prometheus-node-exporter-lua: remove zero values

depending on the configuration there may be multiple
interfaces creating multiple time series always
reporting 0 value. omiting them from the export saves
resources. most notably cpu.

- remove time series with value of zero
- make 'omit_zero_values' configurable
- formating accoding to shfmt and stylua

Signed-off-by: Markus Hube <[email protected]>

Author: NoctivagusObitus

utils/prometheus-node-exporter-lua/files/etc/init.d/prometheus-node-exporter-lua

@@ -11,24 +11,27 @@ _log() {
 start_service() {
 	. /lib/functions/network.sh
 
-	local interface port bind4 bind6
+	local interface port bind4 bind6 omit_zero_values
 
 	config_load prometheus-node-exporter-lua.main
 	config_get keepalive "main" http_keepalive 70
 	config_get interface "main" listen_interface "loopback"
 	config_get port "main" listen_port 9100
+	config_get omit_zero_values "main" omit_zero_values 0
 
 	[ "$interface" = "*" ] || {
-		network_get_ipaddr  bind4 "$interface"
+		network_get_ipaddr bind4 "$interface"
 		network_get_ipaddr6 bind6 "$interface"
 		[ -n "$bind4$bind6" ] || {
 			_log "defering start until listen interface $interface becomes ready"
 			return 0
 		}
-    }
+	}
 
 	procd_open_instance
 
+	[ "$omit_zero_values" -eq 1 ] && procd_set_param env OMIT_ZERO_VALUES=1
+
 	procd_set_param command /usr/sbin/uhttpd -f -c /dev/null -l / -L /usr/bin/prometheus-node-exporter-lua
 	[ $keepalive -gt 0 ] && procd_append_param command -k $keepalive
 
@@ -46,8 +49,7 @@ start_service() {
 	procd_close_instance
 }
 
-service_triggers()
-{
+service_triggers() {
 	local interface
 
 	procd_add_reload_trigger "prometheus-node-exporter-lua"

utils/prometheus-node-exporter-lua/files/usr/bin/prometheus-node-exporter-lua

@@ -8,6 +8,10 @@
 
 socket = require("socket")
 
+-- get configs
+
+local omit_zero_values = os.getenv("OMIT_ZERO_VALUES") == "1"
+
 -- Parsing
 
 function space_split(s)
@@ -22,7 +26,7 @@ function get_contents(filename)
   local f = io.open(filename, "rb")
   local contents = ""
   if f then
-    contents = f:read "*a"
+    contents = f:read("*a")
     f:close()
   end
 
@@ -34,8 +38,8 @@ end
 function print_metric(metric, labels, value)
   local label_string = ""
   if labels then
-    for label,value in pairs(labels) do
-      label_string =  label_string .. label .. '="' .. value .. '",'
+    for label, value in pairs(labels) do
+      label_string = label_string .. label .. '="' .. value .. '",'
     end
     label_string = "{" .. string.sub(label_string, 1, -2) .. "}"
   end
@@ -45,7 +49,9 @@ end
 function metric(name, mtype, labels, value)
   output("# TYPE " .. name .. " " .. mtype)
   local outputter = function(labels, value)
-    print_metric(name, labels, value)
+    if not (omit_zero_values and tonumber(value) == 0) then
+      print_metric(name, labels, value)
+    end
   end
   if value then
     outputter(labels, value)
@@ -67,10 +73,10 @@ end
 function run_all_collectors(collectors)
   local metric_duration = metric("node_scrape_collector_duration_seconds", "gauge")
   local metric_success = metric("node_scrape_collector_success", "gauge")
-  for _,cname in pairs(collectors) do
+  for _, cname in pairs(collectors) do
     if col_mods[cname] ~= nil then
       local duration, success = timed_scrape(col_mods[cname])
-      local labels = {collector=cname}
+      local labels = { collector = cname }
       metric_duration(labels, duration)
       metric_success(labels, success)
     end
@@ -80,7 +86,7 @@ end
 -- Web server-specific functions
 
 function handle_request(env)
-  if env.PATH_INFO ~= '/metrics' then
+  if env.PATH_INFO ~= "/metrics" then
     uhttpd.send("Status: 404 Not Found\r\n")
     uhttpd.send("Server: lua-metrics\r\n")
     uhttpd.send("Content-Type: text/plain\r\n\r\n")
@@ -91,7 +97,7 @@ function handle_request(env)
     uhttpd.send("Content-Type: text/plain; version=0.0.4\r\n\r\n")
     local cols = {}
     for c in env.QUERY_STRING:gmatch("collect[^=]*=([^&]+)") do
-      cols[#cols+1] = c
+      cols[#cols + 1] = c
     end
     if #cols == 0 then
       cols = col_names
@@ -107,12 +113,14 @@ col_names = {}
 ls_fd = io.popen("ls -1 /usr/lib/lua/prometheus-collectors/*.lua")
 for c in ls_fd:lines() do
   c = c:match("([^/]+)%.lua$")
-  col_mods[c] = require('prometheus-collectors.'..c)
-  col_names[#col_names+1] = c
+  col_mods[c] = require("prometheus-collectors." .. c)
+  col_names[#col_names + 1] = c
 end
 ls_fd:close()
 
-output = function (str) uhttpd.send(str.."\n") end
+output = function(str)
+  uhttpd.send(str .. "\n")
+end
 
 if arg ~= nil then
   output = print