feat(depends): Use kubernetes API for depends_on management

We were using netcat to port to check if a service is up, but actually
we can do like Docker / Podman compose and check the status. For now,
I'm using the endpoint status, but maybe we can just check if the object
is "up".

internal/generator/deployment.go

@@ -262,9 +262,21 @@ func (d *Deployment) BindFrom(service types.ServiceConfig, binded *Deployment) {
 
 // DependsOn adds a initContainer to the deployment that will wait for the service to be up.
 func (d *Deployment) DependsOn(to *Deployment, servicename string) error {
-	// Add a initContainer with busybox:latest using netcat to check if the service is up
-	// it will wait until the service responds to all ports
 	logger.Info("Adding dependency from ", d.service.Name, " to ", to.service.Name)
+
+	useLegacy := false
+	if label, ok := d.service.Labels[labels.LabelDependsOn]; ok {
+		useLegacy = strings.ToLower(label) == "legacy"
+	}
+
+	if useLegacy {
+		return d.dependsOnLegacy(to, servicename)
+	}
+
+	return d.dependsOnK8sAPI(to)
+}
+
+func (d *Deployment) dependsOnLegacy(to *Deployment, servicename string) error {
 	for _, container := range to.Spec.Template.Spec.Containers {
 		commands := []string{}
 		if len(container.Ports) == 0 {
@@ -291,6 +303,39 @@ func (d *Deployment) DependsOn(to *Deployment, servicename string) error {
 	return nil
 }
 
+func (d *Deployment) dependsOnK8sAPI(to *Deployment) error {
+	script := `NAMESPACE=${NAMESPACE:-default}
+SERVICE=%s
+KUBERNETES_SERVICE_HOST=${KUBERNETES_SERVICE_HOST:-kubernetes.default.svc}
+KUBERNETES_SERVICE_PORT=${KUBERNETES_SERVICE_PORT:-443}
+
+until wget -q -O- --header="Authorization: Bearer $(cat /var/run/secrets/kubernetes.io/serviceaccount/token)" \
+  --cacert=/var/run/secrets/kubernetes.io/serviceaccount/ca.crt \
+  "https://${KUBERNETES_SERVICE_HOST}:${KUBERNETES_SERVICE_PORT}/api/v1/namespaces/${NAMESPACE}/endpoints/${SERVICE}" \
+  | grep -q '"ready":.*true'; do
+  sleep 2
+done`
+
+	command := []string{"/bin/sh", "-c", fmt.Sprintf(script, to.Name)}
+	d.Spec.Template.Spec.InitContainers = append(d.Spec.Template.Spec.InitContainers, corev1.Container{
+		Name:    "wait-for-" + to.service.Name,
+		Image:   "busybox:latest",
+		Command: command,
+		Env: []corev1.EnvVar{
+			{
+				Name: "NAMESPACE",
+				ValueFrom: &corev1.EnvVarSource{
+					FieldRef: &corev1.ObjectFieldSelector{
+						FieldPath: "metadata.namespace",
+					},
+				},
+			},
+		},
+	})
+
+	return nil
+}
+
 // Filename returns the filename of the deployment.
 func (d *Deployment) Filename() string {
 	return d.service.Name + ".deployment.yaml"

internal/generator/deployment_test.go

@@ -142,6 +142,61 @@ services:
 	if len(dt.Spec.Template.Spec.InitContainers) != 1 {
 		t.Errorf("Expected 1 init container, got %d", len(dt.Spec.Template.Spec.InitContainers))
 	}
+
+	initContainer := dt.Spec.Template.Spec.InitContainers[0]
+	if !strings.Contains(initContainer.Image, "busybox") {
+		t.Errorf("Expected busybox image, got %s", initContainer.Image)
+	}
+
+	fullCommand := strings.Join(initContainer.Command, " ")
+	if !strings.Contains(fullCommand, "wget") {
+		t.Errorf("Expected wget command (K8s API method), got %s", fullCommand)
+	}
+}
+
+func TestDependsOnLegacy(t *testing.T) {
+	composeFile := `
+services:
+    web:
+        image: nginx:1.29
+        ports:
+        - 80:80
+        depends_on:
+        - database
+        labels:
+            katenary.v3/depends-on: legacy
+
+    database:
+        image: mariadb:10.5
+        ports:
+        - 3306:3306
+`
+	tmpDir := setup(composeFile)
+	defer teardown(tmpDir)
+
+	currentDir, _ := os.Getwd()
+	os.Chdir(tmpDir)
+	defer os.Chdir(currentDir)
+
+	output := internalCompileTest(t, "-s", webTemplateOutput)
+	dt := v1.Deployment{}
+	if err := yaml.Unmarshal([]byte(output), &dt); err != nil {
+		t.Errorf(unmarshalError, err)
+	}
+
+	if len(dt.Spec.Template.Spec.InitContainers) != 1 {
+		t.Errorf("Expected 1 init container, got %d", len(dt.Spec.Template.Spec.InitContainers))
+	}
+
+	initContainer := dt.Spec.Template.Spec.InitContainers[0]
+	if !strings.Contains(initContainer.Image, "busybox") {
+		t.Errorf("Expected busybox image, got %s", initContainer.Image)
+	}
+
+	fullCommand := strings.Join(initContainer.Command, " ")
+	if !strings.Contains(fullCommand, "nc") {
+		t.Errorf("Expected nc (netcat) command for legacy method, got %s", fullCommand)
+	}
 }
 
 func TestHelmDependencies(t *testing.T) {

internal/generator/labels/katenaryLabels.go

@@ -36,6 +36,7 @@ const (
 	LabelEnvFrom        Label = KatenaryLabelPrefix + "/env-from"
 	LabelExchangeVolume Label = KatenaryLabelPrefix + "/exchange-volumes"
 	LabelValuesFrom     Label = KatenaryLabelPrefix + "/values-from"
+	LabelDependsOn      Label = KatenaryLabelPrefix + "/depends-on"
 )
 
 var (

internal/generator/labels/katenaryLabelsDoc.yaml

@@ -355,4 +355,25 @@
           DB_USER: database.MARIADB_USER
           DB_PASSWORD: database.MARIADB_PASSWORD
 
+"depends-on":
+  short: "Method to check if a service is ready (for depends_on)."
+  long: |-
+    When a service uses `depends_on`, Katenary creates an initContainer to wait
+    for the dependent service to be ready.
+
+    By default, Katenary uses the Kubernetes API to check if the service endpoint
+    has ready addresses. This method does not require the service to expose a port.
+
+    Set this label to `legacy` to use the old netcat method that requires a port
+    to be defined for the dependent service.
+  example: |-
+    web:
+      image: nginx
+      depends_on:
+        - database
+      labels:
+        # Use legacy netcat method (requires port)
+        {{ .KatenaryPrefix }}/depends-on: legacy
+  type: "string"
+
 # vim: ft=gotmpl.yaml