I wanted some help in understanding the ExternalIP field in Kubernetes services.
Based on the information https://kubernetes.io/docs/concepts/services-networking/service/#external-ips
I understood that I can define a Kubernetes service and assign a Ip address using the ExternalIP field.
To test this i created a Kubernetes environment on AWS using Rancher. In the Kubernetes cluster, i deployed a image and created a Nodeport service and assigned a ElasticIp to the Nodeport service.
My expectation was that i will be able to access the service using the ElasticIP:Nodeport.
However the there is no response. I am getting the error destination not available.
If i run the command
kubectl get svc -n namepace
I could see the ElasticIP under the elastic ip field.
I then deployed the same service without the ExternalIp field. This time the Nodeport service. I could access the deployment using the Nodeipaddress:Nodeport.
Related
I am deploy kubernetes UI using this command:
kubectl apply -f kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v2.2.0/aio/deploy/recommended.yaml
And it response "Unable to connect to the server: dial tcp 185.199.110.133:443: i/o timeout"
I behind proxy, how can i fix it?
All the services that you deployed via the supplied url don't have a kind specified. This means they will be using the default service type which is ClusterIP.
Services of Kind ClusterIP are only accessible from inside your Kubernetes Cluster.
If you want the Dashboard to be accessible from outside your Cluster, you will need a service of type NodePort. A NodePort Service will assign a random high number port on all your nodes on which your application, in this case the k8s dashboard, will be accessible via ${ip-of-any-node}:${assigned-nodeport}.
For more information, please take a look at the official k8s documentation.
If your cluster is behind a proxy, also make sure, that you can reach your clusters node's external ip from wherever you are trying to send the request from.
In order to find out what port number has been assigned to your NodePort service use kubectl describe service ${servicename} or kubectl get service ${servicename} -o yaml
I am deploy kubernetes UI using this command:
kubectl apply -f kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v2.2.0/aio/deploy/recommended.yaml
And it response "Unable to connect to the server: dial tcp 185.199.110.133:443: i/o timeout"
I behind proxy, how can i fix it?
All the services that you deployed via the supplied url don't have a kind specified. This means they will be using the default service type which is ClusterIP.
Services of Kind ClusterIP are only accessible from inside your Kubernetes Cluster.
If you want the Dashboard to be accessible from outside your Cluster, you will need a service of type NodePort. A NodePort Service will assign a random high number port on all your nodes on which your application, in this case the k8s dashboard, will be accessible via ${ip-of-any-node}:${assigned-nodeport}.
For more information, please take a look at the official k8s documentation.
If your cluster is behind a proxy, also make sure, that you can reach your clusters node's external ip from wherever you are trying to send the request from.
In order to find out what port number has been assigned to your NodePort service use kubectl describe service ${servicename} or kubectl get service ${servicename} -o yaml
Every where its mentioned "cluster type of service makes pod accessible within a Kubernetes cluster"
Does it mean, after adding cluster service to a POD, then that POD can be connected only using cluster service IP of POD, we will not be able to connect POD using the IP of POD generated before adding cluster ?
Please help me understanding, am learning Kubernetes so.
When a service is created using the ClusterIP then that service is accessible only inside the cluster as service IP's are virtual IP.
Although if you want to access the pod from outside using the service IP then you can use the nodeport or loadbalancer type service which will allow you to access the pod using the Node's IP or the loadbalancer's IP.
Main reason behind using services to access pod is that it give a fixed location (ClusterIP or service name) to access. Pod's can come an go but service IP will remain same.
I am trying to deploy my sample micro service Docker image in Kubernetes cluster having 2 node. I explored everything about Pods, Services, Deployment, StatefulSets and Daemon-sets etc.
I am trying to create a sample deployment and Service for that. Here I explored about how deployment provides the scalability and load balancing functionality. And exploring about service discovery by providing Services ClusterIp.
I have two questions:
My scenario is that I am trying to deploy microservice on my on-premise Ubuntu machine. The machine has the IP address of 192.168.1.15. When I am referring Kubernetes, service will also have one clusterIP.
If my microservice end point is /api/v1/loadCustomer, how I can call this end point? Do I need to use clusterIP also ? Can I call simply 192.168.1.15:8080/api/v1/loadCustomers ?
What is the role of clusterIP when I am calling my end point ? Can I directly use port?
I am referring to the following link for exploration:
https://kubernetes.io/docs/concepts/services-networking/connect-applications-service/
tldr:
you can not access the application using the clusterIP from the outside of the cluster. you can access the application using either loadbalancer's IP (type=LoadBalaner) or Node's IP (type=NodePort).
benefit of clusterIP:
As you know that pods can be created and terminated during its life-cycle consequently IP (endpoint IP)address created and terminated.Therefore, clusterIP is static which does not depends of the life-cycle of the pods.
Long Answer
In a Kubernetes cluster
an application or pod has following abstraction.
Endpoint IP and Port:It is provided by the CNI Plugins such as flannel, calico.
Each pod has an IP and tragetPort which is UNIQUE.
you can list and watch the endpoints by the following commands.
kubectl get endpoints --all-namespaces
clusterIP and port : It is provided by the kube-proxy component.
The replicated pods share a clusterIP and Port.
Load-balancing of request to the replicated pods.
internally expose so that other pod can discover it
you can list and watch clusterIP and port with the following command
kubectl get services --all-namespaces
externalIP and port: It can be layer 3-4 load balancer's IP and port or node's IP and Nodeport.
if you want to use loadbalancer's IP and port, you can use type=LoadBalaner in service file.
If you want to use node's IP, you need to use type=NodePort in service file.
Is there a way to discover all the endpoints of a headless service from outside the cluster?
Preferably using DNS or Static IPs
By watching changes to a list of Endpoints:
GET /api/v1/watch/namespaces/{namespace}/endpoints
Headless Services are a group of Pod IPs. Pod IPs are not (generally) available outside the cluster/cloud-provider.
Are you trying to get external IPs for a headless service or are you within the same network (e.g. in the GCE project) but not in the cluster?
The DNS addon is exactly what you're after. From the docs:
For example, if you have a Service called "my-service" in Kubernetes
Namespace "my-ns" a DNS record for "my-service.my-ns" is created. Pods
which exist in the "my-ns" Namespace should be able to find it by
simply doing a name lookup for "my-service". Pods which exist in other
Namespaces must qualify the name as "my-service.my-ns". The result of
these name lookups is the cluster IP.
And in the case of a headless service:
DNS is configured to return multiple A records (addresses) for the
Service name, which point directly to the Pods backing the Service.
However, this service is only available inside the cluster. But KubeDNS is just another pod:
kubectl get po --namespace=kube-system
kubectl describe po kube-dns-pod-name --namespace=kube-system
Which means you can create a service with an externally accessible address to expose this service. Just use a selector matching your kube-dns pod label.
http://kubernetes.io/v1.1/docs/user-guide/services.html#dns
https://github.com/kubernetes/kubernetes/blob/release-1.1/cluster/addons/dns/README.md