Thanks for the feedback. I also give a +1 to option a) including Dan's comments.
I'll move the RFC to the Development state and will open a ticket to follow up on the implementation. -Alberto G. On 12/9/19 8:15, Jacob Barrett wrote: > +1 > > I echo Dan’s comments as well. > > Thanks for tackling this. > > -jake > > >> On Sep 11, 2019, at 2:36 PM, Dan Smith <dsm...@pivotal.io> wrote: >> >> +1 - Ok, I think I've come around to option (a). We can go head and add a >> new execute(timeout, TimeUnit) method to the java API that is blocking. We >> can leave the existing execute() method alone, except for documenting what >> it is doing. >> >> I would like implement execute(timeout, TimeUnit) on the server side as >> well. Since this Execution class is shared between both client and server >> APIs, it would be unfortunate to have a method on Execution that simply >> doesn't work on the server side. >> >> -Dan >> >> >>> On Thu, Sep 5, 2019 at 9:25 AM Alberto Gomez <alberto.go...@est.tech> wrote: >>> >>> Hi all, >>> >>> First of all, thanks a lot Dan and Jacob for your feedback. >>> >>> As we are getting close to the deadline I am adding here some conclusions >>> and a refined proposal in order to get some more feedback and if possible >>> some voting on the two alternatives proposed (or any other in between if >>> you feel any of them is lacking something). >>> >>> I also add some draft code to try to clarify a bit the more complex of the >>> alternatives. >>> >>> >>> Proposal summary (needs a decision on which option to implement): >>> >>> ------------------------------------------------------------------------------------------- >>> >>> In order to make the API more coherent two alternatives are proposed: >>> >>> a) Remove the timeout from the ResultCollector::getResult() / document >>> that the timeout has no effect, taking into account that >>> Execution::execute() is always blocking. >>> Additionally we could add the timeout parameter to the >>> Execution::execute() method of the Java API in order to align it with the >>> native client APIs. This timeout would not be the read timeout on the >>> socket but a timeout for the execution of the operation. >>> >>> b) Change the implementation of the Execution::execute() method without >>> timeout to be non-blocking on both the Java and native APIs. This change >>> has backward compatibility implications, would probably bring some >>> performance decrease and could pose some difficulties in the implementation >>> on the C++ side (in the handling of timed out operations that hold >>> resources). >>> >>> >>> The first option (a) is less risky and does not have impacts regarding >>> backward compatibility and performance. >>> >>> The second one (b) is the preferred alternative in terms of the expected >>> behavior from the users of the API. This option is more complex to >>> implement and as mentioned above has performance and backward compatibility >>> issues not easy to be solved. >>> >>> Following is a draft version of the implementation of b) on the Java >>> client: >>> >>> https://github.com/Nordix/geode/commit/507a795e34c6083c129bda7e976b9223d1a893da >>> >>> Following is a draft version of the implementation of b) on the C++ native >>> client: >>> >>> https://github.com/apache/geode-native/commit/a03a56f229bb8d75ee71044cf6196df07f43150d >>> >>> Note that the above implementation of b) in the C++ client implies that >>> the Execution object returned by the FunctionService cannot be destroyed >>> until the thread executing the function asynchronously has finished. If the >>> function times out, the Execution object must be kept until the thread >>> finishes. >>> >>> >>> Other considerations >>> ------------------------- >>> >>> * Currently, in the function execution Java client there is not a >>> possibility to set a timeout for the execution of functions. The closest to >>> this is the read timeout that may be set globally for function executions >>> but this is not really a timeout for operations. >>> >>> * Even if the API for function execution is the same on clients and >>> servers, the implementation is different between them. On the clients, the >>> execute() methods are blocking while on the servers it is non-blocking and >>> the invoker of the function blocks on the getResult() method of the >>> ResultCollector returned by the execute() method. >>> Even if having both blocking and non-blocking implementation of execute() >>> in both clients and servers sounds desirable from the point of view of >>> orthogonality, this could bring complications in terms of backward >>> compatibility. Besides, a need for a blocking version of function execution >>> has not been found. >>> >>> -Alberto G. >>> >>> On 29/8/19 16:48, Alberto Gomez wrote: >>> >>> Sorry, some corrections on my comments after revisiting the native >>> client code. >>> >>> When I said that the timeout used in the execution() method (by means of >>> a system property) was to set a read timeout on the socket, I was only >>> talking about the Java client. In the case of the native clients, the >>> timeout set