RFR: 5050783: Throwable convenience method: String getStackTraceString()
Claes Redestad
claes.redestad at oracle.com
Thu Jan 15 12:24:34 UTC 2015
Hi,
anything directly used by the LambdaMetafactory itself would
of course be impossible to add lambdas to, and as Remi points
out, this makes lambdaified utilities unusable from that subsystem
unless there are ways around them, e.g., exposing a desugared
method along with the lambdaified API (which would defeat the
potential for footprint optimizations).
I think this patch/review should focus on the need for the utility
method itself. As I suggested privately, I think a minimal
implementation of this convenience method using existing code
would be a good starting point:
public String getStackTraceString() {
StringWriter sw = new StringWriter();
printStackTrace(new PrintWriter(sw));
return sw.toString();
}
Your benchmark indicates this would have a 10-15% overhead
over a StringBuilder-based implementation, which I think is OK
for a convenience method such as this. If accepted we can
start to think about ways to optimize the internals.
On that note, I'm thinking loudly about whether or not it'd be
appropriate to extract common methods in PrintStream and
PrintWriter to an interface. java.io.Printable?
This would allow getting rid of most inner classes in j.l.Throwable
along with some duplicated code across the JDK (I've noticed
at least a few places where there are identical methods which
differ only in that one takes a PrintStream, the other a PrintWriter).
This could grow into a larger effort, but maybe it's worth it since
the compatibility risks should be minimal.
/Claes
On 01/14/2015 09:34 PM, Ivan St. Ivanov wrote:
> Hi Remi,
>
> I tried it and, well, the JDK image now does not even compile classes that
> contain lambda expressions:
>
> javac -cp . ./LambdaMetaFactoryTester.java
> Exception in thread "main"
> Exception: java.lang.BootstrapMethodError thrown from the
> UncaughtExceptionHandler in thread "main"
>
> With the old Throwable implementation it printed a long stack trace of
> exceptions, but at least my sample class was compiled.
>
> So, I have two questions:
> 1) Does anyone dump stack traces in such location, even for debugging
> purposes?
> 2) If yes, what are the other JDK classes and methods where we should avoid
> using lambdas?
>
> Thanks,
> Ivan
>
> On Wed, Jan 14, 2015 at 9:44 PM, Remi Forax <forax at univ-mlv.fr> wrote:
>
>> While using a lambda is cool in that context,
>> if someone tries to do a printStackTrace in the LambdaMetafactory (for
>> debugging purpose by example),
>> it will be fun to debug.
>>
>> cheers,
>> Rémi
>>
>>
>> On 01/14/2015 08:25 PM, Ivan St. Ivanov wrote:
>>
>>> Hi Claes, core libs developers,
>>>
>>> As promised, we did yesterday our hackathon in the Bulgarian Java User
>>> Group and incorporated the feedback that we got from you. Here is our next
>>> webrev:
>>>
>>> http://dmitryalexandrov.net/~bgjug/5050783/webrev.01/
>>>
>>> As you can see:
>>>
>>> - We got rid of the inner classes altogether in favor of
>>> java.util.function.Consumer
>>> - The javadoc was updated to follow the standards [1]
>>> - In the tests we use an exception that we create rather than relying on
>>> one from the JDK that potentially could change
>>>
>>> We also ran some microbenchmarks to compare the performance of the new
>>> functionality with the Apache commons solution mentioned in the bug. Here
>>> is the benchmark test:
>>>
>>> @State(Scope.Benchmark)
>>> public class ThrowableStacktraceBenchmark {
>>> Throwable chainedThrowable;
>>> Throwable simpleThrowable;
>>>
>>> @Setup
>>> public void prepare() {
>>> chainedThrowable = createThrowable(64);
>>> simpleThrowable = new Throwable("Simple Throwable");
>>> }
>>>
>>> Throwable createThrowable(int depthLevel) {
>>> Throwable t = null;
>>> for (int i = 0; i < depthLevel; ++i) {
>>> t = new Throwable("My dummy Throwable " + i, t);
>>> }
>>> return t;
>>> }
>>>
>>> @Benchmark
>>> public void benchmarkThrowableGetStackTraceString() {
>>> chainedThrowable.getStackTraceString();
>>> }
>>>
>>> @Benchmark
>>> public void benchmarkThrowableGetStackTraceStringSmall() {
>>> simpleThrowable.getStackTraceString();
>>> }
>>>
>>> @Benchmark
>>> public void benchmarkThrowablePrintStackTraceToStringWriter() {
>>> StringWriter sw = new StringWriter();
>>> chainedThrowable.printStackTrace(new PrintWriter(sw));
>>> sw.toString();
>>> }
>>>
>>> @Benchmark
>>> public void benchmarkThrowablePrintStackTraceToStringWriterSmall() {
>>> StringWriter sw = new StringWriter();
>>> simpleThrowable.printStackTrace(new PrintWriter(sw));
>>> sw.toString();
>>> }
>>> }
>>>
>>> And here are the results (test was run with the following options -wi 5 -i
>>> 5 -t 1):
>>>
>>> Benchmark Mode Samples Score Error Units
>>> o.m.t.ThrowableStacktraceBenchmark.benchmarkThrowableGetStackTraceString
>>> thrpt 50 25351.743 ± 347.326 ops/s
>>> o.m.t.ThrowableStacktraceBenchmark.benchmarkThrowableGetStackTrac
>>> eStringSmall
>>> thrpt 50 134990.643 ± 760.225 ops/s
>>> o.m.t.ThrowableStacktraceBenchmark.benchmarkThrowablePrintStackTr
>>> aceToStringWriter
>>> thrpt 50 22730.786 ± 167.378 ops/s
>>> o.m.t.ThrowableStacktraceBenchmark.benchmarkThrowablePrintStackTr
>>> aceToStringWriterSmall
>>> thrpt 50 115223.025 ± 936.770 ops/s
>>>
>>> Just in any case we ran this test, actually just the last two methods,
>>> with
>>> JDK 1.9 ea build 45. We wanted to compare the result of the Apache commons
>>> solution with inner classes (as it is now) to the same, but with
>>> java.util.function.Consumer. There are the results with the inner classes:
>>>
>>> o.m.t.ThrowableStacktraceBenchmark.benchmarkThrowablePrintStackTr
>>> aceToStringWriter
>>> thrpt 50 22974.324 ± 391.564 ops/s
>>> o.m.t.ThrowableStacktraceBenchmark.benchmarkThrowablePrintStackTr
>>> aceToStringWriterSmall
>>> thrpt 50 114973.452 ± 1051.276 ops/s
>>>
>>> So you can see that the performance is nearly the same (I guess that the
>>> difference is ignorable).
