Deploy a microservice on native docker and openshift

Assumptions

This blog assumes that you have played around with docker and openshift and have deployed an image or two along the way on both the platforms. A few things to ensure before you start running this applicaton are

  • Docker daemon is running ( In my case i am running docker for mac )
  • Openshift is running ( I am using minishift but you could potentially use the real version )
  • oc tool ( The client for accessing openshift ) is in the path and can be accessed from any terminal window

Introduction

The application is a simple rest end point hosted by camel that uses netty as its http layer. It returns the string “Hello world” when invoked.it’s not a applicaton that is “deployed” on a server in fact it comes bundled with an http layer, a la spring boot. The maven file for this project has three plugins that

  • Create a runnable jar
  • Create a docker image and push it up to docker hub
  • Pull down the docker image from docker hub and run it on open shift, also create a route

The bundler

The very first step in the process is to build a jar file that is “runnable”, The application itself is nothing more than a camel route, and a blocking camel main to keep it running. We are using the maven-assembly-plugin to create a jar with all the dependencies bundled up

Logging

The application uses the ubiquitous log4j logging framework and all the logging is routed to a file /tmp/log.out that is configured in the log4j.properties file in src/main/resources folder of the project.

file beat

I have included the filebeat utility ( committed the sin of checking in the binary ) that watches the logfile (/tmp/log.out) created by the application and establishes a pipeline to send the logs to the ELK stack. We are also leveraging the openshift feature of config map which is a bunch of properties that are injected into a container and used in the application as properties. In our case the elk url is in the config map. and can be changed on openshift ( console or UI) to take effect on the pods. We also have to adjust the yml configuration file of file beat so that the properties file is replaced with an environment variable substitution ELK environment variable.

The docker plugin

The fabric8 docker plugin ties the goal of docker image creation to the build phase of install and creates a tar ball of the image. The additional goals of push and start push the newly created image up to docker hub and also start the image locally

Open shift commands

The image that has been pushed up to docker hub is now used by open shift to deploy. The open shifts commands are located in oc-deploy.sh. A brief explanation below

oc login -u=admin -p=admin

The login command tries to login to the open shift server running locally. The default connection settings are saved in ~/.kube/config file.

oc delete all --all

This command removes everything ( services, routes etc ) that have been added via the new-app command

oc new-app svsvenu/fabric-camel-rest:1.0-SNAPSHOT

Creates s new-app by downloading the artifact from docker hub

oc expose svc/fabric-camel-rest --hostname=fabric-camel-rest-my-project.192.168.64.3.nip.io

Creates a route to access the end point independent of the number of containers running in the background

oc logout

Yea, does what it says

The code

You can find the code here Da project

Written on May 15, 2018