CPA aims to horizontally scale the number of Pod replicas based on the cluster’s scale. A common example is DNS services. CPA can dynamically adjust the number of DNS instances based on the current cluster scale, which can be either the number of nodes or the overall CPU capacity.
apiVersion: rbac.authorization.k8s.io/v1kind: Rolemetadata:name: leaderlabels:app: kubernetes-leader-election-examplegroup: org.springframework.cloudrules:- apiGroups:- ""resources:- podsverbs:- watch- get- apiGroups:- ""resources:- configmapsverbs:- watch- get- update# resourceNames:# - <config-map name>
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
labels:
app: kubernetes-leader-election-example
group: org.springframework.cloud
name: leader
roleRef:
apiGroup: ""
kind: Role
name: leader
subjects:
- kind: ServiceAccount
name: default
apiGroup: ""To change the behavior of a pod’s DNS resolver, you can change the DNS config of a pod
apiVersion: v1kind: Podmetadata:namespace: defaultname: dns-examplespec:containers:- name: testimage: nginxdnsPolicy: "None"dnsConfig:nameservers:- 1.2.3.4searches:- ns1.svc.cluster-domain.example- my.dns.search.suffixoptions:- name: ndotsvalue: "2"- name: edns0
In the example above, the dnsPolicy is set to "None", which means that the pod will not use the default DNS settings provided by the cluster. Instead, the dnsConfig field is used to specify custom DNS settings for the pod.
The nameservers field is used to specify the DNS servers that the pod should use for DNS lookups. The searches field is used to specify the search domains that should be used for incomplete domains.
The options field is used to specify custom options for the DNS resolver, such as the ndots and edns0 options in the example above.
These settings will be used by the pod’s DNS resolver instead of the default settings provided by the cluster. For more information on pod DNS configuration, see the official docs.
apiVersion: apps/v1
kind: Deployment
metadata:
name: my-app-deployment
spec:
replicas: 2
selector:
matchLabels:
app: my-app
template:
metadata:
labels:
app: my-app
spec:
containers:
- name: my-app-container
image: my-app-image:latest
ports:
- containerPort: 8081
env:
- name: POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name@RestController
@RequestMapping("/example")
public class MyController {
@Value("${POD_NAME}")
private String podName;
@GetMapping("/getPodName")
public void printPodName() {
System.out.println(podName);
}
}<dependency> <groupId>io.fabric8</groupId> <artifactId>kubernetes-client-bom</artifactId> <version>6.9.2</version> <type>pom</type> <scope>import</scope> </dependency>
<dependency><groupId>io.fabric8</groupId> <artifactId>kubernetes-client</artifactId> <version>6.9.2</version> </dependency>
KubernetesClient kubernetesClient = new DefaultKubernetesClient().inNamespace(namespace);
import io.fabric8.kubernetes.api.model.Namespace;
import io.fabric8.kubernetes.api.model.NamespaceBuilder;
public void createOrReplaceNamespace(String namespaceName) {
Namespace namespace = new NamespaceBuilder()
.withNewMetadata()
.withName(namespaceName)
.endMetadata()
.build();
kubernetesClient.namespaces().createOrReplace(namespace);
}public void deleteNamespace(String namespaceName) {
kubernetesClient.namespaces().withName(namespaceName).delete();
}import io.fabric8.kubernetes.api.model.Pod;
public List<Pod> allPodsStartingWith(String prefix) {
return kubernetesClient.pods().list().getItems().stream()
.filter(p -> p.getMetadata().getName().startsWith(prefix))
.collect(Collectors.toList());
}public void deletePod(String podName) {
kubernetesClient.pods().withName(podName).delete();
}
public void deletePodForcefully(String podName) {
kubernetesClient.pods().withName(podName).withGracePeriod(0).delete();
}public String getPodLog(String podName) {
return kubernetesClient.pods().withName(podName).getLog();
}
public String getPodStatus(String podName) {
Pod pod = kubernetesClient.pods().withName(podName).get();
return pod.getStatus().getPhase();
}import io.fabric8.kubernetes.api.model.LoadBalancerIngress;
import io.fabric8.kubernetes.api.model.Service;
import io.fabric8.kubernetes.api.model.apps.StatefulSetStatus;
public String getServiceExternalIp(String serviceName) {
Service service = kubernetesClient.services().withName(serviceName).get();
if (service == null) {
throw new IllegalStateException("Service '" + serviceName + "' not found");
}
return getIngressIp(service);
}
private static String getIngressIp(Service service) {
List<LoadBalancerIngress> ingress = service.getStatus().getLoadBalancer().getIngress();
if (ingress != null && !ingress.isEmpty()) {
return ingress.get(0).getIp();
}
throw new IllegalStateException("Ingress for '" +
service.getMetadata().getName() + "' not found");
}<dependency> <groupId>io.fabric8</groupId> <artifactId>kubernetes-client-bom</artifactId> <version>6.9.2</version> <type>pom</type> <scope>import</scope> </dependency>
<dependency><groupId>io.fabric8</groupId><artifactId>kubernetes-server-mock</artifactId><version>${fabric8.version}</version><scope>test</scope></dependency>
