CoreDNS Configuration Consistency

Check Items

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 the kubectl command. For details, 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 records.

   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 "
   from __future__ import print_function
   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 access the cluster console. Choose Add-ons in the navigation pane, select CoreDNS, and click Upgrade.
   To retain custom configurations, use either of the following methods:

   • (Recommended) Set parameterSyncStrategy to inherit. In this case, custom settings are automatically inherited. The system automatically parses, identifies, and inherits custom parameters.
   • Set parameterSyncStrategy to force. Manually enter the differential configuration. For details, see CoreDNS.

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, it is a good practice to use the parameter configuration function of CCE add-ons to modify the Corefile configuration for consistency.