Sorry for the delay in getting back to this - I had a long weekend. :)
I think this new approach is great! So it is a big Thumbs Up from me!
Thanks,
David
On 17/10/2014 7:55 PM, Jaroslav Bachorik wrote:
On 10/16/2014 02:14 AM, David Holmes wrote:
On 15/10/2014 11:55 PM, Jaroslav Bachorik wrote:
On 10/15/2014 10:11 AM, David Holmes wrote:
On 15/10/2014 5:50 PM, Jaroslav Bachorik wrote:
On 10/15/2014 02:10 AM, David Holmes wrote:
On 14/10/2014 8:46 PM, Jaroslav Bachorik wrote:
Please, review the following test change
Issue : https://bugs.openjdk.java.net/browse/JDK-8056143
Webrev: http://cr.openjdk.java.net/~jbachorik/8056143/webrev.00
The method jdk.testlibrary.ProcessTools.getOutput(process) waits for
the
given process to finish (process.waitFor()) before grabbing its
outputs.
However, the code does not handle the process.waitFor() being
interrupted correctly - it just goes ahead and tries to obtain the
exit
code which will fail and leave the tested process running.
The correct way is to forcibly destroy the process when
process.waitFor() is interrupted or throws ExecutionException to
make
sure the process has actually exited before checking its exit code.
Why is this correct? What gives the thread calling getOutput the
right
to terminate the target process just because that thread was
interrupted
while waiting? If the interrupting thread intended the interrupt to
mean
"forcibly terminate the process and interrupt all threads waiting on
it"
then that thread should be doing the termination _not_ the one that
was
interrupted!
Process.waitFor() gets interrupted by a thread unknown to the actual
test case - probably the JTreg timeout thread. The interrupting thread
doesn't know that it is supposed to destroy a process. Once JTreg can
take care of cleaning up process tree upon exit this code wouldn't be
needed.
I was contemplating adding the check for "null" returned from
ProcessTools.getOutput() and destroying the process inside the caller
code - but this would have the same results as doing it in
ProcessTools.getOutput() with the drawback of duplicating the same
check
everywhere ProcessTools.getOutput() would be used.
A silent postcondition of ProcessTools.getOuptut() is that the target
process has finished - and it holds for all the code paths except the
InterruptedException handler.
That doesn't mean it is up to getOutput to forcibly terminate the
process. Multi-process cancellation is tricky, and yes eventually jtreg
will handle it. But this seems the wrong place to handle it now.
Part of
the flaw here is that getOutput should itself throw
InterruptedException
so that the caller is forced to deal with this - instead it just
re-asserts the interrupt state. The caller has to be aware that the
thread can be interrupted and do something appropriate - which may mean
punting to its caller. This is akin to a thread catching
InterruptedException and calling System.exit - it simply is not its job
to make that kind of decision at that level!
There is no other decision to make. Not as it is written today. You can
call ProcessTools.getOutput() and check whether the result is null and
then end the test process. There is no other sensible action. The
Process.waitFor() was interrupted you have no data to perform the checks
against so the test will fail and as such it should stop any external
processes it has started.
Yes, I can go through all the tests using ProcessTools.getOutput() and
add `if (output == null) process.destroyForcible();` - would this make
it a better solution than putting this logic inside
ProcessTools.getOutput()?
It would be the correct solution. Hacking it into getOutput() is just a
convenience. Problem is that none of these tests have given enough
thought to the cancellation issue and general process management.
Agreed. My concern was that the test code base would have been littered
with `if (output == null) process.destroyForcible();` checks because
there is no other way to react to the situation when process.waitFor()
is interrupted - at least not in the JTreg context.
Therefore I put the logic of properly ending the external process to
ProcessTools.executeProcess() method and restricted access to the
constructors of OutputBuffer and OutputAnalyzer to enforce their
creation only via ProcessTools.executeProcess().
Also, in order to prevent the started process stdout/stderr overflow I
moved the backround stream pumpers to OutputBuffer so they would be
started ASAP, without waiting for the process to exit (which defeats the
purpose of consuming the attached stdout/stderr streams in backround
anyway).
With these changes the API user doesn't need to worry about the external
process cleanup anymore. The semantics of ProcessTools.executeProcess()
guarantees that there will be no orphan process hanging about once this
method returns.
This change is significantly bigger than the previous attempt because it
spans a lot of tests using the OutputAnalyzer but, hopefully, it
addresses David's concerns.
http://cr.openjdk.java.net/~jbachorik/8056143/webrev.01
-JB-
Sorry.
David
-JB-
David
-JB-
David
Thanks,
-JB-
