A. Sundararajan's Weblog

Scriptifying BTrace?

One of the issues reported with BTrace is that the trace authors have to write "verbose" code [some people say Java is "verbose"!]. In BTrace, we have to repeat the same set of imports, annotations in every btrace file and all methods have to be "public static void" and so on. Instead of inventing a new scripting language, I've added a simple C preprocessor like step in BTrace compilation. This preprocessor is based on the one in the GlueGen project. Thanks to Ken Russell for this code and for reviewing my changes specific to BTrace project. The preprocessor solution does not rule out a scripting solution in future If you have nice ideas or would like contribute in this area, you are always welcome! But, I think preprocessor solution is simple and will be useful to some.

Simple Example:


btracedefs.h
ThreadBean.java

   btrace -I . <pid-of-the-traced-process> ThreadBean.java

( Aug 08 2008, 06:36:08 PM IST ) Permalink Comments [2] | | | | |

Playing with JSqueak

Squeak is a open source implementation of Smalltalk. What is JSqueak? JSqueak is a Squeak interpreter written in Java. You can download JSqueak source code and play with it. I did the following:

• Expanded the downloaded JSqueak.zip under a directory, say c:\JSqueak.
• cd c:\JSqueak
• javac -d . *.java
• copy mini.image.gz JSqueak
• java JSqueak.Main

( Jul 25 2008, 11:37:21 AM IST ) Permalink Comments [0] | | | | |

BTrace and JMX

You can dyanamically attach BTrace to a Java process to inject trace code into it. BTrace client classescollect the trace output via a socket -- these client classes are used by BTrace command line client as well as VisualVM plugin for BTrace. How about attaching a JMX client to collect BTrace's trace data? Yes, it is possible to access a BTrace class's static fields as attributes of a MBean with this RFE.

There are two MBean samples in the BTrace repository. I attached both BTrace samples to a "Java2D demo" process. And then I attached VisualVM to view the Mbean registered by these BTrace samples:

1. ThreadCounterBean.java - this sample instruments java.lang.Thread.start() method to update a counter field. This counter field is accessible by JMX clients.
   
   

   

   
   
   
2. HistogramBean.java - this sample collects histogram of java.awt.Component objects created by an application and exposes the histogram (map) as MBean attribute.

( Jul 18 2008, 07:56:56 PM IST ) Permalink | | | | |

Working from an office -- for a change!

I work from home in Chennai, India. There is maintenance power shutdown in my part of the city today [from 9.00 AM to 5.00 PM). I'm writing this blog from a Sun office in Apeejay Business Centre, Chennai. It is nice to be in an office after quite some time - at least as a change! But, I think I'd rather prefer to avoid travel, preparation to go office etc. every day

( Jun 27 2008, 12:02:22 PM IST ) Permalink Comments [3] | | | | |

BTrace aggregations - contribution from community

If you have used DTrace, chances are that you have used aggregations. For performance issues, aggregated data is often more useful than individual data points. With BTrace, aggregating data is bit painful (you have to manage using Maps explicitly). It would be nice to have DTrace-style aggregation functions such as sum, max, min and so on. Glencross, Christian M (cited in my previous entry) has contributed code changes, doc and a sample for easy-to-use aggregation facility for BTrace. Please refer to the sample code (JdbcQueries.java) that demonstrates aggregations.

Now something unrelated to aggregations, but related to BTrace : I came to know about another use-case of BTrace. See also http://blog.igorminar.com/2008/06/btrace-dtrace-for-java.html

( Jun 26 2008, 12:28:17 PM IST ) Permalink Comments [2] | | | | |

BTrace in the real world

In the last few weeks, I came to know about two cases of real world use of BTrace.

1. Glencross, Christian M (his blog?) wrote about attempting to write a script to track SQL statements executed by a Java application (private email). Thanks to him for permitting me to blog about his BTrace script. I've made few formatting changes to fit his code in this blog and added few explanatory comments (staring with "VERBOSE:").

   
   
   import static com.sun.btrace.BTraceUtils.*;
   
   import java.sql.Statement;
   import java.util.Map;
   import java.util.concurrent.atomic.AtomicLong;
   
   import com.sun.btrace.*;
   import com.sun.btrace.annotations.*;
   
   /**
    * BTrace script to print timings for all executed JDBC statements on an event.
    * <p>
    * 
    * @author Chris Glencross
    */
   @BTrace
   public class JdbcQueries {
   
       private static Map preparedStatementDescriptions = newWeakMap();
   
       private static Map statementDurations = newHashMap();
   
       // VERBOSE: @TLS makes the field "thread local" -- sort of like using java.lang.ThreadLocal
       @TLS
       private static String preparingStatement;
   
       @TLS
       private static long timeStampNanos;
   
       @TLS
       private static String executingStatement;
   
       /**
        * If "--stack" is passed on command line, print the Java stack trace of the JDBC statement.
        *
        * VERBOSE: Command line arguments to BTrace are accessed as $(N) where N is the command line arg position.
        * 
        * Otherwise we print the SQL.
        */
       private static boolean useStackTrace = $(2) != null && strcmp("--stack", $(2)) == 0;
   
       // The first couple of probes capture whenever prepared statement and callable statements are
       // instantiated, in order to let us track what SQL they contain.
   
