I've made a script called debug.sh and placed it under the bin directory (start it with ./debug.sh) to start Tomcat 8 in debugging mode:
set JPDA_ADDRESS=8000
set JPDA_TRANSPORT=dt_socket
set JAVA_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n
bash catalina.sh jpda start
But if it started, there is now message which says, that Tomcat is listening on port 8000. Also if I type
netstat -nat
there is no application listening on port 8000.
What exact configuration do I have to set, to remote debug my Tomcat 8 server which is running on a specific IP or do I have just a little problem in my script?
This answer has been updated following the comments, I did not understand the problem in the first place.
I guess you have followed that doc: this is about developing Tomcat itself.
I am not sure you are using the proper way to configure the port (I don't know your specific configuration details). In a standard environment, the ports are configured in the server.xml (note that several different ports are used by Tomcat for the different services).
To remotely monitor your server, you should use a JMX client. As far as I know, Eclipse doesn't include one (or at least not one documented) - you could code one as this is a Java specification (JSR262). You have one in a standard Java environement (JConsole). By default, JMX is not enabled on Tomcat. If you need to enable it, the fine way is to follow the doc.
Tomcat JMX monitoring and JConsole are both available in most versions of Tomcat and the Java runtime.
The following exchange seems to be about your problem.
Related
I’m using glassfish 3.1.2 on Red Hat Enterprise Linux Server release 5.7 (Tikanga). Glassfish has been installed as part of a piece of bigger software (that I’m developing). It used to work correctly in the past.
I can issue a ‘start-domain’ command. This one will work correctly and glassfish will start. I can see the process and the glassfish admin web console is working fine. However, the command ‘list-domain’ reports my domain as not running. The command ‘stop-domain’ will fail reporting the domain1 as already stopped. This prevents my software to run properly.
As far as I know, nothing has changed on that system. There is no exception/error in the log. I already search the internet for description of similar behaviour. I ensured the embedded firewall (the one coming with the OS) did not prevent the communication. I removed the expired certificate (just in case). I have no idea on what I could do next.
What could I check? Any help appreciated. Add a comment if you need specific details and I will update the question.
Answer to unwichtich's questions:
absolute path to jvm using an absolute path to the admin-cli.jar: /.../java -Duser.home=... -Duser.language=en -Dhttps.protocols=TLSv1.2 -jar /.../glassfish/modules/admin-cli.jar --terse --port 23992 --user admin --passwordfile /.../passwordfile list-domains
There are two lines in the /etc/hosts. The first with the ip mapping to the hostname. The second with 127.0.0.1 mapping to loopback and localhost
My software includes some command line utilities that need to perform operation on Glassfish (like start-domain, stop-domain, list-domains,...).
I am using Jetty 8 and trying to connect from Eclipse. I am using Java 1.6.
While starting jetty in debug mode, I am giving the below command which throws an "Address already in Use" error.
java -Xdebug -agentlib:jdwp=transport=dt_socket,address=8080,server=y,suspend=n -jar start.jar.
To do Remote debugging, I need open the debug mode on the same port in which Jetty server which is going to run.
The reason I suspect is, I am opening a debug port on 8080(done successfully) and when Jetty tries to start the server in default port 8080, it throws the error "Address already in use".
Can you help me?
Yes, the JVM allocates the port you specify for debugging, and it is unavailable for Jetty later. Unless explicitly coded, ports cannot be shared between purposes.
You should use another unused port for either of your purposes. I would suggest using 8000 or 7999 for the debugger port.
Note that modern versions of Eclipse allows for the reverse configuration ("listen"), i.e. that Eclipse listens on the port given and the JVM connects back to it. This might be relevant if you are debugging across a restricted network.
I wrote a Java servlet filter on my local machine and deployed it a remote (machine) web server. Unfortunately, it's been very difficult and time-consuming trying to trace errors reported by Apache Tomcat 5.5, my JSP/servlet engine. I can't keep writing System.out.println(...), saving, deploying, testing JSP pages, and so on. It's taking too long. There has to be a better, faster way.
Is it possible to remotely debug servlet filters? I don't have a web server on my local machine, which is why I'm asking about remote debugging. Specifically, I'm looking for a way to debug, line-by-line, the servlet filter, on-the-fly, as it's happening on the remote web server. Does such a method exist?
Or, is there a better method than writing to standard output. It's taking too long and I feel that must be a more efficient means of debugging Java servlet filters.
Note: I'm using Eclipse for development.
Thank you very much for any help.
Update
Thank you all for your help. I really appreciate it.
I added the JVM argument to Tomcat, restarted Tomcat. Then, on the machine with Eclipse, I entered in the appropriate info in the Debug config, put the breakpoint in, and tested. Unfortunately, it did not work. In the config, I left it as Socket Attach, clicked apply, and that was it. I pressed the debug button and it said the connection was refused. I tried ports 8000 and 8001 and both did not work.
Let me explain what I'm trying to do, that might be better.
