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From "Kristian Waagan (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5608) BaseTestCase.readProcessOutput should read getInputStream() and getErrorStream() in separate threads
Date Wed, 08 Feb 2012 21:21:01 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13204004#comment-13204004
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Kristian Waagan commented on DERBY-5608:
----------------------------------------

Don't know if it is an option, but could readProcessOutput be discarded ([1]) and SpawnedProcess
be extended to deal with this?
SpawnedProcess already does what readProcessOutput does (or should have done), except for
constructing a string from the raw output data. After having read a bit about best practices
for java.lang.Process, there seems to be several common pitfalls associated with its use.
It would be good to deal with them in one place.
SpawnedProcess also has some issues that needs to be fixed. I was planning to deal with that
under DERBY-5601, but maybe this issue is a better fit?


[1] Or keep the method and just use SpawnedProcess in the method implementation.
                
> BaseTestCase.readProcessOutput should read getInputStream()  and getErrorStream() in
separate threads
> -----------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-5608
>                 URL: https://issues.apache.org/jira/browse/DERBY-5608
>             Project: Derby
>          Issue Type: Bug
>          Components: Test
>    Affects Versions: 10.9.0.0
>            Reporter: Kathey Marsden
>            Priority: Minor
>
> BaseTestCase.readProcessOutput() reads the streams from Process.getInputStream() and
Process.getErrorStream() sequentially 
> InputStream is = pr.getInputStream();
> InputStream es = pr.getErrorStream();
> ...
>  output += "<STDOUT> " + inputStreamToString(is) + "<END STDOUT>\n";
>  output += "<STDERR>" + inputStreamToString(es) + "<END STDERR>\n";
> I think that to be really correct the  two streams need to be read in separate threads
because if the error output  is  large it could block and cause a hang  if they are read sequentially
like this.
> I noticed during the DERBY-5601 discussion as Myrna referenced in that  the addition
of draining the error stream caused a different problem (an InterruptException). I don't understand
how it could cause that problem but do think a hang blocking on  reading the input would be
possible if the error output was large enough both  before and after the change to add the
reading of the error stream sequentially.

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