[jira] [Commented] (GROOVY-7414) Process output not always consumed before waitFor() returns

["Paul King (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GROOVY-7414?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14530394#comment-14530394 ] 

Paul King commented on GROOVY-7414:
-----------------------------------

This is "as designed" behavior. The consumeProcessOutput and waitFor methods are low-level primitives if you like which have known limitations but have been left around for people wanting that low-level and for legacy reasons. The higher-level waitForProcessOutput method is the correct abstraction for most users and is the recommended one to use. Perhaps we need to stress that further in the documentation.

> Process output not always consumed before waitFor() returns
> -----------------------------------------------------------
>
>                 Key: GROOVY-7414
>                 URL: https://issues.apache.org/jira/browse/GROOVY-7414
>             Project: Groovy
>          Issue Type: Bug
>          Components: groovy-jdk
>    Affects Versions: 2.4.3
>         Environment: Linux junk 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt9-2 (2015-04-13) x86_64 GNU/Linux running in a VirtualBox VM
>            Reporter: Sergey Gromov
>            Assignee: Guillaume Laforge
>
> Sometimes the {{Process.consumeProcessOutput(Appendable, Appendable)}} and {{Process.waitFor()}} combination does not work as expected. More specifically, sometimes {{waitFor()}} returns before all input is actually written into {{Appendable}}.
> The following script reproduces the problem:
> {code:title=bug.gy}
> 100.times {
>         def out = new StringBuilder()
>         def err = new StringBuilder()
>         def p = 'echo stuff'.execute()
>         p.consumeProcessOutput(out, err)
>         p.waitFor()
>         def s = out.toString()
>         if (s != 'stuff\n') {
>                 println 'Bug!'
>                 println 'OUT: ' + s.inspect()
>         }
> }
> {code}
> The ability to reproduce this issue seems to depend on the system performance. E.g. I can easily reproduce it in my virtual Linux box. The above script fails 2 or 3 times on every launch. OTOH it's quite problematic to reproduce on my host Windows machine even though I increased the number of tries to 1000. Nevertheless I have reproduced it on Windows, too, a couple of times.
> I think this is major because I'm not aware of any viable workaround. The only thing that works is to sleep a bit after waitFor() which is often unacceptable, and it's impossible to guess for how long to sleep.
> Note that {{Process.consumeProcessOutput(OutputStream, OutputStream)}} exhibits the same broken behavior.
> Also note that {{Process.waitForProcessOutput(arg, arg)}} methods work flawlessly.



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