Aggregate Service Status Proposal

aggregate-service-status.md

Aggregate Status (w/ Policy)

Status aggregation is complicated, but I guess we have to start with built-in policies.

I'm not sure what "alive" means to an Service tho, when there's "ready"... Does the policy apply to both?

type StatusPolicy string

const (
	// Alive/Ready if all targets are Alive/Ready
	StatusPolicyAll StatusPolicy = "All"
	// Alive/Ready if half + 1 of the targets are Alive/Ready
	StatusPolicyMajority StatusPolicy = "Majority"
	// Alive/Ready if at least 1 target is Alive/Ready
	StatusPolicyOne StatusPolicy = "One"
	// Alive/Ready if at least N targets are Alive/Ready, where N is PolicyQualifier as an int
	StatusPolicyAtLeast StatusPolicy = "AtLeast"
)

type ServiceSpec struct {
	...
	Policy StatusPolicy `json:"policy,omitempty"`
	PolicyQualifier interface{} `json:"policyQualifier,omitempty"`
}

type ServiceStatus struct {
	...
	Conditions []ServiceCondition `json:"conditions,omitempty"`
	LastUpdateTime util.Time `json:"lastUpdateTime,omitempty"`
	LastTransitionTime util.Time `json:"lastTransitionTime,omitempty"`
}

type ServiceConditionType string

const (
	ServiceAlive ServiceConditionType = "Alive"
	ServiceReady ServiceConditionType = "Ready"
)

type ServiceCondition struct {
	Type ServiceTargetConditionType `json:"type"`
	Status ConditionStatus `json:"status"`
	Reason string `json:"reason,omitempty"`
	Message string `json:"message,omitempty"`
}

I guess a load balencer could then just watch Service or ServiceStatus to know what server target addresses should be routable.