Added a spec regarding the rules for eviction & replacement of pods #133
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neunhoef
requested changes
May 14, 2018
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| ## Replacement | ||
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| Replacement is the process of replacing a pod an another pod that takes over the responsibilities |
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"pod an another" -> "pod by another"
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| ### Image ID Pods | ||
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| The Image ID pods are starter to fetch the ArangoDB version of a specific |
| - Image ID pods can always be restarted on a different node. | ||
| There is no need to replace an image ID pod. | ||
| - `node.kubernetes.io/unreachable:NoExecute` toleration time is set very low (5sec) | ||
| - `node.kubernetes.io/not-ready:NoExecute` toleration time is set very low (5sec) |
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Add (if true): There is no danger at all if two image ID pods happen to run at the same time.
| - Coordinator pods can always be evicted from any node | ||
| - Coordinator pods can always be replaced with another coordinator pod with a different ID on a different node | ||
| - `node.kubernetes.io/unreachable:NoExecute` toleration time is set low (15sec) | ||
| - `node.kubernetes.io/not-ready:NoExecute` toleration time is set low (15sec) |
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Add? "There is no danger at all if two coordinator pods with different ID run concurrently.
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Done (a bit different)
| ### DBServer Pods | ||
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| DBServer pods run an ArangoDB dbserver as part of an ArangoDB cluster. | ||
| It has persistent state potentially tight to the node it runs on and it has a unique ID. |
| ### Single Server Pods | ||
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| Single server pods run an ArangoDB server as part of an ArangoDB single server deployment. | ||
| It has persistent state potentially tight to the node. |
| ### Single Pods in Active Failover Deployment | ||
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| Single pods run an ArangoDB single server as part of an ArangoDB active failover deployment. | ||
| It has persistent state potentially tight to the node it runs on and it has a unique ID. |
| - It is a follower of an active-failover deployment (Q: can we trigger this failover to another server?) | ||
| - Single pods can always be replaced with another single pod with a different ID on a different node. | ||
| - `node.kubernetes.io/unreachable:NoExecute` toleration time is set high to "wait it out a while" (5min) | ||
| - `node.kubernetes.io/not-ready:NoExecute` toleration time is set high to "wait it out a while" (5min) |
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Need to check this, do not know by heart.
| - SyncMaster pods can always be evicted from any node | ||
| - SyncMaster pods can always be replaced with another syncmaster pod on a different node | ||
| - `node.kubernetes.io/unreachable:NoExecute` toleration time is set low (15sec) | ||
| - `node.kubernetes.io/not-ready:NoExecute` toleration time is set low (15sec) |
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Is there any requirement about the same network endpoint or an internal k8s service being set up in case of a replacement?
| - SyncWorker pods can always be evicted from any node | ||
| - SyncWorker pods can always be replaced with another syncworker pod on a different node | ||
| - `node.kubernetes.io/unreachable:NoExecute` toleration time is set a bit higher to try to avoid resynchronization (1min) | ||
| - `node.kubernetes.io/not-ready:NoExecute` toleration time is set a bit higher to try to avoid resynchronization (1min) |
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Same here about network endpoint.
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