>>>
>>> Please share with us the feedback about this proposal!
>>>
>>> Thanks,
>>> Ivan
>>>
>>> [1] http://www.oracle.com/technetwork/articles/java/index-137868.html
>>>
>>> On Wed, Dec 31, 2014 at 3:32 PM, Claes Redestad <
>>> claes.redestad at oracle.com>
>>> wrote:
>>>
>>> Hi,
>>>> seems like a reasonable convenience method. :-)
>>>>
>>>> Process stuff: OCA/JSPA signing aside, the patch needs to be submitted in
>>>> its
>>>> entirety to some part of the OpenJDK infrastructure before it can be
>>>> accepted.
>>>> Attaching the patch in an e-mail to this mailing list is acceptable for a
>>>> small
>>>> patch like this when lacking upload privileges to cr.openjdk.java.net. A
>>>> sponsor
>>>> could help you with the uploading etc.
>>>>
>>>> This request adds a new public method, which means some internal approval
>>>> will be necessary. This is something you'll need help with from an Oracle
>>>> sponsor. I could volunteer to initiate the requests internally.
>>>>
>>>> Code feedback:
>>>>
>>>> The test relies on the message generated when provoking a division by
>>>> zero. I'm not sure this is a good idea nor the place to enforce this
>>>> message format with a test. Perhaps just throwing a RuntimeException
>>>> with some specified message and test for that?
>>>>
>>>> May I suggest to also add a test to ensure the method behaves well for an
>>>> exception with fillInStackTrace overridden to produce stackless
>>>> exceptions?
>>>>
>>>> Just a thought... I noticed PrintWriter, PrintStream and StringBuilder
>>>> all
>>>> inherit from Appendable, so the PrintStreamOrWriter/StackTracePrinter
>>>> classes
>>>> could be replaced with a single StackTraceAppendable taking an
>>>> Appendable.
>>>> One
>>>> static class instead of 1 abstract and 3 concrete static inner classes
>>>> could work
>>>> out to be a good deal, but there's some odd mechanics in
>>>> BufferedWriter/PrintWriter
>>>> to use the value of the line.separator property at object creation time
>>>> which
>>>> would be hard to support without exposing the lineSeparator fields to
>>>> Throwable.
>>>> Perhaps a future consideration.
>>>>
>>>> Performance characteristics might change ever so slightly either way, so
>>>> it
>>>> would be nice with some microbenchmarks to quantify.
>>>>
>>>> /Claes
>>>>
>>>>
>>>> On 2014-12-31 11:51, Ivan St. Ivanov wrote:
>>>>
>>>> Hello,
>>>>> I am Ivan from the Bulgarian Java User Group. As part of our Adopt
>>>>> OpenJDK
>>>>> efforts, we organized hackathon beginning of this month in Sofia. There
>>>>> we
>>>>> worked on the following JIRA issue:
>>>>>
>>>>> https://bugs.openjdk.java.net/browse/JDK-5050783
>>>>>
>>>>> Unfortunately none of us has author privileges, so the issue is still
>>>>> unassigned. But, nevertheless, our JUG has already signed JSPA and some
>>>>> of
>>>>> our members (including myself) have signed OCA. And we informed in a
>>>>> special email this mailing list about our plans prior to the meeting.
>>>>>
>>>>> Our hackathon was already documented by our JUG member Mihail Stoynov:
>>>>>
>>>>> http://mihail.stoynov.com/2014/12/12/building-openjdk-
>>>>> and-submitting-a-solution-on-a-feature-request-with-the-
>>>>> bulgarian-java-user-group/
>>>>>
>>>>> We used the days after the meeting for offline polishing our
>>>>> contribution
>>>>> and adding some more unit tests. Here is the result of our work:
>>>>>
>>>>> http://dmitryalexandrov.net/~bgjug/5050783/webrev.00/
>>>>>
>>>>> We would be very happy if you are able to review it, share your feedback
>>>>> and guide us through the contribution process as this is our first
>>>>> attempt.
>>>>>
>>>>> Thanks and have a very successful year!
>>>>> Ivan
>>>>>
>>>>>
More information about the core-libs-dev
mailing list