Make EnsureTCPLoadBalancerDeleted idempotent

This change allows EnsureTCPLoadBalancerDeleted to be called repeatedly
to reattempt deleting objects that may have failed on a previous run.

Specifically, if the VIP is already deleted, then an attempt is made to
lookup the pool by name.  Returns success when both the VIP and pool are
not found.

Fixes #8352

pkg/cloudprovider/openstack/openstack.go

@@ -443,6 +443,46 @@ func (os *OpenStack) TCPLoadBalancer() (cloudprovider.TCPLoadBalancer, bool) {
 	return &LoadBalancer{network, compute, os.lbOpts}, true
 }
 
+func isNotFound(err error) bool {
+	e, ok := err.(*gophercloud.UnexpectedResponseCodeError)
+	return ok && e.Actual == http.StatusNotFound
+}
+
+func getPoolByName(client *gophercloud.ServiceClient, name string) (*pools.Pool, error) {
+	opts := pools.ListOpts{
+		Name: name,
+	}
+	pager := pools.List(client, opts)
+
+	poolList := make([]pools.Pool, 0, 1)
+
+	err := pager.EachPage(func(page pagination.Page) (bool, error) {
+		p, err := pools.ExtractPools(page)
+		if err != nil {
+			return false, err
+		}
+		poolList = append(poolList, p...)
+		if len(poolList) > 1 {
+			return false, ErrMultipleResults
+		}
+		return true, nil
+	})
+	if err != nil {
+		if isNotFound(err) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+
+	if len(poolList) == 0 {
+		return nil, ErrNotFound
+	} else if len(poolList) > 1 {
+		return nil, ErrMultipleResults
+	}
+
+	return &poolList[0], nil
+}
+
 func getVipByName(client *gophercloud.ServiceClient, name string) (*vips.VirtualIP, error) {
 	opts := vips.ListOpts{
 		Name: name,
@@ -463,10 +503,8 @@ func getVipByName(client *gophercloud.ServiceClient, name string) (*vips.Virtual
 		return true, nil
 	})
 	if err != nil {
-		if e, ok := err.(*gophercloud.UnexpectedResponseCodeError); ok {
-			if e.Actual == http.StatusNotFound {
-				return nil, ErrNotFound
-			}
+		if isNotFound(err) {
+			return nil, ErrNotFound
 		}
 		return nil, err
 	}
@@ -656,45 +694,53 @@ func (lb *LoadBalancer) UpdateTCPLoadBalancer(name, region string, hosts []strin
 func (lb *LoadBalancer) EnsureTCPLoadBalancerDeleted(name, region string) error {
 	glog.V(4).Infof("EnsureTCPLoadBalancerDeleted(%v, %v)", name, region)
 
-	// TODO(#8352): Because we look up the pool using the VIP object, if the VIP
-	// is already gone we can't attempt to delete the pool. We should instead
-	// continue even if the VIP doesn't exist and attempt to delete the pool by
-	// name.
-	vip, vipErr := getVipByName(lb.network, name)
-	if vipErr == ErrNotFound {
-		return nil
-	} else if vipErr != nil {
-		return vipErr
-	}
-
-	// It's ok if the pool doesn't exist, as we may still need to delete the vip
-	// (although I don't believe the system should ever be in that state).
-	pool, poolErr := pools.Get(lb.network, vip.PoolID).Extract()
-	if poolErr != nil {
-		detailedErr, ok := poolErr.(*gophercloud.UnexpectedResponseCodeError)
-		if !ok || detailedErr.Actual != http.StatusNotFound {
-			return poolErr
-		}
-	}
-	poolExists := (poolErr == nil)
-
-	// We have to delete the VIP before the pool can be deleted, so we can't
-	// continue on if this fails.
-	// TODO(#8352): Only do this if the VIP exists once we can delete pools by
-	// name rather than by ID.
-	err := vips.Delete(lb.network, vip.ID).ExtractErr()
+	vip, err := getVipByName(lb.network, name)
 	if err != nil && err != ErrNotFound {
 		return err
 	}
 
-	// Ignore errors for everything following here
-
-	if poolExists {
-		for _, monId := range pool.MonitorIDs {
-			pools.DisassociateMonitor(lb.network, pool.ID, monId)
-			monitors.Delete(monId)
+	// We have to delete the VIP before the pool can be deleted,
+	// so no point continuing if this fails.
+	if vip != nil {
+		err := vips.Delete(lb.network, vip.ID).ExtractErr()
+		if err != nil && !isNotFound(err) {
+			return err
+		}
+	}
+
+	var pool *pools.Pool
+	if vip != nil {
+		pool, err = pools.Get(lb.network, vip.PoolID).Extract()
+		if err != nil && !isNotFound(err) {
+			return err
+		}
+	} else {
+		// The VIP is gone, but it is conceivable that a Pool
+		// still exists that we failed to delete on some
+		// previous occasion.  Make a best effort attempt to
+		// cleanup any pools with the same name as the VIP.
+		pool, err = getPoolByName(lb.network, name)
+		if err != nil && err != ErrNotFound {
+			return err
+		}
+	}
+
+	if pool != nil {
+		for _, monId := range pool.MonitorIDs {
+			_, err = pools.DisassociateMonitor(lb.network, pool.ID, monId).Extract()
+			if err != nil {
+				return err
+			}
+
+			err = monitors.Delete(lb.network, monId).ExtractErr()
+			if err != nil && !isNotFound(err) {
+				return err
+			}
+		}
+		err = pools.Delete(lb.network, pool.ID).ExtractErr()
+		if err != nil && !isNotFound(err) {
+			return err
 		}
-		pools.Delete(lb.network, pool.ID)
 	}
 
 	return nil