I have an in house 5 node cluster running on bare-metal and I am using Calico. The cluster was working for 22 days but suddenly it stopped working. After investigating the problem I found out that the service to pod communication is broken while all the components are up and kubectl is working without a problem.
From within the cluster (component A) if I try to curl another component (bridge) with its IP it works:
$ curl -vvv http://10.4.130.184:9998
* Rebuilt URL to: http://10.4.130.184:9998/
* Trying 10.4.130.184...
* TCP_NODELAY set
* Connected to 10.4.130.184 (10.4.130.184) port 9998 (#0)
> GET / HTTP/1.1
> Host: 10.4.130.184:9998
> User-Agent: curl/7.58.0
> Accept: */*
>
< HTTP/1.1 200 OK
< X-Powered-By: Express
< Accept-Ranges: bytes
< Cache-Control: public, max-age=0
< Last-Modified: Mon, 08 Apr 2019 14:06:42 GMT
< ETag: W/"179-169fd45c550"
< Content-Type: text/html; charset=UTF-8
< Content-Length: 377
< Date: Wed, 23 Oct 2019 09:56:35 GMT
< Connection: keep-alive
<
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
<title>Bridge</title>
<meta content='width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0' name='viewport' />
<meta name="viewport" content="width=device-width" />
</head>
<body>
<h1>Bridge</h1>
</body>
</html>
* Connection #0 to host 10.4.130.184 left intactns lookup for the service is also working (it resolve to the service IP):
$ nslookup bridge
Server: 10.5.0.10
Address 1: 10.5.0.10 kube-dns.kube-system.svc.k8s.local
Name: bridge
Address 1: 10.5.160.50 bridge.170.svc.k8s.localBut the service to pod communication is broken and when I curl to the service name most of the times (60-70%) it stuck:
$ curl -vvv http://bridge:9998
* Rebuilt URL to: http://bridge:9998/
* Could not resolve host: bridge
* Closing connection 0
curl: (6) Could not resolve host: bridgeWhen I check the endpoints of the that service I can see that the IP of that pod is there:
$ kubectl get ep -n 170 bridge
NAME ENDPOINTS AGE
bridge 10.4.130.184:9226,10.4.130.184:9998,10.4.130.184:9226 11dBut as I said the curl (and any other method) that uses the service name is not working. And this is the service description:
$ kubectl describe svc -n 170 bridge
Name: bridge
Namespace: 170
Labels: io.kompose.service=bridge
Annotations: Process: bridge
Selector: io.kompose.service=bridge
Type: ClusterIP
IP: 10.5.160.50
Port: 9998 9998/TCP
TargetPort: 9998/TCP
Endpoints: 10.4.130.184:9998
Port: 9226 9226/TCP
TargetPort: 9226/TCP
Endpoints: 10.4.130.184:9226
Port: 9226-udp 9226/UDP
TargetPort: 9226/UDP
Endpoints: 10.4.130.184:9226
Session Affinity: None
Events: <none>This problem is not limited to just this component and it is like this for all the components.
I restarted the CoreDNS (deleted its pods) but it is still the same. I was facing this problem before and previous time I thought it is related to Weavenet that I was using and I needed the cluster so I tore down the cluster and rebuilt it with Calico but now I am sure that this is not related to CNI and it is something else.
Environment: - Kubernetes version (use kubectl version):
Client Version: version.Info{Major:"1", Minor:"14", GitVersion:"v1.14.1", GitCommit:"b7394102d6ef778017f2ca4046abbaa23b88c290", GitTreeState:"clean", BuildDate:"2019-04-08T17:11:31Z", GoVersion:"go1.12.1", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"16", GitVersion:"v1.16.0", GitCommit:"2bd9643cee5b3b3a5ecbd3af49d09018f0773c77", GitTreeState:"clean", BuildDate:"2019-09-18T14:27:17Z", GoVersion:"go1.12.9", Compiler:"gc", Platform:"linux/amd64"}Cloud provider or hardware configuration: This is a bare-metal cluster of 5 nodes, 1 master and 4 workers. All nodes are running Ubuntu 18.04 and they are connecting to the same subnet.
OS (e.g: cat /etc/os-release):
NAME="Ubuntu"
VERSION="18.04.2 LTS (Bionic Beaver)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 18.04.2 LTS"
VERSION_ID="18.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=bionic
UBUNTU_CODENAME=bionicuname -a):Linux serflex-argus-1 4.15.0-55-generic #60-Ubuntu SMP Tue Jul 2 18:22:20 UTC 2019 x86_64 x86_64 x86_64 GNU/LinuxInstall tools: Kubeadm
Network plugin and version (if this is a network-related bug): Calico "cniVersion": "0.3.1"
After deleting all the kube-proxy pods problem seemed to be solved but I still like to know what caused this problem. Btw I didn't see any error in the kube-proxy logs.