[jira] [Resolved] (ARROW-11841) [R][C++] Allow cancelling long-running commands

["Dewey Dunnington (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-11841?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dewey Dunnington resolved ARROW-11841.
--------------------------------------
    Resolution: Fixed

Issue resolved by pull request 13635
[https://github.com/apache/arrow/pull/13635]

> [R][C++] Allow cancelling long-running commands
> -----------------------------------------------
>
>                 Key: ARROW-11841
>                 URL: https://issues.apache.org/jira/browse/ARROW-11841
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++, R
>            Reporter: Antoine Pitrou
>            Assignee: Dewey Dunnington
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 10.0.0
>
>          Time Spent: 13h 50m
>  Remaining Estimate: 0h
>
> When calling a long-running task (for example reading a CSV file) from the R prompt, users may want to interrupt with Ctrl-C.
> Allowing this will require integrating R's user interruption facility with the cancellation API that's going to be exposed in C++ (see  ARROW-8732).
> Below some information I've gathered on the topic:
> There is some hairy discussion of how to interrupt C++ code from R at https://stackoverflow.com/questions/40563522/r-how-to-write-interruptible-c-function-and-recover-partial-results and https://stat.ethz.ch/pipermail/r-devel/2011-April/060714.html .
> It seems it may involve polling cpp11::check_user_interrupt() and catching any cpp11::unwind_exception that may signal an interruption. A complication is that apparently R APIs should only be called from the main thread. There's also a small library which claims to make writing all this easier: https://github.com/tnagler/RcppThread/blob/master/inst/include/RcppThread/RMonitor.hpp
> But since user interruptions will only be noticed by the R main thread, the solution may be to launch heavy computations (e.g. CSV reading) in a separate thread and have the main R thread periodically poll for interrupts while waiting for the separate thread. This is what this dedicated thread class does in its join method: https://github.com/tnagler/RcppThread/blob/master/inst/include/RcppThread/Thread.hpp#L79



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