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https://issues.apache.org/jira/browse/STORM-442?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14196050#comment-14196050
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ASF GitHub Bot commented on STORM-442:
--------------------------------------
Github user clockfly commented on the pull request:
https://github.com/apache/storm/pull/305#issuecomment-61632248
dashengju is describling a use scenario that parent process blocks while
trying to read error stream data from sub-process (parent java space throw an
exception, which trigger the error handling).
Becasue sub-process is still running, there is no EOF of errorStream, so
errorStream.read() will blocks.
If in this scenario, we can make sure the child process is dead by called
child.destroy(), then there will be an EOF signalled to its error Stream, and
parent process will not block.
> multilang ShellBolt/ShellSpout die() can be hang when Exception happened
> ------------------------------------------------------------------------
>
> Key: STORM-442
> URL: https://issues.apache.org/jira/browse/STORM-442
> Project: Apache Storm
> Issue Type: Bug
> Affects Versions: 0.9.3
> Reporter: DashengJu
>
> In ShellBolt, the _readerThread read command from python/shell process, and
> handle like this:
> try {
> ShellMsg shellMsg = _process.readShellMsg();
> ...
> } catch (InterruptedException e) {
> } catch (Throwable t) {
> die(t);
> }
> And in the die function, getProcessTerminationInfoString will read
> getErrorsString() from processErrorStream.
> private void die(Throwable exception) {
>
> String processInfo = _process.getProcessInfoString() +
> _process.getProcessTerminationInfoString();
>
> _exception = new RuntimeException(processInfo, exception);
>
> }
> so when ShellBolt got exception(for example, readShellMsg() throw NPE ) ,
> but it is not an error from sub process, then
> getProcessTerminationInfoString will be hang because processErrorStream have
> no data to read.
> On the other hand, as [~xiaokang] says ShellBolt should fail fast on
> exception ( https://github.com/apache/incubator-storm/pull/46 ) , I think it
> is not a good idea to read error info from stream.
> Because [~xiaokang] 's PR is based old version, so I will move his code to
> this PR, and modify some other place in ShellSpout.
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