diff options
| -rw-r--r-- | contributors/design-proposals/daemonset-update.md | 74 |
1 files changed, 50 insertions, 24 deletions
diff --git a/contributors/design-proposals/daemonset-update.md b/contributors/design-proposals/daemonset-update.md index 06bafcd1..b3cd7384 100644 --- a/contributors/design-proposals/daemonset-update.md +++ b/contributors/design-proposals/daemonset-update.md @@ -60,6 +60,7 @@ changes: type DaemonSetUpdateStrategy struct { // Type of daemon set update. Can be "RollingUpdate" or "OnDelete". // Default is OnDelete. + // +optional Type DaemonSetUpdateStrategyType // Rolling update config params. Present only if DaemonSetUpdateStrategy = @@ -68,6 +69,7 @@ type DaemonSetUpdateStrategy struct { // TODO: Update this to follow our convention for oneOf, whatever we decide it // to be. Same as DeploymentStrategy.RollingUpdate. // See https://github.com/kubernetes/kubernetes/issues/35345 + // +optional RollingUpdate *RollingUpdateDaemonSet } @@ -96,6 +98,7 @@ type RollingUpdateDaemonSet struct { // it then proceeds onto other DaemonSet pods, thus ensuring that at least // 70% of original number of DaemonSet pods are available at all times // during the update. + // +optional MaxUnavailable intstr.IntOrString } @@ -105,21 +108,21 @@ type DaemonSetSpec struct { // this proposal. // Update strategy to replace existing DaemonSet pods with new pods. + // +optional UpdateStrategy DaemonSetUpdateStrategy `json:"updateStrategy,omitempty"` // Minimum number of seconds for which a newly created DaemonSet pod should // be ready without any of its container crashing, for it to be considered // available. Defaults to 0 (pod will be considered available as soon as it // is ready). + // +optional MinReadySeconds int32 `json:"minReadySeconds,omitempty"` -} -const ( - // DefaultDaemonSetUniqueLabelKey is the default key of the labels that is added - // to daemon set pods to distinguish between old and new pod templates during - // DaemonSet update. - DefaultDaemonSetUniqueLabelKey string = "pod-template-hash" -) + // A sequence number representing a specific generation of the template. + // Populated by the system. Can be set at creation time. Read-only otherwise. + // +optional + TemplateGeneration int64 `json:"templateGeneration,omitempty"` +} // DaemonSetStatus represents the current status of a daemon set. type DaemonSetStatus struct { @@ -129,18 +132,28 @@ type DaemonSetStatus struct { // UpdatedNumberScheduled is the total number of nodes that are running updated // daemon pod + // +optional UpdatedNumberScheduled int32 `json:"updatedNumberScheduled"` // NumberAvailable is the number of nodes that should be running the // daemon pod and have one or more of the daemon pod running and // available (ready for at least minReadySeconds) + // +optional NumberAvailable int32 `json:"numberAvailable"` // NumberUnavailable is the number of nodes that should be running the // daemon pod and have non of the daemon pod running and available // (ready for at least minReadySeconds) + // +optional NumberUnavailable int32 `json:"numberUnavailable"` } + +const ( + // DaemonSetTemplateGenerationKey is the key of the labels that is added + // to daemon set pods to distinguish between old and new pod templates + // during DaemonSet template update. + DaemonSetTemplateGenerationKey string = "pod-template-generation" +) ``` ### Controller @@ -158,9 +171,13 @@ For each pending DaemonSet updates, it will: 1. Check `DaemonSetUpdateStrategy`: - If `OnDelete`: do nothing - If `RollingUpdate`: - - Compare spec of the daemon pods from step 1 with DaemonSet - `.spec.template.spec` to see if DaemonSet spec has changed. - - If DaemonSet spec has changed, compare `MaxUnavailable` with DaemonSet + - Find all daemon pods that belong to this DaemonSet using label selectors. + - Pods with "pod-template-generation" value equal to the DaemonSet's + `.spec.templateGeneration` are new pods, otherwise they're old pods. + - Note that pods without "pod-template-generation" labels (e.g. DaemonSet + pods created before RollingUpdate strategy is implemented) will be + seen as old pods. + - If there are old pods found, compare `MaxUnavailable` with DaemonSet `.status.numberUnavailable` to see how many old daemon pods can be killed. Then, kill those pods in the order that unhealthy pods (failed, pending, not ready) are killed first. @@ -175,6 +192,12 @@ For each pending DaemonSet updates, it will: If DaemonSet Controller crashes during an update, it can still recover. +#### API Server + +In DaemonSet strategy (pkg/registry/extensions/daemonset/strategy.go#PrepareForUpdate), +increase DaemonSet's `.spec.templateGeneration` by 1 if any changes is made to +DaemonSet's `.spec.template`. + ### kubectl #### kubectl rollout @@ -270,21 +293,24 @@ Another way to implement DaemonSet history is through creating `PodTemplates` as snapshots of DaemonSet templates, and then create them in DaemonSet controller: - Find existing PodTemplates whose labels are matched by DaemonSet - `.spec.selector` + `.spec.selector`. - Sort those PodTemplates by creation timestamp and only retain at most - `.spec.revisionHistoryLimit` latest PodTemplates (remove the rest) - - Find the PodTemplate whose `.template` is the same as DaemonSet - `.spec.template`. If not found, create a new PodTemplate from DaemonSet - `.spec.template`: - - The name will be `<DaemonSet-Name>-<Hash-of-pod-template>` - - PodTemplate `.metadata.labels` will have a "pod-template-hash" label, - value be the hash of PodTemplate `.template` (note: don't include the - "pod-template-hash" label when calculating hash) - - PodTemplate `.metadata.annotations` will be copied from DaemonSet - `.metadata.annotations` - -Note that when the DaemonSet controller creates pods, those pods will be created -with the "pod-template-hash" label. + `.spec.revisionHistoryLimit` latest PodTemplates (remove the rest). + - Find the PodTemplate whose `.template` is the same as the DaemonSet's + `.spec.template`. + - If not found, create a new PodTemplate from DaemonSet's + `.spec.template`: + - The name will be `<DaemonSet-Name>-<template-generation>` + - PodTemplate `.metadata.labels` will have a "pod-template-generation" + label, value be the same as DaemonSet's `.spec.templateGeneration`. + - PodTemplate will have revision information to avoid triggering + unnecessary restarts on rollback, since we only roll forward and only + increase templateGeneration. + - PodTemplate `.metadata.annotations` will be copied from DaemonSet + `.metadata.annotations`. + - If the PodTemplate is found, sync its "pod-template-generation" and + revision information with current DaemonSet. + - DaemonSet creates pods with "pod-template-generation" label. PodTemplate may need to be made an admin-only or read only resource if it's used to store DaemonSet history. |