I have my web application running on java 8, which i need to connect through jconsole . I am able to connect jconsole without any change(i am not sure
if i did any change in the past) but my collegue is not able to connect through jconsole
We both are running java application separately on our windows machine with separate jconsole on same box.
So my question in general is do we need to do any configuration/setting to monitor java application/process from jconsole on same machine or remote machine?
I am new to play framework. I have an existing play application. I am supposed to understand it and make enhancements. So I am running the application on my windows 7 machine. It runs fine. On using debug(activator -jvm-debug), the jvm starts listening on default port 9999. Till this point everything is fine. When I start debugging it as a remote java application from my eclipse, the process listening on the port 9999 gets terminated. I have been monitoring the activity on Windows Resource Monitor. I have no clue where to check for the issue. Any help will be greatly appreciated
Thank you
The common things that you can check for a generic situation like
Message: “Failed to connect to remote VM. Connection Refused”
1) Have you setup the remote VM to accept connections?
java -Xdebug -Xrunjdwp:server=y,transport=dt_socket,address=10000,suspend=n yourServer
2) Is there a firewall in the way? Are you specifying the correct host / port?
I want to create a JMX agent that has to be accessible from local host only.
Please advise how can I do that.
Also help with a Simple JMX client on same machine that will connect to that JMX agent.
If somehow we can get away with specifying an explicit port, that will be helpful.
You might find this helpful. It uses the attach API for Oracle's JVM to connect to a running Java process and have it start a local only JMX agent. You would setup whatever MBeans you want to expose as usual. I get the impression that this code is similar to what JConsole does for connecting to local JVM processes. You might also want to investigate the source for Jmxterm which leverages JConsole for connecting to local JVM processes.
I have a lot of experience with jconsole.exe and JVisualVM.exe , in the JDK1.6 and have connected thousands of times from a Windows JVM over to a Windows JVM on another machine via JMX.remote but it fails when I try to monitor a java instance that is running on a Linux host (from a Windows host and I tried JMX listener on redhat and SUSE at Amazon EC2). I also tried using jconsole.exe and get a similar error.
Is there any reason anyone can think of , why this kind of JMX connection would have a problem. Any ideas I can try? Has anyone "actually" done this and can say it will work if I persevere?
The error I get from JVisualVM (on the remote connect attempt) is something like this:
"Cannot connect using service:jmx:rmi:///jndi/rmi://<jmx service ip>:8001/jmxrmi"
My remote JMX service config is like this:
-Dcom.sun.management.jmxremote
-Dcom.sun.management.jmxremote.port=8001
-Dcom.sun.management.jmxremote.authenticate=false
-Dcom.sun.management.jmxremote.hostname=<jmx service ip>
Found a similar question at this link but it didn't answer my question.
I verified that "iptables" is not enabled as a service and is not on and so I don't imaging there is any sort of firewall blockage. Also, both the windows and linux machine are on a 10.0.0.0 private internal subnet together. I am able to telnet into the port 8001 to verify its there , and its listening (netstat -ap) on the linux machine.
See the system property java.rmi.server.hostname. On your Linux server JVM, set this system property to be the public IP of the host. Then use the public IP in you client JMX URL.
I think your problem is that the RMI implementation is kind of hard to work with through firewalls and such as it requires more than the port you specify to work. Things you typically wouldn't notice if you connect to your own machine or a machine on the same network.
This post describes the problems you will run into quite well
If I were you, I would try to setup jmxmp as an alternative protocol. To do so you need to add the jmxremote_optional.jar (free from Oracle, download "JMX Remote API 1.0.1_04 Reference Implementation" from here) to both the server and the jvisualvm classpath but it is worth it.
If you google for jmxmp you will find quite a few examples on how to set things up, one of my first hits are http://pub.admc.com/howtos/jmx/distributed-chapt.html#jmxmp-sect which may be a bit too code oriented but I add it here anyway because it explains the things like like most with jmxmp in a few good sentences.
How to define the server side endpoint is depending on what you are running. Most app servers will let you type in a jmxmp enabled jmx service url but if the server is written from scratch you might have to set it up yourself in code instead of using the -D switches to java you are used to.
Give it a try and return with more specific questions about it if you run into problems.
Edit:
After you have added the jar to the classpath, the only thing you have to do in your code (assuming you are not using a server app that already handles it for you) is the following (omitting declarations, exception handling and such as you will figure it out anyway):
url=new JMXServiceURL(jmxurl);
this.server = JMXConnectorServerFactory.newJMXConnectorServer(url, null, ManagementFactory.getPlatformMBeanServer());
this.server.start();
Have you tried creating an SSH tunnel to the Linux box from your Windows machine? http://oldsite.precedence.co.uk/nc/putty.html
Or if you have cygwin, just try ssh -f your-user#remote-server.com -L 7777:remote-server.com:123 -N where 7777 is the port on YOUR windows machine, and 123 is the port on the remote Linux box that listens to JMX commands.
With either of the above, you can use jconsole or visualvm on your Windows box and connect to localhost:7777.
I know iptables is disabled, but just confirm that JMX is working fine at that port by SSHing into the Linux box and trying to use commandline JMX mode of jconsole for localhost (on the Linux box).
I have actually just tackled this problem myself and figured it out.
I would wager that the problem is the RMI connections - you can't predict which ports it will use and so you can't get it to work with a firewall.
The workaround is to use an SSH proxy:
SSH to the box where your application is running but use the -D option like this:
ssh user#remoteHost -D 9999
As you are on Windows, you can use Cygwin to run the command above, or you can do the same thing with Putty through the GUI (guide here: http://blog.ashurex.com/2012/03/15/creating-ssh-proxy-tunnel-putty/)
This will start a socks proxy on your local machine on port 9999.
Open JVisualVM and in the preferences, under 'network' configure it to use a socks proxy at localhost, on port 9999.
If you do the above, you should then be able to connect to the remote machine as normal and since all the RMI traffic is now going over the SSH proxy, it is punched through the firewall and works nicely.
Good luck :-)
What is your way to debug Java side when nativeProcess.standardInput.write method is invoked by Flex side? I know that it is possible but don't know how?
To be able to attach your Eclipse debugger to a running Java process you need to start that process with the following Java options…
-Xdebug -Xrunjdwp:transport=dt_socket,address=8001,server=y,suspend=n
Once you have done this and have restarted the server, you can use your Eclipse to attach to the running process. From Eclipse go to the Debug manager and create a new Remote Java Application configuration for the process you want to connect to. Set the port number to 8001, the same as that of the options. You will also need to enter the hostname for the machine running the Java process. That is pretty much it…