Re: [Hawkular-dev] [metrics] Looking for advice on ListenableFuture usage

On Jan 16, 2015, at 11:58 AM, John Mazzitelli <mazz(a)redhat.com&gt; wrote: I have no idea if this is relevant, but in the hawkular-bus API, we now have ListenerFuture being used to support async-RPC messaging. https://github.com/hawkular/hawkular-bus/blob/master/hawkular-bus-common/... Send a given message to the bus via sendRPC(), tell it what type of message to expect in return, and you'll get a ListenableFuture back which you can use to obtain the response asyncyronously from the bus. ----- Original Message ----- > I don’t think it necessary to add a ticket for such a small change. I am glad > you mentioned the REST handler code. To be honest, I am not sure. With the > driver, I do know from experience that if you start blocking I/O threads > with work that takes a non-trivial amount of time, you are going to start > seeing client side timeouts. An I/O thread services multiple requests > concurrently. For the REST handler code, we ought to investigate whether or > not it would be better to perform the transformations on a separate thread. > >> On Jan 16, 2015, at 10:48 AM, Thomas Segismont <tsegismo(a)redhat.com&gt; wrote: >> >> Sorry I overlooked the metrics-core code. >> >> Indeed, almost every call where a ListenableFuture returned by the C* >> driver is involved uses the overloaded version (with the metricsTasks >> ListenableExecutor instance). >> Should I open a JIRA for the few places where it's missing? >> >> My understanding from you reply is that: >> * all transformations on ListenableFuture returned by the C* driver should >> happen in a thread of the metricsTasks pool >> ==> use the overloaded version >> * subsequent transformations may happen on the metricsTasks thread or on >> the thread executing the rest handler code >> ==> use the base version >> Is that correct? >> >> Thanks >> >> Le 16/01/2015 14:23, John Sanda a écrit : >>> In the metrics code, at least where a response from the C* driver is >>> involved, the versions that take an executor is used almost everywhere. >>> We do not want to block I/O threads doing work so in general it is best >>> to use the overloaded versions of the methods. >> B> >>>> On Jan 16, 2015, at 4:47 AM, Thomas Segismont <tsegismo(a)redhat.com&gt; >>>> wrote: >>>> >>>> Hi everyone, >>>> >>>> I'm looking for advice on how to use Futures#transform[1] and friends >>>> (#addCallback, #withFallback) >>>> >>>> These methods all have an overloaded version which takes a JDK Executor >>>> instance as additional argument. >>>> >>>> When the base method is called, Guava will use the so-called >>>> "sameThreadExecutor". Consequently, the code will be executed: >>>> * by the caller thread, if the underlying Future has completed already >>>> * otherwise, by the thread completing the underlying Future >>>> >>>> When the overloaded method is called, Guava will submit tasks to the >>>> provided executor. >>>> >>>> In the metrics code right now, the base method is used almost >>>> everywhere. Considering that in most cases it will take more time to get >>>> the response from C* than to complete the REST Handler code, it's the >>>> Datastax driver threads which will execute the chain of callbacks, down >>>> to the call to javax.ws.rs.container.AsyncResponse#resume >>>> >>>> Could that be a problem? I guess it's safe when callbacks only >>>> transforms the data loaded. I'm not sure about the call to >>>> AsyncResponse#resume. >>>> >>>> Thoughts? >>>> >>>> Thanks, >>>> Thomas >>>> >>>> >>>> [1] >>>> http://docs.guava-libraries.googlecode.com/git-history/v16.0.1/javadoc/co... >>>> >>>> _______________________________________________ >>>> Hawkular-dev mailing list >>>> Hawkular-dev(a)lists.jboss.org >>>> https://lists.jboss.org/mailman/listinfo/hawkular-dev >>> >> > > > _______________________________________________ > hawkular-dev mailing list > hawkular-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/hawkular-dev > _______________________________________________ hawkular-dev mailing list hawkular-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/hawkular-dev