Access tomcat running in docker container by JMX

Question

I want to get tomcat's performance by JMX. Tomcat version is 7 and Java version is 1.7.0_79.

Tomcat runs on the docker's container. The port mapping has set up by the following.

docker run -itd -p 18080:8080 -p 19998:19998 -p 62911:62911 sad_jang2 bash

In the tomcat container, setevn.sh was created in the path, /tomcat_home/bin/ with the following content.

export JAVA_OPTS="
-Xdebug -Xrunjdwp:transport=dt_socket,address=62911,server=y,suspend=n
-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=19998
-Dcom.sun.management.jmxremote.authenticate=false
-Dcom.sun.management.jmxremote.ssl=false
-Djava.rmi.server.hostname=172.17.0.16"

I write a simple java code as

JMXServiceURL serviceURL = new JMXServiceURL("service:jmx:rmi:///jndi/rmi://" + "172.17.0.16"+ ":" + "19998" + "/jmxrmi");
JMXConnector connector = JMXConnectorFactory.connect(serviceURL, null);
MBeanServerConnection mbsc = connector.getMBeanServerConnection();

and can get related values by JMX.

However, I run this code in my desktop with the docker host's address and 19998 port such as

JMXServiceURL serviceURL = new JMXServiceURL("service:jmx:rmi:///jndi/rmi://" + "10.70.1.5"+ ":" + "19998" + "/jmxrmi");

The console displayed the following message

java.rmi.ConnectException: Connection refused to host: 172.17.0.16; nested exception is: 
java.net.ConnectException: Connection timed out: connect
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:619)
at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:216)
at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:202)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:130)
at javax.management.remote.rmi.RMIServerImpl_Stub.newClient(Unknown Source)
at javax.management.remote.rmi.RMIConnector.getConnection(RMIConnector.java:2432)
at javax.management.remote.rmi.RMIConnector.connect(RMIConnector.java:308)
at javax.management.remote.JMXConnectorFactory.connect(JMXConnectorFactory.java:270)
at utility.GetStatistic.getTomcatStats(GetStatistic.java:84)
at exec.Main.main(Main.java:53)

Caused by: java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at java.net.Socket.connect(Socket.java:538)
at java.net.Socket.<init>(Socket.java:434)
at java.net.Socket.<init>(Socket.java:211)
at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:40)
at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:148)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:613)
... 9 more

Using the browser to connect the URL http://10.70.1.5:18080 can show the tomcat root's page.

Can anyone give any suggestions? Thanks.

Answer 1

Here's the flags I've successfully used for monitoring my ZooKeeper container via JMX:

-Dcom.sun.management.jmxremote
-Dcom.sun.management.jmxremote.local.only=false
-Dcom.sun.management.jmxremote.authenticate=false
-Dcom.sun.management.jmxremote.port=9010
-Dcom.sun.management.jmxremote.rmi.port=9010
-Djava.rmi.server.hostname=0.0.0.0
-Dcom.sun.management.jmxremote.ssl=false

So the difference would be this entry -Dcom.sun.management.jmxremote.rmi.port which is fix the RMI port to be the same as JMX port.

With this I can just docker run -p 9010:9010 ... and everything is fine for me.

Answer 2

This does not work when you run that container in Docker machine - in VirtualBox. I am not sure what kind of address I should add to java.rmi.server.hostname because when I add there external IP of the Docker container I am connecting from my host, it does not work. So basically situation is like HOST ---> (MACHINE --- CONTAINER) and I can not reach it from HOST to CONTAINER.

Answer 3

I'm not sure if it's necessary but I would recommend adding this to your additional options -Djgroups.bind_addr=172.17.0.16 . Also I'm pretty sure that this kind of options should probably go to CATALINA_OPTS and not JAVA_OPTS but that shouldn't make a difference. Another thing that I noticed is that the rmi server host name you defined is different than the one in the JMXServiceURL constructor. I'm no docker expert but shouldn't this be identical?

Answer 4

This config worked for me:

-Dcom.sun.management.jmxremote
-Dcom.sun.management.jmxremote.local.only=false 
-Dcom.sun.management.jmxremote.authenticate=false 
-Dcom.sun.management.jmxremote.port=10005 
-Dcom.sun.management.jmxremote.rmi.port=10005 
-Djava.rmi.server.hostname=127.0.0.1 
-Dcom.sun.management.jmxremote.ssl=false

The important part was to to configure the rmi server hostname with the local loopback address. If i used 0.0.0.0 i wasn't able to reach the exposed port localy via an SSH Tunnel, with 127.0.0.1 everything worked fine .

Note : if you're running docker inside virtualbox things are different... you have to use the ip which virtualbox gives you here.