Ingress configuration for k8s in different namespaces - kubernetes

Question

I need to configure Ingress Nginx on azure k8s, and my question is if is possible to have ingress configured in one namespace et. ingress-nginx and some serivces in other namespace eg. resources?
My files looks like so:
# ingress-nginx.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: nginx-ingress-controller
namespace: ingress-nginx
spec:
replicas: 3
selector:
matchLabels:
app: ingress-nginx
template:
metadata:
labels:
app: ingress-nginx
annotations:
prometheus.io/port: '10254'
prometheus.io/scrape: 'true'
spec:
containers:
- name: nginx-ingress-controller
image: quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.12.0
args:
- /nginx-ingress-controller
- --default-backend-service=$(POD_NAMESPACE)/default-http-backend
- --configmap=$(POD_NAMESPACE)/nginx-configuration
- --tcp-services-configmap=$(POD_NAMESPACE)/tcp-services
- --udp-services-configmap=$(POD_NAMESPACE)/udp-services
- --annotations-prefix=nginx.ingress.kubernetes.io
- --publish-service=$(POD_NAMESPACE)/ingress-nginx
env:
- name: POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: POD_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
ports:
- name: http
containerPort: 80
- name: https
containerPort: 443
livenessProbe:
failureThreshold: 3
httpGet:
path: /healthz
port: 10254
scheme: HTTP
initialDelaySeconds: 10
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 1
readinessProbe:
failureThreshold: 3
httpGet:
path: /healthz
port: 10254
scheme: HTTP
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 1
# configmap.yaml
kind: ConfigMap
apiVersion: v1
metadata:
name: nginx-configuration
namespace: ingress-nginx
labels:
app: ingress-nginx
---
kind: ConfigMap
apiVersion: v1
metadata:
name: tcp-services
namespace: ingress-nginx
---
kind: ConfigMap
apiVersion: v1
metadata:
name: udp-services
namespace: ingress-nginx
---
# default-backend.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: default-http-backend
labels:
app: default-http-backend
namespace: ingress-nginx
spec:
replicas: 1
selector:
matchLabels:
app: default-http-backend
template:
metadata:
labels:
app: default-http-backend
spec:
terminationGracePeriodSeconds: 60
containers:
- name: default-http-backend
# Any image is permissible as long as:
# 1. It serves a 404 page at /
# 2. It serves 200 on a /healthz endpoint
image: gcr.io/google_containers/defaultbackend:1.4
livenessProbe:
httpGet:
path: /healthz
port: 8080
scheme: HTTP
initialDelaySeconds: 30
timeoutSeconds: 5
ports:
- containerPort: 8080
resources:
limits:
cpu: 10m
memory: 20Mi
requests:
cpu: 10m
memory: 20Mi
---
apiVersion: v1
kind: Service
metadata:
name: default-http-backend
namespace: ingress-nginx
labels:
app: default-http-backend
spec:
ports:
- port: 80
targetPort: 8080
selector:
app: default-http-backend
kind: Service
apiVersion: v1
metadata:
name: ingress-nginx
namespace: ingress-nginx
labels:
app: ingress-nginx
spec:
externalTrafficPolicy: Local
type: LoadBalancer
selector:
app: ingress-nginx
ports:
- name: http
port: 80
targetPort: http
- name: https
port: 443
targetPort: https
# app-ingress.yaml
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: app-ingress
namespace: ingress-nginx
annotations:
kubernetes.io/ingress.class: nginx
nginx.ingress.kubernetes.io/rewrite-target: /
spec:
tls:
- hosts:
- api-sand.fake.com
rules:
- host: api-sand.fake.com
http:
paths:
- backend:
serviceName: api-sand
servicePort: 80
path: /
And then I have some app running in the resources namespace, and problem is that I am getting the following error
error obtaining service endpoints: error getting service resources/api-sand from the cache: service resources/api-sand was not found
If I deploy api-sand in the same namespace where ingress is then this service works fine.

