Upd #63: Gracefully scaledown Postfix

Make sure the queue is flushed when the Postfix container is
shutdown through Kubernetes lifecycle hooks.

helm/mail/templates/statefulset.yaml

@@ -56,6 +56,8 @@ spec:
       {{- tpl .Values.extraInitContainers . | nindent 6 }}
       {{- end }}
 
+      # Allow up to 2 minutes for Postfix to flush / empty the queue  before shutting down the container
+      terminationGracePeriodSeconds: 120
       containers:
         - name: {{ .Chart.Name }}
           image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"
@@ -68,6 +70,17 @@ spec:
           readinessProbe: {{- toYaml .Values.readinessProbe | nindent 12 }}
           livenessProbe: {{- toYaml .Values.livenessProbe | nindent 12 }}
           startupProbe: {{- toYaml .Values.startupProbe | nindent 12 }}
+          lifecycle:
+            # If a container has a preStop hook configured, that runs before the container enters the Terminated state.
+            preStop:
+              exec:
+                command:
+                  - bash
+                  - -c
+                  - touch /tmp/container_is_terminating && while ! [[ "`mailq`" == *empty* ]]; do echo "Flushing queue..." && postfix flush; sleep 1; done
+            {{- if .Values.lifecycle.postStart }}
+            postStart: {{- toYaml .Values.lifecycle.postStart | nindent 14 }}
+            {{- end }}
           envFrom:
             - configMapRef:
                 name: {{ $fullName | quote }}

helm/mail/values.yaml

@@ -131,7 +131,9 @@ readinessProbe:
     command:
       - sh
       - -c
-      - 'printf "EHLO healthcheck\n" | nc 127.0.0.1 587 | grep -qE "^220.*ESMTP Postfix"'
+      - >-
+        [ ! -f /tmp/container_is_terminating ] &&
+        printf "EHLO healthcheck\n" | nc 127.0.0.1 587 | grep -qE "^220.*ESMTP Postfix"
 livenessProbe:
   initialDelaySeconds: 5
   periodSeconds: 5
@@ -156,3 +158,6 @@ startupProbe:
         ps axf | fgrep -v grep | egrep -q '\{supervisord\}|/usr/bin/supervisord' &&
         ps axf | fgrep -v grep | fgrep -q "postfix-script" &&
         ps axf | fgrep -v grep | fgrep -q 'opendkim.sh'
+
+lifecycle:
+  postStart: {}

scripts/common-run.sh

@@ -55,7 +55,9 @@ reown_folders() {
 	chown root: /var/spool/postfix/pid
 
 	do_postconf -e "manpage_directory=/usr/share/man"
-	postfix -c /etc/postfix/ set-permissions || true
+
+	# postfix set-permissions complains if documentation files do not exist
+	postfix -c /etc/postfix/ set-permissions > /dev/null 2>&1 || true
 }
 
 postfix_upgrade_conf() {