There is a command kube-apiserver --feature-gates=APIPriorityAndFairness=true --runtime-config=flowcontrol.apiserver.k8s.io/v1beta1=true,flowcontrol.apiserver.k8s.io/v1beta2=true. But it seems like run on the master machine.
Now I want to remotely call the command in my laptop. I have connected the master machine via kubeconfig already.
Which statement or format of statement should I use to accomplish this function？
Please refer Kubernetes API access documentation how you can programmatically send API requests. Kubernetes supports various mechanisms and various clients in GO, Python, Java etc to send api requests. Below is the sample python code which will list all the pods from all namespaces.
from kubernetes import client, config
config.load_kube_config()
v1=client.CoreV1Api()
print("Listing pods with their IPs:")
ret = v1.list_pod_for_all_namespaces(watch=False)
for i in ret.items:
print("%s\t%s\t%s" % (i.status.pod_ip, i.metadata.namespace, i.metadata.name))
Also when follow command is executed "kubectl get pods -v 9" it will give verbose information of rest request which kubectl tool will send to api server, this will help you to understand how to construct the api requests.
I don't know if it is a real question.
This command kube-apiserver --feature-gates=APIPriorityAndFairness=true --runtime-config=flowcontrol.apiserver.k8s.io/v1beta1=true,flowcontrol.apiserver.k8s.io/v1beta2=true seems not like kubectl xxx. It's not a service that cluster offers to user to use.
I ssh the master machine to modify some flag or properties of the api-server.
Related
How can we obtain the gke pod counts running in the cluster? I found there are ways to get node count but we needed pod count as well. it will be better if we can use something with no logging needed in gcp operations.
You can do it with Kubernetes Python Client library as shown in this question, posted by Pradeep Padmanaban C, where he was looking for more effective way of doing it, but his example is actually the best what you can do to perform such operation as there is no specific method which would allow you just to count pods without retrieving their entire json manifests:
from kubernetes import client , config
config.load_kube_config()
v1= client.CoreV1Api()
ret_pod = v1.list_pod_for_all_namespaces(watch=False)
print(len(ret_pod.items))
You can also use a different method, which allows to retrieve pods only from specific namespace e.g.:
list_namespaced_pod("default")
In kubectl way you can do it as follows (as proposed here by RammusXu):
kubectl get pods --all-namespaces --no-headers | wc -l
You can directly access the kubernetes API using a restful API call. You will need to make sure you provide the authentication token in your call by including a bearer token.
Once you are able to query the api server directly, you can use GET <master_endpoint>/api/v1/pods to list all the pods in the cluster. You can also search for specific namespaces by specifying the namespace /api/v1/namespaces/<namespace>/pods.
Keep in mind that the kubectl cli tool is just a wrapper for API calls, each kubectl command will form a RESTful API call in a similar format to the one listed above, so any interaction you have with the cluster using kubectl can also be achieved through RESTful API calls
How to get Kubernetes cluster name from K8s API mentions that
curl http://metadata/computeMetadata/v1/instance/attributes/cluster-name -H "Metadata-Flavor: Google"
(from within the cluster), or
kubectl run curl --rm --restart=Never -it --image=appropriate/curl -- -H "Metadata-Flavor: Google" http://metadata.google.internal/computeMetadata/v1/instance/attributes/cluster-name
(from outside the cluster), can be used to retrieve the cluster name. That works.
Is there a way to perform the same programmatically using the k8s client-go library? Maybe using the RESTClient()? I've tried but kept getting the server could not find the requested resource.
UPDATE
What I'm trying to do is to get the cluster-name from an app that runs either in a local computer or within a k8s cluster. the k8s client-go allows to initialise the clientset via in cluster or out of cluster authentication.
With the two commands mentioned at the top that is achievable. I was wondering if there was a way from the client-go library to achieve the same, instead of having to do kubectl or curl depending on where the service is run from.
The data that you're looking for (name of the cluster) is available at GCP level. The name itself is a resource within GKE, not Kubernetes. This means that this specific information is not available using the client-go.
So in order to get this data, you can use the Google Cloud Client Libraries for Go, designed to interact with GCP.
As a starting point, you can consult this document.
First you have to download the container package:
➜ go get google.golang.org/api/container/v1
Before you will launch you code you will have authenticate to fetch the data:
Google has a very good document how to achieve that.
