Added system alert in case of ntopng failure (#8040)

scripts/lua/modules/check_definitions/system/system_error.lua

@@ -0,0 +1,49 @@
+--
+-- (C) 2019-22 - ntop.org
+--
+local checks = require("checks")
+local alerts_api = require("alerts_api")
+local alert_consts = require("alert_consts")
+local ERROR_QUEUE = "ntopng.trace_error.alert_queue"
+
+local script = {
+    -- Script category
+    category = checks.check_categories.internals,
+    severity = alert_consts.get_printable_severities().emergency,
+    default_enabled = true,
+
+    -- See below
+    hooks = {},
+
+    gui = {
+        i18n_title = "internals.system_error",
+        i18n_description = "internals.system_error_description"
+    }
+}
+
+-- #################################################################
+
+local function system_error_check(params)
+    -- Fetch the issue from the error queue
+    local error = ntop.rpopCache(ERROR_QUEUE)
+
+    while (error ~= nil) do
+        if not isEmptyString(error) then
+            -- error is a string with the error message
+            local alert = alert_consts.alert_types.alert_system_error.new(error)
+
+            alert:set_score_emergency()
+            alert:store(alerts_api.systemEntity())
+        end
+
+        error = ntop.rpopCache("ntopng.trace_error.alert_queue")
+    end
+end
+
+-- #################################################################
+
+script.hooks.min = system_error_check
+
+-- #################################################################
+
+return script