refactor: duplicate utility to get server ID from ProviderID (#532)

This utility function was duplicated with nearly the exact same
functionality. This commit cleans it up by extracting to a new package
(to avoid cyclic imports).

These two methods are about to get more complicated with #523, better to
clean it up now than to make changes to both locations in the future.

---------

Co-authored-by: Jonas L. <[email protected]>

hcloud/instances.go

@@ -24,6 +24,7 @@ import (
 	cloudprovider "k8s.io/cloud-provider"
 
 	"github.com/hetznercloud/hcloud-cloud-controller-manager/internal/metrics"
+	"github.com/hetznercloud/hcloud-cloud-controller-manager/internal/providerid"
 	"github.com/hetznercloud/hcloud-go/v2/hcloud"
 )
 
@@ -51,7 +52,7 @@ func newInstances(client *hcloud.Client, addressFamily addressFamily, networkID
 func (i *instances) lookupServer(ctx context.Context, node *corev1.Node) (*hcloud.Server, error) {
 	var server *hcloud.Server
 	if node.Spec.ProviderID != "" {
-		serverID, err := providerIDToServerID(node.Spec.ProviderID)
+		serverID, err := providerid.ToServerID(node.Spec.ProviderID)
 		if err != nil {
 			return nil, fmt.Errorf("failed to convert provider id to server id: %w", err)
 		}
@@ -110,7 +111,7 @@ func (i *instances) InstanceMetadata(ctx context.Context, node *corev1.Node) (*c
 	}
 
 	return &cloudprovider.InstanceMetadata{
-		ProviderID:    serverIDToProviderID(server.ID),
+		ProviderID:    providerid.FromServerID(server.ID),
 		InstanceType:  server.ServerType.Name,
 		NodeAddresses: nodeAddresses(i.addressFamily, i.networkID, server),
 		Zone:          server.Datacenter.Name,

internal/hcops/load_balancer.go

@@ -4,8 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"strconv"
-	"strings"
 	"sync"
 	"time"
 
@@ -14,6 +12,7 @@ import (
 
 	"github.com/hetznercloud/hcloud-cloud-controller-manager/internal/annotation"
 	"github.com/hetznercloud/hcloud-cloud-controller-manager/internal/metrics"
+	"github.com/hetznercloud/hcloud-cloud-controller-manager/internal/providerid"
 	"github.com/hetznercloud/hcloud-go/v2/hcloud"
 )
 
@@ -594,7 +593,7 @@ func (l *LoadBalancerOps) ReconcileHCLBTargets(
 
 	// Extract HC server IDs of all K8S nodes assigned to the K8S cluster.
 	for _, node := range nodes {
-		id, err := providerIDToServerID(node.Spec.ProviderID)
+		id, err := providerid.ToServerID(node.Spec.ProviderID)
 		if err != nil {
 			return changed, fmt.Errorf("%s: %w", op, err)
 		}
@@ -1204,28 +1203,6 @@ func (b *hclbServiceOptsBuilder) buildUpdateServiceOpts() (hcloud.LoadBalancerUp
 	return opts, nil
 }
 
-// TODO this is a copy of the function in hcloud/utils.go => refactor.
-func providerIDToServerID(providerID string) (int64, error) {
-	const op = "hcops/providerIDToServerID"
-	metrics.OperationCalled.WithLabelValues(op).Inc()
-
-	providerPrefix := "hcloud://"
-	if !strings.HasPrefix(providerID, providerPrefix) {
-		return 0, fmt.Errorf("%s: missing prefix hcloud://: %s", op, providerID)
-	}
-
-	idString := strings.ReplaceAll(providerID, providerPrefix, "")
-	if idString == "" {
-		return 0, fmt.Errorf("%s: missing serverID: %s", op, providerID)
-	}
-
-	id, err := strconv.ParseInt(idString, 10, 64)
-	if err != nil {
-		return 0, fmt.Errorf("%s: invalid serverID: %s", op, providerID)
-	}
-	return id, nil
-}
-
 func lbAttached(lb *hcloud.LoadBalancer, nwID int64) bool {
 	for _, nw := range lb.PrivateNet {
 		if nw.Network.ID == nwID {

internal/providerid/providerid.go

@@ -0,0 +1,36 @@
+package providerid
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+const (
+	// providerPrefix is the prefix for all provider IDs. It MUST not be changed,
+	// otherwise existing nodes will not be recognized anymore.
+	providerPrefix = "hcloud://"
+)
+
+// ToServerID converts a ProviderID to a server ID.
+func ToServerID(providerID string) (int64, error) {
+	if !strings.HasPrefix(providerID, providerPrefix) {
+		return 0, fmt.Errorf("providerID does not have the expected prefix %s: %s", providerPrefix, providerID)
+	}
+
+	idString := strings.ReplaceAll(providerID, providerPrefix, "")
+	if idString == "" {
+		return 0, fmt.Errorf("providerID is missing a serverID: %s", providerID)
+	}
+
+	id, err := strconv.ParseInt(idString, 10, 64)
+	if err != nil {
+		return 0, fmt.Errorf("unable to parse server id: %s", providerID)
+	}
+	return id, nil
+}
+
+// FromServerID converts a server ID to a ProviderID.
+func FromServerID(serverID int64) string {
+	return fmt.Sprintf("%s%d", providerPrefix, serverID)
+}