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Date: Fri, 26 May 2017 12:11:04 +0000 (UTC)
From: "Dmitry Karachentsev (JIRA)" <jira@apache.org>
To: issues@ignite.apache.org
Message-ID: <JIRA.13030076.1482403074000.302025.1495800664541@Atlassian.JIRA>
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Subject: [jira] [Commented] (IGNITE-4477) Fix IgniteFuture.listen() and
 IgniteFuture.chain() semantics
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archived-at: Fri, 26 May 2017 12:11:10 -0000


    [ https://issues.apache.org/jira/browse/IGNITE-4477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16026197#comment-16026197 ] 

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

[~vozerov],
Fixed, please check.

> 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
>              Labels: important
>             Fix For: 2.1
>
>
> *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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