I am deploying a k8s cluster locally using Kind. The image gets deployed ok and when I view the list of services I see the following
the service I'm trying to access is chatt-service and if you notice the EXTERNAL-IP is pending. I know minikube has a command which makes this accessible, but how do I do it on a Kind cluster ?
for Loadbalancer service type you will not able to get public ip because you're running it locally and you will need to run it in a cloud provider which will provide the LB for you like ALB in aws or LoadBalancer in Digital ocean. however, you can access this service locally using the Kubectl proxy tool.
.
kubectl port-forward service/chatt-service 3002:3002
There are some additional options to work on LoadBalancer under Kind cluster. (While the port forwarding is the simplest way).
https://kind.sigs.k8s.io/docs/user/loadbalancer/
First way:
You can also expose pods and services using extra port mappings
this mean manually set ports in cluster-config.yaml
And maybe second way (but not actually the solution on LoadBalancer):
You may want to check out the Ingress Guide as a cross-platform
workaround
I took IP of pod and assign it to externalIP of service. Also I tried to assign not assigned IP to it. It works in any way and I am not able to find any side effects. Do you see any possible issue with such solution?
The external IP field of a service is only used for tracking purposes, it is descriptive rather than proscriptive. You could put whatever you want there, the only thing I know of which uses that field is external-dns, beyond that it’s only for humans so the system can report back what the IP or hostname is with type LoadBalancer.
As mentioned in the Kubernetes Service documentation:
externalIPs are not managed by Kubernetes and are the responsibility of the cluster administrator.
ExternalIP is good when you want to have the control of your service IP's, from the other side, the High availability will be comprimissed, since if one node of the cluster die you will lost the route to the service.
In this blog there's a good explantion about ExternalIP
I'd like to create a wildcard DNS record that maps to a virtual IP inside my k8s cluster. This is because I want requests from my pods to any subdomain of a given name to map to a specific set of endpoints. I.e. requests from:
something.my-service.my-namespace.svc.cluster.local
something-else.my-service.my-namespace.svc.cluster.local
any-old-thing-my-pod-came-up-with.my-service.my-namespace.svc.cluster.local
to all resolve to the same virtual IP, and therefore to the same cluster (i.e. I would like these requests to be routed to endpoints in the same way a service does).
I've seen some other solutions that involve creating and modifying the cluster DNS service (i.e. kube-dns or CoreDNS) config. This doesn't work for me- the main reason I'm asking this question is to achieve declarative config.
What I've tried:
Service .metadata.name: '*.my-service'. Failed because '*.my-service' is not a valid service name.
Service .spec.ports.name: '*'. Not a valid port name.
Not an option:
Ingress. I cannot expose these services to the wider internet.
Pod hostname/subdomain. AFAIK DNS entries created by pod hostname/subdomain will not have a virtual IP that may resolve to any of a number of pods. (Quoting from https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/#pod-s-hostname-and-subdomain-fields) "DNS serves an A record at that name, pointing to the Pod’s IP."
wild card dns is not supported for kubernetes services. what you can do is front the service with an ingress controller. with ingress you can use wild card dns. refer the below PR
https://github.com/kubernetes/kubernetes/pull/29204
I have an EKS cluster setup in a VPC. The worker nodes are launched in private subnets. I can successfully deploy pods and services.
However, I'm not able to perform DNS resolution from within the pods. (It works fine on the worker nodes, outside the container.)
Troubleshooting using https://kubernetes.io/docs/tasks/administer-cluster/dns-debugging-resolution/ results in the following from nslookup (timeout after a minute or so):
Server: 172.20.0.10
Address 1: 172.20.0.10
nslookup: can't resolve 'kubernetes.default'
When I launch the cluster in an all-public VPC, I don't have this problem. Am I missing any necessary steps for DNS resolution from within a private subnet?
Many thanks,
Daniel
I feel like I have to give this a proper answer because coming upon this question was the answer to 10 straight hours of debugging for me. As #Daniel said in his comment, the issue I found was with my ACL blocking outbound traffic on UDP port 53 which apparently kubernetes uses to resolve DNS records.
The process was especially confusing for me because one of my pods worked actually worked the entire time since (I think?) it happened to be in the same zone as the kubernetes DNS resolver.
To elaborate on the comment from #Daniel, you need:
an ingress rule for UDP port 53
an ingress rule for UDP on ephemeral ports (e.g. 1025–65535)
I hadn't added (2) and was seeing CoreDNS receiving requests and trying to respond, but the response wasn't getting back to the requester.
Some tips for others dealing with these kinds of issues, turn on CoreDNS logging by adding the log configuration to the configmap, which I was able to do with kubectl edit configmap -n kube-system coredns. See CoreDNS docs on this https://github.com/coredns/coredns/blob/master/README.md#examples This can help you figure out whether the issue is CoreDNS receiving queries or sending the response back.
