I just got back from my first ever FOSDEM where I spent half my time at the Universite Libre de Bruxelles in the Free Java room hearing some of the latest and finest scoops on free open source Java. The other half of my time was spent in Brussels' old town sampling some of the earliest and finest beers known to mankind. The Java talks were of a very high standard and very entertaining and the questions and answers revealed just how sharp the audience were. As for the beer, well after a Delirium Tremens and several Kasteel Reds at Delirium Cafe it did not seem that life could get any better.
On Saturday just before heading off for the dinner and then on to A La Mort Subite I gave a talk about Byteman to the assembled Java gurus. Heiko Rupp (JBoss RHQ/JON) was in the audience filming. So, (many) thanks to him you can watch the talk as well as download the slides. The links are also posted on the Byteman docs page along with all the other talks and papers from the last few years.
I was immensely surprised, amused and delighted when on Sunday Karl Helgason included an extra off the cuff demo into his talk on his exceptionally clever MIDI synthesizer project Gervill. Karl was very taken with my Byteman demo and was determined to find a way to apply it. So, after dinner on Saturday night he stayed up late reading the Byteman Programmer's Guide and then proceeded to implement a demo which used Byteman to show off Gervill.
Karl injected Byteman rules into implementations of the add, get and remove methods for interface List so that a note or drumbeat was triggered each time they were called. The rule used the integer index argument either to pitch the note or to select the drum to beat. He ran up Tomcat on OpenJDK and after about 3 seconds of intense cacophony summarised the ensuing calm with the single word "bootstrapped".
Karl proceeded to demo his own musical virtuosity, raising laughs from the whole room as he turned the Web GUI into an instrument simply by clicking on its icons and controls. This included zithering the mouse up and down the icons in the title bar which provided a perfectly pitched rising and falling scale. I don't think anyone has ever provided a better example of Tomcat's scalability, performance and fine-tuning.
Wednesday, 8 February 2012
Tuesday, 10 January 2012
Byteman 2.0.0 Released
Byteman 2.0.0 has been released. It includes a small number of bug fixes and new features and is available from the Byteman download page. If you are using Byteman from maven then the jars are available via the JBoss repository.
The release is accompanied by part two of the Byteman tutorial series, Fault Injection Testing With Byteman.
The release is accompanied by part two of the Byteman tutorial series, Fault Injection Testing With Byteman.
Monday, 9 January 2012
Byteman Squashes Drools Bug
Martin Vecera is a senior member of our JBoss QE staff and one the Byteman project power users. He recognised Byteman's potential in its very early days and has provided valuable feedback during its development and been the project evangelist to our QE team. Martin has written up a very nice example of using Byteman for debugging and diagnosing a problem in Drools.
Using a conventional debugger is infeasible when a program repeatedly invokes the routine you want to investigate inside a long-running control loop. Product trace can help in such circumstances but it often fails because switching it on produces far more data than you actually need and does not always print the information you actually want to see.
So, Martin injected a simple Byteman rule into precisely the calls he is interested in and used a helper class to dump the critical data to a file in exactly the format he wants. Using Byteman he was able to inject the specific, controlled tracing behaviour he needed just where he needed it with out incurring any extra overheads. Enjoy.
Using a conventional debugger is infeasible when a program repeatedly invokes the routine you want to investigate inside a long-running control loop. Product trace can help in such circumstances but it often fails because switching it on produces far more data than you actually need and does not always print the information you actually want to see.
So, Martin injected a simple Byteman rule into precisely the calls he is interested in and used a helper class to dump the critical data to a file in exactly the format he wants. Using Byteman he was able to inject the specific, controlled tracing behaviour he needed just where he needed it with out incurring any extra overheads. Enjoy.
Monday, 3 October 2011
Byteman 1.6.0 Released
Byteman 1.6.0 has been released and can be downloaded
from the Byteman download page
or
via the JBoss maven repository
Byteman 1.6.0 is a patch release which fixes a small number of bugs. The main point of interest is that Byteman can now be used on JDK6 and JDK7.
from the Byteman download page
or
via the JBoss maven repository
Byteman 1.6.0 is a patch release which fixes a small number of bugs. The main point of interest is that Byteman can now be used on JDK6 and JDK7.
Thursday, 4 August 2011
Byteman now gitted and mavenized
The Byteman source code has been moved to github and the build process has been converted to maven. Both of these changes have been made in order to make it easier for other developers to make contributions to the Byteman project or build extra capabilities on top of Byteman.
