Java Posts

Creating a Jenkins Slave Image with Maven 3.6, Java 11 and Skopeo

Openshift have a default maven Jenkins slave image, but too bad it is build on top of Java 8. And on this project which im currently working on, i need a custom Jenkins slave but with Java 11 and the ability to move images between Image Registry. Therefore i create a custom Dockerfile which contains Skopeo, Maven 3.6.3 and Java 11. Below is the detail Dockerfile which i created,

FROM openshift/jenkins-slave-base-centos7:v3.11

MAINTAINER Muhammad Edwin < edwin at redhat dot com >


ENV MAVEN_VERSION=3.6.3 \
    PATH=$PATH:/opt/maven/bin

# install skopeo
RUN yum install skopeo -y && yum clean all

# install java
RUN curl -L --output /tmp/jdk.tar.gz https://download.java.net/java/GA/jdk11/9/GPL/openjdk-11.0.2_linux-x64_bin.tar.gz && \
	tar zxf /tmp/jdk.tar.gz -C /usr/lib/jvm && \
	rm /tmp/jdk.tar.gz && \
	update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk-11.0.2/bin/java 20000 --family java-1.11-openjdk.x86_64 && \
	update-alternatives --set java /usr/lib/jvm/jdk-11.0.2/bin/java
	
# Install Maven
RUN curl -L --output /tmp/apache-maven-bin.zip  https://www-eu.apache.org/dist/maven/maven-3/${MAVEN_VERSION}/binaries/apache-maven-${MAVEN_VERSION}-bin.zip && \
    unzip -q /tmp/apache-maven-bin.zip -d /opt && \
    ln -s /opt/apache-maven-${MAVEN_VERSION} /opt/maven && \
    rm /tmp/apache-maven-bin.zip && \
    mkdir -p $HOME/.m2

RUN chown -R 1001:0 $HOME && chmod -R g+rw $HOME

COPY run-jnlp-client /usr/local/bin/

USER 1001

Build by using this command,

docker build -t jenkins-slave-skopeo-jdk11-new -f skopeo-jdk11.dockerfile .

Pull the image to Openshift,

oc import-image docker.io/edwinkun/jenkins-slave-skopeo-jdk11-new --confirm

Register on Jenkins as a

And try on

node('maven') {
	stage('Clone') {
		sh "git config --global http.sslVerify false"
		sh "git clone https://github.com/edwin/hello-world.git"
	}
	stage('Build') {
		sh "mvn -v"
		sh "mvn clean package -f hello-world/pom.xml"
	}
}

This is the result,

Detail code can be seen on my github page, https://github.com/edwin/jenkins-slave-maven-jdk11-skopeo

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Starting JBoss EAP or Wildfly with a Specific XML Configuration

We can run EAP or Wildfly with a specific XML configuration, not just the default one. For example we have a new configuration with the name of standalone-full-ha_1.xml, and want to run EAP based on it. First we need to put corresponding XML on below directory,

%WILDFLY_DIRECTORY%\standalone\configuration

And run using below command,

standalone.bat -c standalone-full-ha_1.xml

(Y)

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Does JBoss EAP’s “org.jboss.jca.adapters.jdbc.extensions.oracle.OracleValidConnectionChecker” doing a “Select 1 from Dual”?

TL;DR
No it is NOT.

Longer Version :
JBoss EAP and Wildfly have its own internal query validator to check whether connection is active or not before doing connection to Oracle database, it resides on below class.

org.jboss.jca.adapters.jdbc.extensions.oracle.OracleValidConnectionChecker

Why i’m interested in OracleValidConnectionChecker class? Because several days ago, i got a critical question from Habiburrokhman Sjarbini, my fellow RedHat Platform Consultant regarding this. Whether OracleValidConnectionChecker which is embedded in JBoss EAP will do a “select 1 from dual” query?

I have to decompile a lot of classes to see what is running under the hood,

Here is the screenshot of what OracleValidConnectionChecker looks like,

On Oracle database, it will call “oracle.jdbc.driver.OracleConnection” and invoke method “pingDatabase”. Lets check what is the content of “pingDatabase” method,

OracleConnection will call its super class, OracleConnectionWrapper, and invoke pingDatabase method. It goes here and there, until finally it reach oracle.jdbc.driver.PhysicalConnection class on method doPingDatabase.

And as you can see, it runs a “SELECT ‘x’ FROM DUAL” query, instead on “select 1 from dual”. :)

Jar versions :

ojdbc8.jar
ironjacamar-jdbc-1.4.11.Final.jar
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Slowness when Generating SecureRandom with Java on RHEL 7

Today i had a very weird issue where there is slowness on my app when generating random secure number on my server, the weird thing is that it never happen on my Windows machine. After intensive debugging i found out that below code part is causing the slowness,

    static {
        try {
            secureRandom = SecureRandom.getInstanceStrong();
        } catch (Exception e) {
            secureRandom = new SecureRandom();
        }
    }

Replacing it with below code solve my problem,

    static {
        try {
            secureRandom = SecureRandom.getInstance("SHA1PRNG");
        } catch (Exception e) {
            secureRandom = new SecureRandom();
        }
    }
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Deploying Spring Boot with A Dynamic application.properties Location to Openshift

I want to create a simple spring boot app, and deploy it to Openshift 4.2. It supposed to be a straigh forward task, but the problem is that it is required to externalize all configuration to a configmaps or secret so no need to recompile the whole app in case of configuration change.

There are several approach of externalizing configuraton to configmaps, one way is put it as a string literal, include on your pod and call on application via environment variables, or deploy the whole configuration file and mount it on your Openshift pod. The last approach is the one that we will be doing now today.

First lets start with deploying our properties to Openshift as configmaps,

oc create cm myapp-api-configmap --from-file=D:\source\my-app\src\main\resources\application.properties

We can check and validate the result,

oc get cm

oc describe cm myapp-api-configmap

After that, we can mount corresponding configmap to a specific folder on our Pod, on below example modification is done on DeploymentConfig.yaml and mounting application.properties to /deployments/config folder.

kind: DeploymentConfig
apiVersion: apps.openshift.io/v1
metadata:
  ........
    spec:
      volumes:
        - name: myapp-api-configmap-volume
          configMap:
            name: myapp-api-configmap
            defaultMode: 420
      containers:
        - name: myapp-api
          image: >-
            image-registry.openshift-image-registry.svc:5000/openshift/myapp@sha256:1127.....
          ports:
            - containerPort: 8778
              protocol: TCP
            - containerPort: 8080
              protocol: TCP
            - containerPort: 8443
              protocol: TCP
          resources: {}
          volumeMounts:
            - name: myapp-api-configmap-volume
              mountPath: /deployments/config
          terminationMessagePath: /dev/termination-log
          terminationMessagePolicy: File
          imagePullPolicy: Always
      restartPolicy: Always
      terminationGracePeriodSeconds: 30
      dnsPolicy: ClusterFirst
      securityContext: {}
      schedulerName: default-scheduler

A modification is also needed on my Dockerfile, pointing a new path for my properties file by using “spring.config.location” parameter,

FROM registry.access.redhat.com/openjdk/openjdk-11-rhel7

USER jboss
RUN mkdir -p /deployments/image && chown -R jboss:0 /deployments
EXPOSE 8080

COPY target/application-1.0.jar /deployments/application.jar
CMD ["java", "-jar", "/deployments/application.jar", "--spring.config.location=file:///deployments/config/application.properties"]

Build, deploy,and see that application is now taking configuration from external configuration file.

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