Re: core.async/thread failing silently
On 8 Dec 2013, at 05:04, Alex Miller a...@puredanger.com 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 a...@puredanger.com 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))] #_= (!! t))) #_= (catch Throwable e (println e) #'user/thread-add user= (!! (thread-add 10 10)) 20 user= (!! (thread-add 10 2000)) 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 a...@puredanger.com 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 - (!! (thread-add 10 2000)) - then I get the exception printed: Exception in thread async-thread-macro-1999 java.lang.OutOfMemoryError: unable to create new native thread. Whereas if I do this first - (!! (thread-add 10 1000)) - then I get the silent error as you are seeing. This seems pretty repeatable, but I don't really understand. It looks like Exceptions (Throwables, really) will never propagate from the executor that `thread-call` calls, since they're swallowed in core.async: 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 al...@puredanger.com javascript: 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))] #_= (!! t))) #_= (catch Throwable e (println e) #'user/thread-add user= (!! (thread-add 10 10)) 20 user= (!! (thread-add 10 2000)) 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 al...@puredanger.com javascript: 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 javascript: 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 javascript: 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 javascript:. 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.
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 !!]]) nil user= (defn thread-add [x y] #_= (thread #_= (if (zero? y) #_= x #_= (let [t (thread-add (inc x) (dec y))] #_= (!! t) #'user/thread-add This works for small numbers: user= (!! (thread-add 10 10)) 20 user= (!! (thread-add 10 1000)) 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= (!! (thread-add 10 2000)) 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.
