gce_loadbalancer.go

/*
Copyright 2017 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package gce

import (
	"flag"
	"fmt"
	"net"
	"net/http"
	"sort"
	"strconv"
	"strings"
	"time"

	"k8s.io/apimachinery/pkg/types"
	utilerrors "k8s.io/apimachinery/pkg/util/errors"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/kubernetes/pkg/api/v1"
	apiservice "k8s.io/kubernetes/pkg/api/v1/service"
	"k8s.io/kubernetes/pkg/cloudprovider"
	netsets "k8s.io/kubernetes/pkg/util/net/sets"

	"github.com/golang/glog"
	compute "google.golang.org/api/compute/v1"
)

type cidrs struct {
	ipn   netsets.IPNet
	isSet bool
}

var (
	lbSrcRngsFlag cidrs
)

func newLoadBalancerMetricContext(request, region string) *metricContext {
	return &metricContext{
		start:      time.Now(),
		attributes: []string{"loadbalancer_" + request, region, unusedMetricLabel},
	}
}

func newTargetPoolMetricContext(request, region string) *metricContext {
	return &metricContext{
		start:      time.Now(),
		attributes: []string{"targetpool_" + request, region, unusedMetricLabel},
	}
}

func newAddressMetricContext(request, region string) *metricContext {
	return &metricContext{
		start:      time.Now(),
		attributes: []string{"address_" + request, region, unusedMetricLabel},
	}
}

func init() {
	var err error
	lbSrcRngsFlag.ipn, err = netsets.ParseIPNets([]string{"130.211.0.0/22", "35.191.0.0/16", "209.85.152.0/22", "209.85.204.0/22", "35.191.0.0/16"}...)
	if err != nil {
		panic("Incorrect default GCE L7 source ranges")
	}

	flag.Var(&lbSrcRngsFlag, "cloud-provider-gce-lb-src-cidrs", "CIDRS opened in GCE firewall for LB traffic proxy & health checks")
}

// String is the method to format the flag's value, part of the flag.Value interface.
func (c *cidrs) String() string {
	return strings.Join(c.ipn.StringSlice(), ",")
}

// Set supports a value of CSV or the flag repeated multiple times
func (c *cidrs) Set(value string) error {
	// On first Set(), clear the original defaults
	if !c.isSet {
		c.isSet = true
		c.ipn = make(netsets.IPNet)
	} else {
		return fmt.Errorf("GCE LB CIDRS have already been set")
	}

	for _, cidr := range strings.Split(value, ",") {
		_, ipnet, err := net.ParseCIDR(cidr)
		if err != nil {
			return err
		}

		c.ipn.Insert(ipnet)
	}
	return nil
}

// LoadBalancerSrcRanges contains the ranges of ips used by the GCE load balancers (l4 & L7)
// for proxying client requests and performing health checks.
func LoadBalancerSrcRanges() []string {
	return lbSrcRngsFlag.ipn.StringSlice()
}

// GetLoadBalancer is an implementation of LoadBalancer.GetLoadBalancer
func (gce *GCECloud) GetLoadBalancer(clusterName string, service *v1.Service) (*v1.LoadBalancerStatus, bool, error) {
	loadBalancerName := cloudprovider.GetLoadBalancerName(service)
	fwd, err := gce.service.ForwardingRules.Get(gce.projectID, gce.region, loadBalancerName).Do()
	if err == nil {
		status := &v1.LoadBalancerStatus{}
		status.Ingress = []v1.LoadBalancerIngress{{IP: fwd.IPAddress}}

		return status, true, nil
	}
	if isHTTPErrorCode(err, http.StatusNotFound) {
		return nil, false, nil
	}
	return nil, false, err
}

// EnsureLoadBalancer is an implementation of LoadBalancer.EnsureLoadBalancer.
// Our load balancers in GCE consist of four separate GCE resources - a static
// IP address, a firewall rule, a target pool, and a forwarding rule. This
// function has to manage all of them.
//
// Due to an interesting series of design decisions, this handles both creating
// new load balancers and updating existing load balancers, recognizing when
// each is needed.
func (gce *GCECloud) EnsureLoadBalancer(clusterName string, apiService *v1.Service, nodes []*v1.Node) (*v1.LoadBalancerStatus, error) {
	if len(nodes) == 0 {
		return nil, fmt.Errorf("Cannot EnsureLoadBalancer() with no hosts")
	}

	hostNames := nodeNames(nodes)
	hosts, err := gce.getInstancesByNames(hostNames)
	if err != nil {
		return nil, err
	}

	loadBalancerName := cloudprovider.GetLoadBalancerName(apiService)
	loadBalancerIP := apiService.Spec.LoadBalancerIP
	ports := apiService.Spec.Ports
	portStr := []string{}
	for _, p := range apiService.Spec.Ports {
		portStr = append(portStr, fmt.Sprintf("%s/%d", p.Protocol, p.Port))
	}

	affinityType := apiService.Spec.SessionAffinity

	serviceName := types.NamespacedName{Namespace: apiService.Namespace, Name: apiService.Name}
	glog.V(2).Infof("EnsureLoadBalancer(%v, %v, %v, %v, %v, %v, %v)",
		loadBalancerName, gce.region, loadBalancerIP, portStr, hostNames, serviceName, apiService.Annotations)

	// Check if the forwarding rule exists, and if so, what its IP is.
	fwdRuleExists, fwdRuleNeedsUpdate, fwdRuleIP, err := gce.forwardingRuleNeedsUpdate(loadBalancerName, gce.region, loadBalancerIP, ports)
	if err != nil {
		return nil, err
	}
	if !fwdRuleExists {
		glog.V(2).Infof("Forwarding rule %v for Service %v/%v doesn't exist",
			loadBalancerName, apiService.Namespace, apiService.Name)
	}

	// Make sure we know which IP address will be used and have properly reserved
	// it as static before moving forward with the rest of our operations.
	//
	// We use static IP addresses when updating a load balancer to ensure that we
	// can replace the load balancer's other components without changing the
	// address its service is reachable on. We do it this way rather than always
	// keeping the static IP around even though this is more complicated because
	// it makes it less likely that we'll run into quota issues. Only 7 static
	// IP addresses are allowed per region by default.
	//
	// We could let an IP be allocated for us when the forwarding rule is created,
	// but we need the IP to set up the firewall rule, and we want to keep the
	// forwarding rule creation as the last thing that needs to be done in this
	// function in order to maintain the invariant that "if the forwarding rule
	// exists, the LB has been fully created".
	ipAddress := ""

