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Can I open custom hsperfdata_root/PID after process shutdown?

I'm using docker to containerize my application and want to look at it's performance from host machine. I've mapped volume : "/opt/tmp/my_app/:/tmp", which contains hsperfdata_root
Can I somehow open heap and other information from that hsperfdata_root/PID in jmap or some other tool ?
Does container must be in Running state for such debugging or it might be shutdown ?

The JDK includes the jstat tool for doing this. Try jstat -snap file:/tmp/hsperfdata_root.

Profiling tomcat application with VisualVM

I am trying to run visualvm under the username tomcat6 because apparently visualvm can only find applications running under its username. So by default it is only finding applications running under my username. I have been able to connect visualvm with tomcat6 through jmx but that lacks the fine granularity of instrumented profiling.
I tried the following to run visualvm under the username tomcat6 but got the following error that I don't understand.
$ sudo -u tomcat6 jvisualvm
No protocol specified
Exception in thread "main" java.awt.AWTError: Can't connect to X11 window server using ':0' as the value of the DISPLAY variable.
at sun.awt.X11GraphicsEnvironment.initDisplay(Native Method)
at sun.awt.X11GraphicsEnvironment.access$200(X11GraphicsEnvironment.java:65)
at sun.awt.X11GraphicsEnvironment$1.run(X11GraphicsEnvironment.java:115)
...

If the computer running your application is remote -- like a server -- then you can't run GUI applications without some work. It's probably going to be easier to enable remote access to VisualVM.
You can use two techniques to attach to a remote JVM: using jstatd or using JMX. I'm not sure what you think you are losing by using JMX, but evidently jstatd doesn't give you access to profiling tools, CPU monitor, etc.).
You need to configure your JVM and Tomcat to allow for remote access. That requires 3 steps:
Enable remote JMX. Turns out, there's a guide for that.
Fix the "wandering port" used for RMI. There's a guide for that, too.
(Optional) Arrange for secure remote-access to the server. The easiest way to do that would be to use ssh -Lport:localhost:port with a series of -L arguments to forward multiple ports from your workstation to your server. Map all the ports you had to configure in steps #1 and #2. If you don't do this, you'll need to have non-firewalled access to all the aforementioned ports.
Restart your JVM and connect with JVisualVM.
Update 2022-06-01
Note that the "wandering port" problem has been fixed at the JVM level, so there is no need for application (i.e. Tomcat) support for that. Item #1 for Tomcat 8.5 and later contains updated instructions making item #2 unnecessary with a recent JVM.

Unfortunately only sampling is available in remote mode so JMX will lack instrumentation tools.
Actually your approach to running visualvm under tomcat6 user is correct. You should take a look at this question on how to run X11 applications under sudo.
The easiest way to pass DISPLAY and XAUTHORITY environment variables is to use sudo -E command to preserve current user environment.
Also if you can't see your process under tomcat6 user you should check if CATALINA_TMPDIR is pointing to /tmp. Otherwise you should pass it to visualvm
jvisualvm -J-Djava.io.tmpdir="${CATALINA_TMPDIR}"
Actually there is a lot of alternatives like yourkit or jprofiler shipped with java agents which allows remote instrumentation profiling.

The easiest is to open a remote JXM port on Tomcat in order to be able to remotely (from your desktop computer) connect to your remote Tomcat (on your server) with jvisualvm.
You need to pass the following system properties to your JVM :
-Dcom.sun.management.jmxremote
-Dcom.sun.management.jmxremote.port=<whatever_port_you_want>
-Dcom.sun.management.jmxremote.ssl=false
Then open jvisualvm on your local computer (JVM version needs to be the same or newer), File -> Add Remote Host -> Enter the name on the Host. It will create an entry for this host. Right lick on this Entry -> Add JMX connection -> Enter the port -> OK
jvisualvm will then be able to access remotely to your application.
You can also secure the connection if needed by using the following system properties (you need to create the files and locate them where you want :
-Dcom.sun.management.jmxremote.password.file=jmxremote.password
-Dcom.sun.management.jmxremote.access.file=jmxremote.access
These properties needs to be added to the CATALINA_OPTS environment variable. Fr exemple :
export CATALINA_OPTS = "$CATALINA_OPTS -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=8888 "
More info on JMX lies here : https://docs.oracle.com/javase/8/docs/technotes/guides/management/agent.html

I tried to do something similar but I was not allowed to install JVisualVM on the server. Having JVisualVM connect to the remote machine never seemed to work correctly. I suspect firewall rules were blocking part of the the network connections.
The only way I found to remotely profile the server was via an ssh tunnel.
Set the JMX port in CATALINA_OPTS on the server
CATALINA_OPTS="$CATALINA_OPTS -Dcom.sun.management.jmxremote.port=13333 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false; export CATALINA_OPTS
On your desktop machine open an ssh connection to the server
ssh -D 61444 username#tomcat.server.address
Add a flag to JVisualVM so that it will proxy its network connection
"C:\Program Files\Java\jdk1.7.0_79\bin\jvisualvm.exe" -J-Dnetbeans.system_socks_proxy=localhost:61444 -J-Djava.net.useSystemProxies=true
Have JVisualVM connect to the jmxport and the network traffic is tunneled via ssh.
Good luck.

