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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

Linkerd​

This code sample has been tested against Linkerd 2.10

Firstly, let's download Linkerd CLI and configure the path for linkerd. Remember to replace [USER_HOME] with your user home directory path:

curl -sL run.linkerd.io/install | sh
export PATH=$PATH:$HOME/.linkerd2/bin

Once installed, verify the CLI is running correctly with:

linkerd version

To check that your cluster is ready to install Linkerd, run:

linkerd check --pre

If there are any checks that do not pass, make sure to follow the provided links and fix those issues before proceeding.

Now that you have the CLI running locally and a cluster that is ready to go, it's time to install the control plane.

The first step is to install the control plane core. To do this, run:

linkerd install | kubectl apply -f -

Wait for the control plane to be ready (and verify your installation) by running:

linkerd check

Assuming everything is green, we're ready for the next step!

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.

If you want to build your own image, then do not forget to update hazelcast-client.yaml with your own image.

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.

If you want to build your own image, then do not forget to update hazelcast-embedded.yaml with your own image.

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

Summary​

This tutorial demonstrates how to use Hazelcast Embedded and client/server topology in Linkerd environment with Automatic Sidecar Injection. Hazelcast continuously tries to support cloud native technologies and verifies those environments as they evolve.

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