	// Through this process we try to keep track of whether it is safe to
	// release the IP that was allocated.  If the user specifically asked for
	// an IP, we assume they are managing it themselves.  Otherwise, we will
	// release the IP in case of early-terminating failure or upon successful
	// creating of the LB.
	// TODO(#36535): boil this logic down into a set of component functions
	// and key the flag values off of errors returned.
	isUserOwnedIP := false // if this is set, we never release the IP
	isSafeToReleaseIP := false
	defer func() {
		if isUserOwnedIP {
			return
		}
		if isSafeToReleaseIP {
			if err := gce.deleteStaticIP(loadBalancerName, gce.region); err != nil {
				glog.Errorf("failed to release static IP %s for load balancer (%v(%v), %v): %v", ipAddress, loadBalancerName, serviceName, gce.region, err)
			}
			glog.V(2).Infof("EnsureLoadBalancer(%v(%v)): released static IP %s", loadBalancerName, serviceName, ipAddress)
		} else {
			glog.Warningf("orphaning static IP %s during update of load balancer (%v(%v), %v): %v", ipAddress, loadBalancerName, serviceName, gce.region, err)
		}
	}()

	if loadBalancerIP != "" {
		// If a specific IP address has been requested, we have to respect the
		// user's request and use that IP. If the forwarding rule was already using
		// a different IP, it will be harmlessly abandoned because it was only an
		// ephemeral IP (or it was a different static IP owned by the user, in which
		// case we shouldn't delete it anyway).
		if isStatic, err := gce.projectOwnsStaticIP(loadBalancerName, gce.region, loadBalancerIP); err != nil {
			return nil, fmt.Errorf("failed to test if this GCE project owns the static IP %s: %v", loadBalancerIP, err)
		} else if isStatic {
			// The requested IP is a static IP, owned and managed by the user.
			isUserOwnedIP = true
			isSafeToReleaseIP = false
			ipAddress = loadBalancerIP
			glog.V(4).Infof("EnsureLoadBalancer(%v(%v)): using user-provided static IP %s", loadBalancerName, serviceName, ipAddress)
		} else if loadBalancerIP == fwdRuleIP {
			// The requested IP is not a static IP, but is currently assigned
			// to this forwarding rule, so we can keep it.
			isUserOwnedIP = false
			isSafeToReleaseIP = true
			ipAddress, _, err = gce.ensureStaticIP(loadBalancerName, serviceName.String(), gce.region, fwdRuleIP)
			if err != nil {
				return nil, fmt.Errorf("failed to ensure static IP %s: %v", fwdRuleIP, err)
			}
			glog.V(4).Infof("EnsureLoadBalancer(%v(%v)): using user-provided non-static IP %s", loadBalancerName, serviceName, ipAddress)
		} else {
			// The requested IP is not static and it is not assigned to the
			// current forwarding rule.  It might be attached to a different
			// rule or it might not be part of this project at all.  Either
			// way, we can't use it.
			return nil, fmt.Errorf("requested ip %s is neither static nor assigned to LB %s(%v): %v", loadBalancerIP, loadBalancerName, serviceName, err)
		}
	} else {
		// The user did not request a specific IP.
		isUserOwnedIP = false

		// This will either allocate a new static IP if the forwarding rule didn't
		// already have an IP, or it will promote the forwarding rule's current
		// IP from ephemeral to static, or it will just get the IP if it is
		// already static.
		existed := false
		ipAddress, existed, err = gce.ensureStaticIP(loadBalancerName, serviceName.String(), gce.region, fwdRuleIP)
		if err != nil {
			return nil, fmt.Errorf("failed to ensure static IP %s: %v", fwdRuleIP, err)
		}
		if existed {
			// If the IP was not specifically requested by the user, but it
			// already existed, it seems to be a failed update cycle.  We can
			// use this IP and try to run through the process again, but we
			// should not release the IP unless it is explicitly flagged as OK.
			isSafeToReleaseIP = false
			glog.V(4).Infof("EnsureLoadBalancer(%v(%v)): adopting static IP %s", loadBalancerName, serviceName, ipAddress)
		} else {
			// For total clarity.  The IP did not pre-exist and the user did
			// not ask for a particular one, so we can release the IP in case
			// of failure or success.
			isSafeToReleaseIP = true
			glog.V(4).Infof("EnsureLoadBalancer(%v(%v)): allocated static IP %s", loadBalancerName, serviceName, ipAddress)
		}
	}

	// Deal with the firewall next. The reason we do this here rather than last
	// is because the forwarding rule is used as the indicator that the load
	// balancer is fully created - it's what getLoadBalancer checks for.
	// Check if user specified the allow source range
	sourceRanges, err := apiservice.GetLoadBalancerSourceRanges(apiService)
	if err != nil {
		return nil, err
	}

	firewallExists, firewallNeedsUpdate, err := gce.firewallNeedsUpdate(loadBalancerName, serviceName.String(), gce.region, ipAddress, ports, sourceRanges)
	if err != nil {
		return nil, err
	}

	if firewallNeedsUpdate {
		desc := makeFirewallDescription(serviceName.String(), ipAddress)
		// Unlike forwarding rules and target pools, firewalls can be updated
		// without needing to be deleted and recreated.
		if firewallExists {
			glog.Infof("EnsureLoadBalancer(%v(%v)): updating firewall", loadBalancerName, serviceName)
			if err := gce.updateFirewall(loadBalancerName, gce.region, desc, sourceRanges, ports, hosts); err != nil {
				return nil, err
			}
			glog.Infof("EnsureLoadBalancer(%v(%v)): updated firewall", loadBalancerName, serviceName)
		} else {
			glog.Infof("EnsureLoadBalancer(%v(%v)): creating firewall", loadBalancerName, serviceName)
			if err := gce.createFirewall(loadBalancerName, gce.region, desc, sourceRanges, ports, hosts); err != nil {
				return nil, err
			}
			glog.Infof("EnsureLoadBalancer(%v(%v)): created firewall", loadBalancerName, serviceName)
		}
	}

	tpExists, tpNeedsUpdate, err := gce.targetPoolNeedsUpdate(loadBalancerName, gce.region, affinityType)
	if err != nil {
		return nil, err
	}
	if !tpExists {
		glog.Infof("Target pool %v for Service %v/%v doesn't exist", loadBalancerName, apiService.Namespace, apiService.Name)
	}

