Implements system engaged alert upon system alert drops

scripts/plugins/alerts/internals/alerts_drops/user_scripts/system/dropped_alerts.lua

@@ -0,0 +1,63 @@
+--
+-- (C) 2019-20 - ntop.org
+--
+
+local user_scripts = require("user_scripts")
+local alerts_api = require("alerts_api")
+local alert_consts = require("alert_consts")
+
+local script = {
+  -- Script category
+  category = user_scripts.script_categories.internals,
+
+  -- This script is only for alerts generation
+  is_alert = true,
+
+  -- See below
+  hooks = {},
+
+  gui = {
+    i18n_title = "internals.alert_drops",
+    i18n_description = "internals.system_alert_drops_descr",
+  },
+}
+
+-- #################################################################
+
+local function dropped_alerts_check(params)
+   tprint("system: "..tostring(interface.getId()).. " key: "..script.key)
+   -- local dropped_alerts = interface.getStats()["num_dropped_alerts"]
+   -- Fetch system host stats
+   local system_host_stats =  ntop.systemHostStat()
+
+   -- Fetch the number of dropped alerts out of system host stats
+   -- The number fetched is the number of drops occured in the internal queue, that is,
+   -- in the queue currently used to generate alerts from C
+   local dropped_alerts = system_host_stats["alerts_stats"]["alert_queues"]["internal_alerts_queue"]["num_not_enqueued"]
+
+   -- Compute the delta with the previous value for drops
+   local delta_drops = alerts_api.interface_delta_val(script.key, params.granularity, dropped_alerts, true --[[ skip first --]])
+
+   local alert_type = alert_consts.alert_types.alert_dropped_alerts.create(
+      alert_consts.alert_severities.error,
+      alert_consts.alerts_granularities[params.granularity],
+      interface.getId(),
+      delta_drops
+   )
+
+   if(delta_drops > 0) then
+      alerts_api.trigger(params.alert_entity, alert_type, nil, params.cur_alerts)
+   else
+      alerts_api.release(params.alert_entity, alert_type, nil, params.cur_alerts)
+   end
+
+
+end
+
+-- #################################################################
+
+script.hooks.min = dropped_alerts_check
+
+-- #################################################################
+
+return script