Monitor Java application with VisualVM

I have a few Java programs running on my EC2 instance. I want to profile them using VisualVM. they are not web applications that run on Jetty or Tomcat. I did go through the stuff mentioned here, but I dont know how to set up my VisualVM after I generate the jar files with those commands. Can some help me out?
Thanks

You normally attach VisualVM to the PID of the process you want to profile. If that's Jetty or Tomcat or some other Java EE app server, that means the PID of the app server. If not, it's the PID of the JVM that's running your app.
If you've already got a JVM installed on your EC2 instance, I'd recommend looking in the JVM /bin folder to see if jvisualvm.exe is already there. If it is, fire it up in a separate command shell and attach it the PID of your application.

Why can't I attach jvisualvm to an instance of tomcat started from inside osx?

I'm starting tomcat from inside netbeans. I'd like to monitor the heap usage on that instance of tomcat so I fire up jVisualVM. However the process isn't listed. Any ideas?

Are you using Java version 6u24? Then you may fall victim to this bug which will be fixed in 6u25 (in a nutshell, jVisualVM can't find your process' hsperfdata).
Otherwise, you have to enable monitoring via JMX:
Pass the following JVM parameters to Tomcat:
-Dcom.sun.management.jmxremote.port=8888 -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.authenticate=false
Then add the remote process to jVisualVM via File -> Add JMX Connection. You can connect to the process using port 8888
jVisualVM has some other gotchas, e.g. the user starting jVisualVM needs to be the same as the user owning the process you want to monitor (although, I don't think this is your issue). See more here.

Using the Netbeans 6.5 profiler to profile a remote web app?

I'm having trouble using the Netbeans 6.5 profiler to profile the memory usage of a java web app, remotely.
I have followed the steps in the tutorial, and was able to customize a Tomcat instance to start with the profiling agents. I can also attach the Netbeans profiler to the running server: for some seconds, the profiler shows graphs with the memory usage of the server.
However, I am not able to run my deployed web app. After a few seconds, the server is shut down gracefully as if it simply had reached the bottom of its method main (hardly the expected behavior of a web server).
During these seconds, the server is not responsible, and I can't connect to a web application in it, they are simply not deployed.
I do not want to import my app into a new Netbeans project just for profiling it. It's possible to profile a remote app without access to its source, right ? After all, for a few seconds, the server was running and being profiled.
I want to profile a web application in Netbeans 6.5. What did I forget ?

You can use VisualVM tool as well. Follow the below mentioned steps.
1) Run jstatd ( jstat demon process) ( Run on your remote machine where application is running)
jstatd -p 1098 -J-Djava.security.policy=tools.policy ( specify unused port ) if tools.policy file is not specified create it as follows.
tools.policy
grant codebase "file:${java.home}/../lib/tools.jar" {
permission java.security.AllPermission;
};
2) Also specify the following properties before you start your JVM.
#JMX property
JVM_ARGS="${JVM_ARGS} -Dcom.sun.management.jmxremote=true"
JVM_ARGS="${JVM_ARGS} -Dcom.sun.management.jmxremote.port=10992"
JVM_ARGS="${JVM_ARGS} -Dcom.sun.management.jmxremote.authenticate=false"
JVM_ARGS="${JVM_ARGS} -Dcom.sun.management.jmxremote.ssl=false"
3) Start the visual VM on local machine.
a. Under remote tab add remote node.
b. Wait for couple of minutes you will see all the core applications instance will be seen under remote tab.
c. Click on remote node then select Add JMX connections specify node:port (port mentioned above in point 2.)
d. Wait for few seconds you will see JMX connection under remote node.
4) After few seconds you will see new tab appearing under remote node. Double click on the remote_node:10992 you will see the profile table on right hand side.
You can see memory , cpu , thread etc details ..

Are profiling the entire webserver or did you use the profiling filter to profile only your package?
Reducing the interaction between the profiler and the app server itself can solve it.

Check your jvm version. The version used by netbeans should be same as that in tomcat.
Use default ports. If you have changed any ports ensure they are above 1024.
Try to profile the example application in tomcat (remove all other applications). If it is running sucessfully it means there is a memory constraint.
Profiling requires huge memory. use -xms1024m -xmx1024m for tomcat.
If every thing else fail. think of switching to jdk6 and tomcat 6.
After many trials I discoverd that there are lot of limitations in jdk5 and tomcat5. switching to tomcat6 and jdk6 solved the problem for me.
Profiling with netbeans does not work jrockit, ibm jdk etc..
--kiran.kumar