Hi Tristan,
OK, we're getting close. Just a couple things about ShutdownGracefully.java.
It's a bit clumsy to have both a boolean and a message string to keep track of
the state of the test, but by itself this isn't such a big deal.
A bigger deal is the lack of exception chaining. If we catch an unexpected
exception at line 162, its class and message are printed out, but its stack
trace isn't. If this were to occur it might be fiendishly difficult to debug.
The TimeoutException isn't chained up either, but this isn't so bad, since
there's only one place the timeout can occur. Still, it's good to chain
exceptions where possible.
There's another failure case that doesn't have an exception at all, which is
when the registration request we're expecting to fail actually succeeds. This
doesn't have an exception, but we should consider creating one.
Here's an approach to getting rid of the boolean+string and also chaining up
exceptions. The key insight is that an exception can be created in a different
place from where it's thrown.
Instead of the boolean+stream, have a variable of type Exception that's
initialized to null. Anyplace where we catch an exception that indicates
failure, fill in this variable. The idea is that if this exception variable is
non-null, a failure has occurred. The exception being non-null replaces the
boolean, and the exception message replaces the failure string. In addition, the
exception has a stack trace, which is essential for debugging.
For the case where we don't get the expected exception (i.e., registration
succeeds unexpectedly), simply set the exception variable to a newly created
exception, but don't throw it yet. For example,
exception = new RuntimeException(
"The registration request succeeded unexpectedly");
At the place where we catch an unexpected exception, wrap the caught exception
in a new RuntimeException with a message like "caught unexpected exception". The
reason to do this is so we can add an additional message. The stack trace will
also be a bit easier to follow.
For the timeout, just assign the TimeoutException to the exception variable.
Also, at each location where the exception variable is assigned to, print out a
message at that point. It will at least show the state of the test to be a
failure. The reason is that, if rmid.destroy() were to throw an exception from
the finally-block, our carefully recorded exception state will be thrown away.
(An alternative would be to put this into its own try-block, and add any
exceptions caught from it to the suppressed exception list of the exception
variable, but it's not clear to me that this is worth it.)
At the end of the test, if the exception variable is non-null, call
TestLibrary.bomb() with it to fail the test.
Finally, one typo: "prcoess".
Thanks for updating this webrev again.
s'marks
On 2/13/14 12:25 AM, Tristan Yan wrote:
Thank you Stuart
I have fixed comment in JavaVM.java. Dealing with different cases in
ShutdownGracefully.java, two variables were added. One is a flag indicate test
passed or not. Other variable keeps the error message when test failed. I put
TestLibrary.bomb in the bottom of the main method which only shows test fail
message.
Could you review it again
http://cr.openjdk.java.net/~tyan/JDK-8032050/webrev.04/
Tristan
On 02/13/2014 05:29 AM, Stuart Marks wrote:
Hi Tristan,
JavaVM.waitFor looks mostly fine. The indentation of the start of the
waitFor(timeout) javadoc comment is a bit off, though; please fix.
There are still some adjustments that need to be made in
ShutdownGracefully.java. Both have to do with the case where the last
registration succeeds unexpectedly -- this is the one that we expect to fail.
First, if this registration has succeeded unexpectedly, that means rmid is
still running. If that occurs, the call to rmid.waitFor(timeout) will
inevitably time out. It may be worth calling rmid.destroy() directly at this
point.
Second, still in the succeeded-unexpectedly case, at line 154
TestLibrary.bomb() is called. This throws an exception, but it's caught by the
catch-block at lines 157-158, which calls TestLibrary.bomb() again, saying
"unexpected exception". Except that this is kind of expected, since it was
thrown from an earlier call to TestLibrary.bomb(). This is quite confusing.
There are several cases that need to be handled.
1. Normal case. Registration fails as expected, rmid has terminated
gracefully. Test passes.
2. Rmid is still running and has processed the registration request
successfully. Need to kill rmid and fail the test.
3. Rmid is still running but is in some bad state where the registration
request failed. Need to kill rmid and fail the test.
4. Some other unexpected failure. This is what the catch and finally blocks at
lines 157-161 are for.
These four cases need to be handled independently. Ideally they should be
separated from the cleanup code. As noted above, you don't want to throw an
exception from the try-block, because it will get caught by your own catch
block. Similarly, it's tempting to return from the midst of the try-block in
the success case, but this still runs the finally-block. This can be quite
confusing.
A typical technique for dealing with this kind of issue is to record results
of operations from within the try block, and then analyze the results outside,
throwing a test failure (TestLibrary.bomb) at that point, where it won't be
caught by the test's own catch block.
