CoreDNS Configuration Consistency

Check Item

Check whether the current CoreDNS key configuration Corefile is different from the Helm release record. The difference may be overwritten during the add-on upgrade, affecting domain name resolution in the cluster.

Solution

You can upgrade CoreDNS separately after confirming the configuration differences.

1. Configure kubectl, see Connecting to a Cluster Using kubectl.
2. Obtain the Corefile that takes effect currently.

   kubectl get cm -nkube-system coredns -o jsonpath='{.data.Corefile}' > corefile_now.txt
   cat corefile_now.txt

3. Obtain the Corefile in the Helm release record (depending on Python 3).

   latest_release=`kubectl get secret -nkube-system -l owner=helm -l name=cceaddon-coredns --sort-by=.metadata.creationTimestamp | awk 'END{print $1}'`
   kubectl get secret -nkube-system $latest_release -o jsonpath='{.data.release}' | base64 -d | base64 -d | gzip -d | python -m json.tool | python -c "
   import json,sys,re,yaml;
   manifests = json.load(sys.stdin)['manifest']
   files = re.split('(?:^|\s*\n)---\s*',manifests)
   for file in files:
       if 'coredns/templates/configmap.yaml' in file and 'Corefile' in file:
         corefile = yaml.safe_load(file)['data']['Corefile']
         print(corefile,end='')
         exit(0);
   print('error')
   exit(1);
   " > corefile_record.txt
   cat corefile_record.txt
   

4. Compare the output differences between 2 and 3.

   diff corefile_now.txt corefile_record.txt -y;

   Figure 1 Viewing output differences
   

5. Return to the CCE console and click the cluster name to go to the cluster console. On the Add-ons page, select CoreDNS and click Upgrade.
   To retain the different configurations, use either of the following methods:

   • Set parameterSyncStrategy to force. Manually enter the differential configuration. For details, see coredns (System Resource Add-on, Mandatory).
   • If parameterSyncStrategy is set to inherit, differentiated configurations are automatically inherited. The system automatically parses, identifies, and inherits differentiated parameters.

   

6. Click OK. After the add-on upgrade is complete, check whether all CoreDNS instances are available and whether Corefile meets the expectation.

   kubectl get cm -nkube-system coredns -o jsonpath='{.data.Corefile}'

7. Change the value of parameterSyncStrategy to ensureConsistent to enable configuration consistency verification.

   In addition, you are advised to use the parameter configuration function of CCE add-on management to modify the Corefile configuration to avoid differences.