Category Archives: containers

Resolve “dial unix /var/run/docker.sock” error with Docker (Tech Tip #65)

containers, techtip

I’ve played around with Docker configuration on Mac using boot2docker (#62, #61, #60, #59, #58, #57) and starting to play with native support on Fedora 20. Boot2docker starts as a separate VM on Mac and everything is pre-configured. Booting a fresh Fedora VM and trying to run Docker commands there gives:

Debugging revealed that Docker daemon was not running on this VM. It can be easily started as:

And then enable it to start automatically with every restart of the VM as:

Simple, isn’t it?

Enjoy!

Run Java EE Tests on Docker using Arquillian Cube (Tech Tip #62)

containers, javaee, techtip, wildfly, , ,

Tech Tip #61 showed how to run Java EE 7 Hands-on Lab using Docker. The Dockerfile used there can be used to create a new image that can deploy any Java EE 7 WAR file to the WildFly instance running in the container.

For example github.com/arun-gupta/docker-images/blob/master/javaee7-test/Dockerfile can be copied to the root directory of javaee7-samples and be used to deploy jaxrs-client.war file to the container. Of course, you first need to build the sample as:

The exact Dockerfile is shown here:

If you want to deploy another Java EE 7 application, then you need to do the following steps:

  • Create the WAR file of the sample
  • Change the Dockerfile
  • Build the image
  • Stop the previous container
  • Start the new container

Now, if you want to run tests against this instance then mvn test alone will not do it because either you need to bind the IP address of the Docker container statically, or dynamically find out the address and then patch it at runtime. Anyway, the repeated cycle is little too cumbersome. How do you solve it?

Meet Arquillian Cube!

Arquillian Cube allows you to control the lifecycle of Docker images as part of the test lifecyle, either automatically or manually.

The blog entry provide more details about getting started with Arquillian Cube, and this functionality has now been enabled in “docker” branch of javaee7-samples. Arquillian Cube Extension Alpha2 was recently released and is used to provide integration. Here are the key concepts:

  • A new “wildfly-docker-arquillian” profile is being introduced
  • The profile adds a dependency on:
  • Uses Docker REST API to talk to the container. Complete API docs shows the sample payloads and explains the query parameters and status codes.
  • Uses WildFly remote adapter to talk to the application server running within the container
  • Configuration for Docker image is specified as part of maven-surefire-plugin.:

    Username and password are specified are for the WildFly in arungupta/javaee7-samples-wildfly image. All the configuration values can be overridden by arquillian.xml for each test case, as explained here.

How do you try out this functionality?

Here is a complete log of running simple-servlet test:

REST payload from the client to Docker server are shown here. This was verified on a Fedora 20 Virtual Box image. Here are some quick notes on setting it up there:

  1. Install the required packages
  2. Configure Docker
  3. Verify Docker TCP configuration

Boot2docker on Mac still has issue #49, this is Alpha2 after all :-)

Try some other Java EE 7 tests and file bugs here.

Enjoy!

Java EE 7 Hands-on Lab on WildFly and Docker (Tech Tip #61)

containers, javaee, techtip, wildfly, ,

Java EE 7 Hands-on Lab has been delivered all around the world and is a pretty standard application that shows design patterns and anti-patterns for a typical Java EE 7 application. It shows how the following technologies can be used in a close-to-real-world application:

  • WebSocket 1.0
  • JSON Processing 1.0
  • Batch 1.0
  • Contexts & Dependency Injection 1.1
  • Java Message Service 2.0
  • Java API for RESTFul Services 2.0
  • Java Persistence API 2.0
  • Enterprise JavaBeans 3.1
  • JavaSever Faces 2.2

However the lab requires you to download NetBeans (Java EE 7 tooling) and WildFly or GlassFish (Java EE 7 runtime).

If you don’t want to follow the instructions and create the app, a pre-built solution zip file is available. But this still requires you to download Maven and build the app. You still have to download the runtime, which is pretty straight forward for WildFly, but still an extra task.

Maven step can be reduced using a pre-built WAR file, but runtime is still required.

Docker containers allows you to simplify application delivery by packaging all the key components together in an image. So how do you get the first feel of Java EE 7 hands-on lab with Docker ?