	// Ensure health checks are created for this target pool to pass to createTargetPool for health check links
	// Alternately, if the annotation on the service was removed, we need to recreate the target pool without
	// health checks. This needs to be prior to the forwarding rule deletion below otherwise it is not possible
	// to delete just the target pool or http health checks later.
	var hcToCreate *compute.HttpHealthCheck
	hcExisting, err := gce.GetHttpHealthCheck(loadBalancerName)
	if err != nil && !isHTTPErrorCode(err, http.StatusNotFound) {
		return nil, fmt.Errorf("Error checking HTTP health check %s: %v", loadBalancerName, err)
	}
	if path, healthCheckNodePort := apiservice.GetServiceHealthCheckPathPort(apiService); path != "" {
		glog.V(4).Infof("service %v (%v) needs health checks on :%d%s)", apiService.Name, loadBalancerName, healthCheckNodePort, path)
		if err != nil {
			// This logic exists to detect a transition for a pre-existing service and turn on
			// the tpNeedsUpdate flag to delete/recreate fwdrule/tpool adding the health check
			// to the target pool.
			glog.V(2).Infof("Annotation external-traffic=OnlyLocal added to new or pre-existing service")
			tpNeedsUpdate = true
		}
		hcToCreate, err = gce.ensureHttpHealthCheck(loadBalancerName, path, healthCheckNodePort)
		if err != nil {
			return nil, fmt.Errorf("Failed to ensure health check for localized service %v on node port %v: %v", loadBalancerName, healthCheckNodePort, err)
		}
	} else {
		glog.V(4).Infof("service %v does not need health checks", apiService.Name)
		if err == nil {
			glog.V(2).Infof("Deleting stale health checks for service %v LB %v", apiService.Name, loadBalancerName)
			tpNeedsUpdate = true
		}
	}
	// Now we get to some slightly more interesting logic.
	// First, neither target pools nor forwarding rules can be updated in place -
	// they have to be deleted and recreated.
	// Second, forwarding rules are layered on top of target pools in that you
	// can't delete a target pool that's currently in use by a forwarding rule.
	// Thus, we have to tear down the forwarding rule if either it or the target
	// pool needs to be updated.
	if fwdRuleExists && (fwdRuleNeedsUpdate || tpNeedsUpdate) {
		// Begin critical section. If we have to delete the forwarding rule,
		// and something should fail before we recreate it, don't release the
		// IP.  That way we can come back to it later.
		isSafeToReleaseIP = false
		if err := gce.deleteForwardingRule(loadBalancerName, gce.region); err != nil {
			return nil, fmt.Errorf("failed to delete existing forwarding rule %s for load balancer update: %v", loadBalancerName, err)
		}
		glog.Infof("EnsureLoadBalancer(%v(%v)): deleted forwarding rule", loadBalancerName, serviceName)
	}
	if tpExists && tpNeedsUpdate {
		// Generate the list of health checks for this target pool to pass to deleteTargetPool
		if path, _ := apiservice.GetServiceHealthCheckPathPort(apiService); path != "" {
			var err error
			hcExisting, err = gce.GetHttpHealthCheck(loadBalancerName)
			if err != nil && !isHTTPErrorCode(err, http.StatusNotFound) {
				glog.Infof("Failed to retrieve health check %v:%v", loadBalancerName, err)
			}
		}

		// Pass healthchecks to deleteTargetPool to cleanup health checks prior to cleaning up the target pool itself.
		if err := gce.deleteTargetPool(loadBalancerName, gce.region, hcExisting); err != nil {
			return nil, fmt.Errorf("failed to delete existing target pool %s for load balancer update: %v", loadBalancerName, err)
		}
		glog.Infof("EnsureLoadBalancer(%v(%v)): deleted target pool", loadBalancerName, serviceName)
	}

	// Once we've deleted the resources (if necessary), build them back up (or for
	// the first time if they're new).
	if tpNeedsUpdate {
		createInstances := hosts
		if len(hosts) > maxTargetPoolCreateInstances {
			createInstances = createInstances[:maxTargetPoolCreateInstances]
		}
		// Pass healthchecks to createTargetPool which needs them as health check links in the target pool
		if err := gce.createTargetPool(loadBalancerName, serviceName.String(), gce.region, createInstances, affinityType, hcToCreate); err != nil {
			return nil, fmt.Errorf("failed to create target pool %s: %v", loadBalancerName, err)
		}
		if hcToCreate != nil {
			glog.Infof("EnsureLoadBalancer(%v(%v)): created health checks for target pool", loadBalancerName, serviceName)
		}
		if len(hosts) <= maxTargetPoolCreateInstances {
			glog.Infof("EnsureLoadBalancer(%v(%v)): created target pool", loadBalancerName, serviceName)
		} else {
			glog.Infof("EnsureLoadBalancer(%v(%v)): created initial target pool (now updating with %d hosts)", loadBalancerName, serviceName, len(hosts)-maxTargetPoolCreateInstances)

			created := sets.NewString()
			for _, host := range createInstances {
				created.Insert(host.makeComparableHostPath())
			}
			if err := gce.updateTargetPool(loadBalancerName, created, hosts); err != nil {
				return nil, fmt.Errorf("failed to update target pool %s: %v", loadBalancerName, err)
			}
			glog.Infof("EnsureLoadBalancer(%v(%v)): updated target pool (with %d hosts)", loadBalancerName, serviceName, len(hosts)-maxTargetPoolCreateInstances)
		}
	}
	if tpNeedsUpdate || fwdRuleNeedsUpdate {
		glog.Infof("EnsureLoadBalancer(%v(%v)): creating forwarding rule, IP %s", loadBalancerName, serviceName, ipAddress)
		if err := gce.createForwardingRule(loadBalancerName, serviceName.String(), gce.region, ipAddress, ports); err != nil {
			return nil, fmt.Errorf("failed to create forwarding rule %s: %v", loadBalancerName, err)
		}
		// End critical section.  It is safe to release the static IP (which
		// just demotes it to ephemeral) now that it is attached.  In the case
		// of a user-requested IP, the "is user-owned" flag will be set,
		// preventing it from actually being released.
		isSafeToReleaseIP = true
		glog.Infof("EnsureLoadBalancer(%v(%v)): created forwarding rule, IP %s", loadBalancerName, serviceName, ipAddress)
	}

