[
https://issues.apache.org/jira/browse/NIFI-1856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15780981#comment-15780981
]
ASF GitHub Bot commented on NIFI-1856:
--------------------------------------
Github user mattyb149 commented on the issue:
https://github.com/apache/nifi/pull/1355
Many of the commits are merge commits, when this PR is merged it can make
the commit log fairly messy. Do you mind rebasing your own branch against the
latest "upstream" master branch. You may find it helpful to create a branch
specifically for this PR, then reset your own master branch to upstream, then
you can rebase this branch against master without worrying whether to fetch or
pull from upstream in the future. Not a requirement, just a suggestion to help
keep things a bit cleaner :)
> ExecuteStreamCommand Needs to Consume Standard Error
> ----------------------------------------------------
>
> Key: NIFI-1856
> URL: https://issues.apache.org/jira/browse/NIFI-1856
> Project: Apache NiFi
> Issue Type: Bug
> Reporter: Alan Jackoway
> Assignee: Karthik Narayanan
>
> I was using ExecuteStreamProcess to run certain hdfs commands that are tricky
> to write in nifi but easy in bash (e.g. {{hadoop fs -rm -r
> /data/*/2014/05/05}})
> However, my larger commands kept hanging even though when I run them from the
> command line they finish quickly.
> Based on
> http://www.javaworld.com/article/2071275/core-java/when-runtime-exec---won-t.html
> I believe that ExecuteStreamCommand and possibly other processors need to
> consume the standard error stream to prevent the processes from blocking when
> standard error gets filled.
> To reproduce. Create this as ~/write.py
> {code:python}
> import sys
> count = int(sys.argv[1])
> for x in range(count):
> sys.stderr.write("ERROR %d\n" % x)
> sys.stdout.write("OUTPUT %d\n" % x)
> {code}
> Create a flow that goes
> # GenerateFlowFile - 5 minutes schedule 0 bytes size
> # ExecuteStreamCommand - Command arguments /Users/alanj/write.py;100 Command
> Path python
> # PutFile - /tmp/write/
> routing output stream of ExecuteStreamCommand to PutFile
> When you turn everything on, you get 100 lines (not 200) of just the standard
> output in /tmp/write.
> Next, change the command arguments to /Users/alanj/write.py;100000 and turn
> everything on again. The command will hang.
> I believe that whenever you execute a process the way ExecuteStreamCommand is
> doing, you need to consume the standard error stream to keep it from
> blocking. This may also affect things like ExecuteProcess and ExecuteScript
> as well.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
