On Fri, May 23, 2008 at 7:17 PM, sebb <[EMAIL PROTECTED]> wrote: > On 23/05/2008, Niall Pemberton <[EMAIL PROTECTED]> wrote: >> On Fri, May 23, 2008 at 4:51 PM, sebb <[EMAIL PROTECTED]> wrote: >> > On 23/05/2008, Niall Pemberton <[EMAIL PROTECTED]> wrote: >> >> On Fri, May 23, 2008 at 3:31 PM, Luc Maisonobe <[EMAIL PROTECTED]> wrote: >> >> > Niall Pemberton a écrit : >> >> >> On Thu, May 22, 2008 at 9:35 PM, Luc Maisonobe <[EMAIL PROTECTED]> >> wrote: >> >> >>> A few comments on this release. >> >> >>> >> >> >>> Typo in the project description in the pom.xml file: replace >> >> >>> "implmentation" with "implementation". >> >> >>> >> >> >>> Extracting files from the commons-chain-1.2-src.tar.gz archive in a >> >> >>> Linux box leads to an all lower case file name for >> "license-header.txt", >> >> >>> which leads to an error when running "mvn site". Some plugin >> requires a >> >> >>> mixed case LICENSE-header.txt. >> >> >> >> >> >> Thanks, I fixed the typo and checkstyle config in the trunk: >> >> >> http://svn.apache.org/viewvc?view=rev&revision=659361 >> >> >> >> >> >> Anyone think we need a new RC for this? >> >> > >> >> > No, it is really minor. >> >> > >> >> >> >> >> >>> There are 39 findbugs errors. They don't seem too important. Many >> are >> >> >>> serialization related (missing serialVersionUID, transient fields) >> and >> >> >>> many are style related (redeclaration of interfaces from >> superclass). I >> >> >>> think the errors in ContextBase and web.ChainListener are false >> >> >>> positive. The MTIA_SUSPECT_SERVLET_INSTANCE_FIELD may be more >> >> >>> problematic, I know nothing about servlets so cannot judge this. I'm >> >> >>> attaching the findbug.html report file to this message. >> >> >> >> >> >> I don't see it attached - also I added findbugs to the pom and ran it >> >> >> and didn't see such an error >> >> >> http://svn.apache.org/viewvc?view=rev&revision=659363 >> >> > >> >> > Ooops. I forgot to join the page. Here it is. It was generated by >> >> > version 1.1.1 of the findbugs plugin, and the class files were >> compiled >> >> > with SunJDK 1.6 on a linux box. >> >> >> >> >> >> Maybe its getting removed by the mailing list, because I still don't >> >> see it. I tried changing the version to 1.1.1 of findbugs and used JDK >> >> 1.6 - but I still don't see it. AnywayI looked up that error here: >> >> >> >> >> http://findbugs.sourceforge.net/bugDescriptions.html#MTIA_SUSPECT_SERVLET_INSTANCE_FIELD >> >> >> >> ...so I guess it must be referring to these fields: >> >> >> http://people.apache.org/~niallp/chain_1_2_RC2/site/xref/org/apache/commons/chain/web/servlet/ChainProcessor.html#94 >> >> >> >> In thoses cases then this warning is not an issue - since its fine for >> >> all threads to use the same instance variables - three are just the >> >> names of attributes configured for the servlet. CatalogFactory is a >> >> singleton-per-ClassLoader and one instance should be shared by all >> >> threads for the servlet instance. Looking at the code I believe it >> >> "caches" the factory in the servlet to avoid the *synchronized* lookup >> >> in CatalogFactory.getInstance(): >> >> >> > >> > If the same instance is used by multiple threads, then any instance >> > variables need to be either final, volatile or synchronized. >> >> >> I don't think so in this case. These are *private* variables that are >> set up by the Servlet when it is intialized[1] and removed when it >> shut down[2] - these are the only times they're changed and are not >> accesible by multiple threads. Once the servlet is intialialized then >> they are *read* by multiple threads[3] as each request is processed. >> So this is the case of *set-once* in a *thread-safe* manner and then >> unchangable. >> > > The JVM does not guarantee that values written to an instance variable > in one thread will be visible to another thread unless the variables > are final, volatile or protected by synch. using the *same* lock in > both threads. Both the writer *and reader* must synch. on the same > lock.
