Java High Availability With WildFly on Kubernetes
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Java High Availability With WildFly on Kubernetes
if you need session replication, Wildfly instances need to be clustered. To solve this, you can use the Kubernetes discovery protocol for JGroups: KUBE_PING.
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With the advancement of the dockerization of applications, Kubernetes has become a standard in the market, but we must remember that there are still thousands of legacy applications that depend on certain features provided by the application servers. So, if you need to use session replication, you will surely need Wildfly instances to be clustered. To solve this smoothly, you can use the “Kubernetes discovery protocol for JGroups” aka “KUBE-PING”. KUBE_PING is a discovery protocol for JGroups cluster nodes managed by Kubernetes: jgroups-kubernetes.
Walkthrough
I assume you already have a Kubernetes cluster, so let’s just focus on WildFly settings.
The first step is to create a repository that will contain all our files:
Shell
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[root@workstation ~]# mkdir wildfly20-kubeping
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[root@workstation ~]# mkdir -p wildfly20-kubeping/application
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[root@workstation ~]# mkdir -p wildfly20-kubeping/configuration
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[root@workstation ~]# mkdir -p wildfly20-kubeping/kubernetes
Then create a Dockerfile with the necessary steps for image customization:
Dockerfile
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[root@workstation ~]# vi wildfly20-kubeping/Dockerfile
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FROM jboss/wildfly:20.0.0.Final
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LABEL MAINTAINER Mauricio Magnani <msmagnanijr@gmail.com>
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RUN /opt/jboss/wildfly/bin/add-user.sh admin redhat --silent
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ADD configuration/config-server.cli /opt/jboss/
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RUN /opt/jboss/wildfly/bin/jboss-cli.sh --file=config-server.cli
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RUN rm -Rf /opt/jboss/wildfly/standalone/configuration/standalone_xml_history/*
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ADD application/cluster.war /opt/jboss/wildfly/standalone/deployments/
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EXPOSE 8080 9990 7600 8888
In the same directory, create the file “config-server.cli”, which will contain the steps to configure kubeping correctly:
Shell
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[root@workstation ~]# vi wildfly20-kubeping/configuration/config-server.cli
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###start the server in admin-only mode, using/modifying standalone-full-ha.xml
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embed-server --server-config=standalone-full-ha.xml --std-out=echo
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###apply all configuration to the server
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batch
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#/subsystem=logging/logger=org.openshift.ping:add()
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#/subsystem=logging/logger=org.openshift.ping:write-attribute(name=level, value=DEBUG)
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#/subsystem=logging/logger=org.openshift.ping:add-handler(name=CONSOLE)
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/subsystem=messaging-activemq/server=default/cluster-connection=my-cluster:write-attribute(name=reconnect-attempts,value=10)
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/interface=kubernetes:add(nic=eth0)
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/socket-binding-group=standard-sockets/socket-binding=jgroups-tcp/:write-attribute(name=interface,value=kubernetes)
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/socket-binding-group=standard-sockets/socket-binding=jgroups-tcp-fd/:write-attribute(name=interface,value=kubernetes)
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/subsystem=jgroups/channel=ee:write-attribute(name=stack,value=tcp)
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/subsystem=jgroups/channel=ee:write-attribute(name=cluster,value=kubernetes)
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/subsystem=jgroups/stack=tcp/protocol=MPING:remove()
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/subsystem=jgroups/stack=tcp/protocol=kubernetes.KUBE_PING:add(add-index=0,properties={namespace=${env.KUBERNETES_NAMESPACE},labels=${env.KUBERNETES_LABELS},port_range=0,masterHost=kubernetes.default.svc,masterPort=443})
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run-batch
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###stop embedded server
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stop-embedded-server
Now put the “package of your application” to the directory “application”
Shell
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[root@workstation ~]# cp cluster.war wildfly20-kubeping/application
The next step is to create all Kubernetes objects so we can do the tests later. I’m using the namespace “labs”:
Dockerfile
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[root@workstation ~]# vi wildfly20-kubeping/kubernetes/01-wildfly-sa-role.yaml
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apiVersion: v1
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kind: ServiceAccount
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metadata:
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name: jgroups-kubeping-service-account
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namespace: labs
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---
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kind: ClusterRole
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: jgroups-kubeping-pod-reader
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namespace: labs
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rules:
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- apiGroups: [""]
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resources: ["pods"]
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verbs: ["get", "list"]
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---
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apiVersion: rbac.authorization.k8s.io/v1beta1
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kind: ClusterRoleBinding
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metadata:
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name: jgroups-kubeping-api-access
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roleRef:
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apiGroup: rbac.authorization.k8s.io
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kind: ClusterRole
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name: jgroups-kubeping-pod-reader
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subjects:
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- kind: ServiceAccount
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name: jgroups-kubeping-service-account
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namespace: labs
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[root@workstation ~]# vi wildfly20-kubeping/kubernetes/02-wildfly-deployment.yaml
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: wildfly
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namespace: labs
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labels:
