Gracefully drain connections when stopping the gateway

config/300-gateway.yaml

@@ -48,8 +48,13 @@ spec:
             - --base-id 1
             - -c /tmp/config/envoy-bootstrap.yaml
             - --log-level info
+            - --drain-time-s $(DRAIN_TIME_SECONDS)
+            - --drain-strategy immediate
           command:
             - /usr/local/bin/envoy
+          env:
+            - name: DRAIN_TIME_SECONDS
+              value: "15"
           image: docker.io/envoyproxy/envoy:v1.26-latest
           name: kourier-gateway
           ports:
@@ -85,7 +90,27 @@ spec:
           lifecycle:
             preStop:
               exec:
-                command: ["/bin/sh","-c","curl -X POST --unix /tmp/envoy.admin http://localhost/healthcheck/fail; sleep 15"]
+                command:
+                - perl
+                - -e
+                - |-
+                  use strict;
+                  use warnings;
+                  use IO::Socket qw(AF_UNIX SOCK_STREAM SHUT_WR);
+
+                  my $client = IO::Socket->new(
+                    Domain => IO::Socket::AF_UNIX,
+                    Type   => IO::Socket::SOCK_STREAM,
+                    Peer   => "/tmp/envoy.admin"
+                  ) || die "Can't open socket: $IO::Socket::errstr";
+                  $client->autoflush(1);
+
+                  $client->send("POST /drain_listeners?graceful HTTP/1.1\nHost: localhost\nConnection: close\n\n");
+                  $client->shutdown(IO::Socket::SHUT_WR);
+
+                  $client->close();
+
+                  sleep $ENV{DRAIN_TIME_SECONDS};
           readinessProbe:
             httpGet:
               httpHeaders: