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From "Dmitry Karachentsev (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (IGNITE-4477) Fix IgniteFuture.listen() and IgniteFuture.chain() semantics
Date Tue, 04 Apr 2017 08:21:41 GMT

    [ https://issues.apache.org/jira/browse/IGNITE-4477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15953095#comment-15953095
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Dmitry Karachentsev edited comment on IGNITE-4477 at 4/4/17 8:21 AM:
---------------------------------------------------------------------

Vladimir, please review the fix: [PR 1721|https://github.com/apache/ignite/pull/1721]

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.

Here is a link to upsource: [IGNT-CR-156|http://reviews.ignite.apache.org/ignite/review/IGNT-CR-156]


was (Author: dkarachentsev):
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.

Here is a link to upsource: [IGNT-CR-151|http://reviews.ignite.apache.org/ignite/review/IGNT-CR-151]

> 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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