Microservices Demo

This is a demo microservice project based on Microservices Blog on the spring.io website.

This example builds a simple microservice based distributed system, which consists of a service, a client and a discovery service (Netflix Eureka). Each of those services are deployed as a Docker container in one single Host.

Components

• discovery: registration, discovery service.
• service: producer service. It provides a REST endpointm which is being called by the consumer service.
• client: consumer service. It also provides a REST endpoint for testing purpose.

Discovery endpoint:

http://[docker_host_ip]:8761/

Service endpoint:

http://[docker_host_ip]:8880/service

Client endpoint:

http://[docker_host_ip]:8890/client

Calling this URL makes this service to make a discovery call to the service service and then, returning its response. Since there might be more than one service registered with the same id / name, the service will be load balanced as described in the spring.io Blog entry.

Building the containers with the Docker Maven Plugin

In order to build the Docker image, the Docker Machine must be running and connected to the Docker Host. I installed Docker Toolbox in my Windows 10 machine. It installs a VirtualBox, configures it entirely with a Docker Hub image in it, and installs the Docker Machine.

The Docker Maven Plugin makes ones life easier, when changes in the service implementation are made constantly and re-build the docker image has to be done several times.

The Docker Maven Plugin needs a Dockerfile file within each microservice project. This is one plugin configuration I used:

            <plugin>
	            <groupId>com.spotify</groupId>
	            <artifactId>docker-maven-plugin</artifactId>
	            <version>0.4.3</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>

Due to some missing configuration, I faced a problem where some required system variables have not been properly set, so I had to set them manually. Those are the shell commands I used on my command line:

set DOCKER_HOST=tcp://192.168.99.100:2376
set DOCKER_MACHINE_NAME=default
set DOCKER_TLS_VERIFY=1
set DOCKER_TOOLBOX_INSTALL_PATH=C:\Program Files\Docker Toolbox
set DOCKER_CERT_PATH=C:\Users\Admin\.docker\machine\machines\default

After setting these system variables, I have been able to build the project jar file and build a new Docker image (within the Docker Host) with the following maven comand from command line (in each project's directory):

mvn clean package docker:build

Running the docker containers

There are two possibilities to start the containers. First one is to use a Docker Compose file for starting all three containers together and linking them properly. The second one is to start every single one manualy with a docker command.

For the second approach, here are the Docker commands:

# Discovery container
docker run -d -p 8761:8761 -h discovery --name discovery apexitsystems/discovery

# Service container - it is being replicated
docker run -d -p 8880:8880 --link discovery:discovery --name service-1 apexitsystems/service
docker run -d -p 8881:8880 --link discovery:discovery --name service-2 apexitsystems/service

# Client container
docker run -d -p 8890:8890 --link discovery:discovery --name client apexitsystems/client

Note that the discovery container is registering its hostname "-h discovery", so the other services can find it.

Testing the services

About one minute after starting the 3 containers, it ispossible to see the registered services under http://[docker_host_ip]:8761/.

Calling the client service endpoint http://[docker_host_ip]:8890/client on a web browser should show the following message

The client received this response from service: Hello! This is the response from the service. It is working :)

Helpful Docker commands

• Run docker bash

docker run <container id> /bin/bash

• Clean up exited containers

docker ps -a | grep 'Exited' | awk '{print $1}' | xargs --no-run-if-empty docker rm

• Clean up hanging Volumes

docker volume ls -qf dangling=true | xargs -r docker volume rm

• Kill all running containers

docker kill $(docker ps -q)

• Delete all stopped containers (including data-only containers)

docker rm $(docker ps -a -q)

• Delete all 'untagged/dangling' () images

docker rmi $(docker images -q -f dangling=true)