feat(handler) expose dataplane status on control plane

kong/plugins/prometheus/exporter.lua

@@ -5,6 +5,7 @@ local lower = string.lower
 local concat = table.concat
 local select = select
 local balancer = require("kong.runloop.balancer")
+local cjson = require("cjson")
 
 local DEFAULT_BUCKETS = { 1, 2, 5, 7, 10, 15, 20, 25, 30, 40, 50, 60, 70,
                           80, 90, 100, 200, 300, 400, 500, 1000,
@@ -13,6 +14,8 @@ local metrics = {}
 -- prometheus.lua instance
 local prometheus
 
+local cp_metrics
+
 -- use the same counter library shipped with Kong
 package.loaded['prometheus_resty_counter'] = require("resty.counter")
 
@@ -71,6 +74,18 @@ local function init()
                                          "Total bandwidth in bytes " ..
                                          "consumed per service/route in Kong",
                                          {"service", "route", "type"})
+
+
+  -- Hybrid mode status
+  if kong.version_num >= 2000000 then -- 200.00.00 -> 2.0.0 then
+    if kong.configuration.role == "control_plane" then
+      cp_metrics = true
+
+      metrics.dataplane_last_seen = prometheus:gauge("dataplane_last_seen",
+                                                "Last time data plane contacted control plane",
+                                                {"node_id", "hostname", "ip", "hash"})
+    end
+  end
 end
 
 local function init_worker()
@@ -236,6 +251,19 @@ local function collect()
                                         {res.workers_lua_vms[i].pid})
   end
 
+  -- Hybrid mode status
+  if cp_metrics then
+    -- Cleanup old metrics
+    metrics.dataplane_last_seen:reset()
+
+    local shdict = ngx.shared.kong_clustering
+    for _, node_id in ipairs(shdict:get_keys()) do
+      local status = cjson.decode(shdict:get(node_id))
+
+      metrics.dataplane_last_seen:set(status.last_seen, { node_id, status.hostname, status.ip, status.config_hash })
+    end
+  end
+
   prometheus:collect()
 end