in the execute() method is not translated into a socket >>> timeout but it is the time to wait for the operation to complete, i.e., >>> to get all the results back. >>> >>> Things being so, I would change my proposal to: >>> >>> - Change the implementation of execute() on both Java and native clients >>> to be non-blocking (having the blocking/non-blocking behavior >>> configurable in the release this is introduced and leaving only the >>> non-blocking behavior in the next release). >>> >>> - Either remove the execute() with timeout methods in the native clients >>> (with a deprecation release) or implement the execute(timeout) method in >>> the Java client to be blocking (to work as the native client does >>> today). In case the method times out, the connection will not be closed. >>> If the operation times out due to the socket timeout (system property), >>> then the connection will be closed as it is now done in the Java client. >>> >>> - Do not implement the blocking execute(timeout) method on the server >>> and leave the current execute() implementation on the server as it is >>> (non-blocking) >>> >>> Does this make sense? >>> >>> -Alberto >>> >>> On 29/8/19 12:56, Alberto Gómez wrote: >>> >>> >>> Hi Dan, >>> >>> Discussing these matters by e-mail is getting tricky. >>> >>> Let's see if I understand you correctly and also if I am being clear >>> enough. >>> >>> Please, see my comments inline. >>> >>> On 29/8/19 0:49, Dan Smith wrote: >>> >>> >>> Sorry for the slow response, I've been trying to decide what I think >>> is the >>> right approach here. >>> >>> For (1) - conceptually, I don't have a problem with having both blocking >>> and non blocking methods on Execution. So adding blocking versions of >>> execute() with a timeout seems ok. But I do think if we add them we >>> need to >>> implement them on both the client and the server to behave the same way. >>> That shouldn't be too hard on the server since execute(timeout) can just >>> call getResult(timeout) internally. >>> >>> >>> >>> We have to take into account that, currently, the timeout in execute() >>> is not the same thing as the timeout in getResult(). >>> >>> On the one hand, the timeout set in execute() (via System property in >>> the Java client, and with a parameter in the native client) sets a >>> readtimeout on the socket which just means that if nothing is read >>> from the socket after sending the request to the server for the given >>> timeout, the corresponding exception will be thrown. It looks to me >>> more like a protection against possible communication failures rather >>> than a mechanism to decide if results took too long to be provided. So >>> I would not link the presence of the timeout parameter in the method >>> to the nature of the method (blocking or non-blocking). I think we >>> could have this read timeout set and at the same time keep that method >>> as non-blocking. >>> >>> On the other hand, the timeout set in getResult() is a timeout to wait >>> for all the results to be received from the moment the method is invoked. >>> >>> Therefore, I would not implement the blocking version of execute() on >>> the server by calling getResult() at the end. >>> >>> Apart from that, I doubt if it would make sense to set this >>> readTimeout in the execute() methods from servers given that the >>> communication is very different to the one done with clients. I also >>> doubt that anyone would be interested in the blocking version of >>> execute() on the server. >>> >>> My proposal was to add the readtimeout to the execute() methods in the >>> Java client in order to align the Java client and the native client. >>> This change would be independent to the decision we make regarding the >>> change of execute() to non-blocking. To achieve this alignment, >>> alternatively, we could remove the timeout parameter in execute() from >>> the native clients and have it as a global property for the client to >>> be set by whatever mechanism available as it is done in the Java >>> client today. >>> >>> Were you proposing that the execute() methods with timeout were >>> blocking and the ones without timeout non-blocking? Not sure if this >>> is something you meant. >>> >>> >>> >>> >>> For (2) - Although I think the original authors of this API probably did >>> intend for execute() to be non-blocking, the fact is that it does >>> block on >>> the client and most users are probably calling execute from a client. >>> So I >>> do agree we probably shouldn't change the behavior at this point. >>> Perhaps >>> we can just clearly document the current behavior of execute() as >>> part of >>> adding these new methods. Going forward we can add new methods to >>> Execution >>> that are clearly non-blocking (submit?, invoke?) and implement them >>> consistently on *both* the client in the server, but that doesn't >>> have to >>> be in the scope of this proposal. >>> >>> >>> >>> The problem I see with adding new non-blocking methods (new/submit...) >>> is that it would be a solution for the current users of the client >>> regarding backwards compatibility. But, on