Reworks reload of in-mem preferences and runtimeprefs.json dump

scripts/lua/modules/prefs_reload_utils.lua

@@ -0,0 +1,83 @@
+--
+-- (C) 2014-20 - ntop.org
+--
+
+local prefs_reload_utils = {}
+
+-- ###########################################
+
+-- Key used to determine if it is time to reload in-memory preferences.
+-- This key is set by Redis.cpp, when a preference is changed.
+-- NOTE: keep it in sync with ntop_defines.h PREFS_CHANGED
+local prefs_changed_key = "ntopng.cache.prefs_changed"
+
+-- Key used to enable periodic runtime preferences dump to file.
+-- This key, disabled by default, can be enabled when ntopng is run on appliances
+-- that don't feature a persistent Redis. In this case, it may be useful to dump
+-- changed preferences to a file and to restore them during boot in boot.lua.
+local dump_prefs_to_disk_key = "ntopng.prefs.dump_prefs_to_disk"
+
+-- Key used to request the dump of runtime preferences to dump file.
+-- Actual dump is performed in prefs_dump_utils.lua.
+-- NOTE: This key is only set when dump_prefs_to_disk_key is enabled and thus the dump can be requested.
+local prefs_dump_request_key = "ntopng.cache.prefs_dump_request"
+
+-- ###########################################
+
+function prefs_reload_utils.is_dump_prefs_to_disk_enabled()
+   local prefs_to_disk = ntop.getCache(dump_prefs_to_disk_key)
+
+   return prefs_to_disk == "1"
+end
+
+-- ###########################################
+
+function prefs_reload_utils.is_dump_prefs_to_disk_requested()
+   local dump_requested = ntop.getCache(prefs_dump_request_key)
+
+   if dump_requested == "1" then      
+      -- Delete before doing the dump to guarantee no other dump request will be lost
+      ntop.delCache(prefs_dump_request_key)
+
+      return true
+   end
+
+   return false
+end
+
+-- ###########################################
+
+local function are_prefs_changed()
+   local prefs_changed = ntop.getCache(prefs_changed_key)
+
+   if prefs_changed == "1" then
+      -- Make sure to delete BEFORE doing the actual reload
+      -- To guarantee no reload gets missed
+      ntop.delCache(prefs_changed_key)
+
+      return true
+   end
+
+   return false
+end
+
+-- ###########################################
+
+-- @brief Checks and possibly reload in-memory preferences from Redis
+--        Reload is performed when Redis preferences are changed, to re-align them with in-memory preferences
+function prefs_reload_utils.check_reload_prefs()
+   if are_prefs_changed() then
+      -- Do the actual reload
+      ntop.reloadPreferences()
+
+      -- Finally check if preferences dump to disk is enabled and,
+      -- in that case, request for the dump
+      if prefs_reload_utils.is_dump_prefs_to_disk_enabled() then
+	 ntop.setCache(prefs_dump_request_key, "1")
+      end
+   end
+end
+
+-- ###########################################
+
+return prefs_reload_utils