If you are new to Docker, Tech Tip #39 provide more background and details on how to get started. After initial setup, you can pull the Docker image that contains WildFly and pre-built Java EE 7 hands-on lab WAR file as shown:

And then you can run it as:

Find out the IP address where your container is hosted using boot2docker ip command. And now access your Java EE 7 application at http://<IP>/movieplex7. The app would look like:

techtip61-output

Here is the complete log shown by the Docker container:

Source code for this Dockerfile is pretty straight forward and at github.com/arun-gupta/docker-images/blob/master/javaee7-hol/Dockerfile.

Enjoy!

 

Remove Docker image and container with a criteria (Tech Tip #60)

containers, techtip

You have installed multiple Docker images and would like to clean them up using rmi command. So, you list all the images as:

Then try to remove the “arungupta/wildfly-centos” image as shown below, but get an error:

So you follow the recommendation of using -f switch but get another error:

What do you do ?

This message indicates that the image is used by one of the containers and that’s why could not be removed. The error message is very ambiguous and a #9458 has been filed for the same.

In the meanwhile, an easy way to solve this is to list all the containers as shown:

There are lots of containers that are using “arungupta/wildfly-centos” image but none of them seem to be running. If there are any containers that are running then you need to stop them as:

Remove the containers that are using this image as:

The criteria here is specified as a grep pattern.

docker ps command has other options to specify criteria as well such as only the latest created containers or containers in a particular status. For example, containers that exited with status -1 can be seen as:

All running containers, as opposed to meeting a specific criteria, can be removed as:

And now the image can be easily removed as

Just like removing all containers, all images can be removed as:

Enjoy!

Docker Common Commands Cheatsheet (Tech Tip #59)

containers, techtip

Docker CLI provides a comprehensive set of commands. Here is a quick cheat sheet of the commonly used commands:

Purpose Command
Build an image docker build –rm=true .
Install an image docker pull ${IMAGE}
List of installed images docker images
List of installed images (detailed listing) docker images –no-trunc
Remove an image docker rmi ${IMAGE_ID}
Remove all untagged images docker rmi $(docker images | grep “^” | awk “{print $3}”)
Remove all images docker rm $(docker ps -aq)
Run a container docker run
List containers docker ps
Stop a container docker stop ${CID}
Find IP address of the container docker inspect –format ‘{{ .NetworkSettings.IPAddress }}’ ${CID}
Attach to a container docker attach ${CID}
Remove a container docker rm ${CID}
Remove all containers docker rm $(docker ps -aq)

What other commands do you use commonly ?

Pushing Docker images to Registry (Tech Tip #58)

containers, techtip, wildfly,

Tech Tip #57 explained how to create your own Docker images. That particular blog specifically showed how to build your own WildFly Docker images on CentOS and Ubuntu. Now you are ready to share your images with rest of the world. That’s where Docker Hub comes in handy.

Docker Hub is the “distribution component” of Docker, or a place to store and search images. From the Getting Started with Docker Hub docs …

The Docker Hub is a centralized resource for working with Docker and its components. Docker Hub helps you collaborate with colleagues and get the most out of Docker.

Starting and pushing images to with Docker Hub is pretty straight forward.

  • Pushing images to Docker Hub require an account. It can be created as explained here. Or rather easily by using docker login command.

    Searching on WildFly shows there are 72 images:

    Official images are tagged jboss/wildfly.
  • In order to push your own image, it needs to be built as a named image otherwise you’ll get an error as shown:

    This can be easily done as shown:

    docker build command builds the image, -t specifies the repository name to be applied to the resulting image.
  • Once the image is built, it can be verified as:

    Notice the first line shows the named image arungupta/wildfly-centos.
  • This image can then be pushed to Docker Hub as:
  • And you can verify this by pulling the image:

Enjoy!

 

Getting Started with Docker (Tech Tip #39)

containers, redhat, techtip, wildfly,

If the numbers of articles, meetups, talk submissions at different conferences, tweets, and other indicators are taken into consideration, then seems like Docker is going to solve world hunger. It would be nice if it would, but apparently not. But it does solve one problem really well!

