[release-1.7] 🐛 CAPD: verify lb config after writing it

test/infrastructure/docker/internal/docker/loadbalancer.go

@@ -191,6 +191,17 @@ func (s *LoadBalancer) UpdateConfiguration(ctx context.Context, unsafeLoadBalanc
 		return errors.WithStack(err)
 	}
 
+	// Read back the load balancer configuration to ensure it got written before
+	// signaling haproxy to reload the config file.
+	// This is a workaround to fix https://github.com/kubernetes-sigs/cluster-api/issues/10356
+	readLoadBalancerConfig, err := s.container.ReadFile(ctx, loadbalancer.ConfigPath)
+	if err != nil {
+		return errors.WithStack(err)
+	}
+	if string(readLoadBalancerConfig) != loadBalancerConfig {
+		return fmt.Errorf("read load balancer configuration does not match written file")
+	}
+
 	return errors.WithStack(s.container.Kill(ctx, "SIGHUP"))
 }
 

test/infrastructure/docker/internal/docker/types/node.go

@@ -120,6 +120,21 @@ func (n *Node) Delete(ctx context.Context) error {
 	return nil
 }
 
+// ReadFile reads a file from a running container.
+func (n *Node) ReadFile(ctx context.Context, dest string) ([]byte, error) {
+	command := n.Commander.Command("cp", dest, "/dev/stdout")
+	stdout := bytes.Buffer{}
+
+	command.SetStdout(&stdout)
+	// Also set stderr so it does not pollute stdout.
+	command.SetStderr(&bytes.Buffer{})
+
+	if err := command.Run(ctx); err != nil {
+		return nil, errors.Wrapf(err, "failed to read file %s", dest)
+	}
+	return stdout.Bytes(), nil
+}
+
 // WriteFile puts a file inside a running container.
 func (n *Node) WriteFile(ctx context.Context, dest, content string) error {
 	// create destination directory