From c907589a44af6805e21ef54efa0bc45659a93291 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20Th=C3=B6mmes?= <markusthoemmes@me.com>
Date: Mon, 22 Mar 2021 19:04:54 +0100
Subject: [PATCH] Default PeriodSeconds of the readiness probe to 1 if unset
 (#10992)

---
 pkg/reconciler/revision/resources/deploy_test.go |  1 +
 pkg/reconciler/revision/resources/queue.go       | 11 +++++++++--
 pkg/reconciler/revision/resources/queue_test.go  |  5 +----
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/pkg/reconciler/revision/resources/deploy_test.go b/pkg/reconciler/revision/resources/deploy_test.go
index c6408e2b9cd7..70a32cfdfdc9 100644
--- a/pkg/reconciler/revision/resources/deploy_test.go
+++ b/pkg/reconciler/revision/resources/deploy_test.go
@@ -98,6 +98,7 @@ var (
 					}},
 				},
 			},
+			PeriodSeconds: 1,
 		},
 		SecurityContext: queueSecurityContext,
 		Env: []corev1.EnvVar{{
diff --git a/pkg/reconciler/revision/resources/queue.go b/pkg/reconciler/revision/resources/queue.go
index c355fee9ee40..5c215b804fc0 100644
--- a/pkg/reconciler/revision/resources/queue.go
+++ b/pkg/reconciler/revision/resources/queue.go
@@ -250,8 +250,8 @@ func makeQueueContainer(rev *v1.Revision, cfg *config.Config) (*corev1.Container
 
 	// After startup we'll directly use the same http health check endpoint the
 	// execprobe would have used (which will then check the user container).
-	// Unlike the StartupProbe, we don't need to override any of the
-	// timeouts/periods/thresholds here.
+	// Unlike the StartupProbe, we don't need to override any of the other settings
+	// except period here. See below.
 	httpProbe := container.ReadinessProbe.DeepCopy()
 	httpProbe.Handler = corev1.Handler{
 		HTTPGet: &corev1.HTTPGetAction{
@@ -263,6 +263,13 @@ func makeQueueContainer(rev *v1.Revision, cfg *config.Config) (*corev1.Container
 		},
 	}
 
+	// Default PeriodSeconds to 1 if not set to make for the quickest possible startup
+	// time.
+	// TODO(#10973): Remove this once we're on K8s 1.21
+	if httpProbe.PeriodSeconds == 0 {
+		httpProbe.PeriodSeconds = 1
+	}
+
 	return &corev1.Container{
 		Name:            QueueContainerName,
 		Image:           cfg.Deployment.QueueSidecarImage,
diff --git a/pkg/reconciler/revision/resources/queue_test.go b/pkg/reconciler/revision/resources/queue_test.go
index 883b7c83db71..236c41e9c9f8 100644
--- a/pkg/reconciler/revision/resources/queue_test.go
+++ b/pkg/reconciler/revision/resources/queue_test.go
@@ -735,10 +735,7 @@ func TestTCPProbeGeneration(t *testing.T) {
 						}},
 					},
 				},
-				// The ReadinessProbe does not override the user's probe parameters.
-				// (The aggressive probing will have happened on startup, now
-				// we can probe at the user-requested/default interval).
-				PeriodSeconds:    0,
+				PeriodSeconds:    1,
 				TimeoutSeconds:   0,
 				SuccessThreshold: 3,
 			}