What REPL are you using? A rather nasty side-effect of NRepl is that it
tends to send messages from non-main-threads to weird places.
On Sun, Oct 8, 2017 at 10:29 PM, <lawrence.krub...@gmail.com> wrote:
> I just re-wrote much of the code to run on the main thread. And so now I
> can see the error message (which was about a nil value in a place where I
> was certain there would be no nil values). Which is great. But since the
> app does a lot of I/O, I would like to for this app to be multi-threaded.
> But I need to figure out a way that I can see errors that happen in
> background threads.
>
>
> On Sunday, October 8, 2017 at 11:46:26 PM UTC-4, tbc++ wrote:
>>
>> I don't think you can catch an Object on the JVM can you? What happens if
>> you catch Throwable?
>>
>> On Sun, Oct 8, 2017 at 9:43 PM, <lawrence...@gmail.com> wrote:
>>
>>> So, for instance, this says that 10 documents were retried:
>>>
>>> {"message" {:num-slabs 1, :num-active-slabs 1, :enqueued 389, :retried
>>> 10, :completed 378, :in-progress 1}}
>>>
>>> The only place that I call retry! is in this catch block (this function
>>> runs in a background thread):
>>>
>>> (defn advance
>>> [message]
>>> {:pre [
>>> (= (type message) durable_queue.Task)
>>> ]}
>>> (slingshot/try+
>>> (doseq [[k v] @message]
>>> (when-not (or
>>> (= :how-many-rows-and-fields-from-database k)
>>> (= :database-table k)
>>> (= :denormalized-id k)
>>> (= :topic k))
>>> (transform
>>> (get @message :denormalized-id :missing-denormalized-id)
>>> k
>>> v
>>> (get @message :topic :missing-topic)
>>> (get @message :how-many-rows-and-fields-from-database
>>> :missing-how-many-rows-and-fields-from-database))))
>>>
>>> (durable/complete! message)
>>> (catch Object o
>>> (durable/retry! message)
>>> (slingshot/throw+ {
>>> :type ::advance
>>> :error o
>>> }
>>> ))))
>>>
>>> So clearly, the code has a problem with some of the documents, and so an
>>> error is thrown, and it is caught by the catch block. I would love to see
>>> the error. I can not. If I put println in the catch block, the message
>>> never shows up in the terminal. Likewise if I use Timbre.
>>>
>>> I would love to see the error object. My inability to see the error
>>> objects has crippled my productivity.
>>>
>>> Can anyone tell me what I need to do to see these errors?
>>>
>>>
>>>
>>>
>>>
>>> On Sunday, October 8, 2017 at 11:13:10 PM UTC-4, lawrence...@gmail.com
>>> wrote:
>>>
>>>> I'm trying to use a Zach Tellman's durable-queue to pass information
>>>> from one part of my app to another. I have 3 queues. I also have a function
>>>> that runs every 30 seconds, that is suppose to report some statistics for
>>>> me:
>>>>
>>>> (fn []
>>>> (future
>>>> (slingshot/try+
>>>> (errors/log "Resource usage: "
>>>> (monitoring/show-stats-regard
>>>> ing-resources-used-by-this-app))
>>>> (errors/log "Stats about from-mysql-to-tables-queue:
>>>> " (durable/stats from-mysql-to-tables-queue))
>>>> (errors/log "Stats about
>>>> from-tables-to-topics-queue: " (durable/stats from-tables-to-topics-queue))
>>>> (errors/log "Stats about the
>>>> from-topics-to-persistence-queue: " (durable/stats
>>>> from-topics-to-persistence-queue))
>>>> (catch Object o
>>>> (slingshot/throw+ {
>>>> :type
>>>> ::cycle-resource-usage-report
>>>> :error o
>>>> }
>>>> )))))
>>>>
>>>> I think there is an error here, because I see the first (errors/log)
>>>> but typically not anything after that. Can I rely on the fact that this
>>>> should catch anything:
>>>>
>>>> (catch Object o
>>>>
>>>> Because it doesn't seem to work. Instead, the app runs for 8 minutes,
>>>> then prints data about the queues just once, then never again. Assuming an
>>>> error is occuring, why can't I see the error?
>>>>
>>>>
>>>> {:timestamp "17-10-09 01:27:45", :level :trace, :hostname
>>>> "ip-172-31-4-54", :message ("STARTING!!!!")}
>>>>
>>>> Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new
>>>> driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically
>>>> registered via the SPI and manual loading of the driver class is generally
>>>> unnecessary.
