Fixing BTrace on the Mac

Well it is time to fix another Java issue on the Mac... again... Sorry for the sarcasm. I love Java and Groovy and I love my MBP, but as already documented (on fixing Java Memory Tools and Java is a 2nd Class Citizen), these two don't get along as often as I would like. I thought for some crazy reason that I was the only one fighting this issue until all the comments from the fixing the tools article appeared. Glad to know, first that this blog is helpful to others, second that there are number of great people all over the world (offer drinks no less) and third that we are not alone in this fight.

BTrace and the issue
First... if you don't know what btrace is... you have to check it out. In the evolution of debugging tools for the jvm, it is the next big thing! Active in this space is A. Sundararajan, he has a couple of my favorite blogs, one on scripting btrace and another on jmx and btrace. Another great tutorial blog is by Igor Minar.

This blog isn't as much about btrace, as it is about fixing it on the mac. BTrace is new enough though, that it may require just a quick introduction. BTrace is a debugging tool, which injects "probes" (my term) into a running Java process. It is an open source option that has a high possibility of replacing Wily's Introscope. To be fair, Introscope provides a lot of extras which BTrace doesn't at this time... but Introscope is tens of thousands of dollars and BTrace is a free open source tool. I would be shaking in my boots if I was on the Wily team.

We will need to start a Java process in order to illustrate how it works (or in the case of the Mac... doesn't work). For the Java process look in the demo directory, there is a Java2D.jar. On the Mac it is located: /Developer/Examples/Java/JFC/Java2D. At the comand-line type: java -jar Java2D.jar. This will start up a Java process. To get it's pid at another command-line type: jps
If this is the only Java process running on your box, the pid with the jar notation is the pid you are interested in. If you want to be 100% certain type: jps -l . You'll get something like:
7897 sun.tools.jps.Jps
7838 Java2D.jar

Now in the btrace bin directory (I'm assuming you followed one of the referenced tutorials), for our example type: ./btrace 7838 ../samples/ThreadCounter.java . To which you will get:
Connection refused

In the terminal of the running Java process for the jar you would likely see:
btrace DEBUG: adding to boot classpath failed!
btrace DEBUG: java.util.zip.ZipException: error in opening zip file
java.util.zip.ZipException: error in opening zip file
at java.util.zip.ZipFile.open(Native Method)
at java.util.zip.ZipFile.(ZipFile.java:114)
at java.util.jar.JarFile.(JarFile.java:133)
at java.util.jar.JarFile.(JarFile.java:97)
at com.sun.btrace.agent.Main.main(Main.java:108)
at com.sun.btrace.agent.Main.agentmain(Main.java:66)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:323)
at sun.instrument.InstrumentationImpl.loadClassAndCallAgentmain(InstrumentationImpl.java:348)

Yea... epic fail! That is BTrace failing on the mac. If you want more details, go to the btrace script and edit -Dcom.sun.btrace.debug=false to be true. This will indicate the following stacktrace:
btrace DEBUG: debugMode is true
btrace DEBUG: dumpClasses is true
btrace DEBUG: dumpDir is .
btrace DEBUG: probe descriptor path is .
btrace DEBUG: parsed command line arguments
btrace DEBUG: System ClassPath: /System/Library/Frameworks/JavaVM.framework/Versions/1.6/Home/lib/tools.jar
btrace DEBUG: adding to boot classpath failed!
btrace DEBUG: java.util.zip.ZipException: error in opening zip file
java.util.zip.ZipException: error in opening zip file
at java.util.zip.ZipFile.open(Native Method)
at java.util.zip.ZipFile.(ZipFile.java:114)
at java.util.jar.JarFile.(JarFile.java:133)
at java.util.jar.JarFile.(JarFile.java:97)
at com.sun.btrace.agent.Main.main(Main.java:108)
at com.sun.btrace.agent.Main.agentmain(Main.java:66)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:323)
at sun.instrument.InstrumentationImpl.loadClassAndCallAgentmain(InstrumentationImpl.java:348)

The line just above the fail point... hmmm.... it is looking for a tools.jar in the $JAVA_HOME/lib directory. As already noted, Apple likes to slice and dice the JDK... In trying to understand the issue, I uncovered an article released by Apple which says there is no tools.jar file... no tools.jar file!!! It is a classes.jar file and to make it fun it isn't in the $JAVA_HOME/lib directory... no, it isn't even under a subdirectory of $JAVA_HOME... I can't even write that without frothing at the mouth. I could start a rant here... but I'm assuming I'm writing to the choir so to speak.

