prometheus-node-exporter-lua: uci_dhcp_host module

Extract data from configuration file /etc/config/dhcp and create labels
{name, ip, mac, dns} via uci. Those labels are useful in order to craft
complex prometheus queries as replacing the MAC address to a custom
name.  E.g.: wifi_station_signal_dbm * on (mac) group_left(name)
uci_dhcp_host or on (mac) label_replace(wifi_station_signal_dbm, "name",
"$1", "mac", "(.+)")

Signed-off-by: Gérondal Thibault <contact@tycale.be>

utils/prometheus-node-exporter-lua/Makefile

@@ -4,7 +4,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=prometheus-node-exporter-lua
-PKG_VERSION:=2020.06.26
+PKG_VERSION:=2020.07.04
 PKG_RELEASE:=1
 
 PKG_MAINTAINER:=Etienne CHAMPETIER <champetier.etienne@gmail.com>
@@ -40,6 +40,12 @@ define Package/prometheus-node-exporter-lua-nat_traffic
   DEPENDS:=prometheus-node-exporter-lua
 endef
 
+define Package/prometheus-node-exporter-lua-uci_dhcp_host
+  $(call Package/prometheus-node-exporter-lua/Default)
+  TITLE+= (uci_dhcp_host collector)
+  DEPENDS:=prometheus-node-exporter-lua +libuci-lua
+endef
+
 define Package/prometheus-node-exporter-lua-netstat
   $(call Package/prometheus-node-exporter-lua/Default)
   TITLE+= (netstat collector)
@@ -119,6 +125,11 @@ define Package/prometheus-node-exporter-lua-nat_traffic/install
 	$(INSTALL_BIN) ./files/usr/lib/lua/prometheus-collectors/nat_traffic.lua $(1)/usr/lib/lua/prometheus-collectors/
 endef
 
+define Package/prometheus-node-exporter-lua-uci_dhcp_host/install
+	$(INSTALL_DIR) $(1)/usr/lib/lua/prometheus-collectors
+	$(INSTALL_BIN) ./files/usr/lib/lua/prometheus-collectors/uci_dhcp_host.lua $(1)/usr/lib/lua/prometheus-collectors/
+endef
+
 define Package/prometheus-node-exporter-lua-netstat/install
 	$(INSTALL_DIR) $(1)/usr/lib/lua/prometheus-collectors
 	$(INSTALL_BIN) ./files/usr/lib/lua/prometheus-collectors/netstat.lua $(1)/usr/lib/lua/prometheus-collectors/
@@ -167,6 +178,7 @@ endef
 $(eval $(call BuildPackage,prometheus-node-exporter-lua))
 $(eval $(call BuildPackage,prometheus-node-exporter-lua-nat_traffic))
 $(eval $(call BuildPackage,prometheus-node-exporter-lua-netstat))
+$(eval $(call BuildPackage,prometheus-node-exporter-lua-uci_dhcp_host))
 $(eval $(call BuildPackage,prometheus-node-exporter-lua-wifi))
 $(eval $(call BuildPackage,prometheus-node-exporter-lua-wifi_stations))
 $(eval $(call BuildPackage,prometheus-node-exporter-lua-hostapd_stations))

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

@@ -0,0 +1,15 @@
+local uci=require("uci")
+
+local function scrape()
+  local curs=uci.cursor()
+  local metric_uci_host = metric("uci_dhcp_host", "gauge")
+
+  curs:foreach("dhcp", "host", function(s)
+    if s[".type"] == "host" then
+      labels = {name=s["name"], mac=string.upper(s["mac"]), dns=s["dns"], ip=s["ip"]}
+      metric_uci_host(labels, 1)
+    end
+  end)
+end
+
+return { scrape = scrape }