the server side, we would >>> have to move the current logic of execute() which is non-blocking to >>> the new methods and change the current execute() behavior to blocking. >>> We would not impact the users of the client but we would impact the >>> users of the server. >>> >>> Again, I would propose to aim at: >>> >>> a) either leave execute() on the client as blocking >>> >>> b) or change execute() on the client to be non-blocking but on the >>> Geode release this is introduced, have it configurable. The default >>> behavior would be blocking (deprecated behavior) but could be set to >>> non-blocking with a system property. On the next release, the blocking >>> behavior would be removed. >>> >>> - Alberto G. >>> >>> >>> >>> -Dan >>> >>> On Fri, Aug 23, 2019 at 4:28 AM Alberto Gomez <alberto.go...@est.tech >>>> <mailto:alberto.go...@est.tech> >>> wrote: >>> >>> >>> >>> Hi Jake, >>> >>> Please, see my answers below. >>> >>> On 22/8/19 21:16, Jacob Barrett wrote: >>> >>> >>> On Aug 21, 2019, at 8:49 AM, Alberto Gomez <alberto.go...@est.tech >>>> <mailto:alberto.go...@est.tech> >>> >>> wrote: >>> >>> >>> 2. Timeout in ResultCollector::getResult() and Execution::execute() >>> >>> >>> blocking >>> >>> >>> Regarding the timeout in the ResultCollector::getResult() method >>> >>> >>> problem and the blocking/non-blocking confusion for >>> Execution::execute() >>> two alternatives are considered: >>> >>> >>> a) Remove the possibility of setting a timeout on the >>> >>> >>> ResultCollector::getResult() method on the client side as with the >>> current >>> client implementation it is useless. This could be done by removing the >>> method with the timeout parameter from the public API. >>> >>> >>> It would be advisable to make explicit in the documentation that the >>> >>> >>> getResult() method does not wait for results to arrive as that >>> should have >>> already been done in the Execution::execute() invocation. >>> >>> >>> This alternative is very simple and would keep things pretty much as >>> >>> >>> they are today. >>> >>> >>> To be honest I think approach would go against what a user “thinks” is >>> >>> >>> going on. Given that there hasn’t been a timeout on execute I >>> assumed it >>> was asynchronous and that the getResult blocked until timeout or >>> results >>> arrived. Typically these two calls were done back to back. >>> >>> You are right if you look at the Java client. But if you look at the >>> native clients, the timeout is there, both in the C++ and the C# cases >>> which would indicate that it is a blocking call. >>> >>> See >>> >>> >>> https://geode.apache.org/releases/latest/cppdocs/a00725.html#aa918a5e193745950e12ca4feb9c5d776 >>> >>> and >>> >>> >>> https://geode.apache.org/releases/latest/dotnetdocs/a00882.html#ae0a814049482ca424f89c13ab1099c3d >>> >>> >>> >>> b) Transform the Execution::execute() method on the client side >>> into a >>> >>> >>> non-blocking method. >>> >>> >>> This alternative is more complex and requires changes in all the >>> >>> >>> clients. Apart from that it has implications on the public client >>> API it >>> requires moving the exceptions offered currently by the >>> Execution::execute() method to the ResultCollector::getResult() and new >>> threads will have to be managed. >>> >>> >>> I think this is more in line with what users expect is going on >>> based on >>> >>> >>> the current API, I know I have. If were are going to make any change I >>> think this is the one. I don’t think the behavior change is a >>> problem since >>> it's what is expected to be happening anyway. >>> >>> >>> An outline of a possible implementation for option b) would be: >>> >>> * Instead of invoking the ServerRegionProxy::executeFunction() >>> >>> >>> directly as it is done today, create a Future that invokes this >>> method and >>> returns the resultCollector passed as parameter. >>> >>> >>> Do you really think we need to introduce Futures here into the API? I >>> >>> >>> feel like the ResultCollector acts as the Future. I don’t think any >>> change >>> needs to be made to the API in this regard. The ResultCollector >>> implementation would just simply block as implied by the api for the >>> timeout period. I would change the method to have units though and >>> deprecate the method without units. >>> >>> I did not mean to introduce Futures in the API. My idea was to use Java >>> Futures internally so that the ResultCollector returned by the >>> getResult() method would wrap the Java Future with the ResultCollector >>> that would actually hold the result. >>> >>> An alternative would be to leave the logic of blocking to each >>> implementation ResultCollector. In the case of the >>> DefaultResultCollector, we could use a CountDownLatch that would be >>> decremented when endResults() is called and that would make getResult() >>> block by using CountDown.await(...). >>> >>> The advantage of using Futures internally is that the blocking logic >>> would not have to be implemented on every ResultCollector >>> implementation. >>> >>> >>> >>> -Jake >>> >>> >>> >>> >>> - Alberto >>> >>> >>>