Fixing the Issue
I didn't spend a significant amount of time on it... but I didn't get this working by changing the btrace scripts... something is in the code. I have another recommendation towards the end that the script change wouldn't work for as well. So we are left currently with the following work around.

Take the classes.jar and copy it to the lib directory as tools.jar (argghhh!!!) but it works. To be more specific... /System/Library/Frameworks/JavaVM.framework/Versions/1.6/Classes/classes.jar to /System/Library/Frameworks/JavaVM.framework/Versions/1.6/Home/lib/tools.jar. It is important to note that you have to be sudo to make this change and you will have to do this with each Java version you want this to work with. Let's hope that the next version of BTrace will be Mac friendly!

After you get that working... checkout visualvm with the BTrace plugin. It is great stuff and another reason that the script change alone is not a total solution.

Other Issues
OMG... I'm frick'n shaving the yak again... just as I'm getting ready to post this... I was about to trace a grails app. The changes described above, break Groovy and Grails. So pick one :) You can be Groovy or you can BTrace but you can't have both yet. I guess I'll begin digging through code and send a patch tonight...

Speaking on the NFJS Tour 2009

I will be speaking at a number of shows with NFJS this year. Already scheduled is Milwaukee, St. Louis, Minneapolis, Boston, Seattle. I will likely be at Omaha, Atlanta, Denver, Columbus, and Raliegh. That's just the first several months :).

It is always around this time of the year I like to revisit my goals. Commitment comes easy around January of a new year. Around mid to end of Feb, is a good time to check to see which goals you are seriously committed to. One commitment, I've maintained for several years is a commitment to learning and a commitment to excellence. This is easier when surrounded with like-minded and committed individuals who help to hold you accountable. It isn't always easy... just worth it. That is one of the reasons I love NFJS. The caliber of the speakers are top notch and world class.

For some the economy will be a an easy excuse to not attend. Or perhaps an employer will not pay for it this year. What is clear to me is those with the skills and the networks will find it easiest to find the next opportunity. This is the time to pick up new skills. As a local venue, no show makes it easier or less expensive than NFJS.

See you there !

Intellij 8.1 with Git Support

Finally... a good java editor with good git support. I've been waiting for a long time (in internet time) for git integration in the editor. Download Intellij 8.1 for Git support.

I have a number of project demos which are already in Git. I expected that Intellij would just pick up on this fact... and it did not. I then created a new project, did a Git init from Intellij and all was good.

To get IDEA to recognize a project already in Git, under the Version Control menu, select Enable Version Control Integration, then Git.

So far... the Git integration is fantastic!!! Love it! Well done JetBrains!
Happy Coding

Java Memory Management Details

Needing to gather some details to help answer a question regarding JVM memory and the the distinctions of Perm Space. I thought it might be helpful to post the links of what I thought were incredibly great posts from the past... It is now 2009 and the best posts on this matter appear to come from 2006. Hmm.... perhaps there has been a JDK release in some time :)

On the subject of; the reason the permanent space exists. Jon explains the details of instances of objects and their dependencies on instances of classes and the need for their order as it relates to garbage collection. He also discussions the klassKlass... interesting stuff.

On the subject of String intern, XML parsing and it's effect on Perm Space. haakon or what I assume to be Jenny details the effect of String.intern() and how an out of memory can occur. She does a great job of explaining their troubleshooting approach.

And my favorite book on the JVM spec is Inside the JVM. It turns out there are free chapters of this on the web now and chapter 5 is the chapter detailing the taxonomy of the JVM memory space.

The weakest coverage of any subject based on my searches, is the subject of root sets. Brian Goetz's article on Java Theory and Practice is rock solid.

