This project aims to help developers and newbies that would try latest version of SolrCloud (and Zookeeper) in a Kubernetes environment.
Here you'll find basically two different configuration:
- one (or more) Solr instance and one Zookeeper configured as Standalone node
- one (or more) Solr instance and a Zookeeper Ensemble (which means a cluster)
The Zookeeper configuration (and interaction with Solr) is the hardest part of the project. It is important to point out that Zookeeper has two different configuration: Standalone and Ensemble.
- Standalone has only one node
- Ensemble is a cluster and has always an odd number of nodes starting from 3 (i.e. 3, 5, 7, etc.).
Here we need two different configuration (StatefulSet) for Zookeeper, depending if you want have Standalone or Ensemble. Of course if you need to deploy an high availablity configuration, there are no ways, you can't have a single point of failure so you need to start an Ensemble.
Solr on the other hand can run one or more instances transparentely from the zookeeper configuration, it just need to have one or more Zookeeper correctly configured and running a version compatible with the Sor version you choose.
Here are described following Kubernetes Deployment Envs:
- Kubernetes with Docker for Desktop (local)
- Azure Kubernetes Services (AKS)
- Amazon Elastic Kubernetes Service (EKS)
- Google Container Engine (GKE) (this part of the project should be updated)
- Minikube (local)
At end of installation Solr (port 8983) and Zookeeper (port 2181) are reachable via kubernetes services that acts as TCP LoadBalancer.
Note: Use CloudSolrClient in your Java client application only inside the Kubernetes Cluster, from outside better if you use HttpSolrClient via the loadbalancer.
- install Docker for Desktop lastest version aka Community edition.
- Install Google Cloud SDK - https://cloud.google.com/sdk/downloads
- Follow the Kubernetes Engine Quickstart - https://cloud.google.com/kubernetes-engine/docs/quickstart
- Install Azure CLI
- Then run:
az aks install-cli
- install Docker lastest version or Docker for Desktop
- install Minikube latest version
- install a VM driver compatible with your environment (MacOS, Linux, Windows).
If you want try a light configuration with 1 SolrCloud container and 1 Zookeeper container, start with:
git clone https://github.com/freedev/solrcloud-zookeeper-kubernetes.git
cd solrcloud-zookeeper-kubernetes
./start.sh
Then run the command kubectl get pods and kubectl get service to ensure that pods and services were created
correctly:
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
solr-0 1/1 Running 0 2m26s
zk-0 1/1 Running 1 2m31s
$ kubectl get service
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 4d
solr-service LoadBalancer 10.100.213.138 localhost 8983:30955/TCP 1s
solrcluster ClusterIP None <none> <none> 1s
zk-service LoadBalancer 10.109.138.223 localhost 2181:30063/TCP 1s
zkensemble ClusterIP None <none> <none> 1s
So you'll find the SorlCloud cluster at: http://localhost:8983/solr/#/
- You need a Kubernetes Cluster - Azure Kubernetes Service (AKS) quickstart
If you already have an existing eks cluster and only need to get the credentials:
az aks get-credentials --resource-group myResourceGroup --name MyManagedCluster
Now you can start your cluster:
start.sh
To find the services load balancer just run:
$ kubectl get services
EKS) quickstart
- You need a Kubernetes Cluster - Creating an Amazon EKS Cluster
$ eksctl create cluster --name solr-dev --nodegroup-name standard-workers --node-type t3a.medium --nodes 4 --node-ami auto --nodes-min 1 --nodes-max 4
Now you can start your cluster:
start.sh
To find the services load balancer just run:
$ kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.100.0.1 <none> 443/TCP 13m
solr-service LoadBalancer 10.100.115.145 a50c0fe32b57211e9a3fc0ae1e2f29a2-134001589.eu-west-1.elb.amazonaws.com 8983:30107/TCP 107s
solrcluster ClusterIP None <none> <none> 107s
zk-service LoadBalancer 10.100.134.160 a502a5087b57211e9a3fc0ae1e2f29a2-301817188.eu-west-1.elb.amazonaws.com 2181:32609/TCP 108s
zkensemble ClusterIP None <none> <none> 108s
First set default compute/region and compute/zone where create your Kubernetes cluster, for example:
gcloud config set compute/region europe-west4
gcloud config set compute/zone europe-west4-b
I've choosen europe-west4 because is near to me, in your case may be better if you a region/zone near you.
