liberty

Running WebSphere Liberty Containers

In this tutorial you'll run your first Liberty server under Docker using the websphere-liberty image that is available from the online Docker Hub repository.

Running a single container

1. Open the Docker Quickstart Terminal on Windows or a Mac terminal.

2. Populate the local image cache with WebSphere Liberty by using the following command to pull it down from Docker Hub:

   $ docker pull websphere-liberty

This will pull down the layers that make up the image. The total image size, including the base Ubuntu image on which it builds, is just over 500MB. 3. Execute the following command to see the layers that make up the Liberty image:

```bash
$ docker history websphere-liberty
```

The layers represent the commands that were issued when the image was built (specify the --no-trunc option if you want to see the full commands). The bottom layers represent the ubuntu image. After setting the maintainer and installing wget and unzip, the Dockerfile downloads and installs an IBM JRE and the WebSphere Liberty kernel. It then creates a server and then sets the metadata around the image such as the ports to expose and the command to run. It then adds additional features using the installUtility command to build up to the full set of Java EE7 features.

4. You can see the total size of the image by running the command:

   $ docker images websphere-liberty

5. Run the image with the following command (the -i and -t options specify that an interactive terminal is required):

   $ docker run -i -t websphere-liberty

6. The server isn't much use though as we didn't expose any ports to access it. Type Ctrl-C to stop the server. (If you failed to specify the -i -t options then you will have to kill the process from another terminal.)

7. This time map the port 9080 from the container to port 80 on the host virtual machine:

   $ docker run -d -p 80:9080 --name wlp websphere-liberty

Note that this time you have specified the -d option to run the container in the background, and we have given it a name so that we can subsequently refer to it by this name rather than using the generated name or id. 8. Use the following command to follow the logs of the container as it starts up:

```bash
$ docker logs --tail=all -f wlp
```

Once the server is ready to run, type Ctrl-C to return to the command prompt. 9. Run the following Docker Machine command to identify the IP address allocated to the current active virtual machine:

```bash
$ docker-machine ip $(docker-machine active)
```

10. Open a web browser and enter this IP address to view the Liberty welcome page.

11. Return to the terminal and enter the following command to see the processes running in the container:

    $ docker top wlp

You will see the server script and the child Java process. 12. If you execute the following commands, you can see that these processes can also be seen at the level of the Docker host. They are normal Linux processes whose visibility of the rest of the host are constrained by the use of Linux namespaces.

```bash
$ docker-machine ssh
$ ps aux | grep wlp
$ exit
```

13. Docker permits us to run other processes inside the namespaces of an existing container. This is primarily used for diagnostic purposes.
14. For example, type the following command to start an interactive session inside the running container:

```bash
$ docker exec -it wlp bash
```

You will see the command prompt change indicating that you are now running as the root user within the container. 2. Execute the following command to show all of the processes running within the container namespace.

```bash
$ ps aux
```

Note that within the container you do not have visibility of other processes running on the host. 3. Execute the following command inside the container to view the contents of the server log file:

```bash
$ cat /logs/messages.log
```

4. Enter the following command to end the terminal session. The container will continue to run.

```bash
$ exit
```

14. It is also possible to copy files out of the container.

15. For example type the following command to copy the messages.log file from the container wlp to the current directory:

    $ docker cp wlp:/logs/messages.log .

16. Then run execute the following command to view the file:

    $ cat messages.log

17. Finally, run the following commands to clear up the container:

    $ docker stop wlp
    $ docker rm wlp

Handling multiple containers

Explicitly setting ports and names is fine if you only have a single container but what if you are trying to run multiple instances of an image?

1. Type the following command to run the Liberty image again:

   $ C=$(docker run -d -P websphere-liberty)

This time you have specified the -P flag to indicate that Docker should automatically select ports on the host to map those exposed by the image to. You have also saved the identifier for the new container in the variable $C. 2. Run the following command to see the ports on the host that Docker has mapped 9080 and 9443 to:

```bash
$ docker ps
```

3. The docker port command can be used to retrieve the mapping for a specific port. For example, you can retrieve the Liberty welcome page for this container by typing the command:

   $ curl $(docker port $C 9080)

4. Using docker inspect $C reveals lots more interesting information about the running container. The command accepts filters in the golang template format so, for example, it is possible to retrieve just the IP address for the container using:

   $ docker inspect --format '{{ .NetworkSettings.IPAddress }}' $C

5. You can now run another instance of the container using the same command and Docker will allocate different ports:

   $ D=$(docker run -d -P websphere-liberty)

6. Execute the following command to confirm that you now have two containers running:

   $ docker ps

7. Run the following command to see a live stream of stats from the running containers:

   $ docker stats $C $D

Note that, having not expressed any constraints, each container has the full memory allocated to virtual machine available to it. 8. Enter Ctrl-C to terminate the stats stream. 9. Clean up the containers with the following commands:

```bash
$ docker kill $C $D
$ docker rm $(docker ps -aq)
```

Congratulations

Congratulations on completing this tutorial. You may now like to look at the tutorial on Adding an Application.