       /**
        * Capture SQL used to create prepared statements.
        *
        * VERBOSE: +foo in clazz means foo and it's subtypes. Note the use of regular expression
        * for method names. With that BTrace matches all methods starting with "prepare". The
        * type "AnyType" matches any Java type.
        * 
        * @param args - the list of method parameters. args[1] is the SQL.
        */
       @OnMethod(clazz = "+java.sql.Connection", method = "/prepare.*/")
       public static void onPrepare(AnyType[] args) {
           preparingStatement = useStackTrace ? jstackStr() : str(args[1]);
       }
   
       /**
        * Cache SQL associated with a prepared statement.
        *
        * VERBOSE: By default, @OnMethod matches method entry points. Modifying with @Location 
        * annotation to match the method return points.
        * 
        * @param arg - the return value from the prepareXxx() method.
        */
       @OnMethod(clazz = "+java.sql.Connection", method = "/prepare.*/", location = @Location(Kind.RETURN))
       public static void onPrepareReturn(AnyType arg) {
           if (preparingStatement != null) {
               print("P"); // Debug Prepared
               Statement preparedStatement = (Statement) arg;
               put(preparedStatementDescriptions, preparedStatement, preparingStatement);
               preparingStatement = null;
           }
       }
   
       // The next couple of probes intercept the execution of a statement. If it execute with no-args,
       // then it must be a prepared statement or callable statement. Get the SQL from the probes up above.
       // Otherwise the SQL is in the first argument.
   
       @OnMethod(clazz = "+java.sql.Statement", method = "/execute.*/")
       public static void onExecute(AnyType[] args) {
           timeStampNanos = timeNanos();
           if (args.length == 1) {
               // No SQL argument; lookup the SQL from the prepared statement
               Statement currentStatement = (Statement) args[0]; // this
               executingStatement = get(preparedStatementDescriptions, currentStatement);
           } else {
               // Direct SQL in the first argument
               executingStatement = useStackTrace ? jstackStr() : str(args[1]);
           }
       }
   
       @OnMethod(clazz = "+java.sql.Statement", method = "/execute.*/", location = @Location(Kind.RETURN))
       public static void onExecuteReturn() {
   
           if (executingStatement == null) {
               return;
           }
   
           print("X"); // Debug Executed
   
           long durationMicros = (timeNanos() - timeStampNanos) / 1000;
           AtomicLong ai = get(statementDurations, executingStatement);
           if (ai == null) {
               ai = newAtomicLong(durationMicros);
               put(statementDurations, executingStatement, ai);
           } else {
               addAndGet(ai, durationMicros);
           }
   
           executingStatement = null;
       }
   
       // VERBOSE: @OnEvent probe fires whenever BTrace client sends "event" command.
       // The command line BTrace client sends BTrace events when user pressed Ctrl-C 
       // (more precisely, on receiving SIGINT signal)
       @OnEvent
       public static void onEvent() {
           println("---------------------------------------------");
           printNumberMap("JDBC statement executions / microseconds:", statementDurations);
           println("---------------------------------------------");
       }
   
   }
   
   

   And he has expressed few wish lists for BTrace based on his experience with DTrace. We plan to investigate those items in near future.

   
   
   
2. Binod P.G exchanged private e-mails about BTrace usage to track down a memory leak. Subsequently, he has blogged about the same.

( Jun 16 2008, 09:42:17 AM IST ) Permalink Comments [2] | | | | |

BTrace JavaOne2008 BOF slides..

I received emails asking for BTrace BOF (JavaOne-2008) slides. Better late than never... I've uploaded PDF of the slides. The BOF was mostly around demos -- slides do not contain much. But, slides have few pointers that may be useful.

( May 28 2008, 02:01:06 PM IST ) Permalink Comments [4] | | | | |

Thursday May 8, JavaOne

Here are the few highlights from the talks that I attended today:

( May 09 2008, 08:56:14 PM IST ) Permalink | | | | |

Wednesday May 7, JavaOne

Today Bill, Chihiro, Jaya and I talked on Blu-ray. The talk was centered around the open source project @ http://hdcookbook.dev.java.net - a library and a set of tools to build Blu-ray discs. If you haven't checked out code/docs, you may want to checkout and play with the code. All you need is a laptop with blu-ray drive and a BD-RE disc. Optionally, for added fun you may want to have a hardware bluray player such as PS3 -- so that you can see the output on your TV rather than on a laptop. Other than the session, we also had a very informal BOF on blu-ray, OCAP etc. during the evening. It is good to meet experts in respective technologies in one place!

