prometheus-node-exporter-lua: add conntrack collector

Also fix missing dependency of openwrt collector

Signed-off-by: Etienne Champetier <champetier.etienne@gmail.com>

utils/prometheus-node-exporter-lua/Makefile

@@ -4,7 +4,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=prometheus-node-exporter-lua
-PKG_VERSION:=2018.06.26
+PKG_VERSION:=2018.07.23
 PKG_RELEASE:=1
 
 PKG_MAINTAINER:=Etienne CHAMPETIER <champetier.etienne@gmail.com>
@@ -79,6 +79,7 @@ endef
 define Package/prometheus-node-exporter-lua-openwrt
   $(call Package/prometheus-node-exporter-lua/Default)
   TITLE+= (openwrt collector)
+  DEPENDS:=prometheus-node-exporter-lua
 endef
 
 Build/Compile=
@@ -92,6 +93,7 @@ define Package/prometheus-node-exporter-lua/install
 	$(INSTALL_BIN) ./files/usr/bin/prometheus-node-exporter-lua $(1)/usr/bin/prometheus-node-exporter-lua
 	$(INSTALL_DIR) $(1)/usr/lib/lua/prometheus-collectors
 	$(INSTALL_BIN) ./files/usr/lib/lua/prometheus-collectors/cpu.lua         $(1)/usr/lib/lua/prometheus-collectors/
+	$(INSTALL_BIN) ./files/usr/lib/lua/prometheus-collectors/conntrack.lua   $(1)/usr/lib/lua/prometheus-collectors/
 	$(INSTALL_BIN) ./files/usr/lib/lua/prometheus-collectors/filefd.lua      $(1)/usr/lib/lua/prometheus-collectors/
 	$(INSTALL_BIN) ./files/usr/lib/lua/prometheus-collectors/loadavg.lua     $(1)/usr/lib/lua/prometheus-collectors/
 	$(INSTALL_BIN) ./files/usr/lib/lua/prometheus-collectors/meminfo.lua     $(1)/usr/lib/lua/prometheus-collectors/

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

@@ -0,0 +1,8 @@
+local function scrape()
+  metric("node_nf_conntrack_entries", "gauge", nil,
+    string.sub(get_contents("/proc/sys/net/netfilter/nf_conntrack_count"), 1, -2))
+  metric("node_nf_conntrack_entries_limit", "gauge", nil,
+    string.sub(get_contents("/proc/sys/net/netfilter/nf_conntrack_max"), 1, -2))
+end
+
+return { scrape = scrape }