status.go

package controller

import (
	"fmt"
	"time"

	"github.com/golang/glog"
	lru "github.com/hashicorp/golang-lru"

	kapi "k8s.io/kubernetes/pkg/api"
	"k8s.io/kubernetes/pkg/api/errors"
	"k8s.io/kubernetes/pkg/api/unversioned"
	utilruntime "k8s.io/kubernetes/pkg/util/runtime"
	"k8s.io/kubernetes/pkg/util/sets"
	"k8s.io/kubernetes/pkg/watch"

	"github.com/openshift/origin/pkg/client"
	routeapi "github.com/openshift/origin/pkg/route/api"
	"github.com/openshift/origin/pkg/router"
)

// StatusAdmitter ensures routes added to the plugin have status set.
type StatusAdmitter struct {
	plugin     router.Plugin
	client     client.RoutesNamespacer
	routerName string

	contentionInterval time.Duration
	expected           *lru.Cache
}

// NewStatusAdmitter creates a plugin wrapper that ensures every accepted
// route has a status field set that matches this router. The admitter manages
// an LRU of recently seen conflicting updates to handle when two router processes
// with differing configurations are writing updates at the same time.
func NewStatusAdmitter(plugin router.Plugin, client client.RoutesNamespacer, name string) *StatusAdmitter {
	expected, _ := lru.New(1024)
	return &StatusAdmitter{
		plugin:     plugin,
		client:     client,
		routerName: name,

		contentionInterval: 1 * time.Minute,
		expected:           expected,
	}
}

// Return a time truncated to the second to ensure that in-memory and
// serialized timestamps can be safely compared.
func getRfc3339Timestamp() unversioned.Time {
	return unversioned.Now().Rfc3339Copy()
}

// nowFn allows the package to be tested
var nowFn = getRfc3339Timestamp

// findOrCreateIngress loops through the router status ingress array looking for an entry
// that matches name. If there is no entry in the array, it creates one and appends it
// to the array. If there are multiple entries with that name, the first one is
// returned and later ones are removed. Changed is returned as true if any part of the
// array is altered.
func findOrCreateIngress(route *routeapi.Route, name string) (_ *routeapi.RouteIngress, changed bool) {
	position := -1
	updated := make([]routeapi.RouteIngress, 0, len(route.Status.Ingress))
	for i := range route.Status.Ingress {
		existing := &route.Status.Ingress[i]
		if existing.RouterName != name {
			updated = append(updated, *existing)
			continue
		}
		if position != -1 {
			changed = true
			continue
		}
		updated = append(updated, *existing)
		position = i
	}
	switch {
	case position == -1:
		position = len(route.Status.Ingress)
		route.Status.Ingress = append(route.Status.Ingress, routeapi.RouteIngress{
			RouterName: name,
			Host:       route.Spec.Host,
		})
		changed = true
	case changed:
		route.Status.Ingress = updated
	}
	ingress := &route.Status.Ingress[position]
	if ingress.Host != route.Spec.Host {
		ingress.Host = route.Spec.Host
		changed = true
	}
	return ingress, changed
}

// setIngressCondition records the condition on the ingress, returning true if the ingress was changed and
// false if no modification was made (or the only modification would have been to update a time).
func setIngressCondition(ingress *routeapi.RouteIngress, condition routeapi.RouteIngressCondition) bool {
	for i, existing := range ingress.Conditions {
		// ensures that the comparison is based on the actual value, not the time
		existing.LastTransitionTime = condition.LastTransitionTime
		if existing == condition {
			// This will always be the case if we're receiving an update on the host
			// value (or the like), since findOrCreateIngress sets that for us.  We
			// still need to set the last-touched time so that others can tell we've
			// modified this Ingress value
			now := nowFn()
			ingress.Conditions[i].LastTransitionTime = &now
			return false
		}
	}
	now := nowFn()
	condition.LastTransitionTime = &now
	ingress.Conditions = []routeapi.RouteIngressCondition{condition}
	return true
}

func ingressConditionTouched(ingress *routeapi.RouteIngress) *unversioned.Time {
	var lastTouch *unversioned.Time
	for _, condition := range ingress.Conditions {
		if t := condition.LastTransitionTime; t != nil {
			switch {
			case lastTouch == nil, t.After(lastTouch.Time):
				lastTouch = t
			}
		}
	}
	return lastTouch
}