	status := &v1.LoadBalancerStatus{}
	status.Ingress = []v1.LoadBalancerIngress{{IP: ipAddress}}

	return status, nil
}

// UpdateLoadBalancer is an implementation of LoadBalancer.UpdateLoadBalancer.
func (gce *GCECloud) UpdateLoadBalancer(clusterName string, service *v1.Service, nodes []*v1.Node) error {
	hosts, err := gce.getInstancesByNames(nodeNames(nodes))
	if err != nil {
		return err
	}

	loadBalancerName := cloudprovider.GetLoadBalancerName(service)
	pool, err := gce.service.TargetPools.Get(gce.projectID, gce.region, loadBalancerName).Do()
	if err != nil {
		return err
	}
	existing := sets.NewString()
	for _, instance := range pool.Instances {
		existing.Insert(hostURLToComparablePath(instance))
	}

	return gce.updateTargetPool(loadBalancerName, existing, hosts)
}

// EnsureLoadBalancerDeleted is an implementation of LoadBalancer.EnsureLoadBalancerDeleted.
func (gce *GCECloud) EnsureLoadBalancerDeleted(clusterName string, service *v1.Service) error {
	loadBalancerName := cloudprovider.GetLoadBalancerName(service)
	glog.V(2).Infof("EnsureLoadBalancerDeleted(%v, %v, %v, %v, %v)", clusterName, service.Namespace, service.Name, loadBalancerName,
		gce.region)

	var hc *compute.HttpHealthCheck
	if path, _ := apiservice.GetServiceHealthCheckPathPort(service); path != "" {
		var err error
		hc, err = gce.GetHttpHealthCheck(loadBalancerName)
		if err != nil && !isHTTPErrorCode(err, http.StatusNotFound) {
			glog.Infof("Failed to retrieve health check %v:%v", loadBalancerName, err)
			return err
		}
	}

	errs := utilerrors.AggregateGoroutines(
		func() error { return gce.deleteFirewall(loadBalancerName, gce.region) },
		// Even though we don't hold on to static IPs for load balancers, it's
		// possible that EnsureLoadBalancer left one around in a failed
		// creation/update attempt, so make sure we clean it up here just in case.
		func() error { return gce.deleteStaticIP(loadBalancerName, gce.region) },
		func() error {
			// The forwarding rule must be deleted before either the target pool can,
			// unfortunately, so we have to do these two serially.
			if err := gce.deleteForwardingRule(loadBalancerName, gce.region); err != nil {
				return err
			}
			if err := gce.deleteTargetPool(loadBalancerName, gce.region, hc); err != nil {
				return err
			}
			return nil
		},
	)
	if errs != nil {
		return utilerrors.Flatten(errs)
	}
	return nil
}

func (gce *GCECloud) DeleteForwardingRule(name string) error {
	region, err := GetGCERegion(gce.localZone)
	if err != nil {
		return err
	}
	return gce.deleteForwardingRule(name, region)
}

func (gce *GCECloud) deleteForwardingRule(name, region string) error {
	mc := newForwardingRuleMetricContext("delete", region)
	op, err := gce.service.ForwardingRules.Delete(gce.projectID, region, name).Do()

	if err != nil && isHTTPErrorCode(err, http.StatusNotFound) {
		glog.Infof("Forwarding rule %s already deleted. Continuing to delete other resources.", name)
	} else if err != nil {
		glog.Warningf("Failed to delete forwarding rule %s: got error %s.", name, err.Error())
		return mc.Observe(err)
	} else {
		if err := gce.waitForRegionOp(op, region, mc); err != nil {
			glog.Warningf("Failed waiting for forwarding rule %s to be deleted: got error %s.",
				name, err.Error())
			return err
		}
	}
	return nil
}

// DeleteTargetPool deletes the given target pool.
func (gce *GCECloud) DeleteTargetPool(name string, hc *compute.HttpHealthCheck) error {
	region, err := GetGCERegion(gce.localZone)
	if err != nil {
		return err
	}
	return gce.deleteTargetPool(name, region, hc)
}

func (gce *GCECloud) deleteTargetPool(name, region string, hc *compute.HttpHealthCheck) error {
	mc := newTargetPoolMetricContext("delete", region)
	op, err := gce.service.TargetPools.Delete(gce.projectID, region, name).Do()

	if err != nil && isHTTPErrorCode(err, http.StatusNotFound) {
		glog.Infof("Target pool %s already deleted. Continuing to delete other resources.", name)
	} else if err != nil {
		glog.Warningf("Failed to delete target pool %s, got error %s.", name, err.Error())
		return mc.Observe(err)
	} else {
		if err := gce.waitForRegionOp(op, region, mc); err != nil {
			glog.Warningf("Failed waiting for target pool %s to be deleted: got error %s.",
				name, err.Error())
			return err
		}
	}

	// Deletion of health checks is allowed only after the TargetPool reference is deleted
	if hc != nil {
		glog.Infof("Deleting health check %v", hc.Name)
		if err := gce.DeleteHttpHealthCheck(hc.Name); err != nil {
			glog.Warningf("Failed to delete health check %v: %v", hc, err)
			return err
		}
	} else {
		// This is a HC cleanup attempt to prevent stale HCs when errors are encountered
		// during HC deletion in a prior pass through EnsureLoadBalancer.
		// The HC name matches the load balancer name - normally this is expected to fail.
		if err := gce.DeleteHttpHealthCheck(name); err == nil {
			// We only print a warning if this deletion actually succeeded (which
			// means there was indeed a stale health check with the LB name.
			glog.Warningf("Deleted stale http health check for LB: %s", name)
		}
	}
	return nil
}

