Nicolai Ort
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60 lines
2.1 KiB
Markdown
60 lines
2.1 KiB
Markdown
---
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title: "Scaling PDBs: Introducing Multi-Cluster Resilience with x-pdb"
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weight: 6
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tags:
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- rejekts
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- multicluster
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---
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<!-- {{% button href="https://youtu.be/rkteV6Mzjfs" style="warning" icon="video" %}}Watch talk on YouTube{{% /button %}} -->
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<!-- {{% button href="https://docs.google.com/presentation/d/1nEK0CVC_yQgIDqwsdh-PRihB6dc9RyT-" style="tip" icon="person-chalkboard" %}}Slides{{% /button %}} -->
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## Baseline Infra
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- Multiple Clusters across cloud providers
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- Cilium with Clustermesh
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- Stretched CockroachDB and NATS
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TODO: Steal overview from slides
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## PDBs and limits
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- PDB: Classic core component that requires a number of pods with successfull readyness probes per deployment
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- Eviction: Can be stopped by a PDB what has not reached the minimum available
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- Interruptions: Voluntary (New image, updated specs, ...) vs involuntary (Eviction, deletion, node pressule, NoExecute, Node deletion)
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## Stateful across multiple clusters
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- Baseline: PDBs only know about one cluster
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- Problem: If the master pod fails (or get's evicted) on 2/3 clusters
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- Factors: Movement, Maintainance, Chaos-Experiments, Secret rotation
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- Workaround: Just manually check all systems before doing anything
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- Idea: Multi-Cluster PDB
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- Solution: A new hook on the eviciton api that interacts with a new Cluster-Aware CRD
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## How it actually works
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1. Drain API get's called
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2. Check replicas accross cluster
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3. Anwer based on current state
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Actually: There is a lease-mechanism to prevent race conditions across clusters
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TODO: Steal diagram from slides
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## What works
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- Voluntary: 100% supported
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- Involuntary: Yes they hooked into most of the deletion api calls (eviction, pressure, kubectl delete, admissions, node deletion)
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## Demo
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Pretty interesting, watch the video to find out
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## Q&A
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- Do you need a flat network: No just expose the tcp lb
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- Did you think about using etcd to implement the leases instead of objects: They use managed hostplanes and dont want another etcd
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- Have you tried to commit upstream: Nope, pretty much not an option thanks to the managed control-plane not being able to set apropriate flags
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