Lets hear it from @solomonstre – creator of Docker project!

In short, Docker simplifies software delivery by making it easy to build and share images that contain your application’s entire environment, or application operating system.

What does it mean by application operating system ?

Your application typically require a specific version of operating system, application server, JDK, database server, may require to tune the configuration files, and similarly multiple other dependencies. The application may need binding to specific ports and certain amount of memory. The components and configuration together required to run your application is what is referred to as application operating system.

You can certainly provide an installation script that will download and install these components. Docker simplifies this process by allowing to create an image that contains your application and infrastructure together, managed as one component. These images are then used to create Docker containers which run on the container virtualization platform, provided by Docker.

What are the main components of Docker ?

Docker has two main components:

  • Docker: the open source container virtualization platform
  • Docker Hub: SaaS platform for sharing and managing Docker images

Docker uses Linux Containers to provide isolation, sandboxing, reproducibility, constraining resources, snapshotting and several other advantages. Read this excellent piece at InfoQ on Docker Containers for more details on this.

Images are “build component” of Docker and a read-only template of application operating system. Containers are runtime representation, and created from, images. They are “run component” of Docker. Containers can be run, started, stopped, moved, and deleted. Images are stored in a registry, the “distribution component” of Docker.

Docker in turn contains two components:

  • Daemon runs on a host machine and does the heavy lifting of building, running, and distributing Docker containers.
  • Client is a Docker binary that accepts commands from the user and communicates back and forth with daemon

How do these work together ?

Client communicates with Daemon, either co-located on the same host, or on a different host. It requests the Daemon to pull an image from the repository using pull command. The Daemon then downloads the image from Docker Hub, or whatever registry is configured. Multiple images can be downloaded from the registry and installed on Daemon host.

docker-architecture-techtip39

Client can then start the Container using run command. The complete list of client commands can be seen here.

Client communicates with Daemon using sockets or REST API.

Because Docker uses Linux Kernel features, does that mean I can use it only on Linux-based machines ?

Docker daemon and client for different operating systems can be installed from docs.docker.com/installation/. As you can see, it can be installed on a wide variety of platforms, including Mac and Windows.

For non-Linux machines, a lightweight Virtual Machine needs to be installed and Daemon is installed within that. A native client is then installed on the machine that communicates with the Daemon. Here is the log from booting Docker daemon on Mac:

For example, Docker Daemon and Client can be installed on Mac following the instructions at docs.docker.com/installation/mac.

The VM can be stopped from the CLI as:

And then restarted again as:

And logged in as:

The complete list of boot2docker commands are available in help:

Enough talk, show me an example ?

Some of the JBoss projects are available as Docker images at www.jboss.org/docker and can be installed following the commands explained on that page. For example, WildFly Docker image can be installed as:

The image can be verified using the command:

Once the image is downloaded, the container can be started as:

By default, Docker containers do not provide an interactive shell and input from STDIN. So if WildFly Docker container is started using the command above, it cannot be terminated using Ctrl + C.  Specifying -i option will make it interactive and -t option allocated a pseudo-TTY.

In addition, we’d also like to make the port 8080 accessible outside the container, i.e. on our localhost. This can be achieved by specifying -p 80:8080 where 80 is the host port and 8080 is the container port.

So we’ll run the container as:

Container’s IP address can be found as:

The started container can be verified using the command:

And now the WildFly server can now be accessed on your local machine as http://192.168.59.103 and looks like as shown:

Finally the container can be stopped by hitting Ctrl + C, or giving the command as:

The container id obtained from “docker ps” is passed to the command here.

More detailed instructions to use this image, such as booting in domain mode, deploying applications, etc. can be found at github.com/jboss/dockerfiles/blob/master/wildfly/README.md.

What else would you like to see in the WildFly Docker image ? File an issue at github.com/jboss/dockerfiles/issues.

Other images that are available at jboss.org/docker are:

  • KeyCloak
  • TorqueBox
  • Immutant
  • LiveOak
  • AeroGear

 

Did you know that Red Hat is amongst one of the top contributors to Docker, with 5 Red Hatters from Project Atomic working on it ?