I have a login page called login.jsp. On that page, is a form whose action attribute is servlet/LoginServlet. When the user submits the form, it calls servlet/LoginServlet, which is mapped to a class in the web.xml file. Let's call this class com.mysite.mypkg.classA. In class A, it calls a method from another class called com.custom.mypkg.classB. I want to put a breakpoint in classB.
So, using the url with login.jsp page in the Eclipse debugger won't call it. I tried using servlet/LoginServlet and that also did not work.
What should I put in for the URL? Or, do I debug this type of setup?
Thank you.
Update 2
I found this site here, which is pretty comprehensive. I ran netstat -a and noticed that the debug port is not listed. Windows Firewall is turned off, but there could be another thing blocking the port, who knows. Anyway, I placed the VM argument here and it's not working.
Thank you.
For remote debugging you need to start the server in debug mode. There are couple of ways doing that.
1 > start the server using
catinlina.bat jpda start
2 > Add an jvm argument to the tomcat java process
-Xdebug -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n
Once the server is started in debug mode , you need to change the perspective of the project in eclipse to debug.
Then go to Run - > Debug configuration.
Double click remote java application and enter the details such as
Remote IP address
Debug port . Default tomcat debug port is 8000. If you use jvm argument, use the port mentioned in the jvm argument.
Click Apply
Go to the java file you want to debug.
Put a break point in the source code and run the scenario you want to test (Eg Web application using browser)
Also , ensure that the code in the java file is in sync with code deployed on remote server.
Happy Debugging!!!
Peace.
Sanket Raut
You can attach a debugger to a running Tomcat instance, provided that you gave it the right command line options when you launched it.
The Tomcat Development Wiki explains how to do this, and as a bonus gives you instructions on how to set up to debug from the Eclipse or NetBeans IDEs.
Of course, attaching a debugger to a running Tomcat has both security and performance implications*.
* And OH&S issues - you might get badly scratched if you tried this on the wrong kind of tomcat ...
You should run your remote tomcat with the following starup parameter:
bin/catalina.bat jpda start
Then in Eclipse on your local machine go to Run -> Debug Configurations -> Remote Java Application, create new configuration here, use IP of the remote machine as a host and 8000 as a port there
Run this configuration and use the breakpoints in Eclipse for debugging
If Tomcat runs as a Windows service (created using the Windows Tomcat installer) you can't simply enable JMX using -Dcom.sun.management.jmxremote. You also need to set -Dcom.sun.management.jmxremote.port=<port>. This is, among other places, explained here: Unable to use JConsole with Tomcat running as windows service
However, I haven't found an explanation anywhere WHY this is the way it is.
I was a bit lost and confused when I wrote the question. Here's what I've learned in the meantime. Usually the Tomcat Windows service runs under the local system account. That's the main reason for all the fuss.
If you simply set -Dcom.sun.management.jmxremote in the service config's JVM settings JMX will be enabled indeed. If you have a JMX client that runs in the same JVM instance (e.g. because it's baked into the application itself) you can get a hold of the MBeanServer like so: MBeanServerFactory.findMBeanServer(<specific-agent-ID-or-null>). However, JConsole won't list this Tomcat process. It's all explained here: https://blogs.oracle.com/nbprofiler/entry/monitoring_java_processes_running_as.
As explained elsewhere, if this is not good enough you also need to set -Dcom.sun.management.jmxremote.port=<port>. Then you can connect to JMX with JConsole using localhost:<port>. From Java code this can be achieved using:
JMXServiceURL target = new JMXServiceURL("service:jmx:rmi:///jndi/rmi://localhost:<port>/jmxrmi");
JMXConnector connector = JMXConnectorFactory.connect(target);
connector.getMBeanServerConnection();
I'm trying to see if a WAR I just built is even running inside of Tomcat (7.0.19). I am deploying to a linux box and so my only two options are the Tomcat admin console (web app) or, hopefully, determining webapp status through the terminal.
I already know how to get in through the console web app; I am wondering if there is any way to see the status (ACTIVE/INACTIVE/TERMINATED, etc) of deployed web apps from the terminal.
Thanks in advance.
PSI-Probe is a great application for monitoring your applications deployed to a tomcat instance. It will tell you if an application is running or down. If the application is not deployed, it will simply not be in the list.
curl --user user:pass http://localhost:8080/manager/text/list
It prints
OK - Listed applications for virtual host localhost
/manager:running:0:manager
/docs:running:0:docs
/examples:running:0:examples
/host-manager:running:0:host-manager
/myapp:running:0:myapp
Your user needs the manager-script role. Documentation: Manager App HOW-TO, List_Currently_Deployed_Applications
You can probably do it using JMX.
Find appropriate MBean that shows this information on local tomcat using regular JConsole. If you want to connect JConsole to remote you will probably have some problems with firewall, so you have other solution.
Take command line JMX client and run it on the monitored host through SSH terminal. I used the following command line JMX client: cmdline-jmxclient-0.10.3.jar
wget http://<username>:<password>#<hostname>:<port>/manager/list -O - -q
(Not sure about Tomcat 7 though)