prometheus-node-exporter-lua: Add ethtool-stats

Based on ethtool-lua library, add interface statistics to the
prometheus-node-exporter.

Signed-off-by: Kevin Jilissen <info@kevinjilissen.nl>

utils/prometheus-node-exporter-lua/Makefile

@@ -246,6 +246,17 @@ define Package/prometheus-node-exporter-lua-realtek-poe/install
 	$(INSTALL_BIN) ./files/usr/lib/lua/prometheus-collectors/realtek-poe.lua $(1)/usr/lib/lua/prometheus-collectors/
 endef
 
+define Package/prometheus-node-exporter-lua-ethtool-stats
+  $(call Package/prometheus-node-exporter-lua/Default)
+  TITLE+= (ethtool-stats collector)
+  DEPENDS:=prometheus-node-exporter-lua +ethtool-lua
+endef
+
+define Package/prometheus-node-exporter-lua-ethtool-stats/install
+	$(INSTALL_DIR) $(1)/usr/lib/lua/prometheus-collectors
+	$(INSTALL_BIN) ./files/usr/lib/lua/prometheus-collectors/ethtool-stats.lua $(1)/usr/lib/lua/prometheus-collectors/
+endef
+
 $(eval $(call BuildPackage,prometheus-node-exporter-lua))
 $(eval $(call BuildPackage,prometheus-node-exporter-lua-bmx7))
 $(eval $(call BuildPackage,prometheus-node-exporter-lua-dawn))

utils/prometheus-node-exporter-lua/files/usr/lib/lua/prometheus-collectors/ethtool-stats.lua

@@ -0,0 +1,38 @@
+local ethtool = require "ethtool"
+
+local pattern_device = "^%s*([^%s:]+):"
+local pattern_metric = "^([a-zA-Z0-9:_]+)$"
+
+local function get_devices()
+  local devices = {}
+  for line in io.lines("/proc/net/dev") do
+    local dev = string.match(line, pattern_device)
+    if dev then
+      table.insert(devices, dev)
+    end
+  end
+  return devices
+end
+
+local function scrape()
+  local eth = ethtool.open()
+  local metrics = {}
+  for _, dev in ipairs(get_devices()) do
+    local stats = eth:statistics(dev)
+    if stats then
+      for m_name, m_value in pairs(stats) do
+        if string.match(m_name, pattern_metric) then
+          local m = metrics[m_name]
+          if m == nil then
+            m = metric("ethtool_" .. m_name, "counter")
+            metrics[m_name] = m
+          end
+          m({device=dev}, m_value)
+        end
+      end
+    end
+  end
+  eth:close()
+end
+
+return { scrape = scrape }