Monday, 16 May 2011
Byteman Demo at JUDCon
I just got back online after a couple of weeks holiday following the Byteman talk at JUDCon in Boston. JUDCon is the part of Red Hat's JBossWorld/Summit conference where JBoss/Java tecchies get together to present all the neat things they have invented over the last 6 months/year. So, of course, one of the neat things on the agenda was Byteman.
The presentation was very well received and there were lots of interesting questions during and after the talk. A pdf is available from the Byteman docs page. The presentation included a small demo which showed some Byteman rules being injected into a simple Quartz timer bean stolen from one the JBoss EAP5 EJB tutorial. Like all demos it is slightly artificial but it does show just how simple it is to run up Byteman and introduce timing constraints into a threaded application. Since the demo was not recorded I'll present the code example here and show the demo output for those who missed the talk.
The Demo Code
The example code used in the demo displays the Quartz timer capability provided as part of the standard JBoss app server release. The original example was coded for EAP5 but I actually ran it quite happily on AS 6. To avoid introducing too much clutter into the demo output I modified the example code so that only the annotated Quartz timer bean is deployed. Here is the definition I used for the bean:
Running The Demo
The bean is deployed by starting up JBoss AS and then running 'ant' in subdirectory jca_inflow_quartz of the downloaded tutorial code. Here's the output you get when the bean is deployed into JBoss AS 6.
The Byteman Rules
The Byteman demo uses two rules defined as follows:
The first rule is attached to the constructor method for the timer bean class (<init> is the internal name used by the JVM for a constructor method). It is triggered when an instance of the timer bean class is created just before the constructor method returns. The rule uses the standard Byteman built-in operation createRendezvous to create a rendezvous identified using the String "quartz". The call to isRendezvous in the condition ensures that only one rendezvous is ever created.
A rendezvous is used to introduce a synchronization point for some given number of threads (a rendezvous is also commonly referred to as a barrier). Any thread which attempts to enter the rendezvous may be suspended until the required number of threads has arrived. Once the required number of threads have entered all of them are released and allowed to continue past the rendezvous call. In this case the rendezvous count is supplied by the second argument, 3.
Normally when a rendezvous has been met by all the required threads it gets deleted. Any thread which subsequently tries to enter the rendezvous just continues without suspending. The 3rd boolean argument true supplied in the create call makes this a repeatable rendezvous. So, after 3 threads arrive the rendezvous is reinstated allowing a further 3 threads to meet and so on.
The second rule is injected at the start of the timer bean callback method execute and it is this rule which makes the timer threads enter the rendezvous. The condition ensures the rule only fires if the rendezvous is present. The first statement in the rule action is a call to builtin operation traceln which prints a message to System.out saying the thread is entering the rendezvous. The second call to traceln prints a String created by pasting together the prefix "exit *** " and the integer value returned by calling built-in method rendezvous. This printout will not be executed until the call to rendezvous returns.
So, when the first timer callback is created the timer thread will print the enter message, call rendezvous and suspend. 5 seconds later Quartz creates a new thread to run the second callback and this also prints the enter message then calls rendezvous and suspends. 5 seconds later the 3rd callback thread prints its enter message and calls rendezvous. All 3 threads are released and they all print the exit message. The return value is either 0, 1 or 2 depending upon which thread arrived in which order. All 3 threads go on to execute the body of the callback and exit. 5 seconds later the whole cycle starts again.
Running the Demo With Byteman
This time after booting up AS 6 we load the agent into the app server and then load the rule script. The rules need to be loaded before the quartz bean is created so that the <init> rule is in place before the timer bean is created. The agent can be loaded on the JVM command line but it is easier to start up AS 6 and then load the agent once the app server is running.
The script bminstall.sh uploads the byteman agent into a running JVM. You can specify which JVM by supplying as argument either its process id or, as in this case, the name of the application class providing the JVM entry point.
The agent can now be talked to using script bmsubmit.sh. If we provide it with the name of the rule script file as an argument it will upload rules into the JVM ready for injection into the classes mentioned in the rules.
If we now execute bmsubmit.sh with no arguments it will show us that the rules are loaded but not yet injected. This is because the classes they apply to have not yet been deployed It is possible to install rules into classes which have already been loaded into the JVM but in this case we want to trigger the <init> rule when the timer bean is created. That will happen during loading so we need to install the rules before deploying the application.
The listing from the agent shows that the rules are in place. When we deploy the app they get injected into the bean code as it is loaded. The rendezvous gets created and the subsequent timer thread output is delayed until a group of 3 threads have arrived at the rendezvous. The next 3 threads are also grouped and so on.
