Update proposal to reflect current design
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Janet Kuo
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@ -126,25 +126,8 @@ type DaemonSetSpec struct {
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// The number of old history to retain to allow rollback.
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// This is a pointer to distinguish between explicit zero and not specified.
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// Defaults to 2.
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// Defaults to 10.
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RevisionHistoryLimit *int32 `json:"revisionHistoryLimit,omitempty"`
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// The config this DaemonSet is rolling back to. Will be cleared after
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// rollback is done.
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// +optional
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RollbackTo *RollbackConfig `json:"rollbackTo",omitempty`
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}
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// DaemonSetRollback stores the information required to rollback a DaemonSet.
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type DaemonSetRollback struct {
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metav1.TypeMeta `json:",inline"`
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// Required: This must match the Name of a DaemonSet.
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Name string `json:"name"`
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// The annotations to be updated to a DaemonSet
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// +optional
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UpdatedAnnotations map[string]string `json:"updatedAnnotations,omitempty"`
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// The config of this DaemonSet rollback.
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RollbackTo RollbackConfig `json:"rollbackTo"`
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}
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// DaemonSetStatus represents the current status of a daemon set.
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@ -170,11 +153,11 @@ type DaemonSetStatus struct {
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// +optional
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NumberUnavailable int32 `json:"numberUnavailable"`
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// A monotonically increasing counter that tracks hash collisions for
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// the DaemonSet. Used as a collision avoidance mechanism by the
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// DaemonSet controller.
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// Count of hash collisions for the DaemonSet. The DaemonSet controller
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// uses this field as a collision avoidance mechanism when it needs to
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// create the name for the newest ControllerRevision.
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// +optional
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Uniquifier *int64 `json:"uniquifier,omitempty"`
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CollisionCount *int64 `json:"collisionCount,omitempty"`
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}
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const (
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@ -187,7 +170,7 @@ const (
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// DefaultDaemonSetUniqueLabelKey is the default label key that is added
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// to existing DaemonSet pods to distinguish between old and new
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// DaemonSet pods during DaemonSet template updates.
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DefaultDaemonSetUniqueLabelKey string = "pod-template-hash"
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DefaultDaemonSetUniqueLabelKey string = "daemonset-controller-hash"
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)
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```
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@ -198,57 +181,61 @@ const (
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The DaemonSet Controller will make DaemonSet updates happen. It will watch
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DaemonSets on the apiserver.
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DaemonSet controller manages [Controller History](controller_history.md) for
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DaemonSet controller manages [`ControllerRevisions`](controller_history.md) for
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DaemonSet revision introspection and rollback. It's referred to as "history"
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throughout the rest of this proposal.
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For each pending DaemonSet updates, it will:
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1. Find all pods controlled by DaemonSet
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1. Reconstruct DaemonSet history:
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- List existing DaemonSet history controlled by this DaemonSet
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- Find the history of DaemonSet's current target state, and create one if
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not found:
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- The `.name` of this history will be unique, generated from pod template
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hash with hash collision resolution. If history creation failed:
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- If it's because of name collision:
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- Compare history with DaemonSet current target state:
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- If they're the same, we've already created the history
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- Otherwise, bump DaemonSet `.status.collisionCount` by 1, exit and
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retry in the next sync loop
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- Otherwise, exit and retry again in the next sync loop.
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- The history will be labeled with `DefaultDaemonSetUniqueLabelKey`.
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- DaemonSet controller will add a ControllerRef in the history
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`.ownerReferences`.
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- Current history should have the largest `.revision` number amonst all
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existing history. Update `.revision` if it's not (e.g. after a rollback.)
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- If more than one current history is found, remove duplicates and relabel
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their pods' `DefaultDaemonSetUniqueLabelKey`.
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1. Sync nodes:
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- Find all nodes that should run these pods created by this DaemonSet.
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- Create daemon pods on nodes when they should have those pods running but not
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yet. Otherwise, delete running daemon pods that shouldn't be running on nodes.
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- Label new pods with current `.spec.templateGeneration` and
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`DefaultDaemonSetUniqueLabelKey` value of current history when creating them.
