docker Posts

Run Multiple Containerized Keycloak Instances Behind an Apache HTTPD Proxy

On this session im trying to create a sample condition where im having a High-Availability cluster of multiple Keycloaks instances which are located behind an HTTPD Reverse Proxy. HTTPD will do a round robin request to two Keycloaks instances behind it, showing the capability of session sharing between different Keycloak instances.

Im using a containerized Keycloak image and run them by using Docker for simulating a condition of running more than one Keycloak instances with different IP.

The concept is pretty much like below image,

The first thing needed is setuping a database for this. In here im using MySQL, despite Keycloak is able to connect to different type of databases. And for this sample, database is installed on my host laptop and not using a containerized one.

CREATE USER 'keycloak'@'%' IDENTIFIED BY 'password';
CREATE DATABASE keycloak_db;

The next step is running two Keycloak instances by executing below command, in here im putting as the ip for my host machine.

docker run -p 8081:8080 -e PROXY_ADDRESS_FORWARDING=true  \ 
	-e DB_VENDOR="mysql" -e DB_ADDR="" -e DB_USER="keycloak" \ 
	-e DB_PASSWORD="password" -e DB_PORT="3306" -e DB_DATABASE="keycloak_db" \ 
	--add-host=HOST: jboss/keycloak

docker run -p 8082:8080 -e PROXY_ADDRESS_FORWARDING=true  \ 
	-e DB_VENDOR="mysql" -e DB_ADDR="" -e DB_USER="keycloak" \ 
	-e DB_PASSWORD="password" -e DB_PORT="3306" -e DB_DATABASE="keycloak_db" \ 
	--add-host=HOST: jboss/keycloak

The good thing about this keycloak image is that by default it is running a standalone-ha.xml and automatically form a cluster when being run locally at the same time. This can be seen on Keycloak’s log

06:20:53,102 INFO  [org.infinispan.CLUSTER] (non-blocking-thread--p8-t4) 
	[Context=offlineClientSessions] ISPN100010: Finished rebalance with members [a629f48aafa9, 82298394e158], topology id 11
06:20:53,102 INFO  [org.infinispan.CLUSTER] (thread-35,ejb,a629f48aafa9) 
	[Context=sessions] ISPN100010: Finished rebalance with members [a629f48aafa9, 82298394e158], topology id 11
06:20:53,103 INFO  [org.infinispan.CLUSTER] (thread-30,ejb,a629f48aafa9) 
	[Context=work] ISPN100010: Finished rebalance with members [a629f48aafa9, 82298394e158], topology id 11
06:20:53,114 INFO  [org.infinispan.CLUSTER] (thread-30,ejb,a629f48aafa9) 
	[Context=loginFailures] ISPN100010: Finished rebalance with members [a629f48aafa9, 82298394e158], topology id 11
06:20:53,121 INFO  [org.infinispan.CLUSTER] (thread-31,ejb,a629f48aafa9) 
	[Context=actionTokens] ISPN100010: Finished rebalance with members [a629f48aafa9, 82298394e158], topology id 11

The last step would be creating an HTTPD setup for creating reverse proxy with a load-balancing capability. And we can achieve that by editing httpd.conf file, for this sample we are using a round-robin mechanism of lbmethod=byrequests.

<VirtualHost *:80>
	ServerName localhost
	ProxyRequests Off
	ProxyPreserveHost On
	<Proxy "balancer://mycluster">
		BalancerMember http://localhost:8081
		BalancerMember http://localhost:8082
		ProxySet lbmethod=byrequests failontimeout=on
	ProxyPass / balancer://mycluster/
	ProxyPassReverse / balancer://mycluster/

In order to activate loadbalancer and http proxying feature on Apache HTTPD, there are several variables that need to be unremark on httpd.conf file such as proxy_balancer_module and proxy_http_module.

Restart httpd and open browser directly, and we can see that Keycloak is working well.

We can also simulate a condition where one instance suddenly stopped to simulate a failover scenario by killing one Keycloak instance using docker kill command. Have fun with Keycloak 😀

For a better performance, a sticky session approach is recommended compared to a round robin one.