At this point if we run the submit script with no arguments we can see that the rules have been injected into the target methods. The listing now shows the class and method the rule was injected into and the classloader which loaded the rule. It also indicates that the rule was injected, type-checked and compiled correctly.
We can run the script again with the -u flag to remove the rules.
We now see that the injected code is removed, the timer bean reverts to its normal behaviour and once again the messages start being printed every 5 seconds.
The presentation was very well received and there were lots of interesting questions during and after the talk. A pdf is available from the Byteman docs page. The presentation included a small demo which showed some Byteman rules being injected into a simple Quartz timer bean stolen from one the JBoss EAP5 EJB tutorial. Like all demos it is slightly artificial but it does show just how simple it is to run up Byteman and introduce timing constraints into a threaded application. Since the demo was not recorded I'll present the code example here and show the demo output for those who missed the talk.
The Demo Code
The example code used in the demo displays the Quartz timer capability provided as part of the standard JBoss app server release. The original example was coded for EAP5 but I actually ran it quite happily on AS 6. To avoid introducing too much clutter into the demo output I modified the example code so that only the annotated Quartz timer bean is deployed. Here is the definition I used for the bean:
@MessageDriven(activationConfig =
{@ActivationConfigProperty(propertyName =
"cronTrigger", propertyValue = "0/5 * * * * ?")})
@ResourceAdapter("quartz-ra.rar")
public class AnnotatedQuartzMDBBean implements Job
{
private static final Logger log =
Logger.getLogger(AnnotatedQuartzMDBBean.class);
public void
execute(JobExecutionContext jobExecutionContext)
throws JobExecutionException
{
AnnotatedQuartzMDBBean.log.info("************** here in annotated!!!!");
}
}
Running The Demo
The bean is deployed by starting up JBoss AS and then running 'ant' in subdirectory jca_inflow_quartz of the downloaded tutorial code. Here's the output you get when the bean is deployed into JBoss AS 6.
[adinn@localhost adinn]$ $JBOSS_HOME/bin/run.sh
=========================================================================
JBoss Bootstrap Environment
JBOSS_HOME: /home/adinn/jboss/jbossas/jboss-6.0.0.Final
. . .
[6.0.0.Final "Neo"] Started in 22s:617ms
06:12:27,678 INFO [org.jboss.ejb3.deployers.Ejb3DependenciesDeployer] Encountered deployment AbstractVFSDeploymentContext@1809001556{vfs:///ssd/home/adinn/jboss/jbossas/jboss-6.0.0.Final/server/default/deploy/jboss-ejb3-tutorial-jca_inflow_quartz.jar}
. . .
06:12:27,748 INFO [org.jboss.ejb3.deployers.JBossASKernel] Added bean(jboss.j2ee:jar=jboss-ejb3-tutorial-jca_inflow_quartz.jar,name=AnnotatedQuartzMDBBean,service=EJB3) to KernelDeployment of: jboss-ejb3-tutorial-jca_inflow_quartz.jar
06:12:27,800 INFO [org.jboss.ejb3.EJBContainer] STARTED EJB: org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean ejbName: AnnotatedQuartzMDBBean
06:12:30,083 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
06:12:35,010 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
06:12:40,004 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
06:12:45,006 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
06:12:50,004 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
06:12:52,923 INFO [org.jboss.ejb3.EJBContainer] STOPPED EJB: org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean ejbName: AnnotatedQuartzMDBBean
06:12:52,948 INFO [org.jboss.ejb3.instantiator.deployer.BeanInstantiatorDeployerBase] Uninstalled org.jboss.ejb3.instantiator.impl.Ejb31SpecBeanInstantiator@2f385f78 from MC at org.jboss.ejb.bean.instantiator/jboss-ejb3-tutorial-jca_inflow_quartz/jboss-ejb3-tutorial-jca_inflow_quartz/AnnotatedQuartzMDBBean
The Byteman Rules
The Byteman demo uses two rules defined as follows:
RULE set up rendezvous
CLASS AnnotatedQuartzMDBBean
METHOD <init>
AT EXIT
IF NOT isRendezvous("quartz", 3)
DO createRendezvous("quartz", 3, true)
ENDRULE
RULE delay quartz bean
CLASS AnnotatedQuartzMDBBean
METHOD execute
AT ENTRY
IF isRendezvous("quartz", 3)
DO traceln("**** enter quartz rendezvous ");
traceln("*** exit " + rendezvous("quartz"));
ENDRULE
The first rule is attached to the constructor method for the timer bean class (<init> is the internal name used by the JVM for a constructor method). It is triggered when an instance of the timer bean class is created just before the constructor method returns. The rule uses the standard Byteman built-in operation createRendezvous to create a rendezvous identified using the String "quartz". The call to isRendezvous in the condition ensures that only one rendezvous is ever created.