Editoral:
- line 153, there should be a space between 'if' and the opening paren
- line 156, typo, "gracefuuly"
Finally, it would be helpful if you could get webrev to generate the actual
changeset instead of the plain patch, per my other review email.
Thanks,
s'marks
On 2/11/14 9:39 PM, Tristan Yan wrote:
Thank you for your thorough mail. This is very educational. I took you advice
and generated a new webrev for this.
http://cr.openjdk.java.net/~tyan/JDK-8032050/webrev.03/
I appreciate you can review this again.
Regards
Tristan
On Feb 11, 2014, at 8:32 AM, Stuart Marks <stuart.ma...@oracle.com
<mailto:stuart.ma...@oracle.com>> wrote:
Hi Tristan,
Sorry about my recurring delays.
Several comments on these changes.
JavaVM.java --
The waitFor(timeout) method is mostly ok. The new thread started at line 208
and following seems unnecessary, though. This code is reached when a timeout
occurs, so throwing TimeoutException is the only thing necessary in this case.
Should the code to start the new thread be removed?
There should be a similar check for vm == null as in the waitFor() [no args]
method.
ShutdownGracefully.java --
The condition that's checked after calling rmid.waitFor(SHUTDOWN_TIMEOUT) is
incorrect. It's testing the exit status against zero. Offhand, when and if
rmid exits, it might exit with a nonzero exit status. If rmid has exited at
this point, then the test should succeed.
Instead of testing against zero, the code should catch TimeoutException, which
means that rmid is still running. It's probably reasonable to catch
TimeoutException, print a message, and then let the finally-block destroy the
rmid. Calling TestLibrary.bomb() from within the try-block is confusing, since
that method throws an exception, which is then caught by the catch-block, when
then calls TestLibrary.bomb() again.
We should also make sure to test the success case properly. If rmid.waitFor()
returns in a timely fashion without throwing TimeoutException, it doesn't
matter what the exit status is. (It might be worth printing it out.) At that
point we know that rmid *has* exited gracefully, so we need to set rmid to
null so that the finally-block doesn't attempt to destroy rmid redundantly.
Some additional messages about rmid having exited and the test passing are
also warranted for this case.
Some additional cleanup can be done here as well, over and above the changes
you've proposed. (This stuff is left over from earlier RMI test messes.) In
order to shut down an active object, the code here spawns a new thread that
sleeps for a while and then deactivates this object. This isn't necessary. (It
might have been necessary in the past.) It's sufficient simply to unexport
this object and then deactivate it, directly within the shutdown() method. See
test/java/rmi/activation/ActivationSystem/unregisterGroup/UnregisterGroup.java
for an example of this. In addition, the run() method can be removed, and the
"implements Runnable" declaration can also be removed from the
ShutdownGracefully test class.
Finally, revisiting some code farther up in the test, the try-block at lines
135-140 issues a registration request that the test expects to fail. If it
succeeds, the message at line 139 isn't very clear; it should say that the
registration request succeeded unexpectedly. This should cause the test to
fail. We still probably want to go through the waitFor(timeout) path and
eventual rmid cleanup, but a flag should be set here to ensure that the test
indeed fails if the registration succeeds unexpectedly, and the messages
should clearly indicate that this is going on.
A good way to test this last case is to change rmid's security manager to the
normal security manager java.lang.SecurityManager instead of
TestSecurityManager.
Thanks,
s'marks
On 2/10/14 2:59 AM, Tristan Yan wrote:
Hi Stuart
Could you help to review this.
Thank you
Tristan
On Jan 31, 2014, at 4:36 PM, Tristan Yan <tristan....@oracle.com
<mailto:tristan....@oracle.com>
<mailto:tristan....@oracle.com>> wrote:
Thank you for fixing JDK-8023541. Then I leave ActivationLibrary.java for
now.
I still did some clean up following your suggestion.
1. I changed waitFor(long timeout) method, this method is going to use code
like Process.waitFor(timeout, unit). This can be backported to JDK7. Also
exitValue is kept as a return value. For making sure there is no Pipe leak, a
cleanup thread will start when timeout happens.
2. Change in ShutdownGracefully is a little tricky. I think we should just
destroy JVM once exception is thrown. So I move the wait logic into try block
instead keep them in finally block.
Can you receive it again.
http://cr.openjdk.java.net/~tyan/JDK-8032050/webrev.02/
Thank you
Tristan
On 01/29/2014 03:16 PM, Stuart Marks wrote:
Hi Tristan,
I don't want to put the workaround into ActivationLibrary.rmidRunning()
for a
null return from the lookup, because this is only a workaround for an actual
bug in rmid initialization. See the review I just posted for JDK-8023541.
