I need to port forward to my pods from my local machine. It can be done easily with kubectl:
kubectl port-forward my_pod -n namespace --address 0.0.0.0 5000:5000
But I have to achieve this using Python client. I can get the socket to the remote port with:
pf = portforward(api.connect_post_namespaced_pod_portforward, pod_name, namespace, ports='5000')
pf.socket(5000)
Is that possible to bind a local port to this socket so that I can visit the webpage on the remote port from my local browser?
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
Is there a corresponding command with kubectl to:
ssh -L8888:rds.aws.com:5432 example.com
kubectl has port-forward you can also specify --address but that strictly requires an IP address.
The older answer is valid.
Still, a workaround would be to use something like
https://hub.docker.com/r/marcnuri/port-forward
kubectl run --env REMOTE_HOST=your.service.com --env REMOTE_PORT=8080 --env LOCAL_PORT=8080 --port 8080 --image marcnuri/port-forward test-port-forward
Run it on the cluster and then port forward to it.
kubectl port-forward test-port-forward 8080:8080
Short answer, No.
In OpenSSH, local port forwarding is configured using the -L option:
ssh -L 80:intra.example.com:80 gw.example.com
This example opens a connection to the gw.example.com jump server, and forwards any connection to port 80 on the local machine to port 80 on intra.example.com.
By default, anyone (even on different machines) can connect to the specified port on the SSH client machine. However, this can be restricted to programs on the same host by supplying a bind address:
ssh -L 127.0.0.1:80:intra.example.com:80 gw.example.com
You can read the docs here.
The port-forward in Kubernetes works only within the cluster, you can forward traffic that will hit specified port to Deployment or Service or a Pod
kubectl port-forward TYPE/NAME [options] [LOCAL_PORT:]REMOTE_PORT [...[LOCAL_PORT_N:]REMOTE_PORT_N]
--address flag is to specify what to listen on 0.0.0.0 means everything localhost is as name and you can set an IP on which it can be listening on.
Documentation is available here, you can also read Use Port Forwarding to Access Applications in a Cluster.
One workaround you can use if you have an SSH server somewhere on the Internet is to SSH to your server from your pod, port-forwarding in reverse:
# Suppose a web console is being served at
# http://my-service-8f6717ab-e.default:8888/
# inside your cluster:
kubectl exec -it my-job-f523b248-7htj6 -- ssh -R8888:my-service-8f6717ab-e.default:8888 user#34.23.1.2
Then you can connect to the service inside Kubernetes from outside of it. If the SSH server is not local to you, you can SSH to it from your local machine with a normal port forward:
me#my-macbook-pro:$ ssh -L8888:localhost:8888 user#34.23.1.2
Then point your browser to http://localhost:8888/
I have a service which is accessible on 8081. If I do via docker-compose or swarm without any specific changing on port it's work.
http://$(minikube ip):8081
but when i run my app via Kubernetes(minikube) is assign a nodePort in range of 30000-32767.
Then i have to call as follow:
http://$(minikube ip):30546
which is not acceptable from my service. Is there any way to map randomly given port to my own defined port?
When call second url then i am getting connection refused
I also used
kubectl port forward my-service 8081
but still no success.
kubectl port-forward command is incorrect. try below one
kubectl port-forward svc/my-service 8081:8081
then you should be able to access the service at http//:127.0.0.1:8081
This answer is not specific to Minikube but applicable to any Kubernetes cluster running inside a docker container.
In order to send a request from the host machine to the Kubernetes pod running in a container, you have to map ports from host machine to all the way to the pod.
Here is how you do it:
Publish the NodePort you want to use inside container to the host machine using --publish or -p.
# Map port 8080 on host machine to 31080 inside the container
docker run -p 8080:31080 ...
Use a custom NodePort when creating the service:
# You need to specify the exposed port as the nodePort value
# Otherwise Kubernetes will generate a random nodePort for you
kubectl create service nodeport myservice --node-port=31080 --tcp=3000:80
The application inside the pod listens to port 80 which is exposed as a service at port 3000. The traffic received at port 31080 on Kubernetes node will be directed at this service.
The query you send to 8080 on your host machine will follow this path:
Request -> Host Machine -> Docker Container -> Kubernetes Node -> Service -> Pod
↑ ↑ ↑ ↑ ↑
localhost:8080 :31080 :31080 :3000 :80
References:
https://docs.docker.com/engine/reference/commandline/run/
https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#-em-service-nodeport-em-
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.