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https://issues.apache.org/jira/browse/MESOS-1199?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14006585#comment-14006585
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Till Toenshoff commented on MESOS-1199:
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I would like to express my desperate support for this optimization. The
ExternalContainerizer heavily relies on Subprocess, hence shares the problem of
slow reaping. As an extreme example, currently when running the
SlaveRecoveryTests against the ExternalContainerizer (24 Tests), it takes about
170 seconds in total to get through them on my machine. So most of those tests
take 6-10seconds.
> 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
>
> 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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