fix(pod): allow sidecar containers to have probes (#4483)

https://kubernetes.io/docs/concepts/workloads/pods/init-containers/#differences-from-regular-containers

if we check docs, sidecar containers support readiness, liveness and startup probes. I added an extra check to make sure the init container is not sidecar for probe checks.

this way it will be possible to add probes for initcontainers when they are sidecar.

edit: this should be backported to k8s-29/main as well

Fixes #4338

Author: serhatcetinkaya

src/pod.ts

@@ -122,15 +122,15 @@ export abstract class AbstractPod extends base.Resource implements IPodSelector,
   public addInitContainer(cont: container.ContainerProps): container.Container {
 
     // https://kubernetes.io/docs/concepts/workloads/pods/init-containers/#differences-from-regular-containers
-    if (cont.readiness) {
+    if (!this.isSidecarContainer(cont) && cont.readiness) {
       throw new Error('Init containers must not have a readiness probe');
     }
 
-    if (cont.liveness) {
+    if (!this.isSidecarContainer(cont) && cont.liveness) {
       throw new Error('Init containers must not have a liveness probe');
     }
 
-    if (cont.startup) {
+    if (!this.isSidecarContainer(cont) && cont.startup) {
       throw new Error('Init containers must not have a startup probe');
     }
 
@@ -143,6 +143,13 @@ export abstract class AbstractPod extends base.Resource implements IPodSelector,
     return impl;
   }
 
+  // Any initContainer that has `restartPolicy=Always` is a sidecar container. Please refer to
+  // documentation for more details:
+  // https://kubernetes.io/docs/concepts/workloads/pods/sidecar-containers/#differences-from-init-containers
+  private isSidecarContainer(cont: container.ContainerProps) {
+    return cont.restartPolicy === container.ContainerRestartPolicy.ALWAYS;
+  }
+
   public addHostAlias(hostAlias: HostAlias): void {
     this._hostAliases.push(hostAlias);
   }

test/pod.test.ts

@@ -254,6 +254,45 @@ test('init containers cannot have startup probe', () => {
 
 });
 
+test('sidecar containers can have liveness probe', () => {
+
+  const chart = Testing.chart();
+  const pod = new kplus.Pod(chart, 'Pod', { containers: [{ image: 'image' }] });
+
+  pod.addInitContainer({ image: 'image', liveness: Probe.fromTcpSocket(), restartPolicy: ContainerRestartPolicy.ALWAYS });
+
+  const spec = Testing.synth(chart)[0].spec;
+
+  expect(spec.initContainers[0].livenessProbe).toBeTruthy();
+
+});
+
+test('sidecar containers can have readiness probe', () => {
+
+  const chart = Testing.chart();
+  const pod = new kplus.Pod(chart, 'Pod', { containers: [{ image: 'image' }] });
+
+  pod.addInitContainer({ image: 'image', readiness: Probe.fromTcpSocket(), restartPolicy: ContainerRestartPolicy.ALWAYS });
+
+  const spec = Testing.synth(chart)[0].spec;
+
+  expect(spec.initContainers[0].readinessProbe).toBeTruthy();
+
+});
+
+test('sidecar containers can have startup probe', () => {
+
+  const chart = Testing.chart();
+  const pod = new kplus.Pod(chart, 'Pod', { containers: [{ image: 'image' }] });
+
+  pod.addInitContainer({ image: 'image', startup: Probe.fromTcpSocket(), restartPolicy: ContainerRestartPolicy.ALWAYS });
+
+  const spec = Testing.synth(chart)[0].spec;
+
+  expect(spec.initContainers[0].startupProbe).toBeTruthy();
+
+});
+
 test('can specify init containers at instantiation', () => {
 
   const chart = Testing.chart();