A rendezvous is used to introduce a synchronization point for some given number of threads (a rendezvous is also commonly referred to as a barrier). Any thread which attempts to enter the rendezvous may be suspended until the required number of threads has arrived. Once the required number of threads have entered all of them are released and allowed to continue past the rendezvous call. In this case the rendezvous count is supplied by the second argument, 3.
Normally when a rendezvous has been met by all the required threads it gets deleted. Any thread which subsequently tries to enter the rendezvous just continues without suspending. The 3rd boolean argument true supplied in the create call makes this a repeatable rendezvous. So, after 3 threads arrive the rendezvous is reinstated allowing a further 3 threads to meet and so on.
The second rule is injected at the start of the timer bean callback method execute and it is this rule which makes the timer threads enter the rendezvous. The condition ensures the rule only fires if the rendezvous is present. The first statement in the rule action is a call to builtin operation traceln which prints a message to System.out saying the thread is entering the rendezvous. The second call to traceln prints a String created by pasting together the prefix "exit *** " and the integer value returned by calling built-in method rendezvous. This printout will not be executed until the call to rendezvous returns.
So, when the first timer callback is created the timer thread will print the enter message, call rendezvous and suspend. 5 seconds later Quartz creates a new thread to run the second callback and this also prints the enter message then calls rendezvous and suspends. 5 seconds later the 3rd callback thread prints its enter message and calls rendezvous. All 3 threads are released and they all print the exit message. The return value is either 0, 1 or 2 depending upon which thread arrived in which order. All 3 threads go on to execute the body of the callback and exit. 5 seconds later the whole cycle starts again.
Running the Demo With Byteman
This time after booting up AS 6 we load the agent into the app server and then load the rule script. The rules need to be loaded before the quartz bean is created so that the <init> rule is in place before the timer bean is created. The agent can be loaded on the JVM command line but it is easier to start up AS 6 and then load the agent once the app server is running.
[adinn@localhost jca_inflow_quartz]$ ${BYTEMAN_HOME}/bin/bminstall.sh org.jboss.Main
[adinn@localhost jca_inflow_quartz]$
The script bminstall.sh uploads the byteman agent into a running JVM. You can specify which JVM by supplying as argument either its process id or, as in this case, the name of the application class providing the JVM entry point.
The agent can now be talked to using script bmsubmit.sh. If we provide it with the name of the rule script file as an argument it will upload rules into the JVM ready for injection into the classes mentioned in the rules.
[adinn@localhost jca_inflow_quartz]$ ${BYTEMAN_HOME}/bin/bmsubmit.sh rules.btm
install rule set up rendezvous
install rule delay quartz bean
[adinn@localhost jca_inflow_quartz]$
If we now execute bmsubmit.sh with no arguments it will show us that the rules are loaded but not yet injected. This is because the classes they apply to have not yet been deployed It is possible to install rules into classes which have already been loaded into the JVM but in this case we want to trigger the <init> rule when the timer bean is created. That will happen during loading so we need to install the rules before deploying the application.
[adinn@localhost jca_inflow_quartz]$ ${BYTEMAN_HOME}/bin/bmsubmit.sh
# File rules.btm line 13
RULE delay quartz bean
CLASS AnnotatedQuartzMDBBean
METHOD execute
AT ENTRY
IF isRendezvous("quartz", 3)
DO traceln("**** enter quartz rendezvous ");
traceln("*** exit " + rendezvous("quartz"));
ENDRULE
# File rules.btm line 5
RULE set up rendezvous
CLASS AnnotatedQuartzMDBBean
METHOD <init>
AT EXIT
IF NOT isRendezvous("quartz", 3)
DO createRendezvous("quartz", 3, true)
ENDRULE
[adinn@localhost jca_inflow_quartz]$
The listing from the agent shows that the rules are in place. When we deploy the app they get injected into the bean code as it is loaded. The rendezvous gets created and the subsequent timer thread output is delayed until a group of 3 threads have arrived at the rendezvous. The next 3 threads are also grouped and so on.
07:00:44,028 INFO [org.jboss.bootstrap.impl.base.server.AbstractServer] JBossAS [6.0.0.Final "Neo"] Started in 23s:706ms
07:00:59,209 INFO [org.jboss.ejb3.deployers.Ejb3DependenciesDeployer] Encountered deployment AbstractVFSDeploymentContext@1865896779{vfs:///ssd/home/adinn/jboss/jbossas/jboss-6.0.0.Final/server/default/deploy/jboss-ejb3-tutorial-jca_inflow_quartz.jar}
. . .