This really isn't an issue. The servlet container manages the lifecycle of these objects and doesn't allow any threads to access the service() method until initialization is complete. I didn't write this code - it was written by Craig McClanahan[1] who among other things wrote a large part of Tomcat 4 and invented Struts 1. Struts 1's ActionServlet did this as well - since 2000 - the most popular web framework ever - and believe me if it had been an issue, it would have come up. [1] http://svn.apache.org/viewvc?view=rev&revision=142828 Niall > I know it seems strange and counter-intuitive, but the Java memory > model allows threads to cache variables in registers and use various > other techniques for performance reasons. > > Without synchronization, all one can say is that the values seen by > the reader thread will be either the default value or the value > written by the writer thread. > > Though even that may not be true: > if there are two writer threads updating a long or double value > without synch. it is possible that a different thread will see a value > made up of 32 bits set by one thread and 32 bits by another. This > cannot happen here because there is only one thread writing the > variables. > > For the details, I can thoroughly recommend Java Concurrency in Practice. > > Also: > http://today.java.net/pub/a/today/2004/04/13/JSR133.html > >> Niall >> >> [1] >> http://people.apache.org/~niallp/chain_1_2_RC2/site/xref/org/apache/commons/chain/web/servlet/ChainProcessor.html#145 >> [2] >> http://people.apache.org/~niallp/chain_1_2_RC2/site/xref/org/apache/commons/chain/web/servlet/ChainProcessor.html#131 >> [3] >> http://people.apache.org/~niallp/chain_1_2_RC2/site/xref/org/apache/commons/chain/web/servlet/ChainProcessor.html#175 >> >> >> > Without one of these, there is no guarantee of memory visibility - >> > thread A can set the value of "catalog" and thread B may never see >> > it. >> > >> >> >> http://people.apache.org/~niallp/chain_1_2_RC2/site/xref/org/apache/commons/chain/CatalogFactory.html#178 >> >> >> >> So if I'm looking at the right place then I don't believe this is an >> >> issue - if I'm not looking in the right place then please point me to >> >> the line number(s) your findbugs report is showing in the rc2 xref: >> >> http://people.apache.org/~niallp/chain_1_2_RC2/site/xref/index.html >> >> >> >> Thanks >> >> >> >> >> >> Niall >> >> >> >> >> >> > Luc >> >> >> >> >> >> Niall >> >> >> >> >> >>> I don't cast any vote now, waiting for more knowledgeable people to >> look >> >> >>> at these servlet issues. >> >> >>> >> >> >>> Luc >> >> >>> >> >> >>> Oliver Heger wrote: >> >> >>>> +1 >> >> >>>> >> >> >>>> Oliver >> >> >>>> >> >> >>>> Niall Pemberton wrote: >> >> >>>>> The main changes since RC1 are that the ant build now works on >> JDK 1.3 >> >> >>>>> and the Logging dependency has been upgraded to the latest 1.1.1 >> >> >>>>> >> >> >>>>> The artifacts are here: >> >> >>>>> http://people.apache.org/~niallp/chain_1_2_RC2/ >> >> >>>>> >> >> >>>>> SVN Tag: >> >> >>>>> >> http://svn.apache.org/viewvc/commons/proper/chain/tags/CHAIN_1_2_RC2/ >> >> >>>>> >> >> >>>>> Site: >> >> >>>>> http://people.apache.org/~niallp/chain_1_2_RC2/site/ >> >> >>>>> (note m2 generates relative links, so some don't work - but the >> site >> >> >>>>> is for info and not included in the release artifacts) >> >> >>>>> >> >> >>>>> Release Notes: >> >> >>>>> http://people.apache.org/~niallp/chain_1_2_RC2/RELEASE-NOTES.txt >> >> >>>>> >> http://people.apache.org/~niallp/chain_1_2_RC2/site/changes-report.html >> >> >>>>> >> >> >>>>> RAT Report: >> >> >>>>> >> http://people.apache.org/~niallp/chain_1_2_RC2/site/rat-report.html >> >> >>>>> >> >> >>>>> CLIRR Report: >> >> >>>>> >> http://people.apache.org/~niallp/chain_1_2_RC2/site/clirr-report.html >> >> >>>>> >> >> >>>>> RC2 has been built with m2 - but m1 and ant builds are available >> - details here: >> >> >>>>> http://people.apache.org/~niallp/chain_1_2_RC2/site/building.html >> >> >>>>> >> >> >>>>> Note: Chain is targetted at JDK 1.3, but I built with JDK 1.5 >> because >> >> >>>>> of the issue with m2 and JDK 1.4 - but I have tested on JDK 1.3 >> and >> >> >>>>> JDK 1.4 using m1 & ant and JDK 1.5 and JDK 1.6 using m2 >> >> >>>>> >> >> >>>>> Vote is open for 72 hours >> >> >>>>> >> >> >>>>> Thanks in advance for your feedback/votes. >> >> >>>>> >> >> >>>>> Niall >> >> >>>>> >> -------------------------------------------------------------------------------------------------------------> >> >> >>>>> >> >> >>>>> [ ] +1 I support this release >> >> >>>>> [ ] +0 I am OK with this release >> >> >>>>> [ ] -0 OK, but.... >> >> >>>>> [ ] -1 I do not support this release >> >> >>>>> >> >> >>>>> >> --------------------------------------------------------------------- >> >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: [EMAIL PROTECTED] >> For additional commands, e-mail: [EMAIL PROTECTED] >> >> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
