the actual process running the code. It's also > possible that the thread's untaught exception handler doesn't print. I know > that the expectation for async go blocks is that you should catch and > handle any error. Have tried catching Throwable in your thread block and > printing? > > > Yup - that works fine (see below). > > The implication, I guess, is that nrepl doesn't set the default uncaught > exception handler? I find that surprising? > > user=> (require '[clojure.core.async :refer [thread nil > user=> (defn thread-add [x y] > #_=> (thread > #_=> (try > #_=> (if (zero? y) > #_=> x > #_=> (let [t (thread-add (inc x) (dec y))] > #_=> ( #_=> (catch Throwable e (println e) > #'user/thread-add > user=> ( 20 > user=> ( Exception in thread "async-thread-macro-1986" java.lang.OutOfMemoryError: > unable to create new native thread > at java.lang.Thread.start0(Native Method) > at java.lang.Thread.start(Thread.java:691) > at > java.util.concurrent.ThreadPoolExecutor.addWorker(ThreadPoolExecutor.java:943) > at > java.util.concurrent.ThreadPoolExecutor.processWorkerExit(ThreadPoolExecutor.java:992) > at > java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) > at > java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) > at java.lang.Thread.run(Thread.java:722) > > > -- > paul.butcher->msgCount++ > > Silverstone, Brands Hatch, Donington Park... > Who says I have a one track mind? > > http://www.paulbutcher.com/ > LinkedIn: http://www.linkedin.com/in/paulbutcher > Skype: paulrabutcher > > > > > On 8 Dec 2013, at 14:21, Alex Miller > > wrote: > > If you're starting with lein repl then I would expect errors to be printed > at the console - that's the actual process running the code. It's also > possible that the thread's untaught exception handler doesn't print. I know > that the expectation for async go blocks is that you should catch and > handle any error. Have tried catching Throwable in your thread block and > printing? > > -- > -- > 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 > --- > 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. > > > -- -- 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.
