Hotswap agent with remote debugging on JBoss

[Adithya Narayan]

I had few questions on hotswapagent. I don't think i really understand what the HotSwapAgent documentation says on the following. It would be good if someone told in detail.

# Watch for changed class files on watchResources path and reload class definition in the running application.
#
# Usually you will launch debugging session from your IDE and use standard hotswap feature.
# This property is useful if you do not want to use debugging session for some reason or
# if you want to enable hotswap at runtime environment.
#
# Internally this uses java Instrumentation API to reload class bytecode. If you need to use JPDA API instead,
# specify autoHotswap.port with JPDA port.
autoHotswap=false

# Create Java Platform Debugger Architecture (JPDA) connection on autoHotswap.port, watch for changed class files
# and do the hotswap (reload) in background.
#
# You need to specify JPDA port at startup
# 
java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8000
# autoHotswap.port=8000

I am currently having autoHotswap=true and i have specified a port for debugger (8003). My JVM arguments looks as follows:

JAVA_OPTS=-Xms1024M -Xmx2048M -XX:PermSize=1024M -XX:MaxPermSize=1024M -Xss256k -XX:+UseParallelGC -XX:ParallelGCThreads=4 -XX:-UseGCOverheadLimit -Dorg.jboss.resolver.warning=true -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000 -Dsun.lang.ClassLoader.allowArraySyntax=true
-Djobscheduler.disabled=false -Duser.timezone=America/Belize -Dlogin.cache.timeout=120 -XXaltjvm=dcevm -javaagent:"C:\softwares\hotswapagent\hotswap-agent.jar" -DpropertiesFilePath="C:\JBoss\jboss-eap-5.2\jboss-as\bin\hotswap-agent.properties" -Dcom.sungard.gasops.propertyfile="C:\JBoss\jboss-eap-5.2\jboss-as\bin\FactoryOverrides.properties"

My hotswap-agent.properties file is as follows:

# Default agent properties # You can override them in your application by creating hotswap-agent.properties file in class root # and specifying new property values. # Add a directory prior to application classpath (load classes and resources). # # This may be useful for example in multi module maven project to load class changes from upstream project # classes. Set extraClasspath to upstream project compiler output and .class file will have precedence to # classes from built JAR file. extraClasspath=C:/Gas_workspaces/GasOps3.0.0.0.0Dev_New/java/rebel/ # Watch for changes in a directory (resources only). # # Similar to extraClasspath this property adds classpath when searching for resources (not classes). # While extra classpath just modifies the classloader, this setting does nothing until the resource # is really changed. # # Sometimes it is not possible to point extraClasspath to your i.e. src/main/resources, because there are multiple # replacements of resources in a building step (maven filtering resource option). # This setting will leave i.e. src/target/classes as default source for resources, but after the resource is modified # in src/main/resources, the new changed resource is served instead. watchResources=C:/Gas_workspaces/GasOps3.0.0.0.0Dev_New/java/utils/libs/etm_libs/meta/query/ # Load static web resources from different directory. # # This setting is dependent on application server plugin(Jetty, Tomcat, JBoss, ...) webappDir= # Add a directory prior to webapp path (load webapp resources). # # Load web application resources (such as HTML, JSP, CSS, ...) from this directory prior to default processing. # Use this setting to set to serve resources from source directory directly (e.g. src/main/webapp). extraWebappContext= # Comma separated list of disabled plugins # Use plugin name - e.g. Hibernate, Spring, ZK, Hotswapper, AnonymousClassPatch, Tomcat, Logback .... disabledPlugins= # Watch for changed class files on watchResources path and reload class definition in the running application. # # Usually you will launch debugging session from your IDE and use standard hotswap feature. # This property is useful if you do not want to use debugging session for some reason or # if you want to enable hotswap at runtime environment. # # Internally this uses java Instrumentation API to reload class bytecode. If you need to use JPDA API instead, # specify autoHotswap.port with JPDA port. autoHotswap=true # Create Java Platform Debugger Architecture (JPDA) connection on autoHotswap.port, watch for changed class files # and do the hotswap (reload) in background. # # You need to specify JPDA port at startup # java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8003 # autoHotswap.port=8000 # Enables debugging in OsgiEquinox # osgiEquinox.debugMode=true # Logger setup - use entries in the format of # format: LOGGER.my.package=LEVEL # e.g. LOGGER.org.hotswap.agent.plugin.myPlugin=trace # root level LOGGER=trace # Print output into logfile # LOGFILE=agent.logLOGFILE=agent.log

Now, i am having two JDWP debugger ports 9996 and 8003 and i am debugging on 9996. Whenever i debug and make changes in a method, Eclipse tells me that some code changes couldn't be hot swapped and gives me 3 options 'Continue', 'Disconnect' and 'Cancel' (not sure on the 3rd one). I disconnect and i reconnect. Most of the times what i have observed is the code changes aren't reflected / hot swapped. Sometimes when it works i have to do the operation twice to ensure the changes are hot swapped.

Am i doing something wrong ? Can you please help me to correct the configuration if it's wrong ?

[Jiri Bubnik]

Hi,

 

You can either use standard debugging or use autoHotswap.

 

If you want to use eclipse debugger, just set autoHotswap=false. AutoHotswap feature looks for changed class files and creates it’s own debugging session to promote changes to running instance (the same way as eclipse does).

 

Jiri