I have a kubernetes cluster in which in one of the docker container I am running django.
It is listening on port 8999
http://0.0.0.0:8999
Whereas the service is listening on port 8444
I need to access django admin from outside so I did port forward
kubectl port-forward service/django-service 8444:8444
But it is not loading the page. I am not sure if I should port forward the 8444 or 8999.
Please advise.
say your django app is running in a container inside a pod naming -
'django-75f59d57f4-4nd6q'
Verify that the django-75f59d57f4-4nd6q is running in the Pod, and listening on port 8999
kubectl get pod django-75f59d57f4-4nd6q --template='{{(index (index .spec.containers 0).ports 0).containerPort}}{{"\n"}}'
If you get - 8999 in the result
and if you want to port-forward it to 8444
do this -
kubectl port-forward django-75f59d57f4-4nd6q 8444:8999
and if you have named the service as django-service as then do
kubectl port-forward service/django-service 8444:8999
I am testing k8s on ubuntu using virtual box.
I have two nodes, one is master, another is worker node.
I deployed a pod containing nginx server container for test.
I can access the webpage deployed by the pod on master node with commands below
kubectl port-forward nginx-server 8080:80
curl localhost:8080
but I want to open this page on my host os(windows10) using chrome web browser
This is how I set port-forwading on virtual-box...
simply answer your question, use address args for the kubectl command:
kubectl port-forward --address 0.0.0.0 nginx-server 8080:80
here is the explanation:
kubectl port-forward bind to localhost by default
the port forward for your virtual box is bind to 10.100.0.104
0.0.0.0 will bind the port to both localhost and 10.100.0.104
change 0.0.0.0 to 10.100.0.104 will also work for 10.100.0.104 access, but not the localhost
and also, when exposing a port, you could use a NodePort service: https://kubernetes.io/docs/concepts/services-networking/service/#nodeport
I have computer A and B on LAN:
A at IP 192.168.0.104
B at IP 192.168.0.110
On computer B I have a Kubernetes service with ingress:
path hello
host hello-node.com
minikube ip is 192.168.49.2
/etc/hosts has a line:
192.168.49.2 hello-node.com
On B I see the service response to hello-node.com/hello but not to
192.168.49.2/hello. On 192.168.49.2/hello I see 404 error from nginx.
How do I access either hello-node.com/hello or 192.168.49.2/hello from computer A?
I do not want to rely on any 3rd party service (load balancer etc)
info:
minikube version: v1.16.0
$ kubectl cluster-info
Kubernetes control plane is running at https://192.168.49.2:8443
KubeDNS is running at https://192.168.49.2:8443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
Workaround without using ingress, but NodePort expose command. From link from #mariusz-k
kubectl expose deployment/hello-node --type="NodePort" --port 8080
SERVICE_NODE_IP=$(minikube ip)
FORWARD_PORT=8090
SERVICE_NODE_PORT=$(kubectl get services/hello-node -o go-template='{{(index .spec.ports 0).nodePort}}')
ssh -i ~/.minikube/machines/minikube/id_rsa docker#$SERVICE_NODE_IP -NL \*:$FORWARD_PORT:0.0.0.0:$SERVICE_NODE_PORT
You need to get the address of Computer B (the cluster ip) and then connect to it.
# Get the cluster "master" ip
$ kubectl cluster-info
Kubernetes master is running at https://<the desired ip/DNS record>......:443
# use the above ip to get the content of your service
curl -vsI <ip>/hello
You can access your minikube service from another machine by following steps from this github issue:
service_name=web # This is what you need to replace with your own service
service_port=$(minikube service $service_name --url | cut -d':' -f3)
ssh -i ~/.minikube/machines/minikube/id_rsa docker#$(minikube ip) -NL \*:${service_port}:0.0.0.0:${service_port}
After that your service will be available under `<minikube's-host-ip>:
kubectl exposes commands that can be used to create a Service for an application and assigns an IP address to access it from internet.
As far as I understand, to access any application within Kubernetes cluster there should be a Service resource created and that should have an IP address which is accessible from an external network.
But in case of port-forward how does kubectl create a connection to the application without an IP address which is accessible externally?
To start, it's useful to note and remember that in Kubernetes, every pod gets its own ip address from 10.*, that is usable only within the cluster. Now, the port-forward feature of kubectl simply tunnels the traffic from a specified port at your local host machine to the specified port on the specified pod. API server then becomes, in a sense, a temporary gateway between your local port and the Kubernetes cluster.
kubectl port-forward forwards connections to a local port to a port on a pod. Compared to kubectl proxy, kubectl port-forward is more generic as it can forward TCP traffic while kubectl proxy can only forward HTTP traffic.
kubectl port-forward is useful for testing/debugging purposes so you can access your service locally without exposing it.
Below is the name of the pod and it will forward it's port 6379 to localhost:6379.
kubectl port-forward redis-master-765d459796-258hz 6379:6379
which is the same as
kubectl port-forward pods/redis-master-765d459796-258hz 6379:6379
or
kubectl port-forward deployment/redis-master 6379:6379
or
kubectl port-forward rs/redis-master 6379:6379
or
kubectl port-forward svc/redis-master 6379:6379
kubectl port-forward makes a specific Kubernetes API request. That means the system running it needs access to the API server, and any traffic will get tunneled over a single HTTP connection.