func (gce *GCECloud) createTargetPool(name, serviceName, region string, hosts []*gceInstance, affinityType v1.ServiceAffinity, hc *compute.HttpHealthCheck) error {
	var instances []string
	for _, host := range hosts {
		instances = append(instances, makeHostURL(gce.projectID, host.Zone, host.Name))
	}
	// health check management is coupled with targetPools to prevent leaks. A
	// target pool is the only thing that requires a health check, so we delete
	// associated checks on teardown, and ensure checks on setup.
	hcLinks := []string{}
	if hc != nil {
		var err error
		if hc, err = gce.ensureHttpHealthCheck(name, hc.RequestPath, int32(hc.Port)); err != nil || hc == nil {
			return fmt.Errorf("Failed to ensure health check for %v port %d path %v: %v", name, hc.Port, hc.RequestPath, err)
		}
		hcLinks = append(hcLinks, hc.SelfLink)
	}
	glog.Infof("Creating targetpool %v with %d healthchecks", name, len(hcLinks))
	pool := &compute.TargetPool{
		Name:            name,
		Description:     fmt.Sprintf(`{"kubernetes.io/service-name":"%s"}`, serviceName),
		Instances:       instances,
		SessionAffinity: translateAffinityType(affinityType),
		HealthChecks:    hcLinks,
	}

	mc := newTargetPoolMetricContext("insert", region)
	op, err := gce.service.TargetPools.Insert(gce.projectID, region, pool).Do()
	if err != nil && !isHTTPErrorCode(err, http.StatusConflict) {
		return mc.Observe(err)
	}
	if op != nil {
		err = gce.waitForRegionOp(op, region, mc)
		if err != nil && !isHTTPErrorCode(err, http.StatusConflict) {
			return err
		}
	}
	return nil
}

func (gce *GCECloud) updateTargetPool(loadBalancerName string, existing sets.String, hosts []*gceInstance) error {
	var toAdd []*compute.InstanceReference
	var toRemove []*compute.InstanceReference
	for _, host := range hosts {
		link := host.makeComparableHostPath()
		if !existing.Has(link) {
			toAdd = append(toAdd, &compute.InstanceReference{Instance: link})
		}
		existing.Delete(link)
	}
	for link := range existing {
		toRemove = append(toRemove, &compute.InstanceReference{Instance: link})
	}

	if len(toAdd) > 0 {
		add := &compute.TargetPoolsAddInstanceRequest{Instances: toAdd}

		mc := newTargetPoolMetricContext("update", gce.region)
		op, err := gce.service.TargetPools.AddInstance(gce.projectID, gce.region, loadBalancerName, add).Do()
		if err != nil {
			return mc.Observe(err)
		}
		if err := gce.waitForRegionOp(op, gce.region, mc); err != nil {
			return err
		}
	}

	if len(toRemove) > 0 {
		mc := newTargetPoolMetricContext("delete", gce.region)
		rm := &compute.TargetPoolsRemoveInstanceRequest{Instances: toRemove}
		op, err := gce.service.TargetPools.RemoveInstance(gce.projectID, gce.region, loadBalancerName, rm).Do()
		if err != nil {
			return mc.Observe(err)
		}
		if err := gce.waitForRegionOp(op, gce.region, mc); err != nil {
			return err
		}
	}

	// Try to verify that the correct number of nodes are now in the target pool.
	// We've been bitten by a bug here before (#11327) where all nodes were
	// accidentally removed and want to make similar problems easier to notice.
	updatedPool, err := gce.service.TargetPools.Get(gce.projectID, gce.region, loadBalancerName).Do()
	if err != nil {
		return err
	}
	if len(updatedPool.Instances) != len(hosts) {
		glog.Errorf("Unexpected number of instances (%d) in target pool %s after updating (expected %d). Instances in updated pool: %s",
			len(updatedPool.Instances), loadBalancerName, len(hosts), strings.Join(updatedPool.Instances, ","))
		return fmt.Errorf("Unexpected number of instances (%d) in target pool %s after update (expected %d)", len(updatedPool.Instances), loadBalancerName, len(hosts))
	}
	return nil
}

func (gce *GCECloud) targetPoolURL(name, region string) string {
	return fmt.Sprintf("https://www.googleapis.com/compute/v1/projects/%s/regions/%s/targetPools/%s", gce.projectID, region, name)
}

func (gce *GCECloud) ensureHttpHealthCheck(name, path string, port int32) (hc *compute.HttpHealthCheck, err error) {
	newHC := &compute.HttpHealthCheck{
		Name:               name,
		Port:               int64(port),
		RequestPath:        path,
		Host:               "",
		Description:        makeHealthCheckDescription(name),
		CheckIntervalSec:   gceHcCheckIntervalSeconds,
		TimeoutSec:         gceHcTimeoutSeconds,
		HealthyThreshold:   gceHcHealthyThreshold,
		UnhealthyThreshold: gceHcUnhealthyThreshold,
	}

	hc, err = gce.GetHttpHealthCheck(name)
	if hc == nil || err != nil && isHTTPErrorCode(err, http.StatusNotFound) {
		glog.Infof("Did not find health check %v, creating port %v path %v", name, port, path)
		if err = gce.CreateHttpHealthCheck(newHC); err != nil {
			return nil, err
		}
		hc, err = gce.GetHttpHealthCheck(name)
		if err != nil {
			glog.Errorf("Failed to get http health check %v", err)
			return nil, err
		}
		glog.Infof("Created HTTP health check %v healthCheckNodePort: %d", name, port)
		return hc, nil
	}
	// Validate health check fields
	glog.V(4).Infof("Checking http health check params %s", name)
	drift := hc.Port != int64(port) || hc.RequestPath != path || hc.Description != makeHealthCheckDescription(name)
	drift = drift || hc.CheckIntervalSec != gceHcCheckIntervalSeconds || hc.TimeoutSec != gceHcTimeoutSeconds
	drift = drift || hc.UnhealthyThreshold != gceHcUnhealthyThreshold || hc.HealthyThreshold != gceHcHealthyThreshold
	if drift {
		glog.Warningf("Health check %v exists but parameters have drifted - updating...", name)
		if err := gce.UpdateHttpHealthCheck(newHC); err != nil {
			glog.Warningf("Failed to reconcile http health check %v parameters", name)
			return nil, err
		}
		glog.V(4).Infof("Corrected health check %v parameters successful", name)
	}
	return hc, nil
}

