Github user miguno commented on the pull request:
https://github.com/apache/storm/pull/456#issuecomment-77159580
Many thanks for the PR, Kai!
> However if the topology is submitted with `storm shell`, this cannot
track exception because spawnvp seems to return no stdout and stderr.
See [my
comment](https://issues.apache.org/jira/browse/STORM-695?focusedCommentId=14340333&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14340333)
in the STORM-695 JIRA ticket. `os.spawnvp` returns the exit code of the
process:
```python
# return code can be 0 or non-zero, i.e. there will be no exception thrown
like for sub.check_output
return_code = os.spawnvp(os.P_WAIT, JAVA_CMD, all_args)
```
However the problem is that Storm is currently not returning any non-zero
return codes, even in the face of errors. I haven't had the chance to
test-drive your code yet, but the code in the PR might not work for the same
reason:
```python
try:
ret = sub.check_output(all_args, stderr=sub.STDOUT)
print(ret)
except sub.CalledProcessError as e:
```
If I understand the Python docs correctly, the `CalledProcessError` will
only be thrown if the process returns with a non-zero exit code, and with
current Storm this won't happen -- the return code will always be zero I think.
One workaround could be to slightly adjust the code in the PR to simply
grep for error messages in `STDOUT` / `STDERR` -- regardless of what the
return code of the process is -- and, if there is a match, consider the
process/command failed.
(And please correct me if I'm wrong.)
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