07:00:59,334 INFO [org.jboss.ejb3.EJBContainer] STARTED EJB: org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean ejbName: AnnotatedQuartzMDBBean
07:01:00,192 INFO [STDOUT] **** enter quartz rendezvous
07:01:05,018 INFO [STDOUT] **** enter quartz rendezvous
07:01:10,006 INFO [STDOUT] **** enter quartz rendezvous
07:01:10,007 INFO [STDOUT] *** exit 0
07:01:10,007 INFO [STDOUT] *** exit 2
07:01:10,007 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
07:01:10,007 INFO [STDOUT] *** exit 1
07:01:10,007 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
07:01:10,007 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
07:01:15,004 INFO [STDOUT] **** enter quartz rendezvous
07:01:20,004 INFO [STDOUT] **** enter quartz rendezvous
07:01:25,004 INFO [STDOUT] **** enter quartz rendezvous
07:01:25,005 INFO [STDOUT] *** exit 1
07:01:25,005 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
07:01:25,005 INFO [STDOUT] *** exit 2
07:01:25,006 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
07:01:25,006 INFO [STDOUT] *** exit 0
07:01:25,008 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
At this point if we run the submit script with no arguments we can see that the rules have been injected into the target methods. The listing now shows the class and method the rule was injected into and the classloader which loaded the rule. It also indicates that the rule was injected, type-checked and compiled correctly.
[adinn@localhost jca_inflow_quartz]$ bmsubmit
# File rules.btm line 13
RULE delay quartz bean
CLASS AnnotatedQuartzMDBBean
METHOD execute
AT ENTRY
IF isRendezvous("quartz", 3)
DO traceln("**** enter quartz rendezvous ");
traceln("*** exit " + rendezvous("quartz"));
ENDRULE
Transformed in:
loader: BaseClassLoader@25f4cf3c{vfs:///ssd/home/adinn/jboss/jbossas/jboss-6.0.0.Final/server/default/deploy/jboss-ejb3-tutorial-jca_inflow_quartz.jar}
trigger method: org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean.execute(org.quartz.JobExecutionContext) void
compiled successfully
# File rules.btm line 5
RULE set up rendezvous
CLASS AnnotatedQuartzMDBBean
METHOD <init>
AT EXIT
IF NOT isRendezvous("quartz", 3)
DO createRendezvous("quartz", 3, true)
ENDRULE
Transformed in:
loader: BaseClassLoader@25f4cf3c{vfs:///ssd/home/adinn/jboss/jbossas/jboss-6.0.0.Final/server/default/deploy/jboss-ejb3-tutorial-jca_inflow_quartz.jar}
trigger method: org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean.<init>() void
compiled successfully
[adinn@localhost jca_inflow_quartz]$
We can run the script again with the -u flag to remove the rules.
[adinn@localhost jca_inflow_quartz]$ bmsubmit -u
uninstall RULE delay quartz bean
uninstall RULE set up rendezvous
[adinn@localhost jca_inflow_quartz]$
We now see that the injected code is removed, the timer bean reverts to its normal behaviour and once again the messages start being printed every 5 seconds.
07:01:30,010 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
07:01:35,005 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
07:01:40,006 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
07:01:45,005 INFO [org.jboss.tutorial.quartz.bean.AnnotatedQuartzMDBBean] ************** here in annotated!!!!
Wednesday, 2 February 2011
Byteman Release 1.5.1 is now available
The Byteman 1.5.1 patch release is now available from the JBoss maven
repo and from the Byteman project download page.
1.5.1 upgrades the BMUnit contrib package to integrate Byteman into both
the JUnit and (new) TestNG test frameworks. The upgrade also simplifies
the deployment process. In particular, this means that you can now plug
Byteman rules into your maven Surefire tests simply by adding the
Byteman jars as test dependencies. So, now there is no excuse for not
using fault injection in your tests.
Full details are in the BMUnit package README.
repo and from the Byteman project download page.
1.5.1 upgrades the BMUnit contrib package to integrate Byteman into both
the JUnit and (new) TestNG test frameworks. The upgrade also simplifies
the deployment process. In particular, this means that you can now plug
Byteman rules into your maven Surefire tests simply by adding the
Byteman jars as test dependencies. So, now there is no excuse for not
using fault injection in your tests.
Full details are in the BMUnit package README.
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