fix: improve default readiness probe config for shutdown

On shutdown coredns will wait what is configured for lameduck and
continue handling connections. At the same time it will fail readiness
probes.

In order to give readiness checks a chance to remove the instance from
the service we need to lower the failure threshold and the interval.

This is to avoid failing DNS requests in a busy cluster when coredns is
being scaled down.

Signed-off-by: Heiko Voigt <[email protected]>

Author: hvoigt

charts/coredns/Chart.yaml

@@ -1,6 +1,6 @@
 apiVersion: v2
 name: coredns
-version: 1.39.1
+version: 1.39.2
 appVersion: 1.12.0
 home: https://coredns.io
 icon: https://coredns.io/images/CoreDNS_Colour_Horizontal.png
@@ -20,4 +20,4 @@ type: application
 annotations:
   artifacthub.io/changes: |
     - kind: fixed
-      description: align imagePullSecrets in Deployment and ServiceAccount
+      description: improve default readiness probe config for shutdown

charts/coredns/values.yaml

@@ -118,7 +118,7 @@ servers:
   # Serves a /health endpoint on :8080, required for livenessProbe
   - name: health
     configBlock: |-
-      lameduck 5s
+      lameduck 10s
   # Serves a /ready endpoint on :8181, required for readinessProbe
   - name: ready
   # Required to query kubernetes API for data
@@ -174,9 +174,9 @@ livenessProbe:
 readinessProbe:
   enabled: true
   initialDelaySeconds: 30
-  periodSeconds: 10
+  periodSeconds: 5
   timeoutSeconds: 5
-  failureThreshold: 5
+  failureThreshold: 1
   successThreshold: 1
 
 # expects input structure as per specification https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.11/#affinity-v1-core