EB: Replace restart-app cron with systemd timer.

.ebextensions/30-restart.config

@@ -10,9 +10,35 @@ files:
       #!/bin/bash -ex
       kill -SIGUSR1 $(cat /var/pids/web.pid)
 
-  /etc/cron.d/restart:
+  /etc/systemd/system/restart-app.service:
     mode: "000644"
     owner: root
     group: root
     content: |
-      @daily root /opt/restart-app
+      [Unit]
+      Description="Service that runs /opt/restart-app"
+      Requires=restart-app.timer
+      [Service]
+      Type=simple
+      ExecStart=/opt/restart-app
+
+  /etc/systemd/system/restart-app.timer:
+    mode: "000644"
+    owner: root
+    group: root
+    content: |
+      [Unit]
+      Description="Timer for restart-app.service"
+      [Timer]
+      Unit=restart-app.service
+      OnCalendar=daily
+      RandomizedDelaySec=30m
+      [Install]
+      WantedBy=timers.target
+
+container_commands:
+  "01-enable-timer":
+    command: |
+      systemctl daemon-reload
+      systemctl enable restart-app.timer
+      systemctl start restart-app.timer