// Passing nil for requested IP is perfectly fine - it just means that no specific
// IP is being requested.
// Returns whether the forwarding rule exists, whether it needs to be updated,
// what its IP address is (if it exists), and any error we encountered.
func (gce *GCECloud) forwardingRuleNeedsUpdate(name, region string, loadBalancerIP string, ports []v1.ServicePort) (exists bool, needsUpdate bool, ipAddress string, err error) {
	fwd, err := gce.service.ForwardingRules.Get(gce.projectID, region, name).Do()
	if err != nil {
		if isHTTPErrorCode(err, http.StatusNotFound) {
			return false, true, "", nil
		}
		// Err on the side of caution in case of errors. Caller should notice the error and retry.
		// We never want to end up recreating resources because gce api flaked.
		return true, false, "", fmt.Errorf("error getting load balancer's forwarding rule: %v", err)
	}
	// If the user asks for a specific static ip through the Service spec,
	// check that we're actually using it.
	// TODO: we report loadbalancer IP through status, so we want to verify if
	// that matches the forwarding rule as well.
	if loadBalancerIP != "" && loadBalancerIP != fwd.IPAddress {
		glog.Infof("LoadBalancer ip for forwarding rule %v was expected to be %v, but was actually %v", fwd.Name, fwd.IPAddress, loadBalancerIP)
		return true, true, fwd.IPAddress, nil
	}
	portRange, err := loadBalancerPortRange(ports)
	if err != nil {
		// Err on the side of caution in case of errors. Caller should notice the error and retry.
		// We never want to end up recreating resources because gce api flaked.
		return true, false, "", err
	}
	if portRange != fwd.PortRange {
		glog.Infof("LoadBalancer port range for forwarding rule %v was expected to be %v, but was actually %v", fwd.Name, fwd.PortRange, portRange)
		return true, true, fwd.IPAddress, nil
	}
	// The service controller verified all the protocols match on the ports, just check the first one
	if string(ports[0].Protocol) != fwd.IPProtocol {
		glog.Infof("LoadBalancer protocol for forwarding rule %v was expected to be %v, but was actually %v", fwd.Name, fwd.IPProtocol, string(ports[0].Protocol))
		return true, true, fwd.IPAddress, nil
	}

	return true, false, fwd.IPAddress, nil
}

// Doesn't check whether the hosts have changed, since host updating is handled
// separately.
func (gce *GCECloud) targetPoolNeedsUpdate(name, region string, affinityType v1.ServiceAffinity) (exists bool, needsUpdate bool, err error) {
	tp, err := gce.service.TargetPools.Get(gce.projectID, region, name).Do()
	if err != nil {
		if isHTTPErrorCode(err, http.StatusNotFound) {
			return false, true, nil
		}
		// Err on the side of caution in case of errors. Caller should notice the error and retry.
		// We never want to end up recreating resources because gce api flaked.
		return true, false, fmt.Errorf("error getting load balancer's target pool: %v", err)
	}
	// TODO: If the user modifies their Service's session affinity, it *should*
	// reflect in the associated target pool. However, currently not setting the
	// session affinity on a target pool defaults it to the empty string while
	// not setting in on a Service defaults it to None. There is a lack of
	// documentation around the default setting for the target pool, so if we
	// find it's the undocumented empty string, don't blindly recreate the
	// target pool (which results in downtime). Fix this when we have formally
	// defined the defaults on either side.
	if tp.SessionAffinity != "" && translateAffinityType(affinityType) != tp.SessionAffinity {
		glog.Infof("LoadBalancer target pool %v changed affinity from %v to %v", name, tp.SessionAffinity, affinityType)
		return true, true, nil
	}
	return true, false, nil
}

func (h *gceInstance) makeComparableHostPath() string {
	return fmt.Sprintf("/zones/%s/instances/%s", h.Zone, h.Name)
}

func nodeNames(nodes []*v1.Node) []string {
	ret := make([]string, len(nodes))
	for i, node := range nodes {
		ret[i] = node.Name
	}
	return ret
}

func makeHostURL(projectID, zone, host string) string {
	host = canonicalizeInstanceName(host)
	return fmt.Sprintf("https://www.googleapis.com/compute/v1/projects/%s/zones/%s/instances/%s",
		projectID, zone, host)
}

func hostURLToComparablePath(hostURL string) string {
	idx := strings.Index(hostURL, "/zones/")
	if idx < 0 {
		return ""
	}
	return hostURL[idx:]
}

func makeHealthCheckDescription(serviceName string) string {
	return fmt.Sprintf(`{"kubernetes.io/service-name":"%s"}`, serviceName)
}

func loadBalancerPortRange(ports []v1.ServicePort) (string, error) {
	if len(ports) == 0 {
		return "", fmt.Errorf("no ports specified for GCE load balancer")
	}

	// The service controller verified all the protocols match on the ports, just check and use the first one
	if ports[0].Protocol != v1.ProtocolTCP && ports[0].Protocol != v1.ProtocolUDP {
		return "", fmt.Errorf("Invalid protocol %s, only TCP and UDP are supported", string(ports[0].Protocol))
	}

	minPort := int32(65536)
	maxPort := int32(0)
	for i := range ports {
		if ports[i].Port < minPort {
			minPort = ports[i].Port
		}
		if ports[i].Port > maxPort {
			maxPort = ports[i].Port
		}
	}
	return fmt.Sprintf("%d-%d", minPort, maxPort), nil
}

// translate from what K8s supports to what the cloud provider supports for session affinity.
func translateAffinityType(affinityType v1.ServiceAffinity) string {
	switch affinityType {
	case v1.ServiceAffinityClientIP:
		return gceAffinityTypeClientIP
	case v1.ServiceAffinityNone:
		return gceAffinityTypeNone
	default:
		glog.Errorf("Unexpected affinity type: %v", affinityType)
		return gceAffinityTypeNone
	}
}

func makeFirewallName(name string) string {
	return fmt.Sprintf("k8s-fw-%s", name)
}

func makeFirewallDescription(serviceName, ipAddress string) string {
	return fmt.Sprintf(`{"kubernetes.io/service-name":"%s", "kubernetes.io/service-ip":"%s"}`,
		serviceName, ipAddress)
}

