Follow below steps for manual site failover
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. All steps need to be run
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on coredns master node.
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Please note the configuration in all examples for reference: |
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coredns master node IP address: 10.147.101.135 primary site |
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(site1) master node IP address: 10.147.99.140 secondary site |
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(site2) master node IP address: 10.147.101.23 |
- Verify coredns server, to get the existing mapping. (here it is pointing to primary site
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- (site 1
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- ))
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#verify the address for sdnc.example.com resolves to primary site presently
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root@coredns-1:/dockerdata-nfs# nslookup sdnc.example.com Server: 10.96.0.10 Address: 10.96.0.10#53 Name: sdnc.example.com Address: 10.147.99.140 |
2. Edit zone file to comment out SDNC mapping to primary site (site1) and uncomment mapping to secondary site (site2)
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root@coredns-1:~# vi /dockerdata-nfs/zone.db |
3. Edit
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coredns configmap on coredns server to comment out SDNC mapping to primary site (site1) and uncomment mapping to secondary site (site2)
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#Below command opens the |
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codedns configmap for editing. Edit and save the file |
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# Notice the A record for sdnc: "sdnc IN A 10.147.99.140" is commented out by appending ;; to the line (\n;;sdnc IN A 10.147.99.140\n)
# Notice the A record for sdnc: "sdnc IN A 10.147.101.23" is uncommented out by removing;; from the line (\nsdnc\t\t IN A 10.147.101.23)
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root@coredns-1:~# kubectl edit configmap coredns -n kube-system -oyaml # Please edit the object below. Lines beginning with a '#' will be ignored, # and an empty file will abort the edit. If an error occurs while saving this file will be # reopened with the relevant failures. # apiVersion: v1 data: Corefile: | .:53 { errors log health kubernetes cluster.local 10.96.0.0/12 { pods insecure } file /dockerdata-nfs/zone.db example.com prometheus proxy . /etc/resolv.conf cache 30 } zone.db: "$ORIGIN example.com. ; designates the start of this zone file in the namespace\n$TTL 1h ; default expiration time of all resource records without their own TTL value\nexample.com. IN SOA ns.example.com. username.example.com. ( 2007120710 1d 2h 4w 1h )\nexample.com. IN NS ns ; ns.example.com is a nameserver for example.com\nexample.com. IN NS ns.somewhere.example. ; ns.somewhere.example is a backup nameserver for example.com\nexample.com. IN \ A 10.147.101.135 ; IPv4 address for example.com\nns IN \ A 10.247.5.11 ; IPv4 address for ns.example.com\nwww IN \ CNAME example.com. ; www.example.com is an alias for example.com\nwwwtest \ IN CNAME www ; wwwtest.example.com is another alias for www.example.com\nsdnc.example.com. \ IN SRV 30202 10 10 example.com.\n;;site1\n;;sdnc IN A 10.147.99.140\n;;site2\nsdnc\t\t IN A 10.147.101.23" kind: ConfigMap metadata: creationTimestamp: 2018-02-28T20:13:03Z name: coredns namespace: kube-system resourceVersion: "102077" selfLink: /api/v1/namespaces/kube-system/configmaps/coredns uid: c8489771-1cc3-11e8-a0cb-fa163eabcb60 configmap "coredns" edited |
4.
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Note that there is a cache time configured in configmap. Wait for some time (30 seconds here) and then send signal to refresh the settings for
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coredns.
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#substitute the coredns pod name before execution
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root@coredns-1:~# kubectl exec -n kube-system <coredns-pod-name> -- kill -SIGUSR1 1 |
5. Verify the
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"sdnc.example.com" domain points to secondary site now.
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#verify the address for sdnc.example.com resolves to secondary site now
root@kubefed-1:/dockerdata-nfs# nslookup sdnc.example.com
Server: 10.96.0.10
Address: 10.96.0.10#53
Name: sdnc.example.com
Address: 10.147.101.23
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It may take some time to refresh the address for DNS resolver depending on configured cache time. Send the refresh signal again ( |
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in step 4) after sometime if you're not able to see the update. |