Then create the Kubernetes cluster cluster-solr, note that in this tutorial I've choosen a machine-type n1-standard-4 with 4 cores and 15 GB RAM.
gcloud container clusters create cluster-solr --num-nodes 1 --machine-type n1-standard-4 --disk-size=50 --scopes storage-rw,compute-rw
Now you can start your cluster:
start.sh
When your cluster is successfully started, you need to understand how to reach the Solr instance.
You can use kubectl and jq:
$ kubectl get svc solr-service -o json | jq ".spec.ports[0] | .nodePort"
8983
$ kubectl get nodes -o json | jq '.items[0] | .status.addresses[] | select(.type | contains("ExternalIP")) | .address'
123.123.123.123
If your node is still not reachable, probably it's because of Google cloud default network firewall rules.
gcloud compute firewall-rules create allow-8983-from-everywhere --allow=TCP:8983 --direction=INGRESS
gcloud compute firewall-rules create allow-2181-from-everywhere --allow=TCP:2181 --direction=INGRESS
gcloud compute instances add-tags $(kubectl get node -o json | jq -r '.items[0] | .metadata.name ') --tags=allow-8983-from-everywhere,allow-2181-from-everywhere
Execute this to create and configure a virtual machine that runs a single-node Kubernetes cluster.
minikube start --extra-config=apiserver.ServiceNodePortRange=1-50000
Note: Minikube normally does not handle LoadBalancer Services. I've choose LoadBalancer services to expose externally solr and zookeeper. only for Minikube you need to use NodePort Service Type
This command also configures your kubectl installation to communicate with this cluster.
After that you can finally start (create) your SolrCloud cluster with 1 Solr instance and 1 Zookeeper instance:
./start-minikube.sh
Then run the command kubectl get pods to ensure that the pods were created correctly:
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
solr-0 1/1 Running 0 2m26s
zk-0 1/1 Running 1 2m31s
Then run the command minikube service to see where the services are (which port and ip address):
minikube service list
|-------------|----------------------|----------------------------|
| NAMESPACE | NAME | URL |
|-------------|----------------------|----------------------------|
| default | kubernetes | No node port |
| default | solr-service | http://192.168.99.101:8983 |
| default | solrcluster | No node port |
| default | zk-service | http://192.168.99.101:2181 |
| default | zkensemble | No node port |
| kube-system | kube-dns | No node port |
| kube-system | kubernetes-dashboard | No node port |
|-------------|----------------------|----------------------------|
As you can imagine, this is an example of the returned output, there is the ip address and the port for solr-service and zk-service.
So you'll find the SorlCloud cluster at: http://192.168.99.101:8983
Note: The ip address 192.168.99.101 allocated with minikube will change from environment to environment.
If you want shutdown Solr and Zookeeper just run:
./stop.sh
kubectl exec -t -i zk-0 -- tail -100f /store/logs/zookeeper.log
Before to deploy Solr or Zookeeper in Kubernetes, it is important understand what's the difference between Stateless and Stateful applications in Kubernetes.
Stateless applications
A stateless application does not preserve its state and saves no data to persistent storage — all user and session data stays with the client.
Some examples of stateless applications include web frontends like Nginx, web servers like Apache Tomcat, and other web applications.
You can create a Kubernetes Deployment to deploy a stateless application on your cluster. Pods created by Deployments are not unique and do not preserve their state, which makes scaling and updating stateless applications easier.
Stateful applications
A stateful application requires that its state be saved or persistent. Stateful applications use persistent storage, such as persistent volumes, to save data for use by the server or by other users.
Examples of stateful applications include databases like MongoDB and message queues like Apache ZooKeeper.
You can create a Kubernetes StatefulSet to deploy a stateful application. Pods created by StatefulSets have unique identifiers and can be updated in an ordered, safe way.
So a Solrcloud Cluster matches exactly the kind of Stateful application previously described. And we have to create the environment following these steps:
- create configmap where store the cluster configuration
- create statefulsets for Solr and Zookeeper that can write their data on persistent volumes
- map solr and zookeeper as network services (loadbalancer or nodeport)