Answer 1

I would like to simplify the answer a bit further for those who are reletively new to Kubernetes and its ingress options in particular.
There are 2 separate things that need to be present for ingress to work:
Ingress Controller(essentially a separate Pod/Deployment along with
a Service that can be used to utilize routing and proxying. Based on
nginx container for example);
Ingress rules(a separate Kubernetes
resourse with kind: Ingress. Will only take effect if Ingress
Controller is already deployed)
Now, Ingress Controller can be deployed in any namespace and is, in fact, usually deployed in a namespace separate from your app services. It can out-of-the-box see Ingress rules in all namespaces in the cluster and will pick them up.
The Ingress rules, however, must reside in the namespace where the app that they configure reside.
There are some workarounds for that, but this is the most common approach.

Answer 2

Instead of creating the ingress app-ingress in ingress-nginx namespace you should create it in the namespace where you have the service api-sandand the pod.
Alternatively there is way to achieve ingress in one namespace and service in another namespace via externalName.Checkout Kubernetes Cross Namespace Ingress Network
Here is an example referred from here.
kind: Service
apiVersion: v1
metadata:
name: my-service
spec:
type: ExternalName
externalName: test-service.namespacename.svc.cluster.local
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: example-ingress
annotations:
kubernetes.io/ingress.class: "nginx"
spec:
rules:
- host: example.com
http:
paths:
- path: /
backend:
serviceName: my-service
servicePort: 80

Answer 3

It's possible actually, you can define ingress and a service with ExternalName type in namespace A, while the ExternalName points to DNS of the service in namespace B. For further details, please refer to this answer: https://stackoverflow.com/a/51899301/2995449

Answer 4

Outside traffic comes through ingress controller service that is responsible for routing the traffic based on the defined routing rules or what we call ingress rules in k8s world.
In other words, ingress resources are just routing rules (think of it in away that's similar to DNS records) so when you define an ingress resource you just defined a rule for ingress controller to work on and route traffic based on such defined rules.
Solution:
Since Ingress are nothing but routing rules, you could define such rules anywhere in the cluster (in any namespace) and controller should pick them up as it monitors creation of such resources and react accordingly.
Here's how to create ingress easily using kubectl
kubectl create ingress <name> -n namespaceName --rule="host/prefix=serviceName:portNumber"
Note: Add --dry-run=client -oyaml to generate yaml manifest file
Or you may create a service of type ExternalName in the same namespace where you have defined your ingress. such external service can point to any URL (a service that lives outside namespace or even k8s cluster)
Here's an example that shows how to create an ExternalName service using kubectl:
kubectl create service externalname ingress-ns -n namespaceName --external-name=serviceName.namespace.svc.cluster.local --tcp=80:80 --dry-run=client -oyaml
this should generate something similar to the following:
kind: Service
apiVersion: v1
metadata:
name: nginx
namespace: ingress-ns
spec:
type: ExternalName
externalName: serviceName.namespace.svc.cluster.local #or any external svc
ports:
- port: 80 #specify the port of service you want to expose
targetPort: 80 #port of external service
As described above, create an ingress as below:
kubectl create ingress <name> -n namespaceName --rule="host/prefix=serviceName:portNumber"
Note: Add --dry-run=client -oyaml to generate yaml manifest file

Answer 5

The way worked for me is creating ingress for each namespace
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: ingress-service
namespace: production
annotations:
kubernetes.io/ingress.class: nginx
spec:
rules:
- host: api.youtube.com
http:
paths:
- pathType: Prefix
path: "/api/users"
backend:
service:
name: youtube-srv
port:
number: 3000
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: ingress-service
namespace: development
annotations:
kubernetes.io/ingress.class: nginx
spec:
rules:
- host: dev.youtube.com
http:
paths:
- pathType: Prefix
path: "/api/users"
backend:
service:
name: youtube-srv
port:
number: 3000

Answer 6

There is a way to configure your default backend per ingress resource although the documentation says it is usually configured at the ingress controller level.
For example:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: myingress
namespace: myns
spec:
defaultBackend:
service:
name: default-http-backend
port:
number: 80
...
Here default-http-backend must be defined in the same namespace as the ingress resource.