[jira] [Comment Edited] (MESOS-1199) Subprocess is "slow" -> gated by process::reap poll interval

["Ian Downes (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MESOS-1199?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14145123#comment-14145123 ] 

Ian Downes edited comment on MESOS-1199 at 9/23/14 6:07 PM:
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Understood. This race has existed in the codebase for a long time. We could consider looking at /proc/\{pid\}/exe to confirm that the pid at least corresponds to the expected executable - still not perfect though.


was (Author: idownes):
Understood. This race has existed in the codebase for a long time. We could consider looking at /proc/{pid}/exe to confirm that the pid at least corresponds to the expected executable - still not perfect though.

> Subprocess is "slow" -> gated by process::reap poll interval
> ------------------------------------------------------------
>
>                 Key: MESOS-1199
>                 URL: https://issues.apache.org/jira/browse/MESOS-1199
>             Project: Mesos
>          Issue Type: Improvement
>    Affects Versions: 0.18.0
>            Reporter: Ian Downes
>            Assignee: Craig Hansen-Sturm
>         Attachments: wiatpid.pdf
>
>
> Subprocess uses process::reap to wait on the subprocess pid and set the exit status. However, process::reap polls with a one second interval resulting in a delay up to the interval duration before the status future is set.
> This means if you need to wait for the subprocess to complete you get hit with E(delay) = 0.5 seconds, independent of the execution time. For example, the MesosContainerizer uses mesos-fetcher in a Subprocess to fetch the executor during launch. At Twitter we fetch a local file, i.e., a very fast operation, but the launch is blocked until the mesos-fetcher pid is reaped -> adding 0 to 1 seconds for every launch!
> The problem is even worse with a chain of short Subprocesses because after the first Subprocess completes you'll be synchronized with the reap interval and you'll see nearly the full interval before notification, i.e., 10 Subprocesses each of << 1 second duration with take ~10 seconds!
> This has become particularly apparent in some new tests I'm working on where test durations are now greatly extended with each taking several seconds.



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