![]() Alternatively, one can specify a particular port to be used as NodePort in the spec while creating the service. ![]() ![]() The chosen NodePort will be visible in the service spec after creation, as seen above. If we specify a NodePort service, Kubernetes will allocate a port on every node. Here is how a NodePort service spec will look: We can do this by creating a NodePort service for the workload. For this workload, we need to expose the private container port 80 externally. How to define a NodePortĬonsider the workload running the image of Nginx again. One of these types is NodePort, which provides external access to the Kubernetes Service created for your workload pods. If you want to expose the service outside of the Kubernetes cluster, refer to these ServiceType options in Kubernetes. So by default for a service, the yaml is type: ClusterIP. This internal scope is defined using the type parameter of the service spec. So even if the pods switch IP addresses, external clients that depend on the workload launched over these pods can keep accessing the workload without disruption and without knowledge of the back end pod recreation via the Kubernetes Service interface.īy default, a service is accessible within the Kubernetes cluster on an internal IP. The IP address that Kubernetes pods listen to cannot be used as a reliable endpoint for public access to your workload because pods can be destroyed and recreated dynamically, changing their IP address.Ī Kubernetes Service provides a static endpoint to the pods. Kubernetes ServiceĪ Kubernetes Service is a REST object that abstracts access to Kubernetes pods. The same thing will happen when the pods are restarted, and Kubernetes reschedules them on a different node.īefore we dive into how to create a NodePort for exposing your Kubernetes workload, let’s look at some background on the Kubernetes Service. Thus, the IP address where your workload is accessible will change, breaking any external clients of your application. If the host where the pods are running goes down, Kubernetes will have to reschedule the pods to different nodes. If the scale of your workload is more than the number of nodes in your Kubernetes cluster, then the deployment will fail.Īny two workloads that specify the same HostPort cannot be deployed on the same node. Using a HostPort limits the scheduling options for your pod, since only those hosts that have the specified port available can be used for deployment. No other object needs to be created for exposing your application in comparison to a NodePort. The configuration is simple, and the HostPort setting is placed directly in the Kubernetes pod specs. You can request any available port on the host to be exposed via the HostPort setting. Using a HostPort for a Kubernetes pod is equivalent to exposing a public port for a Docker container in Rancher 1.6. workloadselector: deployment-mystack-nginx ![]() Here is how the Kubernetes YAML for our Nginx workload specifying the HostPort setting under the ‘ports’ section looks: Traffic hitting at : is routed to the pod container’s private port. When a HostPort is specified, that port is exposed to public access on the host where the pod container is deployed. Rancher performs this action internally when you select the HostPort for mapping. The HostPort setting has to be specified in the Kubernetes YAML specs under the ‘Containers’ section while creating the workload in Kubernetes. Let’s look at HostPort and NodePort in some detail. Rancher internally adds the necessary Kubernetes HostPort or NodePort specs while creating the deployments for a Kubernetes cluster. These are the options in Kubernetes for exposing a public port for your workload:Īs seen above, the UI for port mapping is pretty similar to the 1.6 experience. Rancher 2.0 also supports adding port mapping to your workloads deployed on the Kubernetes cluster. This public port routed traffic to the private port of the service containers running on that host. Users could choose a specific port on the host or let Rancher assign a random one, and that port would be opened for public access. Rancher 1.6 enabled users to deploy their containerized apps and expose them publicly via Port Mapping. Using load balancing solutions is a wide topic and we can look at them separately in later articles. In this article, we will explore various options for exposing your Kubernetes workload publicly in Rancher 2.0 using port mapping. Standard ways for providing external access include exposing public ports on the nodes where the application is deployed or placing a load balancer in front of the application containers.Ĭattle users on Rancher 1.6 are familiar with port mapping to expose services. Real world applications deployed using containers usually need to allow outside traffic to be routed to the application containers.
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