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1. Check `DaemonSetUpdateStrategy`:
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- If `OnDelete`: do nothing
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- If `RollingUpdate`:
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- Reconstruct DaemonSet history: filter and sort existing DaemonSet history
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owned by this DaemonSet
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- Find the history of DaemonSet's current target state, and create one if
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not found:
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- The `.name` of this history will be unique, generated from pod template
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hash with hash collision resolution. If history creation failed:
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- If it's because of name collision:
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- Compare history with DaemonSet current target state:
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- If they're the same, we've already created the history
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- Otherwise, bump DaemonSet `.status.uniquifier` by 1, exit and
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retry in the next sync loop
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- Otherwise, exit and retry again in the next sync loop.
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- The history will be labeled with `pod-template-hash`.
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- DaemonSet controller will add a ControllerRef in the history
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`.ownerReferences`.
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- For all pods owned by this DaemonSet:
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- If its `pod-template-generation` label value equals to DaemonSet's
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`.spec.templateGeneration`, it's a new pod (don't compare
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`pod-template-hash`, for backward compatibility).
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- Add `pod-template-hash` label to the new pod based on current
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`DefaultDaemonSetUniqueLabelKey`, for backward compatibility).
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- Add `DefaultDaemonSetUniqueLabelKey` label to the new pod based on current
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history, if the pod doesn't have this label set yet.
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- Otherwise, if the value doesn't match, or the pod doesn't have a
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`pod-template-generation` label, check its `pod-template-hash` label:
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- If the value matches any of the history's `pod-template-hash` label,
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`pod-template-generation` label, check its `DefaultDaemonSetUniqueLabelKey` label:
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- If the value matches any of the history's `DefaultDaemonSetUniqueLabelKey` label,
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it's a pod generated from that history.
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- If that history matches the current target state of the DaemonSet,
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it's a new pod.
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- Otherwise, it's an old pod.
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- Otherwise, if the pod doesn't have a `pod-template-hash` label, or no
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- Otherwise, if the pod doesn't have a `DefaultDaemonSetUniqueLabelKey` label, or no
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matching history is found, it's an old pod.
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- If there are old pods found, compare `MaxUnavailable` with DaemonSet
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`.status.numberUnavailable` to see how many old daemon pods can be
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killed. Then, kill those pods in the order that unhealthy pods (failed,
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pending, not ready) are killed first.
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- Clean up history based on `.spec.revisionHistoryLimit`
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- Always keep live history
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1. Find all nodes that should run these pods created by this DaemonSet.
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1. Create daemon pods on nodes when they should have those pods running but not
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yet. Otherwise, delete running daemon pods that shouldn't be running on nodes.
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- Label new pods with current `.spec.templateGeneration` and
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`pod-template-hash` value of current history when creating them.
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1. Clean up old history based on `.spec.revisionHistoryLimit`
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- Always keep live history and current history
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1. Cleanup, update DaemonSet status
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- `.status.numberAvailable` = the total number of DaemonSet pods that have
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become `Ready` for `MinReadySeconds`
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@ -263,6 +250,8 @@ In DaemonSet strategy (pkg/registry/extensions/daemonset/strategy.go#PrepareForU
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increase DaemonSet's `.spec.templateGeneration` by 1 if any changes is made to
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DaemonSet's `.spec.template`.
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This was originally implmeneted in 1.6, and kept in 1.7 for backward compatibility.
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### kubectl
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#### kubectl rollout
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@ -275,14 +264,6 @@ Users can use `kubectl rollout` to monitor DaemonSet updates:
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DaemonSet updates.
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- `kubectl rollout undo daemonset/<DaemonSet-Name>`: to rollback a DaemonSet
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#### API
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Implement a subresource for DaemonSet history (`daemonsets/foo/history`) that
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summarizes the information in the history.
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Implement a subresource for DaemonSet rollback (`daemonsets/foo/rollback`) that
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triggers a DaemonSet rollback.
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## Updating DaemonSets mid-way
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Users can update an updated DaemonSet before its rollout completes.
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@ -357,6 +338,14 @@ In the future, we may:
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- Support pausing DaemonSet rolling update
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- Support auto-rollback DaemonSets
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### API
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Implement a subresource for DaemonSet history (`daemonsets/foo/history`) that
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summarizes the information in the history.
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Implement a subresource for DaemonSet rollback (`daemonsets/foo/rollback`) that
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triggers a DaemonSet rollback.
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### Tests
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- DaemonSet should support at most one daemon pod per node guarantee.
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