How to Solve Openshift “Failed to pull image, unauthorized: authentication required”

Just recently got an unique error, this happens when my application is pulling an image within a different Openshift namespace. In this example, im creating my application in “xyz-project” and try to pull image from “abc-project”. Here’s the complete error detail,

Failed to pull image "image-registry.openshift-image-registry.svc:5000/abc-project/image01@sha256:xxxxxxxxxxxx": 
rpc error: code = Unknown desc = Error reading manifest sha256:xxxxxxxxxxxx in 
image-registry.openshift-image-registry.svc:5000/abc-project/image01: unauthorized: authentication required

Solution for this is quite easy, actually we need to give a specific access right in order for “xyz-project” to be able to pull image from “abc-project”.

oc policy add-role-to-user system:image-puller system:serviceaccount:xyz-project:default -n abc-project

Hope it helps.

How to Remove Docker’s Dangling Image on Windows 10

There are times where i need to clean all unused, dangling docker images on my laptop. Previously im running below command,

docker image prune -a

But it seems like altho almost all images are gone, i can see still some images are still occupying my laptop’s disk. So i have to do something to delete them.

The workaround is quite easy, run PowerShell as Administrator and run below command,

docker rmi $(docker images --quiet --filter "dangling=true") -f

Executing that command will generates this log,

And i can see that my harddisk is now have more free spaces 🙂

Fixing “SSL routines:tls_process_ske_dhe:dh key too small” on Containerized RHEL8

I have a very unique error today, so basically my RHEL 8 (Red Hat Enterpise Linux) cannot connect to another system due to SSL issue. The exception is quite clear, and can be seen below.

error:141A318A:SSL routines:tls_process_ske_dhe:dh key too small

It is quite easy to do it in a standalone infrastructure, but this problem happen on a containerized application which make it much more complicated.

After searching for a solution, i come up with this Dockerfile


user root
RUN update-crypto-policies --set LEGACY 

user 185

Build it,

docker build -f Dockerfile -t application-rhel8-modified:7.8.0 .

Deploy it, and i can see that the previous error is no longer exist.

Building Containerized Images on Openshift 4 and Push the Result to Third Party Image Registry

Sometimes in our pipeline, we need to build a docker images based on a specific Dockerfile and push the result to an external Image Registry such as Quay, Docker Hub or even on-premise Nexus or JFrog.

On this example, im trying to simulate build a simple java application, containerized it, and push it to Quay. The rough concept can be seen below,

1. Jenkins pull latest java code from Github, do testing and Maven build
2. Containerizing Maven build result and push it to Quay
3. Openshift Pre-Prod and Prod will pull from Quay, if build result is considered stable enough

For this example, im using a simple Dockerfile,


MAINTAINER Muhammad Edwin < edwin at redhat dot com >


RUN microdnf install --nodocs java-11-openjdk-headless && microdnf clean all

WORKDIR /work/
COPY target/*.jar /work/application.jar

CMD ["java", "-jar", "application.jar"]

And build it in a Jenkins pipeline, on this example im deploying to Quay

node('maven') {
    stage ('pull code') {
        sh "git clone source"
    stage ('mvn build') {
        dir("source") {
            sh "mvn clean package"
    stage ('build and push') {
        dir("source") {
            sh "oc new-build --strategy docker --name=hello-world-java-docker \
                        --binary --to-docker \
               || true"
            sh "oc start-build hello-world-java-docker --from-dir=. --follow --wait "

One thing you need to remember is that we need to register our Quay credentials in order to be able to push there. And we can achieve it by using this command,

oc create secret docker-registry \
	--docker-username=edwinkun --docker-password=******* \
	--docker-email=unused \

oc secrets link default quay-login

Run our Jenkins pipeline and we can see the result on Jenkins dashboard,

When successfully deployed, we can see the pipeline log result will be like this,

And lastly we can see that the containerized image is successfully deployed to Quay

Code for above example can be found on this Github link,