// recordIngressConditionFailure updates the matching ingress on the route (or adds a new one) with the specified
// condition, returning true if the object was modified.
func recordIngressConditionFailure(route *routeapi.Route, name string, condition routeapi.RouteIngressCondition) (*routeapi.RouteIngress, bool, *unversioned.Time) {
	for i := range route.Status.Ingress {
		existing := &route.Status.Ingress[i]
		if existing.RouterName != name {
			continue
		}

		// we've changed things if we either replaced the host value...
		changed := false
		if existing.Host != route.Spec.Host {
			existing.Host = route.Spec.Host
			changed = true
		}
		// ...or replaced the entire condition list
		// (NB: order matters in this OR -- short circuiting)
		changed = setIngressCondition(existing, condition) || changed

		lastTouch := ingressConditionTouched(existing)
		return existing, changed, lastTouch
	}
	route.Status.Ingress = append(route.Status.Ingress, routeapi.RouteIngress{RouterName: name, Host: route.Spec.Host})
	ingress := &route.Status.Ingress[len(route.Status.Ingress)-1]
	setIngressCondition(ingress, condition)
	return ingress, true, nil
}

// hasIngressBeenTouched returns true if the route appears to have been touched since the last time
func (a *StatusAdmitter) hasIngressBeenTouched(route *routeapi.Route, lastTouch *unversioned.Time) bool {
	glog.V(4).Infof("has last touch %v for %s/%s", lastTouch, route.Namespace, route.Name)
	if lastTouch.IsZero() {
		return false
	}
	old, ok := a.expected.Get(route.UID)
	if ok && old.(time.Time).Before(nowFn().Add(-a.contentionInterval)) {
		// throw out cache entries from before the contention interval, in case this is no longer valid
		// (e.g. the previous updater no longer exists due to scale down)
		glog.V(4).Infof("expired cached last touch of %s", old.(time.Time))
		a.expected.Remove(route.UID)
		ok = false
	}

	if !ok || old.(time.Time).Equal(lastTouch.Time) {
		glog.V(4).Infof("missing or equal cached last touch")
		return false
	}
	glog.V(4).Infof("different cached last touch of %s", old.(time.Time))
	return true
}

// recordIngressTouch tracks whether the ingress record updated succeeded and returns true if the admitter can
// continue. Conflict errors are treated as no error, but indicate the touch was not successful and the caller
// should retry.
func (a *StatusAdmitter) recordIngressTouch(route *routeapi.Route, touch *unversioned.Time, oldTouch *unversioned.Time, err error) (bool, error) {
	switch {
	case err == nil:
		if touch != nil {
			a.expected.Add(route.UID, touch.Time)
		}
		return true, nil
	// if the router can't write status updates, allow the route to go through
	case errors.IsForbidden(err):
		glog.Errorf("Unable to write router status - please ensure you reconcile your system policy or grant this router access to update route status: %v", err)
		if oldTouch != nil {
			// record oldTouch so that if the problem gets rectified in the future,
			// we can proceed as normal
			a.expected.Add(route.UID, oldTouch.Time)
		}
		return true, nil
	case errors.IsConflict(err):
		// just follow the normal process, and retry when we receive the update notification due to
		// the other entity updating the route.
		return false, nil
	}
	return false, err
}

// admitRoute returns true if the route has already been accepted to this router, or
// updates the route to contain an accepted condition. Returns an error if the route could
// not be admitted due to a failure, or false if the route can't be admitted at this time.
func (a *StatusAdmitter) admitRoute(oc client.RoutesNamespacer, route *routeapi.Route, name string) (bool, error) {
	ingress, updated := findOrCreateIngress(route, name)

