Re: Inadequate behavior of agent await?
await takes many steps and is not synchronized, so it would be messy to guarantee how it relates to other threads. -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/b7b707f3-2122-4af6-afbe-c03fbe174fbco%40googlegroups.com.
Re: Inadequate behavior of agent await?
On Thursday, June 11, 2020 at 6:20:19 AM UTC+2, Sean Corfield wrote: > > If you provide an error handler on the agent -- or just specify the error > mode as :continue -- it does not hang. > Thanks for pointing out those solutions. > That makes me think that what you're seeing is "expected behavior" > although it does seem a bit strange...? > Yes, `await` doc says: "Will block on failed agents". We should infer that we should only use `await` when we ensure that the agent continues on exceptions. Looking into the implementation of `await`, it creates a latch, sends a `latch.countDown()` action to the agent, and awaits that latch. It makes sense that it blocks forever if the agent stops processing actions. However, there's a thing I don't understand. `await` doc says: "Blocks the current thread (indefinitely!) until all actions dispatched thus far, *from this thread or agent*, to the agent(s) have occurred." But, considering its implementation, we seem to be waiting for *all *actions to occur, not only the actions dispatched by this thread. Also, we are not allowed to call `await` from inside an agent action; why does it say "from this thread or agent" then? Am I misinterpreting something? Thanks, Ernesto -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/58129eee-b0d9-4fef-8ee4-363249e75c04o%40googlegroups.com.
Re: Inadequate behavior of agent await?
Hey, thanks for the suggestions. ClojureVerse seems to be the most active forum? On Thursday, June 11, 2020 at 5:52:29 AM UTC+2, Sam Griffith wrote: > > You may want to ask this on ClojureVerse or on the official Q/A site at > https://ask.clojure.org/index.php/ -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/e4a1bd86-52a0-42e7-aa6a-3ce668e7fa1bo%40googlegroups.com.
Re: Inadequate behavior of agent await?
If you provide an error handler on the agent -- or just specify the error
mode as :continue -- it does not hang. That makes me think that what you're
seeing is "expected behavior" although it does seem a bit strange...?
On Wed, Jun 10, 2020 at 1:49 AM Ernesto Garcia wrote:
> I have discovered that, in the case of an agent action exception, the
> behavior of agent await depends on timing:
> - If your await happens to execute after the action is completed, it will
> happily throw an exception that the agent is in a failed state.
> - If your await happens to execute before the action is completed, it will
> dangerously block. (!!!)
>
> Shouldn't await behave the same in both cases?
>
> Code example:
>
> (defn await-agent-after-fail []
> (let [agt (agent nil)]
> (send-off agt (fn [_]
> (println "Agent throws exception now")
> (throw (ex-info "fail!" {}
> (Thread/sleep 1000)
> (println "Agent is awaited now...")
> (println "Await timed out?" (not (await-for 1 agt)
>
> (comment
> (await-agent-after-fail))
>
>
> (defn await-agent-before-fail []
> (let [agt (agent nil)]
> (send-off agt (fn [_]
> (Thread/sleep 1000)
> (println "Agent throws exception now")
> (throw (ex-info "fail!" {}
> (println "Agent is awaited now...")
> (println "Await timed out?" (not (await-for 1 agt)
>
> (comment
> (await-agent-before-fail))
>
> --
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>
> .
>
--
Sean A Corfield -- (904) 302-SEAN
An Architect's View -- https://corfield.org/
World Singles Networks, LLC. -- https://worldsinglesnetworks.com/
"Perfection is the enemy of the good."
-- Gustave Flaubert, French realist novelist (1821-1880)
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Inadequate behavior of agent await?
You may want to ask this on ClojureVerse or on the official Q/A site at https://ask.clojure.org/index.php/ -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/bda66482-76e3-49ee-8e2c-bffd1635bc15o%40googlegroups.com.
Inadequate behavior of agent await?
I have discovered that, in the case of an agent action exception, the
behavior of agent await depends on timing:
- If your await happens to execute after the action is completed, it will
happily throw an exception that the agent is in a failed state.
- If your await happens to execute before the action is completed, it will
dangerously block. (!!!)
Shouldn't await behave the same in both cases?
Code example:
(defn await-agent-after-fail []
(let [agt (agent nil)]
(send-off agt (fn [_]
(println "Agent throws exception now")
(throw (ex-info "fail!" {}
(Thread/sleep 1000)
(println "Agent is awaited now...")
(println "Await timed out?" (not (await-for 1 agt)
(comment
(await-agent-after-fail))
(defn await-agent-before-fail []
(let [agt (agent nil)]
(send-off agt (fn [_]
(Thread/sleep 1000)
(println "Agent throws exception now")
(throw (ex-info "fail!" {}
(println "Agent is awaited now...")
(println "Await timed out?" (not (await-for 1 agt)
(comment
(await-agent-before-fail))
--
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