first commit

Author: Alexei Novikov

.gitignore

@@ -0,0 +1 @@
+*.class

Dockerfile

@@ -0,0 +1,17 @@
+FROM java:8
+MAINTAINER "Alexei Novikov <alexeinov@gmail.com>"
+COPY . /usr/src/myapp
+WORKDIR /usr/src/myapp
+RUN javac Hammer.java
+CMD ["java", \
+"-Dcom.sun.management.jmxremote", \
+"-Dcom.sun.management.jmxremote.port=9010", \
+# Uncomment this line when running JMX console on a different host
+#"-Dcom.sun.management.jmxremote.rmi.port=9010", \
+"-Dcom.sun.management.jmxremote.local.only=false", \
+"-Dcom.sun.management.jmxremote.authenticate=false", \
+"-Dcom.sun.management.jmxremote.ssl=false", \
+# Uncomment this line when running JMX console on a different host, use a name of the host where Docker is running
+#"-Djava.rmi.server.hostname=192.168.0.101", \
+"Hammer"]
+EXPOSE 9010

Hammer.java

@@ -0,0 +1,13 @@
+public class Hammer {
+  public static void main(String[] args) {
+    System.out.println("I'm a hammer. I'll be banging forever!");
+    while (true) {
+      try {
+        System.out.print(".");
+        Thread.sleep(3000);
+      } catch (InterruptedException e) {
+        break;
+      }
+    }
+  }
+}

README.md

@@ -1,2 +1,55 @@
 # docker-jmx-demo
-A simple demo getting JMX metrics from a docker container
+## A simple demo getting JMX metrics from a docker container
+
+This demo is a Docker container that starts a simple Java application with pre-configured JMX options. Manipulating the options and running a container and JMX console in different modes demonstrates different cases of JMX monitoring. In all variants, JMX is bound to the port `9010`, so `JConsole` will always be connecting a remote host `hostname:9010`, even when running locally.
+
+### Build an image
+
+Run the `docker build` command in the project's directory.
+```bash
+docker build -t banging-daemon .
+```
+
+### Bridge networking mode
+
+Bridge mode is the default for a Docker container. In this mode only the published container's ports are accessible
+
+#### Local `JConsole`
+
+However, when running `JConsole` on the same machine, RMI options do not need to be advertised. The following lines of the `Dockerfile` may stay disabled.
+
+```dockerfile
+#"-Dcom.sun.management.jmxremote.rmi.port=9010", \
+#"-Djava.rmi.server.hostname=192.168.0.101", \
+```
+Run the container publishing the `JMX` remote port `9010`.  
+
+```bash
+docker run -it --rm --name hammer -p 9010:9010 banging-daemon
+```
+
+#### Remote `JConsole`
+
+When `JConsole` is running on a different machine, RMI options have to be set, as a randomly RMI port is not accessible by the remote machine. It is convenient to set the port `com.sun.management.jmxremote.rmi.port` to the same value as `com.sun.management.jmxremote.port`, which is `9010` in this configuration. Using same port number makes one port mapping configuration less in a Docker container and eventually in a firewall. Parameter `java.rmi.server.hostname` should point at a host where Docker is running.
+
+```dockerfile
+"-Dcom.sun.management.jmxremote.rmi.port=9010", \
+"-Djava.rmi.server.hostname=192.168.0.101", \
+```
+
+### Host networking mode
+
+In the host mode, the container's network is not encapsulated at all. It is accessible alongside the host's network. In this case the RMI options do not need to be configured.
+
+```dockerfile
+#"-Dcom.sun.management.jmxremote.rmi.port=9010", \
+#"-Djava.rmi.server.hostname=192.168.0.101", \
+```
+
+Running `JConsole` locally or remotely does not make any difference.
+
+ The `JMX` remote port does not need to be published:
+
+```bash
+docker run -it --rm --net=host --name hammer banging-daemon
+```