Shutdown tomcat and make sure that it has properly shut down by monitoring the tomcat process.
Once it has completely shutdown, export the following environment variables:
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export JPDA_ADDRESS=8000 export JPDA_TRANSPORT=dt_socket |
Here, we’re setting the jpda address to port 8000. Note this down as you will need this port number in order to connect via your IDE or whatever debugging tool you’re using.
Options above will run tomcat as usual so if you want to debug something that happens early on in the lifecycle, you either need to be really quick about attaching your debugger or add the following JPDA option:
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export JPDA_SUSPEND=y |
This will suspend the tomcat startup until you attach your debugger.
Next, start tomcat jpda using catalina script:
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./catalina.sh jpda start |
At this stage, you can monitor the log in catalina.out file to make sure everything goes smoothly.
Now setup your IDE to connect to tomcat at port 8000. If you are using vagrant as your VM, make sure you are port forwarding 8000 in your network settings. If not, you can always tunnel in:
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vagrant ssh -- -L 8000:localhost:8000 |
Or if its a remote server, you can just use the normal ssh command:
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ssh -L 8000:localhost:8000 user@server.com |
Hope this helps!
Credits
- Conor Restall: For suggesting JPDA_SUSPEND option.
Nice post. I wish you’d written this about 2 weeks ago when I was trying to debug startup problems with a tomcat app running in docker.
A useful and common JPDA debug option is
JPDA_SUSPEND=y/n. The option will cause tomcat not to start until a debugger is attached.Nice one Conor. I’ll add that in. Thanks!