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app: wildfly
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tier: devops
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spec:
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selector:
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matchLabels:
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app: wildfly
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tier: devops
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replicas: 2
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template:
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metadata:
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labels:
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app: wildfly
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tier: devops
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spec:
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serviceAccountName: jgroups-kubeping-service-account
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containers:
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- name: kube-ping
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image: mmagnani/wildfly20-kubeping:latest
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command: ["/opt/jboss/wildfly/bin/standalone.sh"]
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args: ["--server-config", "standalone-full-ha.xml", "-b", $(POD_IP), "-bmanagement", $(POD_IP) ,"-bprivate", $(POD_IP) ]
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resources:
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requests:
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memory: 256Mi
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limits:
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memory: 512Mi
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imagePullPolicy: Always
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ports:
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- containerPort: 8080
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- containerPort: 9990
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- containerPort: 7600
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- containerPort: 8888
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env:
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- name: POD_IP
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valueFrom:
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fieldRef:
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apiVersion: v1
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fieldPath: status.podIP
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- name: KUBERNETES_NAMESPACE
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valueFrom:
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fieldRef:
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apiVersion: v1
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fieldPath: metadata.namespace
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- name: KUBERNETES_LABELS
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value: app=wildfly
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- name: JAVA_OPTS
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value: -Djdk.tls.client.protocols=TLSv1.2
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[root@workstation ~]# vi wildfly20-kubeping/kubernetes/03-wildfly-service.yaml
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apiVersion: v1
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kind: Service
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metadata:
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name: wildfly
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namespace: labs
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labels:
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app: wildfly
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tier: devops
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spec:
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type: ClusterIP
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ports:
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- targetPort: 8080
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port: 8080
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selector:
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app: wildfly
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tier: devops
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[root@workstation ~]# vi wildfly20-kubeping/kubernetes/04-wildfly-ingress.yaml
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---
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apiVersion: extensions/v1beta1
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kind: Ingress
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metadata:
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name: wildfly-ingress
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namespace: labs
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spec:
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rules:
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- host: wildfly.mmagnani.lab
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http:
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paths:
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- path: /
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backend:
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serviceName: wildfly
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servicePort: 8080
Now just run the image build and push this to the docker hub or any other “registry”:
Shell
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[root@workstation ~]# docker build -t mmagnani/wildfly20-kubeping:latest .
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[root@workstation ~]# docker push mmagnani/wildfly20-kubeping
In the context of your Kubernetes cluster, just create those objects:
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[root@k8s-master kubernetes]# kubelet --version
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Kubernetes v1.18.3
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[root@k8s-master kubernetes]# pwd
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/root/wildfly20-kubeping/kubernetes
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[root@k8s-master kubernetes]# kubectl create -f . -n labs
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[root@k8s-master kubernetes]# kubectl get pods -n labs
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NAME READY STATUS RESTARTS AGE
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wildfly-cc8b9546f-df9sw 1/1 Running 0 48s
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wildfly-cc8b9546f-scfdp 1/1 Running 0 48s
Check the logs. You should find two members as we only define 2 replicas:
Plain Text
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[root@k8s-master kubernetes]# kubectl logs -f wildfly-cc8b9546f-df9sw -n labs
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14:23:33,253 INFO [org.infinispan.CLUSTER] (MSC service thread 1-2) ISPN000078: Starting JGroups channel kubernetes
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14:23:33,253 INFO [org.infinispan.CLUSTER] (MSC service thread 1-2) ISPN000094: Received new cluster view for channel kubernetes: [wildfly-cc8b9546f-scfdp|1] (2) [wildfly-cc8b9546f-scfdp, wildfly-cc8b9546f-df9sw]
As I am using “Traefik”, my “ingress” is available:
In the application, it is also possible to add the object to the session:
Topics:
java,
kube_ping,
kubernetes,
session replication,
tutorial,
wildfly
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