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https://issues.apache.org/jira/browse/FLINK-32012?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17723166#comment-17723166
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Gyula Fora commented on FLINK-32012:
------------------------------------

I agree [~nfraison.datadog] it should be possible to unify upgrades and 
rollbacks. After checking if we should rollback we could temporarily reset the 
spec to the latest stable and execute the upgrade as if this was the spec sent 
by the user, also we should modify the upgradeMode to last-state. 

I think the upgrade logic already covers the necessary HA meta checks so this 
should be good in theory :) 

> Operator failed to rollback due to missing HA metadata
> ------------------------------------------------------
>
>                 Key: FLINK-32012
>                 URL: https://issues.apache.org/jira/browse/FLINK-32012
>             Project: Flink
>          Issue Type: Bug
>          Components: Kubernetes Operator
>    Affects Versions: kubernetes-operator-1.4.0
>            Reporter: Nicolas Fraison
>            Priority: Major
>              Labels: pull-request-available
>
> The operator has well detected that the job was failing and initiate the 
> rollback but this rollback has failed due to `Rollback is not possible due to 
> missing HA metadata`
> We are relying on saevpoint upgrade mode and zookeeper HA.
> The operator is performing a set of action to also delete this HA data in 
> savepoint upgrade mode:
>  * [flink-kubernetes-operator/AbstractFlinkService.java at main · 
> apache/flink-kubernetes-operator|https://github.com/apache/flink-kubernetes-operator/blob/main/flink-kubernetes-operator/src/main/java/org/apache/flink/kubernetes/operator/service/AbstractFlinkService.java#L346]
>  : Suspend job with savepoint and deleteClusterDeployment
>  * [flink-kubernetes-operator/StandaloneFlinkService.java at main · 
> apache/flink-kubernetes-operator|https://github.com/apache/flink-kubernetes-operator/blob/main/flink-kubernetes-operator/src/main/java/org/apache/flink/kubernetes/operator/service/StandaloneFlinkService.java#L158]
>  : Remove JM + TM deployment and delete HA data
>  * [flink-kubernetes-operator/AbstractFlinkService.java at main · 
> apache/flink-kubernetes-operator|https://github.com/apache/flink-kubernetes-operator/blob/main/flink-kubernetes-operator/src/main/java/org/apache/flink/kubernetes/operator/service/AbstractFlinkService.java#L1008]
>  : Wait cluster shutdown and delete zookeeper HA data
>  * [flink-kubernetes-operator/FlinkUtils.java at main · 
> apache/flink-kubernetes-operator|https://github.com/apache/flink-kubernetes-operator/blob/main/flink-kubernetes-operator/src/main/java/org/apache/flink/kubernetes/operator/utils/FlinkUtils.java#L155]
>  : Remove all child znode
> Then when running rollback the operator is looking for HA data even if we 
> rely on sevepoint upgrade mode:
>  * [flink-kubernetes-operator/AbstractFlinkResourceReconciler.java at main · 
> apache/flink-kubernetes-operator|https://github.com/apache/flink-kubernetes-operator/blob/main/flink-kubernetes-operator/src/main/java/org/apache/flink/kubernetes/operator/reconciler/deployment/AbstractFlinkResourceReconciler.java#L164]
>  Perform reconcile of rollback if it should rollback
>  * [flink-kubernetes-operator/AbstractFlinkResourceReconciler.java at main · 
> apache/flink-kubernetes-operator|https://github.com/apache/flink-kubernetes-operator/blob/main/flink-kubernetes-operator/src/main/java/org/apache/flink/kubernetes/operator/reconciler/deployment/AbstractFlinkResourceReconciler.java#L387]
>  Rollback failed as HA data is not available
>  * [flink-kubernetes-operator/FlinkUtils.java at main · 
> apache/flink-kubernetes-operator|https://github.com/apache/flink-kubernetes-operator/blob/main/flink-kubernetes-operator/src/main/java/org/apache/flink/kubernetes/operator/utils/FlinkUtils.java#L220]
>  Check if some child znodes are available
> For both step the pattern looks to be the same for kubernetes HA so it 
> doesn't looks to be linked to a bug with zookeeper.
>  
> From https://issues.apache.org/jira/browse/FLINK-30305 it looks to be 
> expected that the HA data has been deleted (as it is also performed by flink 
> when relying on savepoint upgrade mode).
> Still the use case seems to differ from 
> https://issues.apache.org/jira/browse/FLINK-30305 as the operator is aware of 
> the failure and treat a specific rollback event.
> So I'm wondering why we enforce such a check when performing rollback if we 
> rely on savepoint upgrade mode. Would it be fine to not rely on the HA data 
> and rollback from the last savepoint (the one we used in the deployment step)?



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