Basically you have generate a ServiceAccount key and pass it in GOOGLE_APPLICATION_CREDENTIALS environment:
➜ export GOOGLE_APPLICATION_CREDENTIALS=sakey.json
Regarding the information that you want, you can fetch the cluster information (including name) following this example.
Once you do do this you can launch your application like this:
➜ go run main.go -project <google_project_name> -zone us-central1-a
And the result would be information about your cluster:
Cluster "tom" (RUNNING) master_version: v1.14.10-gke.17 -> Pool "default-pool" (RUNNING) machineType=n1-standard-2 node_version=v1.14.10-gke.17 autoscaling=false%
Also it is worth mentioning that if you run this command:
curl http://metadata/computeMetadata/v1/instance/attributes/cluster-name -H "Metadata-Flavor: Google"
You are also interacting with the GCP APIs and can go unauthenticated as long as it's run within a GCE machine/GKE cluster. This provided automatic authentication.
You can read more about it under google`s Storing and retrieving instance metadata document.
Finally, one great advantage of doing this with the Cloud Client Libraries, is that it can be launched externally (as long as it's authenticated) or internally within pods in a deployment.
Let me know if it helps.
If you're running inside GKE, you can get the cluster name through the instance attributes: https://pkg.go.dev/cloud.google.com/go/compute/metadata#InstanceAttributeValue
More specifically, the following should give you the cluster name:
metadata.InstanceAttributeValue("cluster-name")
The example shared by Thomas lists all the clusters in your project, which may not be very helpful if you just want to query the name of the GKE cluster hosting your pod.
I want to access my Kubernetes cluster API in Go to run kubectl command to get available namespaces in my k8s cluster which is running on google cloud.
My sole purpose is to get namespaces available in my cluster by running kubectl command: kindly let me know if there is any alternative.
You can start with kubernetes/client-go, the Go client for Kubernetes, made for talking to a kubernetes cluster. (not through kubectl though: directly through the Kubernetes API)
It includes a NamespaceLister, which helps list Namespaces.
See "Building stuff with the Kubernetes API — Using Go" from Vladimir Vivien
Michael Hausenblas (Developer Advocate at Red Hat) proposes in the comments documentations with using-client-go.cloudnative.sh
A versioned collection of snippets showing how to use client-go.
I was trying to add a command line flag to the API server. In my setup, it was running as a daemon set inside the k8s cluster so I got the daemon set manifest using kubectl, updated it, and executed kubectl apply -f apiserver.yaml (I know, this was not a good idea).
Of course, the new yaml file I wrote had an error so the API server is not starting anymore and I can't use kubectl to update it. I have an ssh connection to the node where it was running and I can see how the kubelet is trying to run the apiserver pod every few seconds with the ill-formed command. I am trying to configure the kubelet service to use the correct api-server command but am not being able to do so.
Any ideas?
The API server definition usually lives in /etc/kubernetes/manifests - Edit the configuration there rather than at the API level
I created a Mongodb service according to the Kubernetes tutorial.
Now my question is how do I gain access to the database itself, with a client like Robomongo or similar clients? Just for making backups or exploring what data have been entered.
The mongo-pod and service only have an internal endpoint, and a single mount.
Is there any way to safely access this instance with no public endpoint?
Internally URI is mongo:27***
You can use kubectl port-forward mypod 27017:27017 and then just connect your mongodb client to localhost:27017.
If you want to stop, just hit Ctrl+C on the same cmd window to stop the process.
The kubernetes cmd-line tool provides this functionality as #ainlolcat stated
kubectl get pods
Retrieves the pod names currently running and with:
kubectl exec -i mongo-controller-* bash
you get a basic bash, which lets you execute
mongo
to get into the database to create dumps, and so on. The bash is very basic and has no features like completion and so on. I have not found a solution for better shell but it does the job
when you create a service in kubernetes you give it a name, say for example "mymongo". After the service is created then
The DNS service of kubernetes (by default is on) will ensure that any pod can discover this servixe simply by its name. so you can set your uri like
uri: mongodb://**mymongo**:27017/mong
In addition the service IP and port will be set as environment variables at the running pod.
MYMONGO_SERVICE_HOST
MYMONGO_SERVICE_PORT
I have in fact wrote a blog that show a step by step example of an app with nodejs web server and mongo that can explain further
http://codefresh.io/blog/kubernetes-snowboarding-everything-intro-kubernetes/
feedback welcome!
Answer from #grchallenge is correct but it is deprecated as of in 2021
All new comers please use
kubectl exec mongo-pod-name -i -- bash