prometheus-node-exporter-lua: add realtek-poe exporter

exposes PoE metrics obtained from realtek-poe

 # HELP realtek_poe_switch_info information about the poe controller
 # TYPE realtek_poe_switch_info gauge
 realtek_poe_switch_info{mcu="ST Micro ST32F100 Microcontroller",firmware="v22.4"} 1

 # HELP realtek_poe_switch_budget_watts overall power budget
 # TYPE realtek_poe_switch_budget_watts gauge
 realtek_poe_switch_budget_watts 77

 # HELP realtek_poe_switch_consumption_watts overall power consumption
 # TYPE realtek_poe_switch_consumption_watts gauge
 realtek_poe_switch_consumption_watts 5

 # HELP realtek_poe_port_priority poe priority of port
 # TYPE realtek_poe_port_priority gauge
 realtek_poe_port_priority{device="lan1"} 1
 realtek_poe_port_priority{device="lan2"} 1
 [...]

 # HELP realtek_poe_port_consumption_watts per port power consumption
 # TYPE realtek_poe_port_consumption_watts gauge
 realtek_poe_port_consumption_watts{device="lan1"} 0
 realtek_poe_port_consumption_watts{device="lan2"} 0
 [...]

 # HELP realtek_poe_port_state per port poe state
 # TYPE realtek_poe_port_state gauge
 realtek_poe_port_state{device="lan1",state="Disabled"} 0
 realtek_poe_port_state{device="lan1",state="Searching"} 1
 [...]
 (states: Disabled, Searching, Delivering power, Fault, Other fault, Requesting power)

 # HELP realtek_poe_port_mode per port poe mode
 # TYPE realtek_poe_port_mode gauge
 realtek_poe_port_mode{device="lan1",mode="PoE"} 0
 realtek_poe_port_mode{device="lan1",mode="PoE+"} 1
 [...]
 (modes: PoE, Legacy, pre-PoE+, PoE+)

Signed-off-by: Gregor Michels <hirnpfirsich@brainpeach.de>

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

@@ -0,0 +1,87 @@
+require "ubus"
+
+local METRIC_NAMESPACE = "realtek_poe"
+
+-- possible poe modes for a port
+--   realtek-poe/src/main.c
+--   static int poe_reply_port_ext_config()
+local POE_MODES = {
+    "PoE",
+    "Legacy",
+    "pre-PoE+",
+    "PoE+"
+}
+
+-- possible poe states for a port
+--   realtek-poe/src/main.c
+--   static int poe_reply_4_port_status()
+local POE_STATES = {
+    "Disabled",
+    "Searching",
+    "Delivering power",
+    "Fault",
+    "Other fault",
+    "Requesting power"
+}
+
+-- --
+-- scraping function
+-- --
+local function scrape()
+    -- connect to ubus
+    local conn = ubus.connect()
+    if not conn then
+        error("Failed to connect to ubusd")
+    end
+
+    -- call poe info
+    local poe_info = conn:call("poe", "info", {})
+    if not poe_info then
+        error("Failed to call 'poe info'. Is realtek-poe installed and running ?")
+    end
+
+    -- close ubus handle
+    conn:close()
+
+    -- helper vars
+    local mcu         = poe_info["mcu"]
+    local ports       = poe_info["ports"]
+    local budget      = poe_info["budget"]
+    local firmware    = poe_info["firmware"]
+    local consumption = poe_info["consumption"]
+
+    -- push info, budget and consumption metric
+    metric(METRIC_NAMESPACE .. "_switch_info", "gauge", { mcu=mcu, firmware=firmware }, 1)
+    metric(METRIC_NAMESPACE .. "_switch_budget_watts", "gauge", nil, budget)
+    metric(METRIC_NAMESPACE .. "_switch_consumption_watts", "gauge", nil, consumption)
+
+    -- push per port priority metrics
+    local priority_metric = metric(METRIC_NAMESPACE .. "_port_priority", "gauge")
+    for port, values in pairs(ports) do
+        priority_metric({ device=port }, values["priority"])
+    end
+
+    -- push per port consumption metrics
+    local consumption_metric = metric(METRIC_NAMESPACE .. "_port_consumption_watts", "gauge")
+    for port, values in pairs(ports) do
+        consumption_metric({ device=port }, (values["consumption"] ~= nil and values["consumption"] or 0))
+    end
+
+    -- push per port state metrics
+    local state_metric = metric(METRIC_NAMESPACE .. "_port_state", "gauge")
+    for _, state in ipairs(POE_STATES) do
+        for port, values in pairs(ports) do
+            state_metric({ device=port, state=state }, (values["status"] == state and 1 or 0))
+        end
+    end
+
+    -- push per port mode metrics
+    local mode_metric = metric(METRIC_NAMESPACE .. "_port_mode", "gauge")
+    for _, mode in ipairs(POE_MODES) do
+        for port, values in pairs(ports) do
+            mode_metric({ device=port, mode=mode }, (values["mode"] == mode and 1 or 0))
+        end
+    end
+end
+
+return { scrape = scrape }