docs: new talk

content/day-2/10_auto-scale.md

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+---
+title: "The auto-scaling part: VPA, HPQ, KEDA, Nodes, How do they dance"
+weight: 10
+tags:
+ - rejekts
+---
+
+<!-- {{% button href="https://youtu.be/rkteV6Mzjfs" style="warning" icon="video" %}}Watch talk on YouTube{{% /button %}} -->
+
+## Hypothesis
+
+- In 2024 27% of cloud spent was wasted
+- 100ms delay => decrease in sales
+
+## Pod resources
+
+- Requests: Informs scheduler's decision
+    - Too low: Schedule on strained nodes
+    - Too high: Wasted resources
+- Limits: Throttels (CPU) or Kills (Memory) if reached
+- QoS: sort the eviction priority during ressource pressure
+    - Quranteed (request=limits)
+    - Burstable (Limits>Requests)
+    - Best effort (Nothing defined) 
+- Gotcha: CPU throtteling can happen before tirggers happen if requests and limits are very close
+
+TODO: Steal table from Slides
+
+Requests | 100m, 256Mi | 100m, 256Mi
+Limits |100m, 256Mi | None or <limits
+QoS | Gurantee | Burstable | Best effort
+
+## Scalers
+
+- VPA: Moar power aka reccomend requests
+- HPA: Moar moar aka more replicas
+- KEDA: Proxy over HPA
+
+### VPA
+
+Modes:
+- Off: Dry-Run
+- Initial: Applies Reccomendations to new Pods (can be used for finding out)
+- Auto/Recreate: Evicts and restarts pods to update resources
+
+Trigger: Usually Memory
+Tip: `maxAllowed` in order to not exhaust stuff
+
+
+### HPA
+
+- Trigger: Usually cpu (percent of requests)
+- Formula: $1+\frac{usage}{target}$
+- Fun fact: Can not scale to 0
+
+### KeDA
+
+- Basicly automates HPA with flexible metrics (from different soruces)
+- Can scale Jobs
+- Can Scale to 0
+
+## Anti patterns
+
+TODO: Steal from slides
+
+| Pattern | Bad | Better
+| CPI limit = Requests | Throtteling before scale | Set requests only |
+
+
+## Demo
+
+Auto scaling meme generator (see slides/video)