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-regarding-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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