Other than the the blu-ray stuff, I did attend other talks/BOF. Just after Blu-ray session, I attended "TS-6000 Improving Application Performance with Monitoring and Profiling Tools" talk. This talk was about OS specific tools, JDK tools and third-party tools for profiling and monitoring. Gregg Sporar and Jaroslav Bachorik (NetBeans Profiler team) presented very well. There were many interesting questions/discussions as well. If you haven't done so already, you may want to download VisualVM. If you want bit more fun doing monitoring/profiling, you may want to check out the sources from http://visualvm.dev.java.net and build it yourself. You can build BTrace VisualVM plugin using the command:

    c:\visualvm\plugins>ant build

    c:\visualvm\plugins>ant -Dbtrace.home=c:\btrace build

    c:\visualvm\plugins>ant -Dbtrace.home=c:\btrace run

I attended and liked the "Class Loader Rearchitected (BOF-6180)" BOF. If you have ever written class loaders, chances are that you have faced mysterious deadlocks or ClassCastException that said "ClassCastException: Foo cannot be cast to Foo" or having to decide between overriding loadClass and findclass, you probably should have attended this talk and gave your opinions/suggestions/ideas If I understood properly, I think there was a suggestion to add class loader info. to the ClassCastException (something like class-loader-class-name@identity-HashCode style string?) so that one can quickly see it is a class loader issue. Also, there were many questions on loading classes from jar files. Looks like there will be changes to class loader API and class loading in VM for JDK 7.

( May 08 2008, 08:28:58 PM IST ) Permalink | | | | |

Tuesday May 6, JavaOne

In today's sessions that I attended I liked the following:

JRuby: Why, What, How... Do It Now

This talk is a good introduction to (J)Ruby the language and important applications of (J)Ruby. And many pointers to related (J)Ruby sessions. Nice summary!

JavaScript programming language: The Language Everybody Loves to Hate

great talk by Roberto Chinnici. Nice summary of functional and prototype-based object orientation aspects of JavaScript. You can easily impress your friends will some neat snippets of JavaScript You may want to continue the fun by reading Doug Crockford's pages, if you have not do already!

At 7.30 PM, we (I and Kannan) talked about BTrace. There were many interesting questions/discussions -- both during and after the BOF! Today (Wed May 7) will be a Blu-ray day -- it starts with TS-5449 Java Technology for Blu-ray and TV: Creating your own Blu-ray Java Discs session. It is about the open source project @ http://hdcookbook.dev.java.net. Meet you all there!

( May 07 2008, 07:52:02 PM IST ) Permalink | | | | |

JVM Languages @ JavaOne 2008

In JavaOne 2008, there are many intesting sessions on "other" JVM languages covering both dynamically typed languages (JavaScript, Groovy, JRuby) and statically typed languages (JavaFX, Scala). As usual, there are many sessions covering application aspects -- like using scripting on Glassfish, Grials (Groovy), Rails (JRuby) and so on. But, my interest is mostly on the programming language aspects and JVM implementation issues. Here is a table of sessions covering those:

( Apr 30 2008, 10:54:42 AM IST ) Permalink | | | | |

BTrace BOF @ JavaOne 2008

We have a BOF on BTrace in this year's JavaOne. But, you will not find the name "BTrace" in session title -- that is because talk was submitted before BTrace was open sourced with that name The details of the BOF is as below. Please visit and let us discuss on dynamic tracing for Java.

( Apr 29 2008, 01:27:31 PM IST ) Permalink Comments [1] | | | | |

Groovy jsr-223 engine updated..

Groovy jsr-223 script engine @ scripting.dev.java.net has been updated to use Groovy version 1.5.6.

( Apr 29 2008, 08:21:13 AM IST ) Permalink | | | | |

Bluray @ JavaOne 2008

If you want to learn more about Blu-ray disc and what Java has to do with it, you may want to attend the following talks/BOFs @ JavaOne 2008!

From our group talk (TS-5449), we will be focusing on the open source project @ https://hdcookbook.dev.java.net. Meet you soon @ JavaOne !!

( Apr 28 2008, 06:35:19 PM IST ) Permalink | | | | |

BTrace - a dynamic tracing tool for Java

Are you interested in a byte code instrumentation (BCI) based dynamic tracing solution for the Java platform? If so, please visit https://btrace.dev.java.net. BTrace is a safe, dynamic tracing solution for Java. You can express tracing code in Java and run it against a running Java application. Your Java application should be running on JDK 6 or above for BTrace to work. You may be using VisualVM, the all-in-one Java troubleshooting tool. VisualVM supports plugin model to extend it's capabilities. BTrace plugin for VisualVM will be available soon. When BTrace plugin is available, you can trace your application from VisualVM tool. In the meanwhile, you can use BTrace command line tools. You may want to check out the user guide for the command line access.

( Mar 07 2008, 06:47:34 PM IST ) Permalink Comments [8] | | | | |