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Clarify daemon sets (fixes #471)

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Jerome Petazzoni
2019-07-25 11:47:43 -05:00
parent ba4ec23767
commit 9a184c6d44
1 changed files with 19 additions and 5 deletions
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slides/k8s/daemonset.md
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- We want one (and exactly one) instance of `rng` per node
- What if we just scale up `deploy/rng` to the number of nodes?
- We *do not want* two instances of `rng` on the same node
- nothing guarantees that the `rng` containers will be distributed evenly
- We will do that with a *daemon set*
- if we add nodes later, they will not automatically run a copy of `rng`
---
- if we remove (or reboot) a node, one `rng` container will restart elsewhere
## Why not a deployment?
- Instead of a `deployment`, we will use a `daemonset`
- Can't we just do `kubectl scale deployment rng --replicas=...`?
--
- Nothing guarantees that the `rng` containers will be distributed evenly
- If we add nodes later, they will not automatically run a copy of `rng`
- If we remove (or reboot) a node, one `rng` container will restart elsewhere
(and we will end up with two instances `rng` on the same node)
- By contrast, a daemon set will start one pod per node and keep it that way
(as nodes are added or removed)
---