ejstatd - Enhanced jstatd

A firewall and Docker friendly and Java policy free version of jstatd.

jstatd is a basic monitoring tool that can be used to remotely monitor you JVM's. It requires 3 ports in order to work by default. The program allows you to pick one of them using the standard command line arguments, while the other 2 are randomly picked. This makes using this tool in larger environments a pain for firewall administrators.

With ejstatd you can control those ports using those 3 parameters: (in addition to classical -p to control RMI registry port):

• -pr <port>: specify the port on which the RMI registry will start (like jstatd's -p)
• -ph <port> (or setting the port number to JVM system property ejstatd.remoteHost.port): control the port on which the sun.jvmstat.monitor.remote.RemoteHost will be exported.
• -pv <port> (or setting the port number to JVM system property ejstatd.remoteVm.port): control the port on which the sun.jvmstat.monitor.remote.RemoteVm will be exported.

ejstatd also gets rid of jstatd usual access denied ("java.util.PropertyPermission" "java.rmi.server.ignoreSubClasses" "write") problem without defining a java.security.policy system property: it writes its own needed java policy file and use it (if you don't define this system property using -Djava.security.policy).

Usage

After having compiled the project (mvn package), one can launch ejstatd using those 2 different ways (replace the ports specified here - 2222, 2223 and 2224 - with your own):

• mvn exec:java -Dexec.args="-pr2222 -ph2223 -pv2224" using Maven

or

• java -cp "target\ejstatd-1.0.0.jar;%JAVA_HOME%\lib\tools.jar" com.github.anthony_o.ejstatd.EJstatd -pr2222 -ph2223 -pv2224 on Windows, if JAVA_HOME is set as an environment variable
• java -cp "target/ejstatd-1.0.0.jar:$JAVA_HOME/lib/tools.jar" com.github.anthony_o.ejstatd.EJstatd -pr2222 -ph2223 -pv2224 on Unix (using Bash), if JAVA_HOME is set as an environment variable

You can also specify the arguments with spaces before the ports, like this:

• mvn exec:java -Dexec.args="-pr 2222 -ph 2223 -pv 2224"

Usage in Docker

In this section we will consider using those 3 ports as example, don't forget to replace them with yours: 2222 for pr, 2223 for ph and 2224 for pv.

Inside a Docker container, don't forget to specify -Djava.rmi.server.hostname=$HOST_HOSTNAME when launching ejstatd. This environment variable should be set to the host's hostname passing for example -e HOST_HOSTNAME=$HOSTNAME to docker run command.

You should as well force the 3 ports (using -pr2222 -ph2223 -pv2224 when launching ejstatd) and expose them to the Docker host specifying -p 2222:2222 -p 2223:2223 -p 2224:2224 to docker run command.

To sum up, here is the minimum Docker run command:

• docker run -e HOST_HOSTNAME=$HOSTNAME -p 2222:2222 -p 2223:2223 -p 2224:2224 myimage

And inside the Docker image myimage, ejstatd should be launched from a script in background in this way:

• mvn -Djava.rmi.server.hostname=$HOST_HOSTNAME exec:java -Dexec.args="-pr 2222 -ph 2223 -pv 2224" &

Then you could access this ejstatd using JVisualVM running on your Desktop PC for example adding a "Remote Host" specifying your Docker hostname as "Host name" and adding a "Custom jstatd Connections" (in the "Advanced Settings") by setting "2222" to "Port".

Prerequisites

1. Install a JDK
2. Install Maven (make sure its bin folder is in the PATH)
3. Clone this Github project
4. cd into the project and create the package using mvn package command

Thanks

This program is based on JDK 7's jstatd (using sources from its Mercurial repository) and highly inspired by jdonofrio728's JakestatD.