>>>>
>>>>
>>>> {:timestamp "17-10-09 01:28:16", :level :trace, :hostname
>>>> "ip-172-31-4-54", :message ("\n\n\n\n\nResource usage: " "Memory in use
>>>> (percentage/used/max-heap): (\"67%\" \"2414M\" \"3568M\")\n\nCPU usage
>>>> (how-many-cpu's/load-average): [4 1.56]\n\nFree memory in jvm:
>>>> [1201758848]")}
>>>>
>>>>
>>>> {:timestamp "17-10-09 01:28:49", :level :trace, :hostname
>>>> "ip-172-31-4-54", :message ("\n\n\n\n\nResource usage: " "Memory in use
>>>> (percentage/used/max-heap): (\"81%\" \"2900M\" \"3568M\")\n\nCPU usage
>>>> (how-many-cpu's/load-average): [4 2.64]\n\nFree memory in jvm:
>>>> [699798216]")}
>>>>
>>>> ;; removing redundant entries
>>>>
>>>> {:timestamp "17-10-09 01:34:48", :level :trace, :hostname
>>>> "UnknownHost", :message ("\n\n\n\n\nResource usage: " "Memory in use
>>>> (percentage/used/max-heap): (\"87%\" \"3118M\" \"3568M\")\n\nCPU usage
>>>> (how-many-cpu's/load-average): [4 3.77]\n\nFree memory in jvm:
>>>> [471249616]")}
>>>>
>>>>
>>>> {:timestamp "17-10-09 01:35:17", :level :trace, :hostname
>>>> "ip-172-31-4-54", :message ("\n\n\n\n\nResource usage: " "Memory in use
>>>> (percentage/used/max-heap): (\"87%\" \"3120M\" \"3568M\")\n\nCPU usage
>>>> (how-many-cpu's/load-average): [4 3.79]\n\nFree memory in jvm:
>>>> [468602192]")}
>>>>
>>>>
>>>> {:timestamp "17-10-09 01:35:35", :level :trace, :hostname
>>>> "ip-172-31-4-54", :message ("\nStats about from-mysql-to-tables-queue: "
>>>> {"message" {:num-slabs 1, :num-active-slabs 1, :enqueued 306671, :retried
>>>> 0, :completed 306660, :in-progress 8}})}
>>>>
>>>>
>>>> {:timestamp "17-10-09 01:35:50", :level :trace, :hostname
>>>> "ip-172-31-4-54", :message ("\nStats about from-tables-to-topics-queue: "
>>>> {})}
>>>>
>>>>
>>>> {:timestamp "17-10-09 01:35:50", :level :trace, :hostname
>>>> "ip-172-31-4-54", :message ("\nStats about the
>>>> from-topics-to-persistence-queue: " {})}
>>>>
>>>>
>>>> {:timestamp "17-10-09 01:36:15", :level :trace, :hostname
>>>> "ip-172-31-4-54", :message ("\n\n\n\n\nResource usage: " "Memory in use
>>>> (percentage/used/max-heap): (\"28%\" \"1007M\" \"3568M\")\n\nCPU usage
>>>> (how-many-cpu's/load-average): [4 4.14]\n\nFree memory in jvm:
>>>> [1868654000]")}
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> So 8 minutes after the app starts, it print the lines with stats about
>>>> the queues, just this one time, and then never again. I think an error must
>>>> occur inside of the function that is suppose to report the queues. What
>>>> would I have to do to see that error?
>>>>
>>>> My core/main function looks like this:
>>>>
>>>> (defn -main [& args]
>>>>
>>>> (slingshot/try+
>>>>
>>>> ;; 2017-10-04 -- see this:
>>>> ;; https://stackoverflow.com/questions/28908835/ssl-peer-shut-
>>>> down-incorrectly-in-java
>>>> (System/setProperty "https.protocols" "TLSv1.1")
>>>>
>>>> (.addShutdownHook (Runtime/getRuntime)
>>>> (Thread.
>>>> #(do (println "addShutdownHook triggered. This
>>>> app is shutting down.")
>>>> (stop))))
>>>>
>>>> ;; 2017-07-12 -- stealing code from here:
>>>> ;; https://stuartsierra.com/2015/05/27/clojure-uncaught-exceptions
>>>> ;; Assuming require [clojure.tools.logging :as log]
>>>> (Thread/setDefaultUncaughtExceptionHandler
>>>> (reify Thread$UncaughtExceptionHandler
>>>> (uncaughtException [_ thread ex]
>>>> (println ex "Uncaught background exception on thread "
>>>> (.getName thread) " Caught by Thread/setDefaultUncaughtExceptionHandler
>>>> in core/main.")
>>>> (throw (ex-info "/setDefaultUncaughtExceptionHandler. The app
>>>> has died!")))))
>>>>
>>>> (start)
>>>> (catch Exception e
>>>> (println e)
>>>> (stack/parse-exception e)
>>>> (throw (ex-info "The app has died!")))
>>>> (catch Object o
>>>> (println o)
>>>> (throw (ex-info "The app has died!")))))
>>>>
>>>> What else could I do to either kill the app at the moment of error or
>>>> catch it at the top and print the error?
>>>>
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>>
>>
>>
>> --
>> “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)
>>
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--
“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)
--
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