Dockerizing Web App Stack

Building Blocks of Docker:

• Image - An image is a portable artifact representing a Docker Container.
• Container - A Docker container is a runnable virtual OS.
• Dockerfile - A Docker file is a text file to adapt existing images according customer needs.
• Docker Hub - The Docker hub is a public registry and repository to publish Docker-Images
• libcontainer - Lib container is the standard interface to Linux kernel virtualization that tandardize the way apps are packed up, delivered, and run in isolation -- and one that developers, not just sys admins, can hook into and implement (also ported to Windows, see https://blog.docker.com/2015/06/open-container-project-foundation/).
• libswarm - Libswarm is a library that make it relatively trivial to compose other disparate tools together, including but not limited to orchestration tools.
• libchan - Libchan is an ultra-lightweight networking library (Docker Plug-In) which lets network services communicate in the same way that goroutines communicate using channels:

Install docker on Ubuntu

sudo apt-get install linux-image-generic-lts-trusty

get latest docker: curl -sSL https://get.docker.com/ | sh

behind a firewall: curl -sSL https://get.docker.com/gpg | sudo apt-key add -

The docker daemon binds to a Unix socket instead of a TCP port. By default that Unix socket is owned by the user root and other users can access it with sudo. For this reason, docker daemon always runs as the root user.

make user part of docker group:

sudo usermod -aG docker mark

If firewall ufw:

/etc/default/ufw
DEFAULT_FORWARD_POLICY="ACCEPT"

On desctop with local DNS 127.0.0.1 and dns masc: /etc/default/docker DOCKER_OPTS="--dns 8.8.8.8" disable dns masc /etc/NetworkManager/NetworkManager.conf #dns=dnsmasq

restart docker: sudo restart docker

• Dockerize your applications.
• Run your own containers.
• Build Docker images.
• Share your Docker images with others.
• And a whole lot more!

Simple docker run docker run ubuntu:14.04 /bin/echo 'Hello world' Hello world

Using Flags: -t assign terminal -i make interactie docker run -t -i ubuntu:14.04 /bin/bash --> open shell in container

-d flag tells Docker to run the container and put it in the background, to daemonize it.

Important commands: docker ps - Lists containers. docker logs - Shows us the standard output of a container. docker stop - Stops running containers.

Dockerize springboot

https://spring.io/guides/gs/spring-boot-docker/#initial

mvn package && java -jar target/gs-spring-boot-docker-0.1.0.jar

Dockerfile generated by Maven plugin (see below)

src/main/docker/Dockerfile

Dockerfile:

FROM java:8
VOLUME /tmp
ADD gs-spring-boot-docker-0.1.0.jar app.jar
RUN bash -c 'touch /app.jar'
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

VOLUME pointing to "/tmp" because that is where a Spring Boot application creates working directories for Tomcat by default. The effect is to create a temporary file on your host under "/var/lib/docker" and link it to the container under "/tmp". This step is optional for the simple app that we wrote here, but can be necessary for other Spring Boot applications if they need to actually write in the filesystem.

RUN command to "touch" the jar file so that it has a file modification time (Docker creates all container files in an "unmodified" state by default). This actually isn’t important for the simple app that we wrote, but any static content (e.g. "index.html") would require the file to have a modification time. 

Maven plugin required (delivered by Transmode, Spotify)

<plugin>
            <groupId>com.spotify</groupId>
            <artifactId>docker-maven-plugin</artifactId>
            <version>0.2.3</version>
            <configuration>
                <imageName>${docker.image.prefix}/${project.artifactId}</imageName>
                <dockerDirectory>src/main/docker</dockerDirectory>
                <resources>
                    <resource>
                        <targetPath>/</targetPath>
                        <directory>${project.build.directory}</directory>
                        <include>${project.build.finalName}.jar</include>
                    </resource>
                </resources>
            </configuration>
        </plugin>

mvn package docker:build docker push mauermbq/gs-spring-boot-docker docker run -p 8080:8080 -t mauermbq/gs-spring-boot-docker

Run spring app behind a reverse proxy (nginx container can be found on docker hub): docker run --name nginx-container -v $(pwd)/html:/usr/share/nginx/html:ro --link spring-app:app -p 80:80 -d -t mauermbq/nginx_img_proxy

Login in to nginx container and check for linked app container: docker exec -it nginx-container bash env | grep APP | sort