Adding JavaVM.waitFor(timeout) is something that would be useful in general,
but it needs to be handled carefully. It uses the new
Process.waitFor(timeout, unit) which is new in Java SE 8; this makes
backporting to 7 more complicated. Not clear whether we'll do so, but I
don't
want to forclose the opportunity without discussion. It's also not clear how
one can get the vm's exit status after JavaVM.waitFor() has returned true.
With the Process API it's possible simply to call waitFor() or exitValue().
With JavaVM, a new API needs to be created, or the rule has to be
established
that one must call JavaVM.waitFor() to collect the exit status as well as to
close the pipes from the subprocess. If JavaVM.waitFor(timeout, unit) is
called without subsequently calling JavaVM.waitFor(), the pipes are leaked.
In ShutdownGracefully.java, the finally-block needs to check to see if rmid
is still running, and if it is, to shut it down. Simply calling
waitFor(timeout, unit) isn't sufficient, because if the rmid process is
still
running, it will be left running.
The straightforward approach would be to call
ActivationLibrary.rmidRunning()
to test if it's still running. Unfortunately this isn't quite right, because
rmidRunning() has a timeout loop in it -- which should probably be removed.
(I think there's a bug for this.) Another approach would be simply to call
rmid.destroy(). This calls rmid's shutdown() method first, which is
reasonable, but I'm not sure it kills the process if that fails. In any
case,
this already has a timeout loop waiting for the process to die, so
ShutdownGracefully.java needn't use a new waitFor(timeout, unit) call.
Removing the commented-out code that starts with "no longer needed" is good,
and removing the ShutdownDetectThread is also good, since that's
unnecessary.
There are some more cleanups I have in mind here but I'd like to see a
revised webrev before proceeding.
Thanks,
s'marks
On 1/25/14 8:57 PM, Tristan Yan wrote:
Hi Stuart
Thank you for your review and suggestion.
Yes, since this failure mode is very hard to be reproduced. I guess it's
make sense to do some hack. And I also noticed in
ActivationLibrary.rmidRunning. It does try to look up ActivationSystem but
doesn't check if it's null. So I add the logic to make sure we will look up
the non-null ActivationSystem. Also I did some cleanup if you don't mind.
Add a waitFor(long timeout, TimeUnit unit) for JavaVM. Which we can have a
better waitFor control.
I appreciate you can review the code again.
http://cr.openjdk.java.net/~tyan/JDK-8032050/webrev.01/
Thank you
Tristan
On 01/25/2014 10:20 AM, Stuart Marks wrote:
On 1/23/14 10:34 PM, Tristan Yan wrote:
Hi All
Could you review the bug fix for JDK-8032050.
http://cr.openjdk.java.net/~tyan/JDK-8032050/webrev.00/
Description:
This rare happened failure caused because when RMID starts. It don't
guarantee
sun.rmi.server.Activation.startActivation finishes.
Fix by adding a iterative getSystem with a 5 seconds timeout.
Hi Tristan,
Adding a timing/retry loop into this test isn't the correct approach for
fixing this test.
The timing loop isn't necessary because there is already a timing loop in
RMID.start() in the RMI test library. (There's another timing loop in
ActivationLibrary.rmidRunning() which should probably be removed.) So the
intent of this library call is that it start rmid and wait for it to
become
ready. That logic doesn't need to be added to the test.
In the bug report JDK-8032050 you had mentioned that the
NullPointerException was suspicious. You're right! I took a look and it
seemed like it was related to JDK-8023541, and I added a note to this
effect to the bug report. The problem here is that rmid can come up and
transiently return null instead of the stub of the activation system.
That's what JDK-8023541 covers. I think that rmid itself needs to be
fixed,
though modifying the timing loop in the RMI test library to wait for rmid
to come up *and* for the lookup to return non-null is an easy way to fix
the problem. (Or at least cover it up.)
The next step in the analysis is to determine, given that
ActivationLibrary.getSystem can sometimes return null, whether this has
actually caused this test failure. This is pretty easy to determine; just
hack in a line "system = null" in the right place and run the test. I've
done this, and the test times out and the output log is pretty much
identical to the one in the bug report. (I recommend you try this
yourself.) So I think it's fairly safe to say that the problem in
JDK-8023541 has caused the failure listed in JDK-8032050.
I can see a couple ways to proceed here. One way is just to close this out
as a duplicate of JDK-8023541 since that bug caused this failure.
Another is that this test could use some cleaning up. This bug certainly
covers a failure, but the messages emitted are confusing and in some cases
completely wrong. For example, the "rmid has shutdown" message at line 180
is incorrect, because in this case rmid is still running and the wait()
call has timed out. Most of the code here can be replaced with calls to
various bits of the RMI test library. There are a bunch of other things in
this test that could be cleaned up as well.
It's up to you how you'd like to proceed.
s'marks