Having this is really useful for debugging (if one specific pod is acting up you can connect to it directly; in a microservice environment you can talk to a back-end service you wouldn't otherwise expose) but it's not an alternative to setting up service objects. When I've worked with kubectl port-forward it's been visibly slower than connecting to a pod via a service, and I've found seen the command just stop after a couple of minutes. Again these aren't big problems for debugging, but they're not what I'd want for a production system.
If you want to forward to a different port in localhost. Try this
kubectl port-forward <pod-name> <locahost-port>:<pod-port>
kubectl port-forward sample-pod-sadasds-sxawdd 8090:6379
The above command forwards to localhost 8090 from pod 6379
The port-forward command, Forwards one (or more) local ports to a pod.
This command is very useful for example in blue/green deployments where you would want to troubleshoot a misbehaving pod.
To take things even further, you could even execute some preliminary tests to the pods you feel could be more error-prone right inside your CI/CD pipeline in Jenkins by using multiple conditions, declarative pipeline.
Usage examples:
Listen on port 8888 locally, forwarding to 5000 in the pod
kubectl port-forward pod/mypod 8888:5000
Listen on port 8888 on all addresses, forwarding to 5000 in the pod
kubectl port-forward --address 0.0.0.0 pod/mypod 8888:5000
Listen on a random port locally, forwarding to 5000 in the pod
kubectl port-forward pod/mypod :5000
Listen on port 8888 on localhost and selected IP, forwarding to 5000 in the pod
kubectl port-forward --address localhost,10.19.21.23 pod/mypod 8888:5000
Listen on ports 5000 and 6000 locally, forwarding data to/from ports 5000 and 6000 in the pod
kubectl port-forward pod/mypod 5000 6000
Listen on ports 5000 and 6000 locally, forwarding data to/from ports 5000 and 6000 in a pod selected by the deployment
kubectl port-forward deployment/mydeployment 5000 6000
Listen on ports 5000 and 6000 locally, forwarding data to/from ports 5000 and 6000 in a pod selected by the service
kubectl port-forward service/myservice 5000 6000
To access something inside the cluster, there ae a couple of different options available to,
Cluster IP service with Ingress-Nginx
NodePort Service to expose the pod directly to the outside world.
Above both approach will require to write config file, In case if you want to access a pod without writing a config file then it comes to third option.
Port Forward: We can run a command at our terminal that tells our kubernets cluster to port-forward a port off a very specific pod inside of our cluster when we use this port forwarding thing that's going to cause our cluster to essentially behaves as though it has a node port service running inside it. It's going to expose this pod or a very specific port on it to the outside world and allow us to connect to it directly from our local machine.
Let's go by an example:
const stan = nats.connect('ticketing', 'abc', {
url: 'http://localhost:5000',
});
Our goal is to establish a connection between stan and a pod inside a kubernets cluster.
first we will need the pod name, you can get the name by command kubectl get pods
kubectl get pods
I am assuming my pod name is nats-depl-855d477f4d-xgbd7, and it is accessiable via a cluster IP service
apiVersion: v1
kind: Service
metadata:
name: nats-srv
spec:
selector:
app: nats
ports:
- name: client
protocol: TCP
port: 4222
targetPort: 4222
now to establish the connection run the below command:
kubectl port-forward nats-depl-855d477f4d-xgbd7 5000:4222
5000: is the port of my local machine
4222 : is the port of the pod I want to get access
kubectl port-forward is the easiest communication method with the Pod, but under the hood, this method is much more complicated. The communication goes through several Kubernetes components, so if anything is broken in the communication path, you will not be able to talk to the pod, even if the pod itself is accessible via regular communication channels.
The server proxy runs via kubectl port-forward command forwards the connection to the Kubernetes API Server living in Master node, then the API Server delivers the connection to the Kubelet on the node hosting your Pod, and then the Kubelet forwards the connection to the application running in the pod's container.
NOTE
The application in the container must be bound to a port on the
loopback device for the Kubelet to reach it. If it listens only on the
pod’s eth0 network interface, you won’t be able to reach it with the
kubectl port-forward command.
Marko Lukša "Kubernetes in Action, Second Edition"
TIP
kubectl port-forward allows you to forward communication also to Services and has several other useful features. Run kubectl port-forward --help to learn more.
I'm using lxc/lxd to play with the kubenetes cluster.
Is there a way to expose a deployed service locally without using minikube, so that I could access it from the local machine?
I can access it from any of the nodes in the cluster but not from outside.
Do you want to acccess the pod being served by the service? if yes, you can use kubectl port-forward to connect to your pod and access it locally
Here is an example:
If you have a service which forwards all the requests to a pod ( nginx ) at port number 80 you can configure it to your local port as follows
kubectl port-forward -n default nginx-5767f4d585-hgtfj 8081:80
Here is the syntax of the same
kubectl port-forward -n NAMESPACE ${POD} local-port:pod-port
If you want to connect to your service directly, you need to do it via kubectl proxy
Here is a reference
Hope it helps.