Hazelcast with Linkerd Service Mesh
Context
You’ll learn how to set up a Hazelcast cluster and connect a Hazelcast client to it. Then, you will also see how to deploy an application with embedded Hazelcast.
Before you Begin
Kubernetes Cluster
In this tutorial, a Google Kubernetes Engine is used but you can use any Kubernetes cluster you choose.
gcloud container clusters create hazelcast-cluster --num-nodes=4
Code Sample
Clone this repository and apply RBAC. RBAC is needed by hazelcast-kubernetes plugin discovery.
git clone https://github.com/hazelcast-guides/linkerd.git cd linkerd kubectl apply -f https://raw.githubusercontent.com/hazelcast/hazelcast-kubernetes/master/rbac.yaml
Linkerd automatically adds the data plane proxy to pods when the linkerd.io/inject: enabled annotation is present on a namespace or any workloads, such as deployments or pods. If you want to implement manual injection with the deployments then you need to use linkerd inject.
kubectl annotate namespace default linkerd.io/inject=enabled
Hazelcast-Linkerd Code Sample
The business logic in both examples are the same to keep it simple. put operation puts a key-value pair to Hazelcast and get operation returns the value together with the Kubernetes Pod name. PodName is used to show that the value is returned from any Pod inside the Kubernetes cluster to prove the true nature of distributed cache.
Hazelcast Client Server
Let’s first switch to the client-server directory.
cd hazelcast-client-server
Client-Server code sample can be built and pushed to your own Docker Hub or some other registry via following command but that is optional.
mvn compile com.google.cloud.tools:jib-maven-plugin:1.8.0:build -Dimage=YOUR-NAME/linkerd-client:1.0
Instead, you can use the already pre-built docker image hazelcastguides/linkerd-client:1.0.
Deploy Hazelcast Cluster:
kubectl apply -f hazelcast-cluster.yaml
You can see that 3 member cluster has been initiated with 3 pods. 2/2 in READY column means that there are 2 containers running in each Pod. One is Hazelcast member and the other is linkerd-proxy.
$ kubectl get pods NAME READY STATUS RESTARTS AGE hazelcast-cluster-0 2/2 Running 0 60s hazelcast-cluster-1 2/2 Running 0 44s hazelcast-cluster-2 2/2 Running 0 27s
Deploy Spring Boot Application with Hazelcast Client:
kubectl apply -f hazelcast-client.yaml
Check logs and see that Spring Boot service is connected to the cluster:
$ kubectl logs hazelcast-client-0 hazelcast-client
...
Members [3] {
Member [10.16.2.14]:5701 - 51274b4d-dc7f-4647-9ceb-c32bfc922c95
Member [10.16.1.15]:5701 - 465cfefa-9b26-472d-a204-addf3b82d40a
Member [10.16.2.15]:5701 - 67fdf27a-e7b7-4ed7-adf1-c00f785d2325
}
...
Let’s now run a container with curl installed and use it to make requests to the springboot-service.
First, observe the Spring Boot Service is up and running:
$ kubectl get svc springboot-service NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE springboot-service ClusterIP 10.19.250.127 <none> 80/TCP 3m29s
Launch a curl container inside Kubernetes cluster:
kubectl run curl --rm --image=radial/busyboxplus:curl -i --tty
Put a value to the cluster using the service name:
$ curl "springboot-service/put?key=1&value=2"
{"value":"2","podName":"hazelcast-client-2"}
Get the value from cluster in a loop and see that it is retrieved from different Pod names:
$ while true; do curl "springboot-service/get?key=1"; sleep 2;echo; done
{"value":"2","podName":"hazelcast-client-1"}
{"value":"2","podName":"hazelcast-client-0"}
...
In this sample, you were able to deploy a Spring Boot based microservice with Hazelcast client-server topology in Linkerd Environment.
Clean up the deployments with the following commands:
kubectl delete -f hazelcast-client.yaml kubectl delete -f hazelcast-cluster.yaml
Hazelcast Embedded
Switch to the embedded code sample directory:
cd hazelcast-embedded
Embedded code sample can be built and pushed to your own Docker Hub or some other registry via following command but that is optional:
mvn compile com.google.cloud.tools:jib-maven-plugin:1.8.0:build -Dimage=YOUR-NAME/linkerd-embedded:1.0
Instead, you can use the already pre-built docker image hazelcastguides/linkerd-embedded:1.0.
Deploy Hazelcast Embedded Sample:
$ kubectl apply -f hazelcast-embedded.yaml statefulset.apps/hazelcast-embedded created service/hazelcast-embedded-headless created service/springboot-service created
You can check that the application started and Hazelcast successfully formed a cluster.
$ kubectl logs pod/hazelcast-embedded-0 hazelcast-embedded
...
Members {size:3, ver:3} [
Member [10.12.1.6]:5701 - 644e6bbf-335a-410b-80ab-0cb648dbc772
Member [10.12.2.8]:5701 - 0ab13148-b6bb-477e-970b-0b5c226ed2aa this
Member [10.12.3.4]:5701 - 72f56c90-f55e-490c-b3c0-d40fe970557f
]
...
When you list the services used, you will see that you have two Kubernetes Services: hazelcast-embedded-headless and springboot-service. hazelcast-embedded-headless is used to handle Hazelcast cluster discovery operation so it has no need to have an IP address. springboot-service is the loadbalancer that is used to receive http requests and forward them to one of the underlying pods to respond.
$ kubectl get svc NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE hazelcast-embedded-headless ClusterIP None <none> 5701/TCP 9s kubernetes ClusterIP 10.19.241.1 <none> 443/TCP 73m springboot-service ClusterIP 10.19.252.76 <none> 80/TCP 9s
Let’s now put a key-value pair into Hazelcast cluster through Spring Boot REST Service and then call get operation in a loop to see the value is returned from different Pods.
Firstly, let’s run a container with curl installed and use it to make requests to the springboot-service.
kubectl run curl --rm --image=radial/busyboxplus:curl -i --tty
Put a value to the cluster using the service name:
$ curl "springboot-service/put?key=1&value=2"
{"value":"2","podName":"hazelcast-embedded-2"}
Get the value from cluster in a loop and see that it is retrieved from different Pod names:
$ while true; do curl "springboot-service/get?key=1"; sleep 2;echo; done
{"value":"2","podName":"hazelcast-embedded-1"}
{"value":"2","podName":"hazelcast-embedded-0"}
...
In this sample, you were able to deploy a Spring Boot based microservice with Hazelcast Embedded in Linkerd Environment. Let’s clean up the deployments with the following command.
kubectl delete -f hazelcast-embedded.yaml