	// keep lastTouch around
	lastTouch := ingressConditionTouched(ingress)

	if !updated {
		for i := range ingress.Conditions {
			cond := &ingress.Conditions[i]
			if cond.Type == routeapi.RouteAdmitted && cond.Status == kapi.ConditionTrue {
				// reduce extra round trips during the contention period by remembering this
				// time, so we don't react later
				if _, ok := a.expected.Get(route.UID); !ok {
					a.expected.Add(route.UID, lastTouch.Time)
				}
				glog.V(4).Infof("admit: route already admitted")
				return true, nil
			}
		}
	}

	// this works by keeping a cache of what time we last touched the route.
	// If the recorded last-touch time matches ours, then we were the ones to do the
	// last update, and can continue forth.  Additionally, if we have no entry in our
	// cache, we continue forward anyways.  Since replicas from a new deployment will
	// have no entry, they will update the last-touch time, and therefore take "ownership"
	// of updating the route.  In the case of a new route being created during a rolling update,
	// there will be a race to determine whether the old or new deployment gets to determine,
	// but this will be corrected on the next event after contentionInterval time.

	if a.hasIngressBeenTouched(route, lastTouch) {
		glog.V(4).Infof("admit: observed a route update from someone else: route %s/%s has been updated to an inconsistent value, doing nothing", route.Namespace, route.Name)
		return true, nil
	}

	setIngressCondition(ingress, routeapi.RouteIngressCondition{
		Type:   routeapi.RouteAdmitted,
		Status: kapi.ConditionTrue,
	})
	glog.V(4).Infof("admit: admitting route by updating status: %s (%t): %s", route.Name, updated, route.Spec.Host)
	_, err := oc.Routes(route.Namespace).UpdateStatus(route)
	return a.recordIngressTouch(route, ingress.Conditions[0].LastTransitionTime, lastTouch, err)
}

// RecordRouteRejection attempts to update the route status with a reason for a route being rejected.
func (a *StatusAdmitter) RecordRouteRejection(route *routeapi.Route, reason, message string) {
	ingress, changed, lastTouch := recordIngressConditionFailure(route, a.routerName, routeapi.RouteIngressCondition{
		Type:    routeapi.RouteAdmitted,
		Status:  kapi.ConditionFalse,
		Reason:  reason,
		Message: message,
	})
	if !changed {
		glog.V(4).Infof("reject: no changes to route needed: %s/%s", route.Namespace, route.Name)
		return
	}

	if a.hasIngressBeenTouched(route, lastTouch) {
		glog.V(4).Infof("reject: observed a route update from someone else: route %s/%s has been updated to an inconsistent value, doing nothing", route.Namespace, route.Name)
		return
	}

	_, err := a.client.Routes(route.Namespace).UpdateStatus(route)
	_, err = a.recordIngressTouch(route, ingress.Conditions[0].LastTransitionTime, lastTouch, err)
	if err != nil {
		utilruntime.HandleError(fmt.Errorf("unable to write route rejection to the status: %v", err))
	}
}

// HandleRoute attempts to admit the provided route on watch add / modifications.
func (a *StatusAdmitter) HandleRoute(eventType watch.EventType, route *routeapi.Route) error {
	switch eventType {
	case watch.Added, watch.Modified:
		ok, err := a.admitRoute(a.client, route, a.routerName)
		if err != nil {
			return err
		}
		if !ok {
			glog.V(4).Infof("skipping route: %s", route.Name)
			return nil
		}
	}
	return a.plugin.HandleRoute(eventType, route)
}

func (a *StatusAdmitter) HandleEndpoints(eventType watch.EventType, route *kapi.Endpoints) error {
	return a.plugin.HandleEndpoints(eventType, route)
}

func (a *StatusAdmitter) HandleNamespaces(namespaces sets.String) error {
	return a.plugin.HandleNamespaces(namespaces)
}