I ran into this as well. I have multiple node groups, and each one was created from a CloudFormation template. The CloudFormation template created a security group for each node group that allowed the nodes in that group to communicate with each other.
The DNS error resulted from Pods running in separate node groups from the CoreDNS Pods, so the Pods were unable to reach CoreDNS (network communications were only permitted withing node groups). I will make a new CloudFormation template for the node security group so that all my node groups in my cluster can share the same security group.
I resolved the issue for now by allowing inbound UDP traffic on port 53 for each of my node group security groups.
So I been struggling for a couple of hours i think, lost track of time, with this issue as well.
Since i am using the default VPC but with the worker nodes inside the private subnet, it wasn't working.
I went through the amazon-vpc-cni-k8s and found the solution.
We have to sff the environment variable of the aws-node daemonset AWS_VPC_K8S_CNI_EXTERNALSNAT=true.
You can either get the new yaml and apply or just fix it through the dashboard. However for it to work you have to restart the worker node instance so the ip route tables are refreshed.
issue link is here
thankz
Re: AWS EKS Kube Cluster and Route53 internal/private Route53 queries from pods
Just wanted to post a note on what we needed to do to resolve our issues. Noting that YMMV and everyone has different environments and resolutions, etc.
Disclaimer:
We're using the community terraform eks module to deploy/manage vpcs and the eks clusters. We didn't need to modify any security groups. We are working with multiple clusters, regions, and VPC's.
ref:
Terraform EKS module
CoreDNS Changes:
We have a DNS relay for private internal, so we needed to modify coredns configmap and add in the dns-relay IP address
...
ec2.internal:53 {
errors
cache 30
forward . 10.1.1.245
}
foo.dev.com:53 {
errors
cache 30
forward . 10.1.1.245
}
foo.stage.com:53 {
errors
cache 30
forward . 10.1.1.245
}
...
VPC DHCP option sets:
Update with the IP of the above relay server if applicable--requires regeneration of the option set as they cannot be modified.
Our DHCP options set looks like this:
["AmazonProvidedDNS", "10.1.1.245", "169.254.169.253"]
ref: AWS DHCP Option Sets
Route-53 Updates:
Associate every route53 zone with the VPC-ID that you need to associate it with (where our kube cluster resides and the pods will make queries from).
there is also a terraform module for that:
https://www.terraform.io/docs/providers/aws/r/route53_zone_association.html
We had run into a similar issue where DNS resolution times out on some of the pods, but re-creating the pod couple of times resolves the problem. Also its not every pod on a given node showing issues, only some pods.
It turned out to be due to a bug in version 1.5.4 of Amazon VPC CNI, more details here -- https://github.com/aws/amazon-vpc-cni-k8s/issues/641.
Quick solution is to revert to the recommended version 1.5.3 - https://docs.aws.amazon.com/eks/latest/userguide/update-cluster.html
As many others, I've been struggling with this bug a few hours.
In my case the issue was this bug https://github.com/awslabs/amazon-eks-ami/issues/636 that basically sets up an incorrect DNS when you specify endpoint and certificate but not certificate.
To confirm, check
That you have connectivity (NACL and security groups) allowing DNS on TCP and UDP. For me the better way was to ssh into the cluster and see if it resolves (nslookup). If it doesn't resolve (most likely it is either NACL or SG), but check that the DNS nameserver in the node is well configured.
If you can get name resolution in the node, but not inside the pod, check that the nameserver in /etc/resolv.conf points to an IP in your service network (if you see 172.20.0.10, your service network should be 172.20.0.0/24 or so)
I have a StatefulSet Kubernetes deployment with 2 worker nodes. I was able to bring the containers up on those 2 nodes using a headless service hence the nodes have hostname as
abc-0.abc.default.svc.cluster.local
abc-1.abc.default.svc.cluster.local
The problem is that I am not able to ping abc-0 from abc-1 and in the opposite direction using the hostname. If I use IP addresses then everything works fine.
There were issues related the DNS resolution with Alpine Linux at some point(https://github.com/gliderlabs/docker-alpine/issues/8#issuecomment-172594887) but seems it was fixed in Alpine Linux 3.4.
What would be the good way to verify that the problem I am facing is not because of the Linux but instead some misconfiguration in Kube-DNS or something?
I assume you mean ping abc-0, did you try ping abc-0.abc ?
The resolv.conf is not enriched with all the statefull service entries search domains, just the namespace one, so when you try to access by only abc-0 it actually resolves to abc-0.default.svc.cluster.local
The problem was that the service I was running didn't get endpoints assigned to it. I am using v1.7.3 so resolved the problem by adding 'selector' on the headless service. Also, looks like this is no longer a problem in v1.8.3.