func (gce *GCECloud) firewallNeedsUpdate(name, serviceName, region, ipAddress string, ports []v1.ServicePort, sourceRanges netsets.IPNet) (exists bool, needsUpdate bool, err error) {
	fw, err := gce.service.Firewalls.Get(gce.projectID, makeFirewallName(name)).Do()
	if err != nil {
		if isHTTPErrorCode(err, http.StatusNotFound) {
			return false, true, nil
		}
		return false, false, fmt.Errorf("error getting load balancer's target pool: %v", err)
	}
	if fw.Description != makeFirewallDescription(serviceName, ipAddress) {
		return true, true, nil
	}
	if len(fw.Allowed) != 1 || (fw.Allowed[0].IPProtocol != "tcp" && fw.Allowed[0].IPProtocol != "udp") {
		return true, true, nil
	}
	// Make sure the allowed ports match.
	allowedPorts := make([]string, len(ports))
	for ix := range ports {
		allowedPorts[ix] = strconv.Itoa(int(ports[ix].Port))
	}
	if !slicesEqual(allowedPorts, fw.Allowed[0].Ports) {
		return true, true, nil
	}
	// The service controller already verified that the protocol matches on all ports, no need to check.

	actualSourceRanges, err := netsets.ParseIPNets(fw.SourceRanges...)
	if err != nil {
		// This really shouldn't happen... GCE has returned something unexpected
		glog.Warningf("Error parsing firewall SourceRanges: %v", fw.SourceRanges)
		// We don't return the error, because we can hopefully recover from this by reconfiguring the firewall
		return true, true, nil
	}

	if !sourceRanges.Equal(actualSourceRanges) {
		return true, true, nil
	}
	return true, false, nil
}

func slicesEqual(x, y []string) bool {
	if len(x) != len(y) {
		return false
	}
	sort.Strings(x)
	sort.Strings(y)
	for i := range x {
		if x[i] != y[i] {
			return false
		}
	}
	return true
}

func (gce *GCECloud) createForwardingRule(name, serviceName, region, ipAddress string, ports []v1.ServicePort) error {
	portRange, err := loadBalancerPortRange(ports)
	if err != nil {
		return err
	}
	req := &compute.ForwardingRule{
		Name:        name,
		Description: fmt.Sprintf(`{"kubernetes.io/service-name":"%s"}`, serviceName),
		IPAddress:   ipAddress,
		IPProtocol:  string(ports[0].Protocol),
		PortRange:   portRange,
		Target:      gce.targetPoolURL(name, region),
	}

	mc := newForwardingRuleMetricContext("create", region)
	op, err := gce.service.ForwardingRules.Insert(gce.projectID, region, req).Do()
	if err != nil && !isHTTPErrorCode(err, http.StatusConflict) {
		return mc.Observe(err)
	}
	if op != nil {
		err = gce.waitForRegionOp(op, region, mc)
		if err != nil && !isHTTPErrorCode(err, http.StatusConflict) {
			return err
		}
	}
	return nil
}

func (gce *GCECloud) createFirewall(name, region, desc string, sourceRanges netsets.IPNet, ports []v1.ServicePort, hosts []*gceInstance) error {
	mc := newFirewallMetricContext("create", region)
	firewall, err := gce.firewallObject(name, region, desc, sourceRanges, ports, hosts)
	if err != nil {
		return mc.Observe(err)
	}
	op, err := gce.service.Firewalls.Insert(gce.projectID, firewall).Do()
	if err != nil && !isHTTPErrorCode(err, http.StatusConflict) {
		return mc.Observe(err)
	}
	if op != nil {
		err = gce.waitForGlobalOp(op, mc)
		if err != nil && !isHTTPErrorCode(err, http.StatusConflict) {
			return err
		}
	}
	return nil
}

func (gce *GCECloud) updateFirewall(name, region, desc string, sourceRanges netsets.IPNet, ports []v1.ServicePort, hosts []*gceInstance) error {
	mc := newFirewallMetricContext("update", region)
	firewall, err := gce.firewallObject(name, region, desc, sourceRanges, ports, hosts)
	if err != nil {
		return mc.Observe(err)
	}
	op, err := gce.service.Firewalls.Update(gce.projectID, makeFirewallName(name), firewall).Do()
	if err != nil && !isHTTPErrorCode(err, http.StatusConflict) {
		return mc.Observe(err)
	}
	if op != nil {
		err = gce.waitForGlobalOp(op, mc)
		if err != nil {
			return err
		}
	}
	return nil
}

func (gce *GCECloud) firewallObject(name, region, desc string, sourceRanges netsets.IPNet, ports []v1.ServicePort, hosts []*gceInstance) (*compute.Firewall, error) {
	allowedPorts := make([]string, len(ports))
	for ix := range ports {
		allowedPorts[ix] = strconv.Itoa(int(ports[ix].Port))
	}
	// If the node tags to be used for this cluster have been predefined in the
	// provider config, just use them. Otherwise, invoke computeHostTags method to get the tags.
	hostTags := gce.nodeTags
	if len(hostTags) == 0 {
		var err error
		if hostTags, err = gce.computeHostTags(hosts); err != nil {
			return nil, fmt.Errorf("No node tags supplied and also failed to parse the given lists of hosts for tags. Abort creating firewall rule.")
		}
	}

	firewall := &compute.Firewall{
		Name:         makeFirewallName(name),
		Description:  desc,
		Network:      gce.networkURL,
		SourceRanges: sourceRanges.StringSlice(),
		TargetTags:   hostTags,
		Allowed: []*compute.FirewallAllowed{
			{
				// TODO: Make this more generic. Currently this method is only
				// used to create firewall rules for loadbalancers, which have
				// exactly one protocol, so we can never end up with a list of
				// mixed TCP and UDP ports. It should be possible to use a
				// single firewall rule for both a TCP and UDP lb.
				IPProtocol: strings.ToLower(string(ports[0].Protocol)),
				Ports:      allowedPorts,
			},
		},
	}
	return firewall, nil
}

