[jira] [Commented] (IGNITE-4477) Fix IgniteFuture.listen() and IgniteFuture.chain() semantics

["Dmitry Karachentsev (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IGNITE-4477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15953095#comment-15953095 ] 

Dmitry Karachentsev commented on IGNITE-4477:
---------------------------------------------

Vladimir, please review the fix: [PR 1710|https://github.com/apache/ignite/pull/1710]

Instead of two async methods for listen and chain I've added one with nullable Executor. I don't think we need to duplicate methods just without last argument.

> Fix IgniteFuture.listen() and IgniteFuture.chain() semantics
> ------------------------------------------------------------
>
>                 Key: IGNITE-4477
>                 URL: https://issues.apache.org/jira/browse/IGNITE-4477
>             Project: Ignite
>          Issue Type: Task
>          Components: general
>    Affects Versions: 1.8
>            Reporter: Vladimir Ozerov
>            Assignee: Dmitry Karachentsev
>             Fix For: 2.0
>
>
> *Problem*
> We allow users to pass continuations to {{IgniteFuture}} which will be executed on future completion. This can be done through {{listen}} or {{chain}} methods.
> However, continuation semantics is broken intrinsically:
> 1) If future is already completed, user code executed in the same thread;
> 2) If future is not completed yet, it will be executed in completion thread.
> Neither of this options are valid because it easily leads to starvation. E.g.:
> {code}
> IgniteFuture fut = cache.getAsync(key2);
> fut.listen(fut0 -> {
>      cache.put(key2, val2); // Possible deadlock, because invoked in sys pool;
> });
> {code}
> *Solution*
> 1) By default callbacks must be executed asynchronously in some common pool (public pool? new "callback pool"? FJP?)
> 2) It should be possible to specify where to execute a callback explicitly:
> {code}
> IgniteFuture.listen(IgniteClosure, ExecutorService);
> {code}
> 3) We may want to expose our public pool on API for convenience.



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