Keep ALTS Flower state across restarts and purge offline workers

roles/alts_flower/defaults/main.yml

@@ -11,3 +11,10 @@ flower_env_file: /etc/sysconfig/alts-flower
 flower_user: alts-mon
 # Must be set, Flower UI allows revoking tasks and controlling workers
 flower_password: ""
+# Seconds after which offline workers are removed from the dashboard
+flower_purge_offline_workers: 1800
+# Keep workers/tasks state across Flower restarts
+flower_persistent: true
+flower_db: /home/{{ test_system_user }}/flower_db
+# Milliseconds between state saves; 0 saves only on clean shutdown
+flower_state_save_interval: 60000

roles/alts_flower/templates/alts-flower.service.j2

@@ -10,7 +10,13 @@ EnvironmentFile={{ flower_env_file }}
 # Start through /bin/sh like alts-scheduler: under SELinux, systemd may not
 # execute binaries labelled as user home content directly
 ExecStart=/bin/sh -c 'exec {{ flower_venv_dir }}/bin/celery -A alts.worker.app flower \
-    --port={{ flower_port }}'
+    --port={{ flower_port }} \
+{% if flower_persistent | bool %}
+    --persistent=True \
+    --db={{ flower_db }} \
+    --state_save_interval={{ flower_state_save_interval }} \
+{% endif %}
+    --purge_offline_workers={{ flower_purge_offline_workers }}'
 StandardOutput=append:{{ flower_log_dir }}/output.log
 StandardError=append:{{ flower_log_dir }}/error.log
 Restart=on-failure