Java is a 2nd Class Citizen on MAC OSX

Having made several comments over the last several months, and in particular over the last couple of days regarding Java on the Mac, several people have asked me to explain myself. So here goes.

When I first moved to the MBP as my primary development machine, I was very pleased. As a developer, I was amazed at how all my development tools were just there. Ruby, Rails, cvs, subversion, 2 Java JDKs, it just worked out of the box.

When I first discovered the difference
I have a standard demo I use when show other developers some of the nifty debugging tools like visualgc or visualvm. In order to show the tool off, I need to start another Java process. So I standardly go to the demo directory and start the Java2d.jar. Oh but wait... where is that on the mac. This lead to the discovery that the jdk is in several different directories /locations.

JAVA_HOME = /System/Library/Frameworks/JavaVM.framework/Versions/1.6/Home
Demos: /Developer/Examples/Java/
Bin:/usr/bin/java
Headers/Lib: /Developer/SDKs/MacOSX10.5.sdk/System/Library/Frameworks/JavaVM.framework/Versions/xxx
Java Lib: /Library/Java/Extensions; /usr/lib/java
Endorsed Dirs:$JAVA_HOME/lib/endorsed
System jars: /System/Library/Frameworks/JavaVM.framework/Versions/1.6/Classes

OK... I'll live with that. I quickly discovered a very useful scipt for switch between JDKs. I've modified the original if anyone interested let me know. But since we are on the subject of being a second class citizen, If you go out to the Sun site and look for the latest jdk, the options are windows, linux, and solaris.

Other Issues in Jakarta
Then the next issue came up... jhat was broken. I wrote a lengthy blog post on how to fix this. The issue... Apple didn't include the javascript libraries, which are necessary for these tools to work.

So now I'm taking a serious look at btrace, which is a great tool. Just trying to do the simple stuff, works fine on Windows... but no joy for the Mac. I'm still looking into it, but it appears that Instrumentation..appendToSystemClassLoaderSearch() fails on the Mac. Could be something else... still looking.

If you are doing standard Java development or Groovy and Grails... you may never notice the Mac difference. When you venture into the debugging and instrumentation realm of Java be prepared for some frustrations. As I get a solution for the btrace issue I will post it.

On the positive side, I enjoy the development experience on the MBP better than my experiences on Windows and linux. The memory management is better and the startup times on Java processes is fantastic.

JSR-299 Web Bean Review

As several JCP specifications are reaching there final stages, I decided to have a look at two of them. Truth be known, I actually was going to look at one of them jsr-299, the specification previously known as web beans, here forth now known as Java Contexts and Dependency Inject. There was sufficient enough mention of ejb-lite that I decided to have a look at its specification, jsr-318.

Before I get started, my position on the subject of ejbs should be known. I actually thought that ejbs were on the way out... with the lack of testability and the extra unnecessary complexity for most projects prior to ejb3. EJB3 greatly improved this, but IMHO was too little too late. Spring + Tomcat already provided what folks were looking for. Additionally the number of clients using JSF is a dying breed. Once again, JSF 1.0 missed the boat with non-bookmarkable pages, etc. While there are shops sticking with these Sun driven standards which are produced out of the JCP, the majority of support appears to come out of vendor interest and not developer interest. My earlier work on projects with JSF led me to appreciate a couple of frameworks; 1. facelets, 2. a4jsf, and 3. SEAM (when working on jboss). jsr-299 (web beans) seems to be the formal standardization of SEAM.

My thoughts on jsr-299
It appears that @ annotations are the new shiny toy, and there is no end to specifications going crazy with them. jsr-299 defines 34 new annotations. The goal of the specification as defined on the spec home page, is to unify JSF managed bean component model with the EJB component model... well I've stated my position on this. So either this specification is too little too late and a benefit mainly to jboss, or perhaps there is something to be gained beyond this spec stated goal.

