How to attach profiler to docker process

Question

I am facing a memory leak issue in job-server which is present in docker container. To analyze what is causing the issue I need to attach the jprofiler or yourkit to docker container process. I am not sure how to do that. can someone put some light on it?

Answer 1

You can try and follow "Configure JProfiler 9.2 to profiling applications running in Docker containers" from Andrew Liu:

It would involve completing your existing Dockerfile with:

RUN wget http://download-keycdn.ej-technologies.com/jprofiler/jprofiler_linux_9_2.tar.gz -P /tmp/ &&\
 tar -xzf /tmp/jprofiler_linux_9_2.tar.gz -C /usr/local &&\
 rm /tmp/jprofiler_linux_9_2.tar.gz

ENV JPAGENT_PATH="-agentpath:/usr/local/jprofiler9/bin/linux-x64/libjprofilerti.so=nowait"
EXPOSE 8849

That would enable you to exec a bash to the running container:

docker exec -it [container-name] bash

cd /usr/local/jrofiler9/
bin/jpenable

---

Alternatively, if you want to enable JProfiler agent at your web server start up and wait for JProfiler GUI connecting from host, instead of putting "ENV JPAGENT_PATH="-agentpath:/usr/local/jprofiler9/bin/linux-x64/libjprofilerti.so=nowait"" in the Dockerfile. Add following line to the JAVA_OPTS. For tomcat, it will be CATALINA_OPTS.
Note: the config.xml will be the place to put your JProfiler license key.

JAVA_OPTS="$JAVA_OPTS -agentpath:/usr/local/jprofiler9/bin/linux-x64/libjprofilerti.so=port=8849,wait,config=/usr/local/jprofiler9/config.xml"

Now you are done at the docker container side. The container is ready to be attached to your JProfiler GUI. The steps below are to be done on the host machine.

1. Download JProfiler 9.2 from https://www.ej-technologies.com/download/jprofiler/files and install it.
2. Open JProfiler and open a new session by press Ctrl + N or Click 'New Session' in Session menu.
3. Select 'Attach to profiled JVM (local or remote)' in Session Type section. Enter the IP address and 8849 as profiling port in Profiled JVM Settings section. Leave the other settings as default. Then click OK.

Answer 2

You can attach your jProfiler to the application inside your docker container like this:

EXPOSE 8849

Exposing the profiling port is important (8849 is default)

RUN wget http://download-keycdn.ej-technologies.com/jprofiler/jprofiler_linux_9_2_1.tar.gz --no-verbose -P /tmp/ && \
  tar -xzf /tmp/jprofiler_linux_9_2_1.tar.gz -C /usr/local && \
  rm /tmp/jprofiler_linux_9_2_1.tar.gz

This downloads and extracts the jProfiler inside your docker container, when the container is build.

ENTRYPOINT exec java -jar /app.jar & \

 echo $! >>/tmp/process.pid && \

 sleep 60s && \

 /usr/local/jprofiler9/bin/jpenable --pid=$(cat /tmp/process.pid) --gui --port=8849 && \

 while true; do sleep 2147483647; done

This is how I dealt with the fact that you can't run two applications inside one docker container. First we execute the jar and save the processId to a file. Then we simply wait 60 seconds and after that we start the jProfiler (jpenable) and attach it to our process (via processId). The while loop is necessary to keep the container running afterwards.