prometheus-node-exporter-lua: use buffered io, remove concat

netclass collector scrape time goes from 230ms to 170ms

Signed-off-by: Etienne Champetier <redacted>

diff --git a/utils/prometheus-node-exporter-lua/Makefile b/utils/prometheus-node-exporter-lua/Makefile
index d2008907743d9a1902347dbad7e67f6e103caf83..725922602e283c6f099152cb466e71388ef94e4a 100644 (file)
--- a/utils/prometheus-node-exporter-lua/Makefile
+++ b/utils/prometheus-node-exporter-lua/Makefile
@@ -4,7 +4,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=prometheus-node-exporter-lua
-PKG_VERSION:=2025.06.24
+PKG_VERSION:=2025.06.29
 PKG_RELEASE:=1
 
 PKG_MAINTAINER:=Etienne CHAMPETIER <champetier.etienne@gmail.com>

diff --git a/utils/prometheus-node-exporter-lua/files/usr/bin/prometheus-node-exporter-lua b/utils/prometheus-node-exporter-lua/files/usr/bin/prometheus-node-exporter-lua
index f42595587c83b87a0705df57d5217bf0c1f8ed24..2aab28179cb6f52208022476f016734f67b76280 100755 (executable)
--- a/utils/prometheus-node-exporter-lua/files/usr/bin/prometheus-node-exporter-lua
+++ b/utils/prometheus-node-exporter-lua/files/usr/bin/prometheus-node-exporter-lua
@@ -32,21 +32,24 @@ end
 -- Metric printing
 
 function print_metric(metric, labels, value)
-  local label_string = ""
   if type(value) == "nil" then
     return
   end
+  out:write(metric)
   if labels then
+    out:write("{")
+    coma = ""
     for label,value in pairs(labels) do
-      label_string =  label_string .. label .. '="' .. value .. '",'
+      out:write(coma, label, '="', value, '"')
+      coma = ","
     end
-    label_string = "{" .. string.sub(label_string, 1, -2) .. "}"
+    out:write("}")
   end
-  output(string.format("%s%s %s", metric, label_string, value))
+  out:write(" ", value, "\n")
 end
 
 function metric(name, mtype, labels, value)
-  output("# TYPE " .. name .. " " .. mtype)
+  out:write("# TYPE ", name, " ", mtype, "\n")
   local outputter = function(labels, value)
     print_metric(name, labels, value)
   end
@@ -83,15 +86,18 @@ end
 -- Web server-specific functions
 
 function handle_request(env)
+  -- use buffered output instead uhttpd.send()
+  out = io.open("/proc/self/fd/1", "a+")
+  out:setvbuf("full")
   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")
-    uhttpd.send("ERROR: File Not Found.")
+    out:write("Status: 404 Not Found\r\n")
+    out:write("Server: lua-metrics\r\n")
+    out:write("Content-Type: text/plain\r\n\r\n")
+    out:write("ERROR: File Not Found.")
   else
-    uhttpd.send("Status: 200 OK\r\n")
-    uhttpd.send("Server: lua-metrics\r\n")
-    uhttpd.send("Content-Type: text/plain; version=0.0.4\r\n\r\n")
+    out:write("Status: 200 OK\r\n")
+    out:write("Server: lua-metrics\r\n")
+    out:write("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
@@ -101,6 +107,7 @@ function handle_request(env)
     end
     run_all_collectors(cols)
   end
+  out:flush()
 end
 
 -- Main program
@@ -115,9 +122,7 @@ for c in ls_fd:lines() do
 end
 ls_fd:close()
 
-output = function (str) uhttpd.send(str.."\n") end
-
 if arg ~= nil then
-  output = print
+  out = io.output()
   run_all_collectors(col_names)
 end