Make shutdown grace periods to more reasonable defaults

Note that post-shutdown-grace-period doesn't seem to contribute to graceful shutdown,
see #8095 for discussion.

pkg/flags/flags.go

@@ -222,9 +222,11 @@ Takes the form "<host>:port". If not provided, no admission controller is starte
 
 		statusUpdateInterval = flags.Int("status-update-interval", status.UpdateInterval, "Time interval in seconds in which the status should check if an update is required. Default is 60 seconds")
 
-		shutdownGracePeriod = flags.Int("shutdown-grace-period", 0, "Seconds to wait after receiving the shutdown signal, before stopping the nginx process.")
+		shutdownGracePeriod = flags.Int("shutdown-grace-period", 10, "Seconds to wait after receiving the shutdown signal, before stopping the nginx process.")
 
-		postShutdownGracePeriod = flags.Int("post-shutdown-grace-period", 10, "Seconds to wait after the nginx process has stopped before controller exits.")
+		postShutdownGracePeriod = flags.Int("post-shutdown-grace-period", 0, `[IN DEPRECATION] Seconds to wait after the nginx process has stopped before controller exits.
+Note that increasing this value doesn't seem to contribute to graceful shutdown of the ingress controller.
+If you would like to configure period for accepting requests before shutting down, use 'shutdown-grace-period' instead.'`)
 
 		deepInspector = flags.Bool("deep-inspect", true, "Enables ingress object security deep inspector")
 

pkg/util/process/sigterm.go

@@ -17,12 +17,11 @@ limitations under the License.
 package process
 
 import (
+	klog "k8s.io/klog/v2"
 	"os"
 	"os/signal"
 	"syscall"
 	"time"
-
-	klog "k8s.io/klog/v2"
 )
 
 type exiter func(code int)
@@ -41,8 +40,11 @@ func HandleSigterm(ngx Controller, delay int, exit exiter) {
 		exitCode = 1
 	}
 
-	klog.Infof("Handled quit, delaying controller exit for %d seconds", delay)
-	time.Sleep(time.Duration(delay) * time.Second)
+	if delay > 0 {
+		klog.Warning("[DEPRECATED] Delaying controller exit for %d seconds", delay)
+		klog.Warning("[DEPRECATED] 'post-shutdown-grace-period' does not have any effect for graceful shutdown - use 'shutdown-grace-period' flag instead.")
+		time.Sleep(time.Duration(delay) * time.Second)
+	}
 
 	klog.InfoS("Exiting", "code", exitCode)
 	exit(exitCode)