// ComputeHostTags grabs all tags from all instances being added to the pool.
// * The longest tag that is a prefix of the instance name is used
// * If any instance has no matching prefix tag, return error
// Invoking this method to get host tags is risky since it depends on the format
// of the host names in the cluster. Only use it as a fallback if gce.nodeTags
// is unspecified
func (gce *GCECloud) computeHostTags(hosts []*gceInstance) ([]string, error) {
	// TODO: We could store the tags in gceInstance, so we could have already fetched it
	hostNamesByZone := make(map[string]map[string]bool) // map of zones -> map of names -> bool (for easy lookup)
	nodeInstancePrefix := gce.nodeInstancePrefix
	for _, host := range hosts {
		if !strings.HasPrefix(host.Name, gce.nodeInstancePrefix) {
			glog.Warningf("instance '%s' does not conform to prefix '%s', ignoring filter", host, gce.nodeInstancePrefix)
			nodeInstancePrefix = ""
		}

		z, ok := hostNamesByZone[host.Zone]
		if !ok {
			z = make(map[string]bool)
			hostNamesByZone[host.Zone] = z
		}
		z[host.Name] = true
	}

	tags := sets.NewString()

	for zone, hostNames := range hostNamesByZone {
		pageToken := ""
		page := 0
		for ; page == 0 || (pageToken != "" && page < maxPages); page++ {
			listCall := gce.service.Instances.List(gce.projectID, zone)

			if nodeInstancePrefix != "" {
				// Add the filter for hosts
				listCall = listCall.Filter("name eq " + nodeInstancePrefix + ".*")
			}

			// Add the fields we want
			// TODO(zmerlynn): Internal bug 29524655
			// listCall = listCall.Fields("items(name,tags)")

			if pageToken != "" {
				listCall = listCall.PageToken(pageToken)
			}

			res, err := listCall.Do()
			if err != nil {
				return nil, err
			}
			pageToken = res.NextPageToken
			for _, instance := range res.Items {
				if !hostNames[instance.Name] {
					continue
				}

				longest_tag := ""
				for _, tag := range instance.Tags.Items {
					if strings.HasPrefix(instance.Name, tag) && len(tag) > len(longest_tag) {
						longest_tag = tag
					}
				}
				if len(longest_tag) > 0 {
					tags.Insert(longest_tag)
				} else {
					return nil, fmt.Errorf("Could not find any tag that is a prefix of instance name for instance %s", instance.Name)
				}
			}
		}
		if page >= maxPages {
			glog.Errorf("computeHostTags exceeded maxPages=%d for Instances.List: truncating.", maxPages)
		}
	}
	if len(tags) == 0 {
		return nil, fmt.Errorf("No instances found")
	}
	return tags.List(), nil
}

func (gce *GCECloud) projectOwnsStaticIP(name, region string, ipAddress string) (bool, error) {
	pageToken := ""
	page := 0
	for ; page == 0 || (pageToken != "" && page < maxPages); page++ {
		listCall := gce.service.Addresses.List(gce.projectID, region)
		if pageToken != "" {
			listCall = listCall.PageToken(pageToken)
		}
		addresses, err := listCall.Do()
		if err != nil {
			return false, fmt.Errorf("failed to list gce IP addresses: %v", err)
		}
		pageToken = addresses.NextPageToken
		for _, addr := range addresses.Items {
			if addr.Address == ipAddress {
				// This project does own the address, so return success.
				return true, nil
			}
		}
	}
	if page >= maxPages {
		glog.Errorf("projectOwnsStaticIP exceeded maxPages=%d for Addresses.List; truncating.", maxPages)
	}
	return false, nil
}

func (gce *GCECloud) ensureStaticIP(name, serviceName, region, existingIP string) (ipAddress string, created bool, err error) {
	// If the address doesn't exist, this will create it.
	// If the existingIP exists but is ephemeral, this will promote it to static.
	// If the address already exists, this will harmlessly return a StatusConflict
	// and we'll grab the IP before returning.
	existed := false
	addressObj := &compute.Address{
		Name:        name,
		Description: fmt.Sprintf(`{"kubernetes.io/service-name":"%s"}`, serviceName),
	}

	if existingIP != "" {
		addressObj.Address = existingIP
	}

	mc := newAddressMetricContext("create", region)
	op, err := gce.service.Addresses.Insert(gce.projectID, region, addressObj).Do()
	if err != nil {
		if !isHTTPErrorCode(err, http.StatusConflict) {
			return "", false, fmt.Errorf("error creating gce static IP address: %v",
				mc.Observe(err))
		}
		// StatusConflict == the IP exists already.
		existed = true
	}
	if op != nil {
		err := gce.waitForRegionOp(op, region, mc)
		if err != nil {
			if !isHTTPErrorCode(err, http.StatusConflict) {
				return "", false, fmt.Errorf("error waiting for gce static IP address to be created: %v", err)
			}
			// StatusConflict == the IP exists already.
			existed = true
		}
	}

	// We have to get the address to know which IP was allocated for us.
	address, err := gce.service.Addresses.Get(gce.projectID, region, name).Do()
	if err != nil {
		return "", false, fmt.Errorf("error re-getting gce static IP address: %v", err)
	}
	return address.Address, existed, nil
}

func (gce *GCECloud) deleteFirewall(name, region string) error {
	mc := newFirewallMetricContext("delete", region)
	fwName := makeFirewallName(name)
	op, err := gce.service.Firewalls.Delete(gce.projectID, fwName).Do()

	if err != nil && isHTTPErrorCode(err, http.StatusNotFound) {
		glog.V(2).Infof("Firewall %s already deleted. Continuing to delete other resources.", name)
	} else if err != nil {
		glog.Warningf("Failed to delete firewall %s, got error %v", fwName, err)
		return mc.Observe(err)
	} else {
		if err := gce.waitForGlobalOp(op, mc); err != nil {
			glog.Warningf("Failed waiting for Firewall %s to be deleted.  Got error: %v", fwName, err)
			return err
		}
	}
	return nil
}

func (gce *GCECloud) deleteStaticIP(name, region string) error {
	mc := newAddressMetricContext("delete", region)
	op, err := gce.service.Addresses.Delete(gce.projectID, region, name).Do()
	if err != nil && isHTTPErrorCode(err, http.StatusNotFound) {
		glog.Infof("Static IP address %s is not reserved", name)
	} else if err != nil {
		glog.Warningf("Failed to delete static IP address %s, got error %v", name, err)
		return mc.Observe(err)
	} else {
		if err := gce.waitForRegionOp(op, region, mc); err != nil {
			glog.Warningf("Failed waiting for address %s to be deleted, got error: %v", name, err)
			return err
		}
	}
	return nil
}