Schedule Unpause Trigger Config Design

Signed-off-by: Tiger Kaovilai <[email protected]>

design/schedule-unpaused-triggers-config_design.md

@@ -0,0 +1,74 @@
+# Schedule Unpaused Triggers Config Design
+## Abstract
+User want to configure what happens when schedule is unpaused. Either run backup immediately or at the next cron schedule.  This design proposes to add a new field to the schedule spec to allow user to configure the behavior
+
+## Background
+Currently, the default behavior is to run the trigger immediately and may not be desired by all users (https://github.com/vmware-tanzu/velero/issues/6517)
+
+## Goals
+- Make schedule unpaused behavior configurable
+
+## Non Goals
+- Changing the default behavior
+
+
+## High-Level Design
+Add a new field with to the schedule spec to allow user to configure the behavior defaulting to prior behavior of triggering backup immediately.
+
+## Detailed Design
+### CLI Changes
+`velero schedule unpause` will now take an optional bool flag `--unpause-triggers` to allow user to override the behavior configured in the schedule spec.
+
+`velero schedule unpause schedule-1 --unpause-triggers=false` will unpause the schedule but not trigger the backup immediately.
+
+`velero schedule unpause schedule-1 --unpause-triggers=true` will unpause the schedule and trigger the backup immediately.
+
+`velero schedule unpause schedule-1` will unpause the schedule and trigger the backup immediately. This is the same behavior as before.
+
+### API Changes
+```
+// ScheduleSpec defines the specification for a Velero schedule
+type ScheduleSpec struct {
+	// Template is the definition of the Backup to be run
+	// on the provided schedule
+	Template BackupSpec `json:"template"`
+
+	// Schedule is a Cron expression defining when to run
+	// the Backup.
+	Schedule string `json:"schedule"`
+
+	// UseOwnerReferencesBackup specifies whether to use
+	// OwnerReferences on backups created by this Schedule.
+	// +optional
+	// +nullable
+	UseOwnerReferencesInBackup *bool `json:"useOwnerReferencesInBackup,omitempty"`
+
+	// Paused specifies whether the schedule is paused or not
+	// +optional
+	Paused bool `json:"paused,omitempty"`
+
+    // UnpauseTriggers specifies whether to trigger backup immediately when schedule is unpaused
+    // +kubebuilder:default:=true
+    // +kubebuilder:validation:Optional
+    UnpauseTriggers bool `json:"unpauseTriggers,omitempty"`
+}
+```
+
+## Alternatives Considered
+
+`velero server` flags to configure the behavior. This is not ideal as it is a global setting. This behavior should be configurable per schedule.
+
+
+## Security Considerations
+None
+
+## Compatibility
+Upon upgrade, the new field will be added to the schedule spec automatically and will default to the prior behavior of triggering backup immediately.
+
+Since this is a new field, it will be ignored by older versions of velero.
+
+## Implementation
+TBD
+
+## Open Issues
+A discussion of issues relating to this proposal for which the author does not know the solution. This section may be omitted if there are none.