Open bdols opened 1 year ago
jonathan-innis
commented
1 year ago Just to make sure that I understand correctly, this is effectively an ask to ignore certain PDBs when evaluating nodes for eviction because this PDB is in place so that Strimzi can handle the eviction process when a node eviction is requested and not the standard eviction manager?
jonathan-innis
commented
1 year ago This definitely seems like an interesting use-case but I'm curious how common this use-case is in the ecosystem.
does not necessarily correspond to the replicas being in sync
It seems odd to me that Kafka readiness wouldn't be based on the pod actually being fully replicated and being in-sync. Is this something that is being considered upstream in Kafka so that this node drain cleaner component doesn't have to be built on top of the existing eviction manager to handle this case?
bdols
commented
1 year ago Just to make sure that I understand correctly, this is effectively an ask to ignore certain PDBs when evaluating nodes for eviction because this PDB is in place so that Strimzi can handle the eviction process when a node eviction is requested and not the standard eviction manager?
yes. I am not speaking for their project or anything.
This definitely seems like an interesting use-case but I'm curious how common this use-case is in the ecosystem.
I can think of another possible use. ElasticSearch has an option in its shutdown API for removing/replacing nodes versus an in-place restart, which is more of a consideration for local HostPath volumes vs EBS. https://www.elastic.co/guide/en/elasticsearch/reference/current/put-shutdown.html
If karpenter deprovisioning was configured with ttlSecondsUntilExpired, a 'replace' would be appropriate instead of the 'restart' default, but currently, it appears that ECK only allows for one setting via an env var on the running container: https://www.elastic.co/guide/en/cloud-on-k8s/2.8/k8s-prestop.html
There may be other HA data storage services that handle their own orchestration. I had a thought that PodSpec could be enhanced with something like a "disruptableness" to indicate whether an application is not able to handle a disruption while still be ready to service requests. Or, including the Elastic case, now, "drainableness". For Kafka , I could see a pod marking itself as "drainable" once all the replicas are rebalanced off.
k8s-triage-robot
commented
9 months ago The Kubernetes project currently lacks enough contributors to adequately respond to all issues.
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jonathan-innis
commented
9 months ago /remove-lifecycle stale
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6 months ago The Kubernetes project currently lacks enough contributors to adequately respond to all issues.
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5 months ago The Kubernetes project currently lacks enough active contributors to adequately respond to all issues.
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4 months ago The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.
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k8s-ci-robot
commented
4 months ago @k8s-triage-robot: Closing this issue, marking it as "Not Planned".
jonathan-innis
commented
4 months ago /reopen
k8s-ci-robot
commented
4 months ago @jonathan-innis: Reopened this issue.
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commented
4 months ago This issue is currently awaiting triage.
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jonathan-innis
commented
4 months ago /remove-lifecycle rotten
k8s-triage-robot
commented
1 month ago The Kubernetes project currently lacks enough contributors to adequately respond to all issues.
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tinder-robolague
commented
1 month ago /remove-lifecycle stale
Description
What problem are you trying to solve?
For Strimzi's Kafka Operator, to achieve HA, it's important to let its operator drain pods based on its internal readiness. To do this, Strimzi recommends using their Drain Cleaner (Strimzi blog post announcement) , which essentially creates a ValidatingWebhook for pod evictions and adds an annotation to the pods (kafka and zookeeper) that it manages. This then means that to make use of the Drain Cleaner that a PDB with maxUnavailable of 0 needs to be set, and, so, this does not allow for karpenter to consolidate any node with kafka or zookeeper pods running on them. Karpenter creates a DeprovisioningBlocked Event for this: "Cannot deprovision node due to pdb--zookeeper prevents pod evictions"
Some potential features that could address this: provide a capability for the Provisioner to set a pod annotation to mark a pod for eviction for specific workloads which then may not require the Strimzi Drain Cleaner. I imagine that this would need an accompanying timeout for successful eviction on cordoned nodes. Or, a Provisioner setting to ignore/override PDBs and drain the node anyway, but seems like that would break the PDB contract.
How important is this feature to you?
The workaround for this is to have dedicated hardware sized for the workloads along with a dedicated provisioner that set node taints, but zookeeper, for example, may not require a lot of CPU/memory so this can be considered idle waste. Ideally, it would be better to have a choice on whether these workloads can run on nodes capable of handling other workloads.