There were several interesting ideas out of the specification. The first was the creation of an extensible annotation model. So if there are not enough annotations in the world for you, you can create your own that work with the framework. This is accomplished through the new javax.inject.@BindingType. This appears to provide fine grain autowiring qualifier. One of the examples given defines
@LDAP
class LdapAuthenticator
implements Authenticator { ... }

followed by the declared injection of an LDAP Authenticator:
@LDAP Authenticator authenticator

Another interesting idea is producers... I really like the concept here. Page 3 and 4 illustrate an example where a @SessionScoped @Model Login class has a @Produces @LoggedIn User getCurrentUser() method. Abbreviated below:
@SessionScoped @Model public class Login {
@Current Credentials credentials;
@PersistenceContext EntityManager userDatabase;
private User user;

@Produces @LoggedIn User getCurrentUser() {
if (user==null) {
throw new NotLoggedInException();
} else {
return user;
}
}

Then the getCurrentUser() method is invoked for the inject as listed below:
@Model
public class DocumentEditor {
@Current Document document;
@LoggedIn User user;
@PersistenceContext EntityManager docDatabase;
public void save() {
document.setCreatedBy(currentUser);
em.persist(document);
}
}

The last interesting part of the specification is the event framework. I don't understand why this is in the specification. There appears to be no dependency for the event framework on the other parts of the specification. It doesn't comply with the stated goal of unification of JSF and EJB. It would make sense for this to be separate. Mainly to use it separate from all other aspects of web beans.

Thoughts on jsr-318
I did not review the entire specification yet. I was checking out some of the mentioned ejb-light details mentioned in jsr299. As mentioned, outside of being required by clients to help them with ejbs or ejb light projects, I'm really not interested. There is however one very interesting addition to the ejb specification, that is the @Asynchronous annotation. This is long over due. In addition to its obvious benefits, a method annotated as asynchronous can also return a value defined as java.util.concurrent.Future where V is the return value type. The return of the Future object provides the ability to check status (isDone()) or to cancel the request. Very cool. For a quick list of EJB 3.1 changes, checkout Ken Saks blog.
The concept of EJB-lite is lost on me... I already have that it is Spring.

Summary
If you are looking to stay in the world of EJBs and JSF, then these newly defined specifications are of great value to you and your shop. jsr-299 fills a number of gaps in the jee space and provides the power of Spring in a standardized way. Clearly jsr-299 will be part of the new jee 1.6 specification, at least in several of the profiles. If you are not using either JSF or EJB or nether, then it is unclear what value this brings to the community. It will be interesting to see if a vendor implements this specification (or a portion of it), in a world without JSF. It appears that the jsr-299 specification helps vendors more than it helps developers.

Windows 7 Download Frustration

The danger in posting this blog entry is that I will be counted as a anti-Microsoft person... which is just not true. I happen to like using the best tool for the job which is not all the time from Microsoft (and sometimes it is). In 2008 I switch my primary system to an Apple Mac. There were many factors as to why and frankly I love it! But I'll always be a technical junkie.

With a number of friends (such as Denny Boynton and Ted Neward) posting about their experiences with Windows 7, I thought it was time to take a look. I thought it was going to be a matter of download, get key, start up vmware fusion and I way I go... but I was wrong.

First I went to the public beta site: http://www.microsoft.com/windows/windows-7/beta-download.aspx and selected the 64-bit version in english and got this. WTF?? Repeated attempts resulted in the same. An oops page with a pre-canned search. Where did I go wrong? Well as you can tell, I'm on my Mac. So I pulled out fusion to launch Windows XP for round 2 of the attempt.

I thought this is just wrong, but determined to get a look, I switch to windows and my suspicions were confirmed when I got one page further. I got the download page with a couple of large buttons on the bottm of the page and one read "Download Now". Hey, that's what I want... I want to download now. I clicked the button and... nothing. Click... Nothing... No way... they didn't. Round 2 was in XP, but with firefox.

Round 3 as you would expect is XP with IE. That combination was successful and I'm now 29% into my download.

BTW... In the process of testing a few more times in writing up this blog, the round 1 mac failure was fixed to the point where you will get download page (nice response time msft), however the download button fails.

Why is it necessary to be like this? Why is it so hard to put up a link to a download which is platform neutral? Wouldn't Microsoft want to attract customers from other platforms? Does it always have to be all or nothing?