How do we define a Kubernetes Ingress for the backend kind Kubernetes Job?
Could not find specific reference from the documentation https://kubernetes.io/docs/concepts/services-networking/ingress/
A Job creates Pods as implementation.
An Ingress uses a Service to reach the correct Pods.
In order to make an Ingress for Pods created by a Job make sure that a Service exists with a selector that matches the labels of the Pods created by the Job.
Use that Service in the Ingress as target.
Related
Is it possible to create a Kubernetes service and pod in different namespaces, for example, having myweb-svc pointing to the actual running myweb-pod, while myweb-svc and myweb-pod are in different namespaces?
YAML manifest to create both the pod and the service in their respective namespaces. You need to specify the ‘namespace’ field in the ‘metadata’ section of both the ‘pod’ and ‘service’ objects to specify the namespace in which they should be created.
Also, if you want to point your Service to a Service in a different namespace or on another cluster you can use service without a pod selector.
Refer to this link on Understanding kubernetes Object for more information.
Kubernetes API objects that are connected together at the API layer generally need to be in the same namespace. So a Service can only connect to Pods in its own namespace; if a Pod references a ConfigMap or a Secret or a PersistentVolumeClaim, those need to be in the same namespace as well.
In Openshift/kubernetes, how to create a service with pod selector that could discover pods across namespaces?
I tried to use the same label for all the pods in multiple namespaces and used that as pod selector in openshift 4.10 service but that did NOT work, i only see pods discovered by service from same namespace where it is created.
You can not.
By design, a Service is a namespace scoped object. When setting a selector, discovering Pods eligible to act as a backend for that Service, you would always stay within your namespace.
One way to have your Service pointing to something outside of your namespace would be to work without selectors. In your case, maybe an ExternalName could let you create one Service, making it an alias of another Service, in a remote namespace. See Kubernetes docs
I have questions about my basic understanding about the setup of my k8s cluster.
I have a K8s running on Hetzner-cloud and allocated a "physical" Loadbalancer (which can be controlled via annotations on a Service.)
I use a nginx (or traefik) as my ingress-controller.
Please correct me if I am wrong:
I create the service Loadbalancer with the annotations in the same namespace of my ingress-controller right?
Then I create an ingress with label kubernetes.io/ingress-controller=nginx in my default namespace with the settings to point to my services in the default namespace (one for frontend, one for backend)
Is this the correct way to set this up?
1.- No. Ingress Controller and your workload doesn't have to be in the same namespace. In fact, you will have the Ingress Controller running in a separate namespace than your workload.
2.-Yes. Generally speaking your Ingress rules, meaning your Ingress object, meaning your Ingress yaml and your Service must be in the same namespace. So Ingress can't transpass a namespace.
Note: There is a way to have an Ingress object to send trafffic to a Service in a different namespace.
I create the service Loadbalancer with the annotations in the same
namespace of my ingress-controller right?
No ideally your ingress controller will be running in different namespace in which your workload must not be running.
You should be keeping only the Nginx service with type : Loadbalancer other services of your workload should be ClusterIP.
So all your traffic comes inside the cluster from one point. Your flow will be something like
DNS > LB > Ingress > Service > Pods > Container
Then I create an ingress with label
kubernetes.io/ingress-controller=nginx in my default namespace with
the settings to point to my services in the default namespace (one for
frontend, one for backend)
You mentioned label ideally, it should be an annotation kubernetes.io/ingress-controller=nginx.
Yes, it's perfect. You can create different ingress with different annotation rules as per requirements for different services that you want to expose publicly.
Keep your workload in default namespace for the controller you can use different namespaces like ingress-controller in future also if you have any requirement of setting up the Monitoring tools also you can create namespace and use it for monitoring only.
Good morning guys, so I took down a staging environment for a product on GCP and ran the deployment scripts again, the backend and frontend service have been setup. I have an ingress resource and a load balancer up, however, the service is not running. A look at the production app revealed there was something like an nginx-ingress-controller. I really don't understand all these and how it was created. Can someone help me understand because I have not seen anything online that makes it clear for me. Am I missing something?
loadBalancer: https://gist.github.com/davidshare/5a571e56febe7dacd580282b373f3095
Ingress Resource: https://gist.github.com/davidshare/d0f53912bc7da8310ec3d64f1c8a44f1
Ingress allows access to your Kubernetes services from outside the Kubernetes cluster. There are different kubernetes aka K8 resources alternatively you can use like (Node Port / Loadbalancer) which you can use to expose.
Ingress is independent resource to your service , you can specify routing rules declaratively, so each url with some context can be mapped to different services.
This makes it decoupled and isolated from the services you want to expose.
So to work ingress it needs an Ingress Controller for your cluster.
Like deployment resource in K8, ingress can be created simply by
kubectl create -f ingress.yaml
First, you have to implement Ingress Controller in order to apply Ingress resource, as described in #Shubhu answer. Ingress controller, as an edge router, applies specific logical structure with aim to route external traffic to your Kubernetes cluster underlying services via basic pattern routing rules defined in Ingress resource.
If you select Nginx Ingress Controller then it might be useful to proceed with installation guide approaching some specific prerequisites based on cloud provider environment. In order to simplify Nginx Ingress controller installation procedure it is also possible to use Helm package manager and install appropriate stable/nginx-ingress Helm chart.
I have kubeadm and Kubernetes v1.12 without AWS or Google Cloud.
I want to know if the Kubernetes cluster installed already has an ingress controller and if it has two what is the default.
Thanks :)
You can check for pods implementing ingress controllers (actually with ingress in the name) with:
kubectl get pods --all-namespaces | grep ingress
And services exposing them with:
kubectl get service --all-namespaces | grep ingress
As #Prafull Ladha says, you won't have an ingress controller by default. The documentation states that in "environments other than GCE/Google Kubernetes Engine, you need to deploy a controller as a pod".
There will not be any ingress or ingress-controller defined on the kubernetes cluster defined by kubeadm.
You can define your own ingress resource, read more about it here
For ingress resource to work you must have ingress-controller running. This controller is unlike other controller, which runs as a part of kube-controller-manager and automatically created as a part of cluster creation.
You need to choose the ingress controller implementation that suits your cluster. Kubernetes currently supports and manages Nginx and google ingress controller. You can also choose other ingress controller like Traefik or kong.
Hope this helps