fix(prometheus): expose metrics in no service route

changelog/unreleased/kong/prometheus_expose_no_service_metrics.yml

@@ -0,0 +1,3 @@
+message: "Expose metrics for serviceless routes"
+type: bugfix
+scope: Plugin

kong/plugins/prometheus/exporter.lua

@@ -273,17 +273,16 @@ local function log(message, serialized)
     return
   end
 
-  local service_name
+  local service_name = ""
   if message and message.service then
     service_name = message.service.name or message.service.host
-  else
-    -- do not record any stats if the service is not present
-    return
   end
 
   local route_name
   if message and message.route then
     route_name = message.route.name or message.route.id
+  else
+    return
   end
 
   local consumer = ""

spec/03-plugins/26-prometheus/05-metrics_spec.lua

@@ -64,6 +64,25 @@ for _, strategy in helpers.each_strategy() do
         }
       }
 
+      local route1 = bp.routes:insert{
+        name = "serverless",
+        protocols = {"https"},
+        hosts = {"status.example.com"},
+        paths = {"/serverless"},
+        no_service = true,
+      }
+
+      assert(bp.plugins:insert {
+        name = "request-termination",
+        route = { id = route1.id },
+        config = {
+          status_code = 200,
+          message = "request terminated by request-termination plugin",
+          echo = true,
+        },
+      })
+
+
       bp.plugins:insert{
         name = "prometheus", -- globally enabled
         config = {
@@ -158,5 +177,38 @@ for _, strategy in helpers.each_strategy() do
       assert.matches('kong_nginx_connections_total{node_id="' .. UUID_PATTERN .. '",subsystem="' .. ngx.config.subsystem .. '",state="%w+"} %d+', body)
     end)
 
+    it("expose metrics in no service route", function()
+      local res = assert(proxy_ssl_client:send{
+        method = "GET",
+        path = "/serverless",
+        headers = {
+          ["Host"] = "status.example.com"
+        }
+      })
+      assert.res_status(200, res)
+
+      local res = assert(proxy_ssl_client:send{
+        method = "GET",
+        path = "/metrics",
+        headers = {
+          ["Host"] = "status.example.com"
+        }
+      })
+      assert.res_status(200, res)
+
+      helpers.wait_until(function()
+        local res = assert(admin_ssl_client:send{
+          method = "GET",
+          path = "/metrics"
+        })
+        local body = assert.res_status(200, res)
+
+        assert.matches('kong_nginx_metric_errors_total 0', body, nil, true)
+
+        return body:find('kong_http_requests_total{service="",route="serverless",code="200",source="kong",consumer=""} 1',
+          nil, true)
+      end)
+    end)
+
   end)
 end

spec/fixtures/blueprints.lua

@@ -180,8 +180,15 @@ function _M.new(db)
   end)
 
   res.routes = new_blueprint(db.routes, function(overrides)
-    return {
-      service = overrides.service or res.services:insert(),
+    local service
+    if overrides.no_service then
+      service = nil
+      overrides.no_service = nil
+    else
+      service = overrides.service or res.services:insert()
+    end
+    return {
+      service = service,
     }
   end)